Welding surface hardened 1045 steel shaft to mild steel plate

[kjoiner]

Hello,

I have an application where I need to weld a hardened shaft to a mild steel plate (10 ga CRS). The plate will attach to an extruded tube. The shaft supports the plate and tube but the hardened surface is necessary for use with a drawn cup roller bearing (i.e. one way clutch bearing - needs RC 58). The shaft is nitride coated and I have checked to confirm that it is surface hardened (Rc 60) and not through hardened. My main concern is cracking after welding. Does anyone have concerns with TIG welding the shaft to the plate? Cost and time pressures are one reason I am looking at using pre-hardened shafting.
Also, are the preparation steps needed before welding such as removing the surface coating?

Thanks,

Kyle

 

[Tmoose]

How far away is the roller track from the welding?
What is the "hardened shaft" base material ?
Is the nitriding the reason the shaft is hard? Check with your bearing supplier. The effective depth of nitriding hardening can be quite limited ( a few .001 inches) , and the loading from hard working roller bearings or gear teeth can need hardness depths > .06"/1.5 mm.

3 down,

 

Only trouble lies this way.
Consider brazing.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[MintJulep]

Ironic metallurgist is correct, only failure follows welding precision hardened shaft.

Reevaluate your requirement.

It is unlikely that you NEED TO WELD. Rather what you need to do is attach.

Look though the catalogs or web pages of the many suppliers of liner motion systems. There are many proven methods to attach precision bearing shafts to other things. Pick the one that works best for your application.

 

[kjoiner]

Hello,

Thank you for the responses and confirming my concerns about welding. I sent follow up questions to the bearing manufacturer, Koyo, about the required depth of hardening. Their requirements for shaft hardening have to do with brinelling the shaft when the bearing is locked.

I've also been thinking of some other options for attaching the shaft to the plate. For my mockup, I 3D printed a hub and epoxied the shaft into its bore. I may need to consider machining an aluminum hub with sufficient bore length and bonding the shaft to the hub with some Loctite shaft retaining compound. The shaft needs to transmit around 200 oz-in of torque and the radial load is around 10lb so the loads are fairly light. Also, the duty cycle is low - around 3 seconds and will occur 50 times per day.

Kyle

 

[kjoiner]

Hello,

I've redesigned the mounting plate and made it into an aluminum plate with a hub, similar to a timing pulley, to provide more engagement between the shaft and bore. I ran torque calculations using information provided by Loctite to evaluate the use of shaft retaining compound ( I have Loctite 641 on hand). The calculations show a torque rating of 883 oz-in which should be sufficient (over 4:1 safety factor) for my application.

The bearing manufacturer recommends a minimum case depth of .015 when hardening so the nitrided shaft is not going to work. A case hardened steel or SSTL shaft will be required.

Another option I am exploring since I have to machine the plate/hub is to provide tapped holes for set screws. Doing this will require selective hardening of the shaft but I may go this direction. I might specify hardening of only the area where the bearing will ride.

Selective hardening may open up the possibility of welding the shaft again. The area requiring a hardened surface is about 2.25 inches away from the weld

One piece of information I did not add to my original post is that I need to slit the end of the shaft to mount the tang of a small power spring. The slit does not need to be precise. It is 2.38 inches away from where I would harden the shaft.

Here is a summary of what I'm considering:

1. Machine aluminum hub, bond hardened shaft to hub using shaft retaining compound. I've used it in R&D but not in a production environment
2. Machine aluminum hub, add set screws. Selectively harden shaft and attach to hub with set screws (and possibly retaining compound)
3. Selectively harden shaft, keep original thinner plate and TIG weld unhardened section of shaft to plate

What do you think?

I also plan to consult with our machine shop to get their feedback.

Thanks,

Kyle

 

[MintJulep]

See pages 202 - 203 for examples of end machining that would be available from most any supplier of linear bearing shafts.

https://www.thomsonlinear.com/downloads/bearings_guides/RoundRail_LinearGuides_Components_cten.pdf

Or

http://www.nookindustries.com/Product/ProductLine/End-Machining

 

[kjoiner]

Hello,

My apologies for not responding for a few days. I was having trouble accessing the eng-tips site. Our IT manager got it straightened out.

@MintJulep - thank you for sending the links for shaft modifications. I've looked at a few vendors for threaded shaft ends. Based on your recommendations that gives me another option - a threaded shaft into a threaded hub secured with Loctite. The torque provided by the timing pulley will screw the shaft tighter into the hub which is good.

I'm awaiting a response from our machine shop regarding the options I posted. In the meantime, I machined a hub in house and will experiment with shaft retaining compound. I might even machine another one with a 1/4-20 or 3/8-16 internal thread to experiment with threaded shafts.

I'll post an update as soon as I have some further information.

Thank you all again for your assistance.

Kyle