The Steel Pier closed its doors on Labor Day Weekend for the final time. The smell of the ocean, sea air, cotton candy, popcorn and hot dogs is gone forever. The Pier extended into the Atlantic Ocean – almost 1,000 feet.

In the 1940s, the place to go in Atlantic City was the Steel Pier. The Pier opened in 1898. In its most popular period, entertainers flocked to the Pier to entertain visitors especially on Labor Day Weekend. Charlie Chaplin, the Three Stooges, Bob Hope and Frank Sinatra were a few of the fabulous entertainers who thrilled the crowds. Everyone knew about the Diving Horse. The horse and rider leaped approximately forty feet into the ocean.

Well, times change and progress is here. The Pier is being replaced for new development. Shops, stores and condominiums will replace the rides on the boardwalk. Children will miss the pier most. While adults gambled in the casinos, the children, who were not allowed into the casino floor, were entertained on the Steel Pier in an appropriate environment.

The music of the carousel, made in Italy and hand painted with scenes from old Atlantic City, could be heard mixed with the laughter and screams of the children while rock music pulsed from the other end of the Pier.

I find it sad that progress has eliminated another landmark which is irreplaceable. After one hundred and eight years, the pier is now silent waiting for the wrecking balls to decimate it. I have been privileged to know and love the Steel Pier as a child and can share this memory with my grandchildren in the future.

MAAS Stainless Steal Cleaner works great because it cleans so well and also polishes and protects the metal. I use it on my kitchen appliances and the stainless steel on my boat and motor home too. Out at the airport it works well on aluminum, oleo struts and aircraft fittings.

If you own a stainless steal BBQ you know how important a good stainless steal cleaner is and MAAS is easy to use in with the aerosol spray container, as it is easy to apply and then simply wipe dry, piece of cake.

It works best when there is no wind or little wind. I shake the can up for about 10-20 seconds and start spraying at either 6 or 8 inches away to coat the metal and then let it dwell for a few minutes and wipe dry.

Having been in the cleaning business for a number of years prior to retirement, I have always found that you must try all the products on the market if you want to find the best ones.

Indeed many consumer products do hold up against the professional cleaning products we use in the industry and MAAS Stainless Steel Cleaner is one of them and I use it on my toys as well.

Sheet metal stamping is the system wherein metal sheets are used for producing final products. When a metal sheet is inserted into the die or the press, it is molded into the required shape and size. Metal sheets of only a certain thickness can be inserted into metal stamping machines. The maximum limit for most metal stamping machines is ¼ inch. However, machines can be designed to accommodate sheets of greater thickness also. Even the kind of metal sheets that can be processed in metal stamping are also specific. Only certain metals or alloys can be used like aluminum, brass, steel (hot rolled or cold rolled), galvanized steel, stainless steel, copper, zinc and titanium.

Before the metal sheet is inserted into the machine, the customer provides the prototype or at least a diagram of the final product. In case the customer doesn’t have a clear idea of what the final product should look like, most metal stamping producers also offer engineering services for designing the products as well. Even some secondary services such as deburring and plating are provided by the metal stamping companies after the metal sheet is stamped.

There are three main components in sheet metal stamping -- the die, the punch and the binder/blank holder. The sheet is kept between the blank holder and the die and the punch is driven into the die wherein the sheet spreads over the die because of the drawing and stretching. The blank holder provides the restraining force that is required to control the sheet flow into the die. This force prevents wrinkling and tearing of the sheet as the quantity of material going into the machine can be controlled. For some processes where the blank holder force is too high for the material, draw beads are used to create the restraining force.

Sheet metal stampings are also known as thin stampings. Sheet metal stamping is used most primarily in the case-building process. It is also the most important part as each of the panels has to be stamped one by one. First the motherboard tray is stamped, then one-side panels on the right and left from bottom to top and back.

Most cutting tools have replaceable attachments. These are called cutting tool inserts. They can be of various shapes and sizes – round, triangular, square, rectangular, rhombic, five-sided or even eight-sided. Cutting tool inserts are used in varied applications – from cutting and drilling to boring, grooving, sawing, threading, mining and milling. Some of them are so adjustable that when the edges become worn out, other unused edge portions come into use!

Besides their shape, inserts also come with different angles for their tips. A ball nose mill is used for grooves or semicircles. A radius tip mill is used on milling cutters. A chamfer tip mill is ideal for an angled cut or a chamfered edge. A dogbone tip is two-edged and is used for grooving.

What are inserts made of? They are usually made of carbide, high-speed steel, silicon nitride, ceramic, cobalt, diamond particles, etc. They are then coated with substances like titanium aluminum nitride, zinc nitride or chromium nitride to make them even stronger. Some of these composite alloys go up to a hardness of 60 RC. These new age super alloys are becoming very popular in industry today. They withstand a high amount of shock and heat and resist wear and tear. So economizing on inserts may not be such a good idea for a manufacturing unit because they pay for themselves in a very short time. However, investing in costly inserts without warranting it would not be advisable because working them with wrong speeds and feeds would be detrimental to the life of these tools.

Advice and training from an acknowledged cutting tool inserts manufacturer would go a long way in ensuring you get the best possible output from your investment. Today, there are cutting tool inserts that last up to 40% longer than they used to. High cutting force, feed without vibration and the same insert used for various applications are some of the advantages of today’s inserts.

Steel and aluminum are the favored materials for metal shed building. Both of them are strong and light enough to make sheds. Metal sheds are very easy to construct since they do not require foundations. They can be constructed and placed in their suitable locations much as one would buy and keep a cupboard inside the house.

Metal shed designs are quite monotonous and they have flat or slightly V-shaped roofs. In metal sheds, the emphasis is on storage space and there are several shelves already attached to their inner walls. In metal sheds, utility wins over elegance. Homeowners buy metal sheds more for their durability rather than their looks.

Yet, to their advantage, metal sheds are marginally cheaper than wood sheds. If one needs a shed just for stowing certain tools in an obscure corner of their lawn, then it is wise to have a metal shed. Houses with small gardens may go for metal sheds. Also, metal sheds are easy to construct. They can be raised by the homeowners themselves from do-it-yourself kits with a little knowledge of carpentry. Metal sheds not only cut costs on the material, but also on the labor that is needed to construct them.

