Bending and weldability of differing alloys on same part 1

[engamopar]

Currently making a product of 4130. Is a .312" dia. shaft and H'treated to Rc32-37. Useable length is ~9.25". An additional .81" extends into and gets button welded in a HANDLE. HANDLE starts out as a straight piece at .56" dia. X 1.25"lg, reducing to .375" dia. for approx 3.75". It is also made from 4130, NOT H'Treated - but is Stress relieved at 1-1.25"hrs at 1200dF in atmosphere. After stress relief is bent in the 3/8" dia to form a HANDLE bent at 80degrees. HANDLE is bent 2.25" from the end of the 3/8" diameter the bend radius being .25" (to the inside).
Problem: Excessive rate of cracking from the bending - ~8%fallout. We would like to go to a different handle mat'l that will: 1-be compatible to weld with 4130; 2- be more malleable; 3- be easier to get than 4130; & 4- be less expensive. We're thinking 1010-1050 steel, or perhaps 1100 series. Given the 4 points we need to accomplish, any suggestions - or other alternates?

 

[metengr]

It is also made from 4130, NOT H'Treated - but is Stress relieved at 1-1.25"hrs at 1200dF in atmosphere

What is the original heat treatment or condition (hardness) of the 4130 material used for the handle? It may well be that the bend radius is to tight for this material condition.

 

[engamopar]

Lot#s indicate that both 4130 AND 4140 have been used for the HANDLE - 4140 being the majority. HARDNESS typically is HRc 20. The 4140 is received as "CF ANN" IAW ASTM A331. THe 4130 is NORMALIZED Aircraft Quality bar. The only reason we use these materials now is that customer's drawing is based on 1-piece construction, offering no alternate material for the HANDLE only in the [allowed] 2pc construction option.
We wish to go to a less expensive material for the HANDLE and then petition the customer for the change to whatever that material might be.

 

[metengr]

engamopar;
You better do your homework (design review regarding service stresses and other influences) if you intend to modify the material from that specified by the customer. Also, for this bend radius and bar diameter, you can attempt to use localized but controlled heating (remain below 1250 deg F)in the bend region to facilitate forming.