welding 9317 and 8620

[rmetzger]

does anyone know of a good reference to determine a weld material (TIG) to join these two metals. The 8620 will need to be carburized either before or after the welding (masking of weld area is possible). This is a hollow shaft assembly that will be carrying torque and compressive load at the welded joint

 

[metengr]

Could you please elaborate on your joint design and application of these materials? What needs to be carburized relative to the two alloy steels and proximity of the weld, etc. Prior to any welding, in addition to chemical composition, the specified heat treatment condition for the 8620 and 9317 alloy steels need to be known.

 

[Carburize]

Two problems that you have to overcome.
1) if you weld the parts together before carburizing how does the weld metal respond to the carburizing cycle? Typically the weld metal will be extremely soft after the carburize heat treatment cycle because welds get their strength from a completely different mechananism that heat treated alloy steels.
2)if you weld after carburize how do you deal with the post weld heat treatment of the weld heat affected zone without seriously degrading the hardness of the carburized surfaces.If the carburized area gets above 350 or 400F it will soften but you need temperatures well above this in the weld area to post weld heat treat.

If local PWHT is possible the carburize then weld route may be an option and there are a number of TIG wires available from ESAB and others which will give good properties

If you have to weld before carburize then the choice is more difficult and you will need a weld metal which deposits a chemistry similar to one of your base metals and the choice here is almost none existent unless you make some filler metal from your own base material.

 

[Goahead]

Could you consider friction welding instead of TIG? This would simplify both welding and carburizing.

http://www.welding-advisers.com/

 

[rmetzger]

It appears the the current part in question was welded. machined, then heat treated. The chemistry is still out on the weld material so I'm not sure how it was affected by the heat treatment.

The area of carburization is directly in touch with the weld affected area. An image of the part is below:

.

The helictical thread is carburized and the internal spline is as well - the blue area denotes the weld.

 

[Carburize]

What are the dimensions of the part?

 

[rmetzger]

The total shaft is slightly over 4.6" long, the smooth cylindrical portion is .93" OD with a .09" wall, the exterior of the helix is 1.3" and the spline ID is .75". The weld area fills a gap 1.15" OD, 1.05" ID and .08" deep roughly

 

[Carburize]

Why was it made in two parts?
Could it not be made as a one-piece construction and avoid the welding issue? If the weld is absolutely necessary could the two pieces be fitted together with no gap then seal welded with an autogenous run with no filler metal?

 

[BillPSU]

If your volumes are sufficient you may want to consider laser or EB weld.

 

[rmetzger]

This is a part from India we are purchasing - we're trying to resolve what they are doing and what is the best way for them to assemble the components they have on hand for our application. Hopefully we'll be changing designs (to one of ours that actually has documentation and design input from an engineer) but knowing the speed at which the system operates it'll be over a year before it happens. This is a make the best of a non-optimal situation solution. Unfortunately the manufacturer is slow and low on details and their capabilities (modern welding techniques and anything approaching new technology) is non-existant.

Gotta love overseas outsourcing huh?

 

[TVP]

As Carburize mentioned, this part could be forged/extruded as one piece, or even machined if the quantities are too low to justify forging tools. 8620 would be preferable to 9317 for a one piece forging.

 

[rmetzger]

It was a single piece construction (and probably will be again) but right now we have to deal with fixing the manufacturing oftwo piece that they are currently supplying.

 

[Carburize]

rmetzger - how did you get the image into your message?

 

[rmetzger]

I copied it to a source online (in this case my Boatertalk image gallery) the linked to it using what looks like pseodo HTML code "img

http://images.boatertalk.com/gallery/ronzo/COMPOSITE_SHAFT.jpg"

surrounded by [] brackets. Check in the "preview post" notes and you'll find the code there as well.

 

[CoryPad]

I agree with Goahead's message above - friction welding would be a very good solution for these parts.

Regards,

Cory

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