Steel and aluminum are both corroding metals. Metallurgical companies treat these metals for rust and corrosion at the extraction stage itself. Despite that, a prolonged exposure to humid environments may cause them to get rusty and corroded. A rusty shed is a terrible eyesore in the lawn of any house. Alloys of aluminum like duralumin and magnalium, the same alloys that heavy vehicles and aircraft are made, are also used for manufacturing metal sheds and are known to be non-rusting, but are more expensive than typical metal.

Metal sheds are hazardous if there are children in the house. Their edges are usually rough and can be incredibly sharp. While constructing a metal shed, it is extremely important to check that there are no sharp edges or loose screws left.

Metal sheds are utilitarian and are usually not objects to be flaunted. People generally keep their metal sheds in hidden corners of their gardens or lawns and they are primarily used for storage.

Austenitize - to convert the matrix of a ferrous alloy to austenite by heating above the transformation temperature.
Batch - the component raw materials properly weighed, proportioned, and mixed for delivery to a processing unit. Also, the product output from a processing unit in which there is essentially no product output until all component materials are charged and processed.
Carbide, primary - carbide precipitated in cast iron during solidification.
Cast iron - a generic term for a series of alloys primarily of iron, carbon, and silicon in which the carbon I in excess of the amount which can be retained in solid solution in austenite at the eutectic temperature.
Cementite - a very hard and brittle compound of iron and carbon corresponding to the empirical formula Fe3C, commonly known as iron carbide.
Cementite, primary - cementite precipitated in cast iron during solidification. Also known as primary carbide.
Chilled iron - a cast iron that would normally solidify as a gray cast iron which is purposely caused to solidify as white cast iron locally or entirely by accelerated cooling caused by contact with a metal surface, that is, a chill.
Direct reduced iron - iron ores that have been reduced to essentially metallic iron by heat and reducing agents, but without melting, and processed into suitable shapes for use as a charge material in a melting operation.
Dual metal - two metals of different composition that are fusion bonded at all interfacial surfaces by casting metal of one composition against metal of a second composition.
Ductile iron - a cast iron that has been treated in the liquid state so as to cause substantially all of its graphitic carbon to occur as spheroids or nodules in the as-cast condition.
Ferritize - to increase the quantity of ferrite in the matrix of a ferrous casting through an appropriate heat treatment.
Ferritizing anneal - the process of producing a predominantly ferritic matrix in cast iron through an appropriate heat treatment.
Graphite, compacted - a graphite shape that is intermediate between flake graphite and nodular graphite that typically appears in a polished section as thick flakes with blunt ends.
Graphite, flake - an irregularly shaped particle of graphite, usually appearing in a polished section as curved plates, such as found in gray cast irons.
Graphite, nodular - spheroidal shaped graphite typically found in ductile irons and compact clusters of graphite typically found in malleable irons.
Graphite, primary - graphite precipitated in cast iron during solidification.
Graphite rosette - arrangement of graphite flakes in which the flakes extend radially from centers of crystallization in gray cast iron.
Graphite, spheroidal - spheroidal shaped graphite having a polycrystalline radial structure, usually found in ductile iron and to a controlled, limited extent in compacted graphite iron.
Graphitize - to precipitate graphite in an iron-carbon alloy.
Gray iron - cast iron that has a relatively large proportion of the graphitic carbon present in the form of flake graphite. The metal has a gray fracture.
Heat - the total molten metal output from a single heating in a batch melting process or the total metal output from essentially a single heating in a continuous melting operation using basically constant charge and processing conditions and targeted at a fixed metal chemistry at the furnace spout. A heat can also be defined as a fixed time period for a continuous melting operation provided that it is shorter than the time period covered by the above definition.
Inoculating alloy - an alloy added to molten iron for the principle purpose of nucleating a primary phase such as graphite. Inoculating alloys are frequently used to avoid the formation of primary carbide by enhancing the nucleation of graphite.
Malleable, ferritic - a ferrous alloy that is cast as white is converted by an appropriate heat treatment to a microstructure of temper carbon embedded in a ferritic matrix essentially free of pearlite and carbide.
Malleable iron - a cast iron of such composition that it solidifies as white iron, which upon proper heat treatment is converted to a metallic matrix with nodules of temper carbon.
Malleable, pearlitic - a ferrous alloy that is cast as white iron but which is converted by an appropriate heat treatment to a microstructure of temper carbon embedded in a matrix containing a controlled quantity, form, and distribution of pearlite or tempered martensite.
Malleableize - to convert white iron into malleable iron through an appropriate graphitizing heat treatment.
Melt - the total molten metal produced in a single heat.
Merchant pig iron - pig iron produced for commercial sale to foundries.
Mottled iron - a cast iron containing a mixed structure of gray iron and white iron of variable proportions. The fracture has a mottled appearance.
Nodular graphite - graphite in the form of nodules or spheroids in iron castings.
Nodularity - the volumetric proportion of spheroidal or nodular graphite to total graphite in a ductile iron or a compacted graphite iron matrix.
Nodularity, degree of - the volumetric proportion of spheroidal or nodular graphite to total graphite in a ductile iron matrix.
Nodulizing alloy - an alloy added to molten iron for the primary purpose of causing the formation of spheroidal graphite during solidification.
Pig iron - the high carbon iron product obtained by the reduction of iron ores, typically in a blast furnace or an electric furnace, and cast into uniform shapes having physical and chemical characteristics suitable for end as foundry melting stock.
Sample - one or more portions of a liquid or solid material taken in an unbiased manner from a batch, heat, lot or process stream to be representative of the whole, for subsequent testing to determine the chemical, physical, mechanical, or other quality characteristics of the material, or combination thereof.
Temper carbon - compact aggregates or nodules of graphite found in malleable iron as a result of heat treatment.
Test bar - a bar-shaped coupon that is tested with or without subsequent preparation for the determination of physical or mechanical properties.
Test coupon - specially designed casting, or portion thereof, that is used to provide a representative sample of the iron from which it was cast.
Test lug - a sample produced as an appendage on a casting, that may be removed and tested to qualify the casting or the iron which it was produced.
Test specimen - a test object, suitably prepared from a sample, for evaluation of the chemical, physical, mechanical, or metallurgical quality of the sample.
Treated iron - molten cast iron to which all basic alloys and nodulizing alloys have been added but not necessarily all inoculating alloy additions.
White iron - cast iron in which substantially all of the carbon is in solution and in the combined form. The metal has a white fracture.

