EB welding of 4145H to 4330V

[Kulungi]

I have a challenge to EB weld 4145H to 4130V. The final product must meet ASME 9. The EB weld is .688 deep and has a step joint configuration. I am trying to avoid hot tears after welding. What type of pre and post heating would be best to prevent hot tears if any? Any other ideas would be appreciated. Thanks

 

[metengr]

Kulungi;
For this type of joint design and weld thickness, you will need to preheat at 400 deg F minimum. For post weld heat treatment temperature, you need to determine what the original heat treatment is for the 4145 and 4130V steels. Review the original material mill test report to determine the tempering temperature and post weld heat treat 50 deg F below this temperature.

For production welds, after Section IX procedure qualification, I would recommend you specify nondestructive testing - surface and volumetric – if this is a critical load carrying weld.

 

[Kulungi]

They are critical load carrying welds. I was planning to try preheating using a defocused beam using thermal couples in various locations on the samples. If I try to heat them in an oven I will lose most of the heat getting into the chamber and pumping down. I plan to weld using a narrow beam is that better then a wide beam? I figure the less heat and melting of base material might help stop hot tears from forming. Is cooling the issue when the material cools fast the hot tears form or does this matter? Thanks for any information you can supply.

 

[metengr]

For your application, preheat is required to reduce the cooling rate and avoid harmful formation of martensite, which is a structure that forms upon rapid cooling of the heat affected zone of most low alloy steel base metals. Also, sufficient preheat will reduce thermal stresses, which can contribute to crack initiation and propagation during and after welding.

 

[CoryPad]

A narrow beam is not always best. If the joint is deep with respect to the beam/joint width, then the small volume of metal that is liquified and solidified will be stressed highly due to the high contraction caused be thermal conduction into the surrounding parts.