Steel that won't anneal

[outofthefire]

One of the cold saw blades shattered the other day, they do every now and again. I obviously grabbed the bits for knife making I've tried everything I know to soften the steel a bit, but can't get it below 75rc and drills won't touch it. Is this steel just silly hard and I'm not going to get it any softer or is there something else I can try. I've tried heats from blood red to sparking white each time burying it on hot sand to slow the cooling. The pics are a chunk of the blade and a leather cutter I ground out of smaller chunk @TechnicAl

 

[Maker]

It's HSS, it can't be annealed.

 

[outofthefire]

It's HSS, it can't be annealed.

heat kills hss drill bits

 

[mtt.tr]

as above hss can be glowing red, though the egde will roll when cooled its hard again

carbide will drill it

 

[TechnicAl]

There are loads of different tool steels and HSS is just one group.....The annealing temp can be as high as 1200 oC (possiblty higher) but the important part is to cool very very slowly (about 50oC an hour).....The 75Rc is because it form carbides and youre hitting one....normally martensitic steel, which is the hardest steel, wont get any more than 65Rc
The compositions vary quite a lot so really you need to know which one it is and thats not easy to find out.......so I would go for 1200 and very very slow cool

 

[Gareth J]

Hard to cool something so thin slowly without a temperature controlled furnace?

 

[Agroshield]

It's HSS, it can't be annealed.

HSS can be annealed. It is just that it is quite an involved process.

Why not ask the manufacturer of the blade what grade or type of HSS it is made from, or look on their website to see if it is stated? Then research information on annealing that grade.

As an example, M42 is a common type of HSS. Data on its heat treatment is easy to find:

M42 High Speed Steel

M42 high speed steel. High red-hardness from this high cobalt steel with excellent cutting performance. M42 steel supplied from stock local and nationwide delivery.

www.steelexpress.co.uk

This page suggests that the standard cold saw material is M2:

HSS Circular Saw Blades | KR Saws

We offer a comprehensive range of HSS circular saw blades, designed for cutting pipes, sections & solid ferrous materials.

www.krsaws.co.uk

and to anneal it, instructions are here:

M2 High Speed Steel - Steel Express

M2 high-speed steel supplied from stock. M2 is a tungsten-molybdenum high-speed steel, it combines excellent toughness with high wear resistance. M2 is commonly used in the manufacture of drill bits and taps.

www.steelexpress.co.uk

 

[outofthefire]

I think anealing is beyond the equipment I've got access to I can get it hot, but can't accuratley cool it down slowly over those sort of times if I ever get a glass kiln I might try again. I'll just stick to using it for small ground blades, it sharpens nicely, but it's going to be too hard for much else.

 

[hotponyshoes]

Hard to cool something so thin slowly without a temperature controlled furnace?

It's hard to do it with any consistency/accuracy yes.

You can improv, one way is to sandwich the thin bit inbetween 2 big thick lumps of steel, heat it all up and give it a good heat soak then leave it all in the forge to cool. Block the forge ports with some plugs of insulation.
I can get about 6hr cool down on mine doing it that way.

For 24hrs+ dig a hole in the ground, light up some charcoal in there, take half out when its burning well, drop the hot steel in, dump the charcoal back in top. Fill back up with dirt. Leave it for a couple of days and it will still be warm when you dig it up..

Buckets of sand etc also work but you really need to heat it up first and you need a lot of it.

 

[Maker]

I'll just stick to using it for small ground blades, it sharpens nicely, but it's going to be too hard for much else.

I've got a cracked cold saw blade I've been planning on cutting into parting tools for the lathe, had it about six years so it'll probably get done day now.

There are loads of different tool steels and HSS is just one group.....The annealing temp can be as high as 1200 oC (possiblty higher) but the important part is to cool very very slowly (about 50oC an hour).....The 75Rc is because it form carbides and youre hitting one....normally martensitic steel, which is the hardest steel, wont get any more than 65Rc
The compositions vary quite a lot so really you need to know which one it is and thats not easy to find out.......so I would go for 1200 and very very slow cool

I must admit I wasn't happy with the "Impossible" answer but I've never seen or heard otherwise. I've even tigged HSS to mild steel to make a quick dirty boring bar and not noticeably affected the hardness, it will have cooled down quickly though so that makes sense. Good to know it can be done.

 

[Agroshield]

You can improvise, one way is to sandwich the thin bit in between 2 big thick lumps of steel, heat it all up and give it a good heat soak then leave it all in the forge to cool. Block the forge ports with some plugs of insulation.

A test run with the two large bits of steel and something like this:

Thermocouple ThermaData Logger | High Temperature Data Loggers

Thermocouple ThermaData data loggers for high temperature applications. IP65 protected and compatible with either type K or type T thermocouple probes

thermometer.co.uk

in there would give you a temperature/time profile so you can see how close it is to the recommended way. The same type of thermocouple data logger is probably available at AliBang for a lot less.

 

[outofthefire]

I reckon it'll be easier for me just to make a carbide drill, we make them for stonemasons so i'll regrind one of them.

 

[brightspark]

hss is easy to drill using a sharp carbide drill .spot heat the hss with an oxyacetylene torch to bright red and drill it while hot . it will go through like butter. ive shortened a fair few mechanical hacksaw blades and redrilled doing it

 

[johnny7]

Could use a Dremel type tool with diamond coated bits to make the pin holes in the tang, I used one to remove a broken in tap from a Theoben fenman, I thought it was a broken in stockscrew so I tried drilling it, Not a chance!!, I removed as much as I could with the dremel then tapped it with a pin pinch to shatter it, Ran my own tap down then to make sure the threads were still ok


John