Historically, the first classification of cast iron was based on its fracture. Two types of iron were initially recognized:

* White iron: Exhibits a white, crystalline fracture surface because fracture occurs along the iron carbide plates; it is the result of metastable solidification (Fe-C eutectic)
* Gray iron: Exhibits a gray fracture surface because fracture occurs along the graphite plates (flakes); it is the result of stable solidification (Gr eutectic)

Special cast irons differ from the common cast irons mainly in the higher content of alloying elements which promote microstructures having special properties for elevated-temperature applications, corrosion resistance, and wear resistance.

The goal of the metallurgist is to design a process that will produce a structure that will yield the expected mechanical properties. This requires knowledge of the structure-properties correlation for the particular alloy under consideration as well as of the factors affecting the structure.

When discussing the metallurgy of cast iron, the main factors of influence on the structure that one needs to address are:

* Chemical composition
* Cooling rate
* Liquid treatment
* Heat treatment.

In addition, the following aspects of combined carbon in cast irons should also be considered:

* In the original cooling or through subsequent heat treatment, a matrix can be internally decarbonized or carburized by depositing graphite on existing sites or by dissolving carbon from them.
* Depending on the silicon content and the cooling rate, the pearlite in iron can vary in carbon content. This is a ternary system, and the carbon content of pearlite can be as low as 0.50% with 2.5% Si.
* The conventionally measured hardness of graphitic irons is influenced by the graphite, especially in gray iron. Martensite micro hardness may be as high as 66 HRC, but measures as low as 54 HRC conventionally in gray iron (58 HRC in ductile).
* The critical temperature of iron is influenced (raised) by silicon content, not by carbon content.

For common cast iron, the main elements of the chemical composition are carbon and silicon. High carbon content increases the amount of graphite or Fe3C. High carbon and silicon contents increase the graphitization potential of the iron as well as its castability.

The manganese content varies as a function of the desired matrix. Typically, it can be as low as 0.1% for ferrule irons and as high as 1.2% for pearlitic irons, because manganese is a strong pearlite promoter.

From the minor elements, phosphorus and sulfur are the most common and are always present in the composition. They can be as high as 0.15% for low-quality iron and are considerably less for high-quality iron, such as ductile iron or compacted graphite iron.

The main effects of chemical composition to nodular (ductile) iron are similar to those described for gray iron, with quantitative differences in the extent of these effects and qualitative differences in the influence on graphite morphology. The carbon equivalent has only a mild influence on the properties and structure of ductile iron, because it affects graphite shape considerably less than in the case of gray iron. Nevertheless, to prevent excessive shrinkage, high chilling tendency, graphite flotation or a high impact transition temperature, optimum amounts of carbon and silicon must be selected. Minor elements can significantly alter the structure in terms of graphite morphology, chilling tendency, and matrix structure. Minor elements can promote the spheroidization of graphite or can have an adverse effect on graphite shape.

The general influence of various elements on graphite shape. The elements in the first group - the spheroidizing elements - can change graphite shape from flake through compacted to spheroidal. The most widely used element for the production of spheroidal graphite is magnesium. The amount of residual magnesium required to produce spheroidal graphite is generally 0.03 to 0.05%. The precise level depends on the cooling rate. A higher cooling rate requires less magnesium. The amount of magnesium to be added in the iron is a function of the initial sulfur level. A residual magnesium level that is too low results in insufficient nodularity. This in turn results in a deterioration of the mechanical properties of the iron. If the magnesium content is too high, carbides are promoted.

The presence of antispheroidizing minor elements may result in graphite shape deterioration, up to complete graphite degeneration. Therefore, upper limits are set on the amount of deleterious elements to be accepted in the composition of cast iron. These values can be influenced by the combination of various elements and by the presence of rare earths in the composition. Furthermore, some of these elements can be deliberately added during liquid processing in order to increase nodule count.

Alloying elements have in principle the same influence on structure and properties as for gray iron. Because better graphite morphology allows more efficient use of the mechanical properties of the matrix, alloying is more common in ductile iron than in gray iron.

Cooling Rate. When changing the cooling rate, effects similar to those discussed for gray iron also occur in ductile iron, but the section sensitivity of ductile iron is lower. This is because spheroidal graphite is less affected by cooling rate than flake graphite.

The liquid treatment of ductile iron is more complex than that of gray iron. The two stages for the liquid treatment of ductile iron are:

* Modification, which consists of magnesium or magnesium alloy treatment of the melt, with the purpose of changing graphite shape from flake to spheroidal.
* Inoculation (normally, postinoculation that is, after the magnesium treatment) to increase the nodule count. Increasing the nodule count is an important goal, because a higher nodule count is associated with less chilling tendency and a higher as-cast ferrite/pearlite ratio.

Heat treatment is extensively applied on ductile iron because better advantage can be taken of the matrix structure than for gray iron. The heat treatments usually applied are as follows:

* Stress relieving
* Annealing to produce a feritic matrix
* Normalizing to produce a pearlitic matrix
* Hardening to produce tempering structures
* Austempering to produce a ferritic bainite.

The advantage of austempering is that it results in ductile irons with twice the tensile strength for the same toughness. Compacted graphite (CG) irons have a graphite shape intermediate between spheroidal and flake. Typically, compacted graphite looks like type IV graphite.

The chemical composition effects are similar to those described for ductile iron. Carbon equivalent influences strength less obviously than for the case of gray iron, but than for ductile iron. The graphite shape is controlled, as in the case of ductile iron, through the content of minor elements. When the goal is to produce compacted graphite, it is easier from the stand point of controlling the structure to combine spheroidizing (magnesium, calcium, and/ or rare earths) and antispheroidizing (titanium and/or aluminum) elements.

The cooling rate affects properties less for gray iron but more for ductile iron. In other words, CG iron is less section sensitive than gray iron. However, high cooling rates are to be avoided because of the high propensity of CG iron for chilling and high nodule count in thin sections.

The usual microstructure of gray iron is a matrix of pearlite with graphite (flakes dispersed throughout). Foundry practice can be varied so that nucleation and growth of graphite flakes occur in a pattern that enhances the desired properties. The amount, size, and distribution of graphite are important.

Cooling that is too rapid may produce so-called chilled iron, in which the excess carbon is found in the form of massive-carbides. Cooling at intermediate rates can produce mottled iron, in which carbon is present in the form of both primary cementite (iron carbide) and graphite. Very slow cooling of irons that contain large percentages silicon and carbon is likely to produce considerable ferrite and pearlite throughout the matrix, together with coarse graphite flakes.

