AISI 4130 vs AISI 8620

[gafoorkti]

We have received Choke Valve (API 6A, PSL-2, Material class EE) with body material grade AISI 8620 whereas our purchase order clearly calls for body material garde .

Can we accept AISI 8620 inplace of AISI 4130?
Manufacturer claims that both above grades are equivalent.

Any comments will be appreciated.

Thanks

 

[gafoorkti]

We have received Choke Valve (API 6A, PSL-2, Material class EE) with body material grade AISI 8620 whereas our purchase order clearly calls for body material garde AISI 4130.

Can we accept AISI 8620 inplace of AISI 4130?
Manufacturer claims that both above grades are equivalent.

Any comments will be appreciated.

Thanks

 

[arunmrao]

No ,please in my view.8620 is a case hardening steel,while4130 is not. I am not familiar with the codes,fyi.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[metengr]

Can we accept AISI 8620 inplace of AISI 4130?
Manufacturer claims that both above grades are equivalent.

The Grades are not equivalent, the 8620 contains lower carbon content and nickel for starters. Also, compare strength differences and compare weldability (carbon equivalent).

 

[salmon2]

We use API 6A as well and it does not specify any specific grade except some chemical limitations. As far as I know 8620 and 4130 are both acceptable chemically. So 4130 is something specified by you, not API 6A, which is why your valve manufacturer said they are equivalent. We use 8630 and 4130 interchangeabily for some parts as they both belong to low alloy carbon steel family and can be heat treated to the design strength level, if no welding involved. This is clearly a non-conformance from your PO or Spec, but it may be acceptable. You have to check your design requirement carefully to make sure.

 

[gafoorkti]

Yes, agree with Salmon2. API 6A doesn't address about specific material grade AISI 4130 or any.
But as per the review of as-built drawing it is noted that "Body-AISI 8620" welded to outlet component AISI 4130 - 4" class 1500 RTJ Flanges.

Any consequences if welding involved?

Looking for better discussion.


Thanks

 

[salmon2]

Weldability of 8620 may be slightly worse than 4130. Calculate their actual carbon equivalents and you will see. Both 4130 and 8620 won't be straightforward on welding as they may require pre-heat and post weldment heat treatment, depends on the parent material heat treatment and your joint design. But this substitution may be beneficial for you since now you are welding same material together and it is usually easier than joining dissimilar material.

 

[stanweld]

8620 and 4130 can be welded together with proper preheat and PWHT and appropriate welding filler metal to provide the required strength and ductility of the joint.

 

[bhollands]

What mechanical properties are required? 8620 will not harden as much as 4130. Depending on the impact requirements 8620 is only good to about 115ksi/95ksi (tensile/yield). 4130 can be made stronger.

4130 should have a carbon equivalent of about .70 where 8620 would be between .50 and .55.

Bob

 

[redpicker]

As has been mentioned above, the two materials are not equivalent and they are not interchangeable. Both can be used to produce valve bodies per API 6A, depending on PSL level and vlave size.

If your PO called for 4130 and they supplied 8620, you should run this material substitution thorugh your technical group, since changing grades may affect welding procedures, working temperatures, or other characteristics of the inetnded application.

rp

 

[gafoorkti]

We have received weldeability test results and forwarded to our welding speacialist. Finally approved!!!

Gents thanks for your valuable input.