Forging 4130 Prolongation piece for test 1

[Giuseppe76]

Hello,

I would like to know if anyone has experiences in cutting a prolongation for 4130 forging before or after the final heat treatment.
Supplier proposes to me to cut before the final heat treatment the prolongation and put everything in the same batch for the heat treatment.
I have been told from supplier that, depends on thickness, cut after the final heat treatment can downgrade the material properties (which sound logical) and cut after final heat treatment will not permit to use the entire prolongation piece.
Do you have any experiences on that? if yes, which is the best solution for you?

Thanks
Rgds
Giuseppe

 

[redpicker]

Generally, the reason for using a prolongation instead of a separate test bar is to be sure the heat treatment of the test material matches, as close as possible, that of the material it qualifies. That is, you should remove the prolongation after final heat treatment. Yes, the mechanical properties of the test bar would likely be better by removal of the prolongation prior to heat treatment, but it is unlikely it would change the mechanical properties of the material it qualifies much. That is, if you remove the prolongation prior to heat treatment, you are likely to report mechanical properties that are not representative of the parts it qualifies.

What specification are you working to? That specification should be clear on the issue.

rp

 

[tbuelna]

Giuseppe76-

The only reason for using a prolong to perform destructive QA processes is to save the cost of using a complete forging. In some applications it is required to perform the metallurgical QA on a sample forging, while in other applications it is acceptable to use a prolong.

If the size, shape, and location of the prolong on the forging is such that it may have an effect on the heat treatment results then it would be prudent to remove it prior to heat treating, and process it as a separate piece with the batch/lot it came from. With a steel alloy like 4130, if you process the prolong separately you'll want to make sure the prolong sample has the proper size and shape to produce a heat treat result representative of the forging itself.

Hope that helps.
Terry

 

[Giuseppe76]

Thanks both for your answers.
I think that in same cases it can be accepted to cut before heat treatment, this is because of the shape and geometry. The specification is API 6A and it is not clear at all on this subject.

Rgds

 

[redpicker]

Thanks both for your answers.
I think that in same cases it can be accepted to cut before heat treatment, this is because of the shape and geometry. The specification is API 6A and it is not clear at all on this subject.

Rgds

I am sorry it has taken me a while to reply, but you are incorrect.

Section 5.7.1 of API 6A is pretty clear about this

When a prolongation is used, it shall remain integrally attached during all heat treatment operations, except postweld heat treatment, stress relief, and any re-tempering or re-aging that can be required. For tubular components, bar stock, mill shapes and other raw material with a uniform cross-section, the prolongation shall have the same cross-section as that of the raw material. For a production part with a complex shape or varying cross-section, it is not necessary that the prolongation be an extension of the largest cross-section of the part. However, the extension shall meet or exceed the minimum ER required for a separate QTC.

If you remove the prolongation prior to final heat treatment, you will not be meeting the requirements of the specification.

rp