Gauge plate to Silver steel problem

[Gavin Melville]

I needed to tig a tube of silver steel to the same thickness (5mm) of gauge plate. Everything, and there wasn't much, said to use 312 filler rod, and keep the heat down. Did that and after two weeks of fairly hard use the gauge plate cracked 0.5mm from the weld. I'm guessing this happened at the edge of the heat affected zone. I didn't need any further heat treatment, the steel was hard enough as it was.

I don't have a photo, I've had to re-weld and put back in service. Think a cotton reel with a big centre hole sitting on top of two matchboxes.

I've found out that what I buy as silver steel (no silver haha) is also called O1 oil hardening tool steel.

Does anyone have experience welding tool steels?

 

[Kent]

Not on the thin stuff. Generally pre-heat and low hydrogen on thicker stuff. Sounds very much like a bodge job on a bucket rubbing strip that without pre-heat and std consumables. The break follows the outside of the weld.
I am assuming the weld wasn't undercut and put under a lot of strain here?
Is there a better way to set out the join for purpose? Thinking backing strap or double lap etc? Often this is way quicker and more reliable than "doing things technically better" on what is not an ideal anyhow

 

[Wendelspanswick]

I needed to tig a tube of silver steel to the same thickness (5mm) of gauge plate. Everything, and there wasn't much, said to use 312 filler rod, and keep the heat down. Did that and after two weeks of fairly hard use the gauge plate cracked 0.5mm from the weld. I'm guessing this happened at the edge of the heat affected zone. I didn't need any further heat treatment, the steel was hard enough as it was.

I don't have a photo, I've had to re-weld and put back in service. Think a cotton reel with a big centre hole sitting on top of two matchboxes.

I've found out that what I buy as silver steel (no silver haha) is also called O1 oil hardening tool steel.

Does anyone have experience welding tool steels?

Did you allow it to cool normally or did you quench it with water, if the latter you would have hardened it and it would have then needed tempering.

 

[Gavin Melville]

Allowed to cool at room temperature. I did try a test weld first with two pieces of gauge plate. I had to beat the daylight savings out of it, and eventually it broke the steel itself, but 5-6mm from the weld.

Of course this is New Zealand, so right now we put things in a fridge to keep them warm.

 

[Wendelspanswick]

My daughter has just gone out to NZ for 3 years to do her PhD so she is looking forward to having a summer birthday for the first time as its in February. She is on the North Island though so I imagine a bit warmer than Christchurch.

Back to your problem I think I would have gone for normal A15 filler rather than Stainless filler as your base metal is tool steel.

 

[bill_gj]

As both 'silver steel' and 'gauge plate' are effectively the same material and are both hardenable, the HAZ will be more critical than in low-carbon steels and so a post-weld heat treatment to re-structure the grain in and around the weld would have helped stop, or at least limit the cracking.

 

[Bladevane]

Post weld heat treatment is going to be the answer. After welding heat it to 770 -800C (bright red) and quench in water. Then heat to no higher than blue colour (300C) and slow cool.

 

[Sidewinder]

I wouldn't harden and temper, unless you need the toughness, I would normalise, heat the whole item to normalising temperature for the material then allow to cool to room temperature, out of the influence of air currents, ideally within a baffle to retain the heat.

The reason, if you don't need the hardening and tempering, then as the materials are of differing sections they will have differing cooling rates.
Thus the hardness and temper will still vary through the components.

If they were for example heated to normalising temperature within a furnace then left in the closed furnace to cool, grain growth would be minimised because the temperature for this would not be reached, and the whole item would cool at a uniform rate determined by the surroundings rather than the component, thus you would have uniform properties across the physical structure.

Also, Silver steel & Gauge plate are BO1/B01 which is an oil hardening material, water quench, especially for small section parts could well be too excessive and result in micro, or full scale cracking or crack nucleation in the structure, which would compromise the strength, and reduce the fatigue resistance regardless of the subsequent heat treatment.

 

[Kent]

Never quench! Pre and post heat ok but don't go quenching a weld