Flake graphite is one of seven types (shapes or forms) of graphite established in ASTM A 247. Flake graphite is subdivided into five types (patterns), which are designated by the letters A through E. Graphite size is established by comparison with an ASTM size chart, which shows the typical appearances of flakes of eight different sizes at 100x magnification.

Type A flake graphite (random orientation) is preferred for most applications. In the intermediate flake sizes, type A flake graphite is superior to other types in certain wear applications such as the cylinders of internal combustion engines.

Type B flake graphite (rosette pattern) is typical of fairly rapid cooling, such as is common with moderately thin sections (about 10 mm) and along the surfaces of thicker sections, and sometimes results from poor inoculation.

The large flakes of type C flake graphite are typical of kish graphite that is formed in hypereutectic irons. These large flakes enhance resistance to thermal shock by increasing thermal conductivity and decreasing elastic modulus. On the other hand, large flakes are not conducive to good surface finishes on machined parts or to high strength or good impact resistance.

The small, randomly oriented interdendritic flakes in type D flake graphite promote a fine machined finish by minimizing surface pitting, but it is difficult to obtain a pearlitic matrix with this type of graphite. Type D flake graphite may be formed near rapidly cooled surfaces or in thin sections. Frequently, such graphite is surrounded by a ferrite matrix, resulting in soft spots in the casting.

Type E flake graphite is an interdendritic form, which has a preferred rather than a random orientation. Unlike type D graphite, type 6 graphite can be associated with a pearlitic matrix and thus can produce a casting whose wear properties are as good as those of a casting containing only type A graphite in a pearlitic matrix.

Solidification of Gray Iron. In a hypereutectic gray iron, solidification begins with the precipitation of kish graphite in the melt. Kish grows as large, straight, undistorted flakes or as very thick, lumpy flakes that tend to rise to the surface of the melt because of their Sow relative density. When the temperature has been lowered sufficiently, the remaining liquid solidifies as a eutectic structure of austenite and graphite. Generally, eutectic graphite is finer than kish graphite.

The term cast iron, like the term steel, identifies a large family of ferrous alloys. Cast irons are multicomponent ferrous alloys. They contain major (iron, carbon, silicon), minor (<0.01%),>0.01%) elements.

Cast iron has higher carbon and silicon contents than steel. Because of the higher carbon content, the structure of cast iron, as opposed to that of steel, exhibits a rich carbon phase. Depending primarily on composition, cooling rate and melt treatment, cast iron can solidify according to the thermodynamically metastable Fe-Fe₃C system or the stable Fe-Gr system.

When the metastable path is followed, the rich carbon phase in the eutectic is the iron carbide; when the stable solidification path is followed, the rich carbon phase is graphite. Referring only to the binary Fe-Fe₃C or Fe-Gr system, cast iron can be defined as an iron-carbon alloy with more than 2% C. Important notice is that silicon and other alloying elements may considerably change the maximum solubility of carbon in austenite (g). Therefore, in exceptional cases, alloys with less than 2% C can solidify with a eutectic structure and therefore still belong to the family of cast iron.

The formation of stable or metastable eutectic is a function of many factors including the nucleation potential of the liquid, chemical composition, and cooling rate. The first two factors determine the graphitization potential of the iron. A high graphitization potential will result in irons with graphite as the rich carbon phase, while a low graphitization potential will result in irons with iron carbide.

The two basic types of eutectics - the stable austenite-graphite or the metastable austenite-iron carbide (Fe₃C) - have wide differences in their mechanical properties, such as strength, hardness, toughness, and ductility. Therefore, the basic scope of the metallurgical processing of cast iron is to manipulate the type, amount, and morphology of the eutectic in order to achieve the desired mechanical properties.

Classification

Historically, the first classification of cast iron was based on its fracture. Two types of iron were initially recognised:

• White iron: Exhibits a white, crystalline fracture surface because fracture occurs along the iron carbide plates; it is the result of metastable solidification (Fe₃C eutectic)
• Gray iron: Exhibits a gray fracture surface because fracture occurs along the graphite plates (flakes); it is the result of stable solidification (Gr eutectic).

With the advent of metallography, and as the body of knowledge pertinent to cast iron increased, other classifications based on microstructural features became possible:

• Graphite shape: Lamellar (flake) graphite (FG), spheroidal (nodular) graphite (SG), compacted (vermicular) graphite (CG), and temper graphite (TG); temper graphite results from ? solid-state reaction (malleabilization.)
• Matrix: Ferritic, pearlitic, austenitic, martensitic, bainitic (austempered).

This classification is seldom used by the floor foundryman. The most widely used terminology is the commercial one. A first division can be made in two categories:

• Common cast irons: For general-purpose applications, they are unalloyed or low alloyed
• Special cast irons: For special applications, generally high alloyed.

The correspondence between commercial and microstructural classification, as well as the final processing stage in obtaining common cast irons, is given in Fig. 2.

Special cast irons differ from the common cast irons mainly in the higher content of alloying elements (>3%), which promote microstructures having special properties for elevated-temperature applications, corrosion resistance, and wear resistance. A classification of the main types of special cast irons is shown in Fig. 1.

Fig. 1. Classification of special high - alloy cast iron

Fig.2. Basic microstructures and processing for obtaining common commercial cast irons

It has been shown that the structures of grey cast irons are similar to those of ordinary steels but with the addition of graphite flakes which break up the continuity of the iron. Thus with a totally pearlitic structure cast iron should approach in tensile strength and toughness the properties of a 0.95%. carbon normalised steel; the limiting factor being the shape and distribution of the graphite and fineness of the pearlite (Fig. 9 from the article Relation between CE structure and mechanical properties).
Such irons have tensile strengths of up to 370 MPa.

Modification of the micro-structure and properties of cast iron can be brought about by:

1. The use of special melting and casting technique.
2. The addition of alloying elements.
3. Heat-treatment, particularly of white iron.

1. High-duty irons due to casting technique

The gradual introduction of so-called semi-steel during 1914-18 marked the real commencement in improved properties. It is made by adding to the cupola steel scrap which slightly reduces the carbon content and in particular the amount of free graphite together with the production of a pearlitic matrix.
Other methods consist of superheating the molten metals in a separate furnace, whereby the graphite is greatly refined. Alternatively, an iron which would normally cast white can be graphitised by inoculation with ferro silicon (75% Si), sometimes with addition strontium in the ladle to give strength of 370 MPa.

