Non-oriented silicon steels do not use a secondary recrystallization process to develop their properties, and high temperature annealing is not essential. Therefore, a lower limit on silicon, such as is required for the oriented grades, is not essential.

Non-oriented grades contain between 0.5 and 3.25% Si plus up to 0.5% Al, added to increase resistivity and lower the temperature of primary recrystallization. Grain growth is very desirable in the nonoriented grades, but is generally much smaller than for the oriented grades.

Processing to hot rolled band is similar to that described for the oriented grade. After surface conditioning, the bands are usually cold rolled directly to final gage, and sold to the transformer manufacturer in one of two conditions - fully-processed, or semi processed. After final cold rolling, the strip is annealed, decarburizing it to 0.005% C or lower and developing the grain structure needed for the magnetic properties. Samples are then taken from each coil end, and tested.

Fully processed nonoriented silicon steels are generally used in applications in which:

* Quantities are too small to warrant stress relieving by the consumer, or
* Laminations are so large that good physical shape would be difficult to maintain after an 843°C stress relief anneal.

Non-oriented steels are not as sensitive to strain as the oriented product. Consequently, shearing strains constitute the only strain effects, which should degrade the magnetic quality. Because laminations are generally large, these shearing strains can be tolerated. Most of the fully processed grades are used as stamped laminations in such applications as rotors and stators.

The non-oriented steels have a random orientation. They are commonly used in large rotating equipment, including motors, power generators, and AC alternators. Fully processed steels are given a "full" strand anneal (to develop the optimum magnetic quality), making them softer and more difficult to punch than semi-processed products. Grades with higher alloy content are harder and thus easier to punch.

Improved punchability can be provided in fully processed steels by adding an organic coating, which acts as a lubricant during stamping and gives some additional insulation to the base scale. If good inter-lamination resistance is required, fully processed material can be purchased with core plate.

Semi processed products are generally given a lower-temperature decarburizing anneal after the final cold rolling. Carbon is not necessarily removed to the same low level as in fully processed material. The transformer manufacturer will subsequently stress relief anneal the material in a wet decarburizing atmosphere to obtain additional decarburization and develop the magnetic properties. Samples are taken after the mill decarburization anneal, cut into specimens, decarburized at 843°C for at least one hour and tested to grade the coil.

Semi processed nonoriented silicon steels are used for applications in which the customer does the stress relief anneal. In general, such products have good punching characteristics, and are used in a variety of applications including small rotors, stators, and small power transformers. Semi processed steels can be purchased with a tightly adherent scale, or with an insulating coating over the oxide. The organic coating acts as a lubricant during punching, but it does not withstand stress relief annealing temperatures; therefore, it is not applied to semi-processed material.
Table 1. The most important silicon steel designations specified by different standards

IEC 404-8-4 (1986)	EN 10106 (1995)	AISI	ASTM A677 (1989)	JIS 2552 (1986)	GOST 21427 0-75
-	M235-50A	-	-	-	-
250-35-A5	M250-35A	M 15	36F145	35A250	2413
270-35-A5	M270-35A	M 19	36F158	35A270	2412
300-35-A5	M300-35A	M 22	36F168	35A300	2411
330-35-A5	M330-35A	M 36	36F190	-	-
-	M250-50A	-	-	-	-
270-50-A5	M270-50A	-	-	50A270	-
290-50-A5	M290-50A	M 15	47F168	50A290	2413
310-50-A5	M310-50A	M 19	47F174	50A310	2412
330-50-A5	M330-50A	M 27	47F190	-	-
350-50-A5	M350-50A	M 36	47F205	50A350	2411
400-50-A5	M400-50A	M 43	47F230	50A400	2312
470-50-A5	M470-50A	-	47F280	50A470	2311
530-50-A5	M530-50A	M 45	47F305	-	2212
600-50-A5	M600-50A	-	-	50A600	2112
700-50-A5	M700-50A	M 47	47F400	50A700	-
800-50-A5	M800-50A	-	47F450	50A800	2111
-	M940-50A	-	-	-	-
-	M310-65A	-	-	-	-
-	M330-65A	-	-	-	-
350-65-A5	M350-65A	M 19	64F208	-	-
400-65-A5	M400-65A	M 27	64F225	-	-
470-65-A5	M470-65A	M 43	64F270	-	-
530-65-A5	M530-65A	-	-	-	2312
600-65-A5	M600-65A	M 45	64F360	-	2212
700-65-A5	M700-65A	-	64F400	-	2211
800-65-A5	M800-65A	-	-	65A800	2112
-	-	M 47	64F500	-	-
1000-65-A5	M1000-65A	-	64F550	65A1000	-