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What is the difference between AISI 4130 and the Chinese 30crmo [Oman] 

May 6, 2007

I am about to build a vessel of AISI 4130 [link is to info about spec at TechStreet] but finding it very hard to find as i need it to stand 10,000 psi WP. I went to China in search of this and was told that the equivalent is 30CRMO. I contacted the ASME office in China and they said they can't say whether the two materials are equivalent,
Can someone please shed some light on these two materials and what are the differences if any.

Many thanks

Abdullah ismaily
Consumer - Muscat, Oman

AISI 4130 and 30CrMo are nearly equivalent in composition. From the Internet:

AISI 4130: C 0.28-0.33, Cr 0.8-1.1, Mn 0.4-0.6, Mo 0.15-0.25, P 0.035 max, S 0.04 max, Si 0.15-0.35.
30CrMo: C 0.26-0.34, Cr 0.8-1.0, Mn 0.4-0.7, Mo 0.30 max, P 0.035 max, S 0.035 max, Si 0.17-0.37, Cu 0.20 max [compositions in weight %].

For pressure vessels, the heat treatment and quality requirements must also be specified, as by giving an ASTM or ASME specification and grade. 4130 isn't usually used for pressure vessels (except for non-welded gas cylinders). E.g., the C content is too high and the Mo is too low to meet any of the grade requirements in ASTM A387, 'Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum.' For deep drawing quality alloy steel as for gas cylinders, one can specify 4130 per ASTM A 507, 'Standard Specification for Drawing Alloy Steel, Sheet and Strip, Hot-Rolled and Cold-Rolled.'

Ken Vlach - Goleta, California