2. Addition of alloying elements

The most common of the special elements added to cast iron are nickel, chromium, copper and molybdenum. Nickel tends to produce grey iron, in which respect it is less powerful than silicon. Consequently in castings of widely varying section the silicon can be reduced slightly and nickel added to prevent chilling in the thin sections, but still retaining a close structure in the thick ones. On the other hand, chromium, by forming carbides, acts in the opposite way to nickel, but at the same time it exerts a grain refining action. These elements, singly or together, are commonly found in motor cylinder irons.

Molybdenum strengthens the matrix by promoting a fine pearlite, but it is used preferably with other elements such as nickel to produce acicular structures.

A rough classification of the types of alloy iron is:

1. Pearlitic Irons

0,5-2% nickel (chromium up to 0,8% and molybdenum up to 0,6%). Used for many general castings. The addition of tin in amounts up to 0,1% promotes a fully pearlitic matrix. High carbon Ni-Cr-Mo cast iron is useful for resisting thermal shock in applications such as die-casting moulds and brake-drums. The nickel and chromium give the desired closeness of grain and molybdenum helps to strengthen the matrix. The considerable graphite reduces the tendency to "crazy crack". Chromium (0,6)-molybdenum (0,6) irons are useful for engine liners, press sleeves, dies, etc., where wear resistance in relatively heavy sections is important. Cast iron with 1 % each of chromium and molybdenum is used for piston-ring pots which are heat-treated to give a high transverse breaking strength coupled with a high elasticity value.

2. Acicular Irons.

Carbon 2,9-3,2, nickel 1,5-2,0, molybdenum 0,3-0,6%. Copper can replace nickel up to 1-5%. This rigid, high-strength, shock-resisting material is used for diesel crankshafts, gears and machine columns. With the correct amounts of nickel and molybdenum correlated with the cooling rate of a particular casting the pearlitic change point can be suppressed and an acicular intermediate constituent (ferrite needles in austenitic matrix) can be produced with high mechanical properties. Acicular cast iron is very much tougher than any of the pearlitic cast irons of lower strength. The tensile strength of acicular cast iron with a carbon content of about 3,0% will vary from 380 to 540 MPa but these figures can be maintained in quite large sections. Phosphorus should not exceed about 0,15% in the presence of molybdenum, otherwise a compound is formed which impoverishes the matrix of molybdenum. Quite large variations in silicon content can be tolerated, but chromium in excess of 0,4% is harmful. The structure changes rapidly at 600-750°C and these irons should not be used at temperatures greater than 300°C.

3. Martensitic Irons.

5-7% nickel with other elements. Very hard irons used for resisting abrasion (Fig. 1), e.g. metal working rolls.

4. Austenitic Irons.

Non-magnetic, with 11-33% nickel but below 20% it is necessary to add about 6% copper or 6% manganese to maintain fully austenitic structures e.g. Nomag irons contain 11% Ni with 6% Mn. These have a good resistance to corrosion and heat, e.g. Ni-Resist.

The outstanding characteristics of the austenitic cast irons, as compared with ordinary cast iron, are:
a) resistance to corrosion;
b) marked resistance to heat;
c) non-magnetic, with suitable compositions;
d) a high electrical resistance coupled with a low temperature coefficient of resistance;
e) a high coefficient of thermal expansion;
f) no change points.

5. Spheroidal graphite cast iron.

The production of spheroidal graphite as in Fig. 2 in the as-cast state is an outstanding development of a new iron, initially due to the use of cerium by Morrogh (BCIRA, 1946 BP 645862) and later, magnesium by the International Nickel Co. (1947 BP 630.070). The use of magnesium, to give 0,04-0,06% residual content proved to be the more adaptable and economic of the two processes. The production of spheroidal structure is prevented, however, by certain trace elements, e.g. 0,1 Ti, 0,009 Pb, 0,003 Bi, 0,004% Sb, but their effect can be eliminated by 0,005-0,01% cerium. For most raw materials the combined use of cerium and magnesium followed by ferro-silicon as an inoculent is used to produce spheroidal graphite iron. Remelting causes a reversion to flake graphite due to loss of magnesium. Magnesium treatment desulphurises the iron to below 0,02% before alloying with the iron, and for economic reasons the sulphur content should be as low as possible. The SG iron can be used with a pearlite matrix or ferrite after a short annealing or with an acicular or austenitic matrix when suitably alloyed.

The stress strain curve is similar to that of steel, with measurable elongation. The ferrite grade of SG iron has a strength of 370 MPa with 17% El whereas a normalised pearlitic SG iron has a strength of 700 MPa with a minimum of 2% El. The strength can be increased to 925 MPa by special heat treatment or by the addition of alloying elements. Damping capacity is lower but shock, heat and growth resistance and weldability are higher than for flake graphite iron. SG iron can, therefore, compete successfully with malleable iron for thick sections, cast steel and alloy flake graphite cast iron. SG cast irons are not so section sensitive as normal iron, e.g. a variation of 25-150 mm section causes grey iron to change from 278 to 154 MPa whereas a SG iron would change from 664 to 587 MPa.

A new iron contains fine vermicular graphite similar but finer than undercooled graphite. It has a worm-like form which enables high strengths to be obtained with 2-3% El. Very precise production control is necessary and this limits commercial production at the moment. The sulphur content must be below 0,002% and casting must be cooled rapidly.

Figure 1. Martensitic iron (Ni-hard). Cementite (white masses) in martensite austenite matrix (x 200) BH = 700	Figure 2. Spheroidal cast iron. Spheroidal graphite in pearlite matrix (x 200)

Stress relief of grey cast iron

Stress is completely removed at 650°C, but grain growth commences at 550°C and is serious at 600°C. Current practice is to heat slowly to 475-500°C, hold at temperature for 1 hour per 25 mm section and cool in furnace to 300°C.

