Bureau of Indian Standard shortly BIS uses the following designation. Symbolic Letters and Numbers to designate the steel grade (e.g. Mechanical, Physical, and Chemical). The standard IS No. is 7598:1990.
Classification of Steel names
For the purpose of designation, steels are classified into two types. They are:
- Group 1
- Group 2
Group 1 – According to their application and Mechanical or Physical properties
Group 2 – According to their Chemical composition
Principal symbols:
G – Steel casting
P – Steel for pressure purposes
D – Flat products for cold forming
R – Rails
nnn – specified minimum yield strength for the smallest thickness range
Cnn – Cold rolled
Dnn – Hot rolled for direct cold forming
Xnn – Product where rolled conditions are not specified
Additional Symbols:
B – Gas bottles
M – Thermo-mechanically rolled
N – Normalized rolled
Q – Quenched / Tempered
S – Simple pressure vessels
T – Tubes
G – Other
H – High Temperature
L – Low Temperature
R – Room Temperature
X – High and Low temperature
Designation of Plain carbon steels
These are denoted like x, C, y
Where,
x – Number 100 times the average percent of carbon
y – Number 100 times the average percent of Manganese
Example:
30C8
Where,
30 = 100 times average % of Manganese
8 = 100 times average % of Carbon
Average % of Carbon = 30/100 = 0.3%
Average % of Manganese = 8/100 = 0.08%
Actual means, the actual carbon % is not 0.3, but varies between 0.2 – 0.4%, so that the average becomes (0.2 + 0.4)/2 = 0.3%, and
Manganese from say 0.07 – 0.09%, so that the average (0.07+0.09)/2 = 0.08%
Designation of Alloy Steels
Alloy steels are denoted by arranging the alloying elements in the descending order of their proportion, and the average % of each element is shown with its chemical symbol before that number. The letter C is omitted here, and just the number is written to denote carbon percentage. When an alloying element is less than 1% that element is denoted by an underline, after written up to two decimal places.
Example:
An alloy steel of the following composition is to be designated
Carbon = 0.13 to 0.17%; Silicon = 0.1 to 0.4%; Chromium = 0.5 – 0.8%; Manganese = 0.4 – 0.5%
Here,
Carbon varies from 0.13 to 0.17
Therefore average % of C = (0.13 + 0.17)/ 2 = 0.15
Among the other alloying elements, Chromium is largest in composition with average % being 0.5 to 0.8%
Therefore average % of Cr = (0.5 + 0.8) / 2 = 0.65
Therefore the above example’s designation will be 15 Cr 65
Note: since it is less than 1% it is shown by an underline
Tags: BIS designation of steel, BIS designation of materials, Bureau of Indian Standards for steel, Designation system of steel, Designation of steel as per BIS, Designation of steel alloys
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What is the value for X15Cr16Ni2