Steel designations are the letters and numbers that are used when talking about grades of steel. The designations associated with steel grades changed with the introduction of EN10025 which replaced BS 4360. This changed how grades were referred to, some still use the old designations so for s275 J0 you would have 43C or for s355 j2 you would have 50D. In this post we are looking at the designations under the EN10025 standard.
The majority of steel grades we offer are structural steels, this is noted by the S in front of the grade, there are various steel groups including P for pressure vessel steels and L for line pipe steels, we do offer some E grades which stands for engineering steels but the majority is structural steel.
Next is a number this refers to the minimum yield strength which is part of the steels mechanical characteristics. Yield strength is effectively how strong the steel is and is critical for the design of some steel parts. The number refers to the point at which the steel becomes deformed when a force is applied to it so in the case of 275 we know that this means the particular grade deforms when 275 newton millimeters of force is applied. In our case the number can be grades like 275, 355, 690, or 460.
You may also then get a letter and number which also refers to mechanical characteristics. This could be JR, J0 or J2 for example. These refer to charpy impact tests. When you see the J before the number of letter this means the test was conducted with 27 joules of energy. The variance in the number refers to the temperature the test were conducted at. So JR is room temperature or plus 20 degrees. J0 is 0 degrees, J2 is -20 degrees.
You will also see K instead of J this shows the tests were conducted with 40 joules of energy with the numbers referring to temperature as with the Js. The temperature and joules value is important as it will impact on the performance of the steel which will have implications on what it could be used for.
Then we have any treatments the steel has undergone which could include M for thermo-mechanically rolled, N for normalised or AR for as rolled. Again the treatments the material has gone through will impact what it can or should be used for.
If we have a look at some examples we offer S 275 JR so this is a structural steel with a minimum yield of 275 newtons per square millimetre with the charpy test conducted at 27 joules at room temperature
Another example would be S 355 J2 plus N this is a structural steel with 355 yield strength tested to 27 joules and minus 20 degrees which has been normalised.
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