A useful first attempt to relate composition and structure was shown in Fig. 3 of the article Cast Irons but it had limited use in the foundry. Figure 1 shows a more useful relationship between CE value, structure, tensile strength in 30 mm dia bars and section size. A cylindrical test bar of given dia cools more rapidly than a flat plate of equivalent thickness, hence the section is expressed as bar diameter or section thickness. Line H is the boundary of unmachinable irons while line P is the boundary between soft and pearlitic irons. Thus an iron of carbon equivalent 4,35 should not be made thicker than 20 mm as a bar or 10 mm as a plate to attain a pearlitic iron. To avoid an unmachinable chilled casting the bar should not be less than 8 mm dia or plate less than 4 mm thick.

T S. MPa in 30 mm dia. bar

Figure 1. Diagram relating section size, CE value, tensile strength and structure (After BCIRA)

A melting furnace usually produces iron of a constant CE value and silicon is the element normally used to control chill. Alloying elements are added to cast iron to confer special properties and also to control the chill.

Formation of graphite

Flake. Neglecting the effect phosphorus, and the presence of primary austenite dendrites, the successive stages in the growth from the liquid of flake graphite is shown in Fig. 2a The eutectic begins to solidify at nuclei from each of which is formed a roughly spherical lump, referred to as a eutectic cell. In this cell there has been simultaneous growth of austenite and graphite, the latter being in continuous contact with the liquid. The normal appearance of graphite in a micrograph suggests that the structure is made up of a number of separate flakes, but now it is considered that within each eutectic cell there is a continuous branched skeleton of graphite, like a cabbage. The skeleton is branched more frequently with a rapid radial growth of the cell such as occurs when increasing the rate of cooling of an iron which produces undercooling, and therefore finer graphite in the micrograph (Fig. 3).

Figure 2.

Figure 3. Medium size graphite outlining dendrites (x60)

The diameter of a eutectic cell, therefore, has a major effect on mechanical properties, e.g. the greater the number of cells per unit volume the higher the tensile strength, but soundness is affected adversely. Superheating or holding time of the molten iron reduce the number of nuclei, while inoculants such as ferro-silicon and also sulphur increase nuclei.

Spheroidal. Fig. 2b show the growth of spherulitic graphite in a magnesium-treated iron. In this case the spherulitic graphite is quickly surrounded by a layer of austenite and growth of the spheroid occurs by diffusion of carbon from the liquid through the austenite envelope. If diffusion distances become large there will be a tendency for the remaining liquid to solidify as white iron eutectic, hence inoculation in this iron is highly desirable in order to increase the number of graphite centres. Temper carbon nodules. At the malleabilising temperature (800-950°C) the solid white iron consists of eutectic matrix of cementite, austenite and sulphide inclusions. Nucleation of graphite then occurs at austenite cementite interfaces and at sulphide inclusions. The cementite gradually dissolves in the austenite and the carbon diffuses to the graphite nuclei. The MnS tends to form a flake aggregate and the FeS a spherulitic nodule (Fig. 2c).

Micro-structure of cast iron

In preparing the specimens care is required, otherwise, erroneous results might arise. The graphite is readily removed during polishing and in this case the cavities can be either burnished over or enlarged. The various types of micro-structure can be classified into groups without considering the presence of phosphorus.
The graphite can vary in size and form as illustrated in Figs. 3-5. The coarse flaky graphite is found in common iron, while the fine curly type, frequently outlining the dendrites, is found in high-class iron, especially when superheated before casting. Spheroidal graphite is found in magnesium treated irons (Fig. 6). The nodular form is found in annealed irons in which the cementite has decomposed at 800-950°C. Thus we have:

Figure 4. Coarse graphite flakes. Matrix unetched (x 60)	Figure 5. Temper carbon in a malleable iron; ferrite crystals etched (x 100)
Figure 6. Enlarged view of graphite spheroid. Polarised light (x 600)	Figure 7. Hypo-eutectic white cast iron, cementite and pearlite(black) (x 100) BH =100
Figure 8. Hyper-eutectic white cast iron (x 100). White primary crystals of cementite in eutectic (cementite and pearlite)	Figure 9. Grey iron. High duty; pearlite and graphite (x 200)

Pearlite + cementite (i.e. eutectic cementite in hypoeutectic irons (Fig. 7) and primary andeutectic cementite in hyper-eutectic irons (Fig. 8)	white, hard, unmachinable.
Cementite + graphite + pearlite	mottled, difficult to machine.
Graphite + pearlite (Fig. 9)	grey, machinable, high strength.
Graphite + pearlite + ferrite (Fig. 4 from the Cast Iron article)	grey, soft, weaker,
Graphite + ferrite	grey, very soft, easily machined.

The ferrite is of course much less pure than that in carbon steels.

Phosphide eutectic

Most cast irons contain phosphorus in amounts varying from 0,03 to 1,5%, consequently another micro-constituent is frequently present in the structure, in addition to those phases mentioned above. It occurs in white irons as a laminated constituent (ternary eutectic), consisting of:

Iron, 91,19%	Ferrite (with a little phosphorus).
Carbon, 1,92%	Cementite, Fe3C.
Phosphorus, 6,89 %	Iron phosphide, Fe3P.

The melting-point is in the region of 960°C, consequently it is the last constituent to solidify and forms islands in the interstices of the dendrites.

Although this constituent is very brittle it does not unduly weaken the iron when in small amounts (up to 1%) due to the fact that continuous cells are not formed round the grains. The structure is illustrated in Fig. 4 from the Cast Iron article which shows the structure of the phosphide eutectic, together with graphite, ferrite and pearlite. Phosphorus will thus form this additional constituent in any of the "grouped" structures already discussed.

