WPS for Welding Gouge in Shaft

Date 07-14-2016 14:24

Greetings All -

I'll try to make this short and sweet. Our company turns shafts from forgings in a large CNC lathe. We had a bit of a snafu on the last 7'' diameter forging that came in: the programmer made a mistake that caused the threading tool rapid into and gouge the finished main journal of the shaft (literally on the last turning operation).

We're going to weld the gouge, put the shaft in a manual machine, turn the bead back down and polish the shaft.

Our customer wants a weld procedure for this.

Process: FCAW
Material: ASTM A668, Class E
Wire: E81T1

First I'll say, I have no experience writing welding procedures that are NOT prequalified. However, I question whether or not a procedure is actually required. All we are doing is filling a gouge on a 7'' diameter solid shaft. As long as "sound engineering judgement" is used for wire and and pre/post heat process, and the welder knows how to run the wire (is given the recommended parameters), I don't see this falling into any category in Section 4 in D1.1

The first issue I ran into when trying to write the procedure was defining the joint. I suppose it's a PJP Groove, but we aren't joining two pieces. This is more of an overlay than anything. I don't know, I'm probably complicating things.

Any thoughts on the matter would be much appreciated.

Thank you,

Kyle

By pipewelder_1999 (****)

Date 07-14-2016 17:41

That is a normalized and tempered material and I would suggest qualification of a procedure that verifies the mechanical properties intended for end use are maintained.

A written procedure should be required but formost it should be one that maintains the desired properties of the base metal in a manner that is suitable for the application.

In my experience gouges at the journal were less critical than those in the body of the shaft however that was decided by the engineering department of the company.

The joint would be a Surfacing Weld. If this is a rotating element of equipment, D1.1 would not apply unless mentioned by the MFG. If the end product you are providing must meet the requirements of the A668 Gr E, then look in that specification for limitations on weld repairs.

This (IMO) would be an engineered repair and should be looked at closely.

Gerald

By GMI Kyle (*)

Date 07-14-2016 18:35

Thank you for the reply.

I agree that there needs to be a procedure, and I agree that it may not fall within the bounds of D1.1, as you mentioned.

Unfortunately, I don't have access to D14.6 Standards and Specifications of Rotating Elements of Equipment, nor do I have access to the ASTM A668 Standard Specification for Steel Forgings, Carbon and Alloy, for General Industrial Use.

However, we do know that 1040 steel is similar to A668, Class E. Based on the similarity in composition and carbon content, we determined preheat of 450F and post-heat of 1100F will be required.

Furthermore, using ESAB's handbook "Recommended Filler Metals for Welding the ASTM Steels" found here, we were able to match our material to some FCAW wires that might be suitable.

My welding supply company told me that ESAB's Dual Shield II 80-Ni1 would be equivalent to Lincoln's Ultracore 81Ni1A75H, which he had on the shelf.

I suppose my remaining questions have to deal with the joint designation or lack thereof. Are "surfacing welds" addressed in D1.1?

Thanks again,

Kyle

By pipewelder_1999 (****)

Date 07-14-2016 18:54

Surfacing or Buttering is only used in reference to correcting dimensions for fitup. If you are using A668 and concerned about D1.1 compliance unnderstand that there is more to it than the joint design as the material is not listed.

Filler Metal Match is a small part of the whole process.

SIMILAR TO is a statement that should be used with caution. I don't have enough experience with that specific material but if you were making me a new product, an I specified that product be made from A668, I would expect you to assure that any processing that could change the properties would be performed in accordance with the requirments of the material specification.

I suggest not worrying about what D1.1 says and testing to assure that the properties required are maintained. Sometimes there is more to the QC than having a document that references a code. Weld a sample, do some testing on the BM and HAZ to verify properties fall within range of the original material.

It is possible that I am overthinking the whole scenario and those with more experience with the materials and applications are bettter suited to tell you what you need. Have patience with my ramblings. :)

Gerald

By 803056

Date 07-14-2016 20:22 Edited 07-14-2016 20:28

The customer should review the situation and provide authorization to attempt a welded repair.

The specifications you don't have access to are available, but they must be purchased. They are not free.

The base metal specification may include provisions for a welded repair or may include a prohibition for welded repairs.

You didn’t provide much detail for the proposed repair, i.e., the depth of the gouge, whether a localize repair involving filling the gouge is planned or if the entire circumference of the shaft will be welded.

ASTM A668 is a specification for forged shafts. Grade E is tempered to control hardness. Notch toughness is often a requirement for shafts used for large motor, pumps, and turbines. Since this is a 7 inch diameter shaft, notch toughness for the base metal is highly likely.

Shafts are often subject to fatigue. Any change in microstructure, i.e., the HAZ, can result in a metallurgical notch, a stress riser that acts to increase the stress intensification factor. Careful consideration must be given when selecting a filler metal to ensure a chemical match and matching properties after PWHT.

A welded repair would need to be qualified to demonstrate the weld, HAZ, and adjacent base metal can still meet the required properties of the original forging. If a welded repair is permitted by the base metal specification, the conditions under which the repair is permitted will be specified. The project specification/purchase order, etc. should be reviewed to determine if there are restrictions imposed by the customer.

This repair should be engineers by someone that knows metallurgy and welding. The customer should be informed and involved with the repair. The customer should agree to the repair before it is attempted.

Good luck - Al