As per the categorization of steel, they are divided into 4 different basic groups that is based on their chemical composition –
- Alloy steel
In the alloy steel, there can be silicon, manganese, nickel, copper, titanium, chromium and also aluminum in varying proportion.
- Carbon steel
90 percent of the steel production is carbon steel and carbon steel are further categorized as follows:
- Low carbon steel having maximum 0.3% carbon content.
- Medium carbon steel containing 0.3 to 0.6% carbon content.
- High carbon steel containing more than 0.6% of carbon
- Tool steel
Tool steel will contain cobalt, molybdenum, tungsten and vanadium in variable proportion for increasing its durability and heat resistance.
- Stainless steel
The stainless steel usually contains 10 to 20 % chromium and they are grouped into 3 groups based on crystalline structure –
Usually, all steel contains iron and certain amount of carbon. The proportion of carbon and few other alloys decide the property of each type of iron.
Houston is well known for supplying steel to everywhere and Houston steel is considered as one of the best steels in the world.
Steel numbering systems
Steel industries of the world uses two major numbering systems, which was first developed by American Iron & Steel Institute, and the Society of Automotive Engineers.
These systems have been based on 4-digit code numbers to identify the base carbon along with alloy steels. Few selections of alloys which have 5-digit codes instead.
If the first digit indicates 1 then it is carbon steel. Therefore, all carbon steels will be indicated as 1xxx in both SAE and AISI system. Further they are subdivided into 4 categories because of particular underlying properties.
Plain Carbon Steel within the series of 10xx will be containing 1.00%.
Re-Sulfurized Carbon steel will be encompassed within 11xx series steel
Re-Sulfurized and also Re-Phosphorized Carbon Steel will be encompassed within 12xx series steel
Non-Re-Sulfurized High-Manganese carbon steel will be encompassed within 15xx series steel.
The first digit for all other type of alloy steels will then be classified as following:
- 2 as Nickel steel.
- 3 as Nickel-chromium steel.
- 4 as Molybdenum steel.
- 5 as Chromium steel.
- 6 as Chromium-vanadium steel.
- 7 as Tungsten-chromium steel.
- 8 as Nickel-chromium-molybdenum steel
- 9 as Silicon-manganese steel and also various other steel of SAE grade.
Second digit of this series will indicate the concentration of major element as percentage.
The last 2-digits of this series will indicate carbon concentration up to 0.01%.
As an example: SAE 5130 will be chromium alloy steel that containing about 1% chromium and approx. 0.30% of carbon.