Flake graphite iron finds use due to: its cheapness and ease of machining; low-melting temperature (1140-1200°C); ability to take good casting impressions; wear resistance; high damping capacity; a reasonable tensile strength of 108-340 MPa associated with a very high compressive strength, making it very suitable for applications requiring rigidity and resistance to wear. The different types vary from grey iron which is machinable to either mottled or white iron which is not easily machinable. The white irons of suitable composition can be annealed to give malleable cast iron. During the last thirty years much development work has taken place and it has been found worth while to add even expensive elements to the cheap metal because vastly improved properties result. The new irons formed by alloying or by special melting and casting methods are becoming competitors to steel. The various irons can be classified as shown in Fig. 1 based on the form of graphite and the type of matrix structure in which it is embedded. The metallurgical structure, composition and section of the casting largely govern the engineering properties. One of the differences between cast iron and steel is the presence of a large quantity of carbon, generally 2-4%, and frequently high silicon contents. While carbon in ordinary steel exists as cementite (Fe3C), in cast iron it occurs in two forms: stable form-graphite; unstable form-cementite, analysed as combined carbon. CAST IRON Grey machinable iron White, unmachinable iron no graphite Flake Graphite Spheroidal Graphite Pearlitic Martensitic Ferritic Pearlitic Austenitic Martensitic Malleable iron temper carbon graphite Ferritic Pearlitic Blackheart Thin Whiteheart Whiteheart Special Malleable Figure 1. Classification of cast iron (Pearce) Graphite is grey, soft, and occupies a large bulk, hence counteracting shrinkage; while cementite is intensely hard, with a density of the same order as iron. On the relative amounts, shape and the distribution of these two forms of carbon largely depend the general properties of the iron. The factors mainly influencing the character of the carbon are: The rate of cooling. The chemical composition. The presence of nuclei of graphite and other substances. 1. Rate of cooling. A high rate of cooling tends to prevent the formation of graphite, hence maintains the iron in a hard, unmachinable condition. If the casting consists of varying sections then the thin ones will cool at a much greater rate than the thick. Consequently, the slowly cooled sections will be grey and the rapidly cooled material will be chilled. These points are illustrated in Fig. 2, which shows the variation in hardness of a step casting. Figure 2. The relation between the rate of cooling and hardness as indicated by sections of varying thickness 2. The effect of chemical composition. Carbon lowers the melting-point of the metal and produces more graphite. Hence it favours, a soft, weak iron. Silicon slightly strengthens the ferrite but raises the brittle transition temperature, Indirectly, however, it acts as a softener by increasing the tendency of the cementite to slip up into graphite and ferrite. Fig. 3 shows the relation between the carbon and silicon contents in producing the different irons for one rate of cooling. It will be noted that either a high carbon and low silicon or low carbon and high silicon content give grey iron; the fracture can, therefore, be misleading as to analysis, especially if the rate of cooling is not considered. The amounts of silicon, giving the maximum values for various properties, are also shown in Fig. 3. The percentage of silicon is varied according to the thickness of the casting. Sulphur and manganese. Sulphur can exist in iron, as either iron sulphide, FeS, or manganese sulphide, MnS. Sulphur as FeS tends to promote cementite producing a harder iron. When manganese is added, MnS is formed which rapidly coalesces and rises to the top of the melt. The first effect of the manganese is, therefore, to cause the formation of graphite due to its effect on the sulphur. The direct effect of manganese is to harden the iron, and this it will do when it exists in amounts greater than that required to combine with the sulphur-1 part sulphur to 1,72 part manganese. Phosphorus has a little effect on the graphite-cementite ratio; but renders the metal very fluid indirectly through the production of a low-melting constituent, which is readily recognised in the micro-structure (Fig. 4). In the production of sound castings of heavy section, phosphorus should be reduced to about 0,3% in order to avoid shrinkage porosity. Trace elements not normally considered in routine analyses can exert a profound influence upon the characteristics of cast iron. Examples are 0,1% of aluminium graphitises, antimony embrittles, lead, tellurium promotes carbide but reduces strength of iron; 0,003% of hydrogen can greatly affect soundness of castings and tends to coarsen graphite. Nitrogen behaves as a carbide stabiliser; oxygen has no specific effect. Figure 3. Diagram indicating the structures of iron resulting from variation of silicon and carbon contents Figure 4. Common grey iron showing ferrite (F), pearlite (P) and phosphide eutectic (PH) (x250). Ferrite is associated with the graphite. Note banded structure in the phosphide eutectic The carbon equivalent value. From Fig. 5 it will be seen that the eutectic E is at 4,3% carbon and irons with a greater carbon content will (under suitable conditions) start freezing by throwing out kish graphite of large size. With carbon contents progressively less than 4,3% normal graphite is formed in diminishing quantities until a mottled or white iron range is reached. Naturally other elements, especially silicon and phosphorus, affect the composition of the eutectic point in a complex alloy and a carbon equivalent value is suggested as an index which converts the amount of these elements into carbon replacement values. Figure 5. Iron-cementite equilibrium diagram Carbon equivalent value (CE) = Total C% + 1/3 (Si% + P%) For a given cooling rate the carbon equivalent value, therefore, determines how close a given composition of iron is to the eutectic (CE 4,3) and therefore how much free graphite is likely to be present, and consequently the probable strength in a given section: the carbon equivalent value is also a useful guide to chilling tendency of a given section, although it must be borne in mind that pouring temperature, cooling rate and alloying elements have a marked influence.

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Many moving mechanical parts are surface hardened whilst their cores remain in the original structural condition. In order to evaluate the wear characteristics it is advantageous to use a nondestructive method for measuring the thickness of the hardened surface layer, that is hardness depth. Different solutions have therefore been published:

• using the magnetic and magnetic-electrical characteristics of this layer,
• using the sound velocity of ultrasonic waves, and
• using the backscatter of ultra-sonic waves.

Backscatter method was originally developed for determination of the hardness depth of large cast-steel rolls. However nowadays, due to the further development of instrument technology, it can be used on parts having small dimensions and, as shown here, can even be carried out with a portable ultrasonic flaw detector.

With hardening of steels, by chilling after previous heating, the structure is converted from austenite to martensite. The surface layer has a fine structure and therefore does not scatter the ultrasonic waves so much as the non-converted core.

If transverse waves are used having a high frequency with a low bandwidth then a suitable ratio of grain size/wave length can be found so that the stepwise change in structure is visible on the display of the ultrasonic instrument by a stepwise change of the backscatter amplitude. In this case narrow band pulses are used with a center frequency of 20 MHz.

The transverse waves are beamed at an angle in order to measure, free from any interference, the time of flight between beam entry into the test object and the beginning of increased backscatter. The ultrasonic backscatter method directly reacts to changes in structure caused by the hardening of the surface layer.

The time of flight is measured between the sound entry and the beginning of the increased backscatter. Together with the known sound velocity Vtrans and the known angle of incidence , the thickness t of the hardened layer (hardness depth) is calculated according as:

t = (τ/2) x Vtrans x cosβ

Hardness depth

German DIN standard 50190 refers to the measurement of a hardness curve measured with indenters on test objects which have been cut, i.e. destructive testing. The hardness depth is, according to this standard, a point in the vertical direction which corresponds to a predetermined limit value (boundary hardness).

