Tool Steel O1 grade

[rosinante]

Hi All , I have a requirement to make some replacement blades for a shoulder plane,I have some small pieces of unhardened O1 guage plate but not long enuff for the complete blade,Q can I weld this to mild steel with 316 rods [I have some of these] and then harden /temper in the normal way,all help welcome,PS these are 3 mm thick.
The old blade C100yrs is made of 2 pieces,the cutting edge is very fine grained and pale in colour ,the rest is soft and can be filed,I had the hardness tested at work and it came out at 60.8 Rockwell C,this is what i would like to replicate,
cheers for reading
Chris

 

[pedrobedro]

The old blade may have been selectively hardened and tempered at the cutting edge. You can buy 01 cheap enough from Cromwell tools and other places in many different sizes and thicknesses.

 

[TechnicAl]

O1 is quite a complex steel. It can be heat treated to impart quite different properties.
When you say the blade is in 2 parts I assume to mean the cutting edge and the backing plate.
It will be a bit of an unknown if you weld with 316 as we wont really know what structure you will end up with

Easiest would be to get a complete blade

Its probably martempered which is a complex treatment

If you are determined to weld it I would soften the 01 at 780 oC cool in the oven to 650 oC and then its oK to cool in air. Preheat it to 250 oC and weld it using mild steel. Then heat to 850 for 30 mins followed by a quench into a bath at 225oC and soak for 10 mins and then cool in air. This will give you 60/62 HRc

Hardening will end up at about 65 HRC but tempering will drop it to 40 odd

 

[Drains]

Al, when you say quench at 225oC, then soak, do you mean a heated oil bath, and soak in it?

Edit- I've looked up martempering, and the answer to my question is probably yes.

How do they find these things out? And would the original blade for the plane have been treated like that, 100 years ago?

I'm well aware that selective hardening has been around for hundreds of years and that old plane blades are far superior to the average modern ones.
When I were a woodworker, curiously, my best chisels were a pair of cheap Chinese "Diamond Brand" ones. They took and held an edge better than any Marples or Stanley stuff I had.

 

[pedrobedro]

When I do 01 I heat it to non magnetic with a propane burner then dunk it in oil to quench it, don't stir it round. Then put it in the oven at 250° C for an hour and let it cool naturally in there after. It works for knife blades.

 

[TechnicAl]

Al, when you say quench at 225oC, then soak, do you mean a heated oil bath, and soak in it?

Edit- I've looked up martempering, and the answer to my question is probably yes.

How do they find these things out? And would the original blade for the plane have been treated like that, 100 years ago?

I'm well aware that selective hardening has been around for hundreds of years and that old plane blades are far superior to the average modern ones.
When I were a woodworker, curiously, my best chisels were a pair of cheap Chinese "Diamond Brand" ones. They took and held an edge better than any Marples or Stanley stuff I had.

They do dilatometry......google it....I havent so Id be interested what it says

Basically you measure a piece of the steel as you heat it. Changes in structure are usually associated with a slight volume change so you can measure these points.

Martensite structure has a Start temp (Mf) and a finish temp (Ms) martempering means you quech it to somewhere between these temps.

There are also Jominy tests.......pieces of steel heated and then quenched from one end......thus providing a gradient

Otherwise they do trials

 

[TechnicAl]

When I do 01 I heat it to non magnetic with a propane burner then dunk it in oil to quench it, don't stir it round. Then put it in the oven at 250° C for an hour and let it cool naturally in there after. It works for knife blades.

In other words you austenitise it (non magnetic) which is about 800 -850 oC same as Im saying.
That will (and obviously does) work but it will not be as ductile as if it was martempered. To be honest I dont have any numbers for the difference.........to use a technical term it may be ****** all.

Now you know why the old craftsmen can do it by eye (red hot etc etc)

Metallurgists just put numbers on what craftsmen do by skill

I love it