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Up Topic Welding Industry / Technical Discussions / welding AISI 4150
- - By Jarhead1 (**) Date 07-21-2016 16:34
Gentleman,

We had a screw up in are machining area on some 4150 part (not heat treated) and need to repair and need to fill a slot approx. 1/2" deep and 1" wide and re-machine. Parts are 4" thick. After repairs these part will be heat treated to 32-38 Rc.
Need some help on MIG wire(s) to use and preheat temps, slow cool.

Weld process.

Thanks in advance...
Parent - - By Trackergd (**) Date 07-21-2016 16:46
Is the 4150 you are using the "free machining" grade with the high sulphur content?
Parent - By Jarhead1 (**) Date 07-21-2016 17:51
AISI/SAE 4150 Alloy Steel Similar to 4140 with higher carbon content. Sulfur 0.04 max.

http://www.alro.com/divsteel/metals_gridpt.aspx?gp=0072&gpn=4150%20HR%20Annealed&Mat=ALLOY&Type=Bars

Thank You
Parent - - By Jarhead1 (**) Date 07-21-2016 19:33
I was thinking on using Cor-Met Cor Alloy 4140 FC. FCAW Wire...
Appears to meet the material specs. Also, good for repairs.
Thoughts?
Parent - - By Trackergd (**) Date 07-21-2016 19:51
I did some looking around and went through some notes.  I kept seeing ER80S-D2, but the pre, interpass and post heat were a real challenge as it has to cool slowly.   There was a bit of a metallurgy lesson mixed in.  Seems that a very concentrated HAZ develops directly next to the deposited weld that can pose cracking issues.

The high sulphur free machining version of 4140 is very prone to heat cracking when welded.

I'll let the more knowledgeable folks here chime in so we both can learn a thing or two.  :)
Parent - - By TimGary (****) Date 07-21-2016 20:13 Edited 07-21-2016 20:20
He's going to need to use a base metal strength matching filler.
ER 80S is good when attaching lesser strength due to greater ductility.

Is there a procedure qualified, or are you going to have to start from scratch?

FCAW and deep square grooves = slag entrapment, IMHO...
I would try Lincoln's Superarc LA-100.
High Restraint Cracking? Vibratory weld conditioning? just thinking out loud...

How many parts are we talking about?

Tim
Parent - By Trackergd (**) Date 07-21-2016 20:22
I saw a couple of comments about using the ER 80S and than cap passes with higher strength fill.

I agree on the slag entrapment, but WAG'd that aggressive cleaning after at each pass might help.

One of the processes was a darn near all day affair considering the pre, interpass and post heat and very, very slow cooling....and that was with 2" thickness.

Depending on what process is most likely to succeed (material, labor and time), sad to say the repair may be more expensive than scrapping the part(s) and starting over.  I have been there, more than once.
Parent - - By Jarhead1 (**) Date 07-21-2016 20:46
Qty (4) parts although pretty expensive. approximately 40 hrs of machining on each part already.

After doing some research ER90S-D2 wire would be another good choice?

I will check the SUPERARC LA-100.

Thanks
Parent - - By TimGary (****) Date 07-21-2016 21:04
LA-90 might work, but you'd have a better chance of meeting the min tensile with the 100.
We use a lot of the LA-100 on armor plate and find it pretty easy to work with.
Not using it in high restraint square grooves though, mainly fillets.
How long is the groove, and does it dead end in the part?

Tim
Parent - - By Jarhead1 (**) Date 07-22-2016 13:18
I need to repair/fill a 3/8" deep x 4" long milled keyway. Was supposed to be 1/4" deep. The weld will go from edge on one side of part to opposite edge.
These parts will be heat treated to 32-38Rc after weld repair and re-machining. I have seen repair welds peel off after heat treat in the past. Concern with this one.
I'm also tossing around GTAW or GMAW.

Thanks
Parent - By Trackergd (**) Date 07-22-2016 13:32
Trying to get this solved for you before they chain and padlock this place... :sad:
Parent - By Trackergd (**) Date 07-23-2016 00:40
Jarhead1,

Any chance you can leave as is and use deeper key stock?   Seems less risky than trying to weld and re-machine.

Unless someone else chimes in, everything I have looked up seemed to be a 50/50 shot with heat cracking.  I would worry what would happen down the road like delamination from repeated cyclic stress.

Just a thought...can you cut a short length of shaft, cut a 3/8 keyway, weld it up, section and etch it to see what happens?

:confused:
Parent - - By Trackergd (**) Date 07-22-2016 13:27
Tim,

I have some concern about welding in a restrained slot creating a HAZ that would be prone to heat cracking.

Everywhere I am searching there is all sorts of charts for pre, interpass and post heat and the care that needs to be exercised.

Check this out:

http://www.midalloy.com/html/pdf/low_alloy/TB%20ER4130%20Weld.pdf
Parent - - By TimGary (****) Date 07-22-2016 14:57
Agreed, pre and post heat are important. Perhaps stress relieving as well.
I think it's helpful that the keyway doesn't dead end in the part, but cracking is still a concern.

Looking into the future... if this repair weld fails under use and the key pops out, what will be the result? Lives at risk? High dollar equipment failure? If it's no big deal, that's one thing. If the loose key winds up stripping the teeth from a million dollar reduction gear, that's another thing all together.

A typical PQR of end choice filler / parameters would be good, but wouldn't necessarily replicate the experience this repair will undergo.
I wouldn't proceed without a PQR though. After that, it's a gut check call comparing the cost savings of repairing the material, vs the risk of what happens in the case of a failure.

Perhaps someone else will pop in that has been in this exact scenario before.
My personal experience with weld repairs on this material, which was cracked fillet welds only, is that it is a crap shoot.

Tim
Parent - By In Tension (**) Date 07-23-2016 05:31
I don't have much experience to draw on regarding WPS development for 4150 but have performed quite a bit of NDE on 4140 weldments.  I'm sure I'm not telling you anything you don't already know but cracking is a major concern for this material and I'd expect this to be the case even more so with 4150.  Cracking tends to be in the HAZ and/or associated with slag inclusion.  Depending on the service these machined items may anyways receive surface NDE but for a weld repair I'd strongly suggest volumetric examination after HT.  Regardless of whatever code criteria that may or may not apply I'd be wary of accepting any weld-induced indications.
Parent - By Jarhead1 (**) Date 07-29-2016 21:00
Hello everyone,

Just wanted to thank you to all the experts and non-experts in the field for the input and help regarding this issue and all issues posted in the past. That is why I continue to stay a member.

Anyway, i ended up repairing these parts with a 4130 TIG rod following the recommended preheats, interpass temps and slow cool.

The parts came out to perfect and to spec after weld repair, re-machining and heat treat

http://www.midalloy.com/html/pdf/low_alloy/TB%20ER4130%20Weld.pdf

Thanks Again.
Up Topic Welding Industry / Technical Discussions / welding AISI 4150

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