Ultrasonic backscatter does react to changes in structure, however it can not be linked to a determined hardness value using the indentation method. If there is a sudden transition between the surface zone and the core then there is a strong in crease in backscatter. Due to the fact that there is a steep drop in the hardness curve at this boundary, this interface will approximately correspond to the position of the backscatter signal according to the hardness depth for such a case.

If there is a transitional structure, then the hardness curve and the backscatter curve will be flatter. The location of the boundary hardness and the location of the maximum backscatter do not coincide.

Measurement limitations using backscatter

The method cannot be used when no backscatter signals are received or if they cannot be separated from the interface echo; because the time measurement requires clear start and stop signals. Very thin layers below a thickness of 1.5 mm can therefore not be measured.

All hardness processes which cause rapid structure conversion (with sound velocity) mostly produce a good detectable backscattering layer.

In all hardness processes which cause slow structure conversion, e.g. diffusion processes either produce a layer which is too thin, as nitriding does, or produce a wide zone with transition structure, as case hardening does, a steep increase of backscatter cannot be detected. The hardness depth, measured on the ground section according to DIN 50 190 Part 1, is 1.5 mm. Such a hardness depth could still be measured with the backscatter due to the narrow interface echo (entry). However, the steep increase of backscatter is missing in the transition from the surface layer to the core zone.

When the conversion process during hardening is incomplete, coarse grains remain in the hardened surface layer, so that strong backscatter of ultrasonic waves already take place there. Determination of the hardness depth via backscatter is, in these cases, at least erroneous if not impossible.

Calibration of the ultrasonic instrument

As already mentioned, the backscatter method is based on a time of flight measurement. This can be very accurately carried out by digital ultra sonic instruments. Readouts from digital displays also produce a very high degree of accuracy.

A direct read off of the measured time of flight, even as a digital value, is possible when the display of the ultrasonic instrument is calibrated in time (in microseconds). The hardness depth t must be calculated with the displayed time of flight τ, the known sound velocity Vtrans and the known angle of incidence β according.

A second possibility offers the calibration of the display as half the sound path for transverse waves. The displayed half of the sound path s only needs to be multiplied by the factor cosβ.

With serial tests it is of advantage to let the instrument carry out this multiplication. This is achieved by using the calibration possibility for angle-beam probes.

Charpy impact test method for metallic materials is specified by European EN 10045 standard. This specification defines terms, dimension and tolerances of test pieces, type of the notch (U or V), test force, verification of impact testing machines etc.

For certain particular metallic materials and applications, Charpy impact test may be the subject of specific standards and particular requirements. The test consists of breaking by one blow from a swinging pendulum, under conditions defined by standard, a test piece notched in the middle and supported at each end. The energy absorbed is determined in joules. This absorbed energy is a measure of the impact strength of the material.

The designations applicable to this standard are as indicated in the Table 1 and on the Figure1.

Table 1. Characteristics of test piece and testing machine

Reference (Figure 1)	Designation	Unit
1	Length of test piece	mm
2	Height of test piece	mm
3	Width of test piece	mm
4	Height below notch	mm
5	Angle of notch	Degree
6	Radius of curvature of base of notch	mm
7	Distance between anvils	mm
8	Radius of anvils	mm
9	Angle of taper of each anvil	Degree
10	Angle of taper of striker	Degree
11	Radius of curvature of striker	mm
12	Width of striker	mm
-	Energy absorbed by breakage KU or KV	Joule

Figure 1. Charpy impact test

Test pieces

The standard test piece shall be 55 mm long and of square section with 10 mm sides. In the centre of the length, there shall be a notch. Two types of notch are specified:

1. V notch of 45°, 2 mm deep with a 0,25 mm radius of curve at the base of notch. If standard test piece cannot be obtained from the material, a reduced section with a width of 7,5 mm or 5 mm shall be used, the notch being cut in one of the narrow faces.
2. U notch or keyhole notch, 5 mm deep, with 1 mm radius of curve at the base of notch. The test pieces shall be machined all over, except in the case of precision cast foundry test pieces in which the two faces parallel to the plane of symmetry of the notch can be unmachined.

The plane of symmetry of the notch shall be perpendicular to the longitudinal axis of the test piece.

The tolerances of the specified dimensions of the test piece are given by standard as well. For the standard test piece, machining tolerance in length is 0.6 mm for both type of tests, and tolerances in height are 0.11 mm for U and 0.06 mm for V notch test piece. Tolerances for angle between plane of symmetry of the notch and longitudinal axis of test piece as well as for angle between adjacent longitudinal faces of test piece are ± 2° only.

Comparison of results is only of significance when made between test pieces of the same form and dimensions. Machining shall be carried out in such a way that any alternation of the test piece, for example due to cold working or heating, is minimized. The notch shall be carefully prepared so that no grooves, parallel to the base of the notch, are visible to the naked eye. The test piece may be marked on any face not in contact with the supports or anvils and at a point at least 5 mm from the notch to avoid the effects of cold working due to marking.

Testing machine

The testing machine shall be constructed and installed rigidly and shall be in accordance with European Standard 10 045 part 2.

Standard test condition shall correspond to nominal machine energy of 300±10J at the use of a test piece of standard dimensions. The reported absorbed energy under these conditions shall be designated by the following symbols:

• KU for a U notch test piece
• KV for a V notch test piece

Testing machines with different striking energies are permitted, in which case the symbol KU or KV shall be supplemented by an index denoting the energy of the testing machine.

For example KV 150 denotes available energy of 150 J, and KU 100 denotes available energy of 100 J. KU 100 = 65 J means that:

• nominal energy is100 J
• standard U notch test piece is used
• energy absorbed during fracture is 65 J.

For tests on a subsidiary V notch test piece, the KV symbol shall be supplemented by indices denoting first the available energy of the testing machine and second the width of the test piece, e.g.:

• KV 300 / 7,5: available energy 300 J, width of test piece 7.5 mm
• KV 150 / 5: available energy 150 J, width of test piece 5 mm
• KV 150 / 7,5 = 83 J denotes:
• nominal energy 150 J
• reduced section test piece of width 7,5 mm
• energy absorbed during fracture: 83 J.

The test piece shall lie against the anvils in such a way that the plane of symmetry of the notch shall be no more than 0.5 mm from the plane of symmetry of the anvils. If the test temperature is not specified in the product standard, it shall be about 23°C.