HAZ Hardness Problems 316L Overlay 4130 1

[MrGezus]

I have done about 5 coupons/tests on this procedure and cannot seem to get the HAZ hardness better than 5-10 too hard in Vickers (255-260).

We are using pulsed TIG machines.
0.2/0.2 high/low
50% background current
~270 amps
0.9 inch Z step per revolution
400-500F preheat
7-10 IPM travel speed *table*
~80 IPM wire feed speed

After welded we wrap it up and cool down.

Does anyone have an idea of where to go from here? We are conforming to NACE/API/ASME.

 

[redpicker]

Are you sure you are getting a good preheat? Check part temperature 5 minutes after removal from the preheat heating source and if the temparature has dropped more than 30-50F then the preheat has not soaked.

Gas composition could be an issue, too, but I would check the preheat, first.

rp

 

[racookpe1978]

Can you do a post weld heating treatment?

 

[MrGezus]

We were using torches to preheat. Today we are going to redo it and preheat it in the oven to 500F for a few hours and start welding at 475F. Do you think that would help?

 

[redpicker]

What size are you trying to heat? "A few hours" sounds a bit excessive, but if your section is a few inches thick, perhaps not so much. But, yes, I would expect a well-soaked preheat to help, if the original problem was an inadequate preheat.

Are you sure you are dealing with straight 4130, or has it been modified with extra Mo, extra Cr, or perhaps some V? If it's been modified, you might have problems.

A postheat operation may sensitize the 316, so be careful.

rp

 

[MrGezus]

I say a few hours. Its a 12" OD tube coupon with 1" walls. I am thinking at least an hour and then I will check the material. It's straight 4130. The Vanadium is 0.027% which is a bit high but I wouldn't think that it would cause such a big issue.

Does anyone know if my settings are near correct?

 

[weldstan]

Recommend dumping the part into vermiculite immediately after weld overlay completion.

 

[MrGezus]

Where can I get vermiculite? This slows the cooling rate?

 

[metengr]

The preheat for a 12" OD x 1" wall pipe should be 450 deg F and held for 30 minutes at temperature before welding. If your preheat is adequate, I believe you may need to modify your bead placement sequence to achieve better bead overlap and in-situ tempering.

I have another option for your consideration - why don't you use a butter layer of 309 over the 4130, PWHT the 4130 to have the hardness where you need to be and complete the weld joint using 309 stainless to 316 to avoid sensitization?? Seems like a better way to go versus all of the above. In lieu of 309 you can use Inconel.

 

[weldstan]

Yes, it slows the cooling rate. Google it.

 

[arunmrao]

Where can I get vermiculite? This slows the cooling rate?

If you cannot get vermiculite, get a hot topping agent , commonly used in foundries.

 

[MrGezus]

I ended up finding some at Lowe's. The coupon is sitting in a metal can filled with the stuff. I will let you guys know how it turned out.

 

[mahadhatu]

The weldment is going to require PWHT to get the hardess lower. Slowing down the cooling rate after welding will only do so much which is what you found out from your 5 coupons. Refer to the tempering temperature for 4130 and temper the weldment at the minimum required temperature. The PWHT cycle will not affect the performance of your overlay.

Let us know what you ended up doing.

--------------------------------------
There is always some thing better out there...
Mahadhatu

 

[EdStainless]

If his PWHT temp is over 800F he will sensitize the stainless overlay and destroy its corrosion resistance.
Using a high Ni stainless butter layer, PWHT, and then overlay is the safe way to do this.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[tbuelna]

What condition was the thick walled 4130 substrate in prior to beginning the weld process? You mentioned the 4130 part was heated using gas torches during the initial process. I can imagine the outer surface of the 4130 part being heated and air-quenched to a high hardness from using gas torches to pre-heat it.

If a specific max hardness was required post-weld in the HAZ of this thick section 4130 part, wouldn't it have been a good idea to make sure the 4130 part was in the appropriate HT condition prior to welding?

 

[MrGezus]

The weldment is going to require PWHT to get the hardess lower. Slowing down the cooling rate after welding will only do so much which is what you found out from your 5 coupons. Refer to the tempering temperature for 4130 and temper the weldment at the minimum required temperature. The PWHT cycle will not affect the performance of your overlay.

Let us know what you ended up doing.

We were sort of following what the suggested/recommended PWHT ranges were in their specifications. I am new to this industry and welding in general. Will cooking it at this lower temperature help with the HAZ hardness?

The temper is at 1202ºF and we are cooking 1175-1190 per suggested spec.

I don't think for the application we are using that using a different wire to butter will be acceptable. If it comes to that I will check out that solution.