This "utility stainless steel" is a proprietary modification of Grade 409 chromium stainless steel. It has been developed as a readily fabricated, low cost grade, exhibiting good resistance to wet abrasion and mildly corrosive environments. National specifications cover this grade by designations 1.4003 and UNS S40977 / S41003. The designation "3CR12" is a registered trade mark of Columbus Stainless, the original developers of the grade, and who are still active in research into its production, fabrication and application. Proprietary 3CR12 conforms to EN 10088.2 grade 1.4003, ASTM A240/A240M grades UNS S40977 and S41003 and ASME SA240 grades UNS S40977 and S41003. 1.4003 is also included in EN 10028.7 covering stainless steels for pressure purposes.

Key Properties

These properties are specified for flat rolled product (plate, sheet and coil) in Euronorm EN 10088.2 1.4003 and ASTM A240/A240M S40977 and S41003. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications. Composition Typical compositional ranges for grade 3CR12 stainless steels are given in table 1. Table 1. Composition ranges for 3CR12 grade stainless steel Grade C Mn Si P S Cr Mo Ni N 1.4003 S40977 min. max. - 0.030 - 1.50 - 1.00 - 0.040 - 0.015 10.50 12.50 - 0.30 1.00 - 0.030 S41003 min. max. - 0.03 - 1.50 - 1.00 - 0.040 - 0.030 10.5 12.5 - - 1.50 - 0.030 Mechanical Properties Typical mechanical properties for grade 3CR12 stainless steels are given in table 2. Table 2. Mechanical properties of 3CR12 grade stainless steel Grade Tensile Strength (MPa) min Yield Strength 0.2% Proof Stress (MPa) min Elongation (% in 50mm) min Hardness Rockwell (HR) max Brinell (HB) max 1.4003 450 650 280 (long.) 320 (trans.) 20 - - S40977 450 280 18 HR B88 180 S41003 455 275 18 HR C20 223 Physical Properties Typical physical properties for annealed grade 3CR12 stainless steels are given in table 3. Table 3. Physical properties of 3CR12 grade stainless steel in the annealed condition Grade Density (kg/m3) Elastic Modulus (GPa) Mean Coefficient of Thermal Expansion (mm/m/°C) Thermal Conductivity (W/m.K) Specific Heat 0-100°C (J/kg.K) Electrical Resistivity (nW.m) 0-100°C 0-300°C) 0-700°C at 100°C at 500°C 3CR12 7740 200 10.8 11.3 12.5 30.5 40 480 570 Grade Specification Comparison Approximate grade comparisons for 3CR12 stainless steels are given in table 4. Table 4. Grade specifications for 3CR12 grade stainless steel Grade UNS No Old British Euronorm Swedish SS Japanese JIS BS En No Name 3CR12 S40977 - - 1.4003 X2CrNi12 - - These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted. Possible Alternative Grades Possible alternative grades to grade 3CR12 stainless steels are given in table 5. Table 5. Possible alternative grades to 3CR12 grade stainless steel Grade Why it might be chosen instead of 3CR12 304 Better corrosion resistance and fabrication properties are required. 430 Better corrosion resistance and appearance is required. Weldability not needed. Galvanised steel A lower cost is required, and the reduced corrosion resistance and fabrication characteristics of galvanised steel are acceptable. Weathering steel A lower cost is required, and the reduced corrosion resistance and fabrication characteristics of weathering steel are acceptable. Corrosion Resistance 3CR12 is effective in many applications where carbon steel, galvanised, aluminised or painted steel or aluminium give unsatisfactory life. It is not attacked by strong alkalies, and often gives adequate resistance in acidic conditions. 3CR12 strongly resists chloride stress corrosion cracking, but is less resistant than 304 to pitting and crevice corrosion in chloride environments. 3CR12 is likely to resist water with chloride contents of up to 150 to 200 mg/L at ambient temperatures. The presence of sulphate or nitrate ions will reduce the corrosivity of chlorides. Light surface rust can form in many atmospheres, making the material unsuitable for decorative applications. Heat Resistance In air 3CR12 offers scaling resistance to 600°C continuous or 750°C intermittent, but if under stress the temperature should be limited to 450°C continuous or 600°C intermittent. 3CR12 suffers negligible embrittlement after extended exposure at temperatures of 450-550°C; it can be used safely at these temperatures without loss of room temperature impact resistance. Heat Treatment Annealing - heat to 700-750°C, soak for 1½ hours per 25mm section. Air cool. The maximum temperature of 750°C should not be exceeded. Annealing should usually be followed by pickling and passivating. This grade should not be hardened by heat treatment; quenching treatments may reduce the corrosion resistance and mechanical properties. Welding 3CR12 can be readily welded using similar techniques to austenitic stainless steels. Low heat input processes are preferred - particularly GTAW (TIG) and GMAW (MIG). Filler wire pre-qualified by AS 1554.6 (3CR12 referred to as "4003") is grade 309, but 309L, 309Mo, 316L and 308L have been successfully used. Argon plus 1-2% oxygen shielding gases are recommended. Discolouration of the weld should be removed by pickling, except possibly in wear applications; effective purging and use of backing gases is often a better option. Machining 3CR12 has a machinability similar to that of grade 430, ie about 60% of that of mild steel. The work hardening rate is lower than that of austenitic stainless steels, so reducing the need for special machining techniques. Finishes 3CR12 is available in standard HRAP (Hot Rolled Annealed and Pickled) finish in plate, and 2B or 2D in coil. "Black" finish is also produced; this is hot rolled and with the high temperature scale left on the steel. The resulting dark oxidised surface has good low friction characteristics and a corrosion resistance that is useful for many wear applications, even although slightly less resistant than the "white" pickled finish.

Applications Typical applications include: · Mining and mineral processing and transport equipment · Rail wagons for coal and iron ore · Sugar processing equipment · Furnace and oven parts