3/8" THK 4130 BM Help
3/8" THK 4130 BM Help
(OP)
Good morning! I have done several 4130 procedures in the past, however I am having trouble with the mechanicals and testing on a thinner specimen.
Codes:
API 6A
DNV OS E101
ASME IX
NACE MR0175
I have tried using SMAW/FCAW/GMAW-spray.
Preheat: I have tried 400 & 600
SMAW: 10018 D2 (1/8")
GTAW Root: ER100S-G
I've had welders try welding wall->wall->middle fill all the way out.
*EDIT* PWHT 1190F @ 8 Hours and 1175F at 4 hours.
The biggest problem I am having is with the NACE hardness requirement of 250 Vickers in the HAZ. I've used propane torches for preheat and resistance ceramic blankets both which were wrapped in insulating material during and after welding to control heat loss. As far as I know the cooling rate has a big effect on the HAZ hardness.
Both tests I have tried were using a roll out on a piece of pipe. I could use some advice so I don't just keep trying to make something happen that may or may not work. It could just be something that I am missing.
Codes:
API 6A
DNV OS E101
ASME IX
NACE MR0175
I have tried using SMAW/FCAW/GMAW-spray.
Preheat: I have tried 400 & 600
SMAW: 10018 D2 (1/8")
GTAW Root: ER100S-G
I've had welders try welding wall->wall->middle fill all the way out.
*EDIT* PWHT 1190F @ 8 Hours and 1175F at 4 hours.
The biggest problem I am having is with the NACE hardness requirement of 250 Vickers in the HAZ. I've used propane torches for preheat and resistance ceramic blankets both which were wrapped in insulating material during and after welding to control heat loss. As far as I know the cooling rate has a big effect on the HAZ hardness.
Both tests I have tried were using a roll out on a piece of pipe. I could use some advice so I don't just keep trying to make something happen that may or may not work. It could just be something that I am missing.





RE: 3/8" THK 4130 BM Help
RE: 3/8" THK 4130 BM Help
RE: 3/8" THK 4130 BM Help
What hardness values are you getting with the PWHTs you have tried?
How about tensile values at those PWHTs?
What is the welding heat input? On thinner/smaller diameter pipes, welders tend to want to go faster and turn down the amperage, which would directly affect your hardness in the HAZ.
What are your cooling rates after welding?
RE: 3/8" THK 4130 BM Help
I have come across customers who will allow us to do a Rockwell survey if the Vickers does not meet the 250 mark. However NACE MR0175-2 states "The HRC method may be used for welding procedure qualification if the design stress does not exceed two thirds
of SMYS and the welding procedure specification includes post-weld heat treatment. The use of the
HRC method for welding procedure qualification in all other cases shall require the agreement of the
equipment user." Is the two thirds SMYS a hard requirement? I have had other companies say it's fine.
RE: 3/8" THK 4130 BM Help
Everything looks pretty good to me other than the welding heat input, that does look a little low. I have run similar qualification tests and my KJ/in was in the range of 50-60, while stringently keeping the preheat at or above 400F. Do you have to perform impact testing also? The reason I ask is that you will begin to walk a fine line if you have to meet impact requirements and begin increasing your heat input.
The reason I asked about the tensile test is because the only other way to decrease your hardness will be to increase your PWHT temperature.
RE: 3/8" THK 4130 BM Help
RE: 3/8" THK 4130 BM Help
RE: 3/8" THK 4130 BM Help
RE: 3/8" THK 4130 BM Help
What impact values are you required to achieve at -50F?
You can also try a PWHT temperature increase to around 1250F and cut your time at least in half. If you have any left over coupons you should try that.
RE: 3/8" THK 4130 BM Help
RE: 3/8" THK 4130 BM Help
It appears (scaling) that the total wall thickness is <18 mm. true?The 3/8 thickness is wall thickness, right? Heat pads are the outside, and the center is insulated.
Are you actually annealing the part, not performing the PWHT only as you expect?
Which ASME Sect IX page are you working from?
RE: 3/8" THK 4130 BM Help
RE: 3/8" THK 4130 BM Help
Too hot for a short time, or "almost too hot" for too long a time, and you re-anneal the metal; or, worse, you completely screw up the crystal structure across the whole heated zone.
Typically, a hard finish is characterized by a quick cooling to "freeze" the carbon and other alloys in the crystal borders between each grain. (It's more complex than that, but I hope you get my point.) Go too long at a hot temperature, and the crystals grow and the inclusions disperse as the move through the grains.
Don't get hot enough, and the stresses induced by the welding remain. But 3/8 thick is very thin, and at that thickness, I've never needed more than an hour at temperature for the alloys my company welds.