With superior strength and good workability, this Chromium Molybdenum based alloy has a rich history in usage across Aerospace and Motorsport industries. This High Strength Steel (HSS) has many acronyms, but is more commonly referred to 4130, its Society of Automotive Engineers (SAE) designation or Chromoly, which is a more palatable version of Chromium Molybdenum.
The 4130 standard falls under the SAE (Society of Automotive Engineering) and AISI (American Iron & Steel Institute) four digit numbering system where;
4
4
Designates the material type as a Molybdenum steel
1
1
Designates the material further as a Chromium-Molybdenum steel
30
30
Designates the material as Chromium-Molybdenum steel with an average Carbon content 0.30%, hence the final designation as 30.
4
Designates the material type as a Molybdenum steel
1
Designates the material further as a Chromium-Molybdenum steel
30
Designates the material as Chromium-Molybdenum steel with an average Carbon content 0.30%, hence the final designation as 30.
The 4130 designation gives guidance to the base grade, but in conjunction with further specifications, we have a product with chemical and mechanical limits, along with manufacturing guidelines and thermal treatments. 4130 manufactured in conjunction with these further specifications, builds a product which should be consistent in mechanical properties.
Due to the strength to weight ratio of this steel, it was widely used in the aerospace industry, and was adopted under the SAE’s Aerospace Material Specification committee. Subsequently, an AMS standard was published to give guidance on manufacturing processes, thermal treatments, chemistry, and mechanical requirements.
Technical Specification
Specification
Material
Publication Date
AMS6360
Steel Tubing, Seamless
01/12/1939
AMS6361
Steel Tubing, Seamless
01/06/1942
AMS6362
Steel Tubing, Seamless
01/06/1942
AMS6371
Steel Mechanical Tubing
01/12/1942
MIL-T-6736
Tubing, Chrome-Molybdenum
01/06/1950
AMS-T-6736
Tubing, Chrome-Molybdenum
01/12/1990
AMS6348
Steel, Bars
01/10/1979
AMS-S-6758
Steel, Chrome-Molybdenum Bars and Reforging Stock
01/07/1998
AMS6370
Steel, Bars, Forgings and Rings
01/12/1939
AMS6350
Steel, Sheet, Strip and Plate
01/12/1942
AMS6345
Steel, Sheet, Strip and Plate
01/11/1996
In an attempt to try and unify the designations used, a system called the Unified Numbering System was developed by the American Society for Testing and Materials (ASTM) and Society of Automotive Engineers (SAE) in 1972.
Technical Data
How strong is it?What's it made of?
Specification
Tensile Strength
Yield Strength
Elongation
AMS6360
95 ksi min
75 ksi min
12% min
AMS6361
125 ksi min
100 ksi min
12% min
AMS6362
150 ksi min
135 ksi min
10% min
AMS6345
95 ksi min
75 ksi min
10% min
4130 Chromoly per AMS6360
Element
Lower %
Upper %
Carbon
0.280%
0.330%
Manganese
0.400%
0.600%
Silicon
0.150%
0.350%
Phosphorus
-
0.025%
Sulfur
-
0.025%
Chromium
0.800%
1.100%
Molybdenum
0.150%
0.250%
Nickel
-
0.250%
Copper
-
0.350%
Iron
Balance
Balance
So what’s the deal with the weight of 4130 vs. standard steels? Truth is, nothing at a non-micro scale. Refer to our description section for the origins of the chromoly and 4130 name, but essentially it’s an alloy steel categorized in the Molybdenum Chromium family. What’s this got to do with weight? Well ultimately, the family this steel lives in sounds fun, but it's still 96.7% minimum iron, and therefore, iron has the greatest impact when looking at the weight. The table below shows the chemical differences between 4130 and a ERW (Electric Resistance Welded) tube.
Typical ERW per E220
Element
Average %
Carbon
0.140%
Manganese
0.700%
Silicon
0.350%
Phosphorus
0.025%
Sulfur
0.025%
Iron
Balance
Based on the above examples, we see 4130 with a minimum iron percentage of 96.7%, and ERW with an average iron percentage of 98.7%. It would be fair to say that iron is the common denominator, and the balance elements are in real terms, a very small percentage, so the overall density of the material in hand would be very similar. So unless you have some super tolerance scales, you will not see the difference in like for like material sizes. Strength, consistency of product, and manufacturing processes however are a different thing all together.
