dgadee
Well-Known Member
Stainless work hardens. Does it - if left for a time - lose that hardened property by itself? Or is it hardened for good?
Stainless de-work-hardening
- Thread starter dgadee
- Start date
Catalina36
N/A
Dunno, but Samurai swords wouldn't be up to much if they went soft in the cupboard.
How long have you got to wait on this job?
How long have you got to wait on this job?
Seastoke
Well-Known Member
I think neither.
dgadee
Well-Known Member
Swords are carbon steel.
HissyFit
Well-Known Member
Once work hardened you have to heat treat stainless steel to soften it. The process is called annealing. There are specific temperature ranges that need to be reached to get the right effect.
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HissyFit
Well-Known Member
Traditional samurai sword blades are forged out of a single die of tamagahane or jewel steel, produced from iron sand. It is folded many, many times, creating a damasc 'grain' , which gives the steel its strength whilst remaining flexible. The blade edge is protected from the heat of the process used to harden the main body of the blade by applying a clay slip. In quenching, the resulting difference in temperature across the blade gives the blade its distinctive curved shape. The edge is still relatively soft, and it is at this point that the sword is sent to the sharpener's. The sharpener used to specialise in only this aspect of sword manufacture. Once sharpened, the sword is returned to the swordsmith who heat treats the whole sword, thus hardening the blade edge. It is then polished, has the handle installed and the scabbard is matched to it. Swords made the traditional way cannot be re-sharpened, and are the only samurai sword allowed to be imported into the UK. To have a set would cost approx £2500, and its export would have to be specially certificated.
earlybird
Well-Known Member
Austenitic steels, the type we use for marine stuff, cannot be hardened by heat treatment. They harden when subjected to mechanical deformation, ie bending, drilling etc. Once hard it stays that way until annealed by heat treatment. This requires temperatures of around 900- 1000 deg. C. and controlled cooling. Not a domestic DIY task.
vyv_cox
Well-Known Member
Not quite correct. Austenite is stable to room temperature so no need for controlled cooling. Quenching would be ok but this might harden any retained ferrite so I would just allow it to cool. Theoretical annealing temperature is 730C but a bit more would be best. Dull red heat.
dgadee
Well-Known Member
I suppose my original question was because I was wondering that if metals hardened with age (does copper do this?) then there might be a reverse effect. Obviously not if annealing is necessary. But is there actually such a thing as age hardening?
rotrax
Well-Known Member
I needed to make a repair at a race track to enable me to be on the start line for the final. It was a seat support, made from S/S 25 X 3mm strip.
I had some of the strip, but unshaped and undrilled. A fellow competitor took it away to his nearby workshop where, to put it bluntly, he buggered it up.
He shaped it OK - a simple bending job -but work hardened the holes. He used a battery drill and blunt bits.
Fortunately my final was postponed untill the following morning directly after the practice for the European Longtrack boys. I scrounged a better workshop with proper kit and managed to fix it.
I heated the strip cherry red and quickly bored 2 X 6.5mm holes using a drill press, lube and heavy pressure. It was required to sharpen the bit between the boring procedure.
It can be done, but requires a slow speed, heavy pressure and good lube.
And bloody sharp bits!
I had some of the strip, but unshaped and undrilled. A fellow competitor took it away to his nearby workshop where, to put it bluntly, he buggered it up.
He shaped it OK - a simple bending job -but work hardened the holes. He used a battery drill and blunt bits.
Fortunately my final was postponed untill the following morning directly after the practice for the European Longtrack boys. I scrounged a better workshop with proper kit and managed to fix it.
I heated the strip cherry red and quickly bored 2 X 6.5mm holes using a drill press, lube and heavy pressure. It was required to sharpen the bit between the boring procedure.
It can be done, but requires a slow speed, heavy pressure and good lube.
And bloody sharp bits!
earlybird
Well-Known Member
Age-hardening is an industrial process. The word "age" really refers to lengthy periods of time, (hours), of appropriate alloys under controlled heat conditions. I'm not aware of any metal that, in reality, changes properties under normal conditions over long periods of time. Copper doesn't and neither do bits on your boat or car. ( external chemical or mechanical processes excluded! Google "precipitation hardening".
rotrax
Well-Known Member
From direct experience Copper and soft aluminium harden with age. To the extent that to bend old copper tube requires it to be annealed. Ditto for solid copper cylinder head gaskets. Annealing those was always required before putting the cylinder head back on.
My old mate Jim - he was Eric Broadley's chassis man - made me a custom alloy tank for a F1 Kawasaki powered race bike. Almost freehand.
First thing he did, with a soft and smokey oxy acetylene flame, was anneal the two sheets of alluminium. They became very soft and easy to work.
Before the annealing process they were virtually unworkable in the way he needed to carry out the beating and shaping.
No TIG or Argon welding then, all done with oxy acetylene.
From that, it appears some metals DO change with age, including copper.
My old mate Jim - he was Eric Broadley's chassis man - made me a custom alloy tank for a F1 Kawasaki powered race bike. Almost freehand.
First thing he did, with a soft and smokey oxy acetylene flame, was anneal the two sheets of alluminium. They became very soft and easy to work.
Before the annealing process they were virtually unworkable in the way he needed to carry out the beating and shaping.
No TIG or Argon welding then, all done with oxy acetylene.
From that, it appears some metals DO change with age, including copper.
HissyFit
Well-Known Member
I think you are mistaking the reason why the aluminium was hardened in the first place. Just because you witnessed that it was too hard to work does not prove that it had hardened through age. As mentioned before, 'age' hardening is a low temperature heat treatment process, also known as precipitation hardening.
Age hardening of aluminium
The aluminium you witnessed was in sheet form, which is processed by rolling. Rolling is enough to work harden aluminium to the point that it needs to be annealed to be hand worked.
vyv_cox
Well-Known Member
Many years ago at school I made a copper bowl in metalwork by beating it in a leather pad. Gradually it would work harden, requiring annealing to soften by annealing.
As has been explained, age hardening is a complex two stage low temperature heat treatment process. Also may be known as precipitation hardening, so e.g the 17/4PH of Wichard fittings is made this way.
As has been explained, age hardening is a complex two stage low temperature heat treatment process. Also may be known as precipitation hardening, so e.g the 17/4PH of Wichard fittings is made this way.
boatmike
Well-Known Member
Neither Copper or Stainless harden with age. They both work harden though and as others have said can be annealed. The only exception to this (stainless) is that it can "fatigue" over time and break due to vibration or "working" below the elastic limit which some put down to hardening (not strictly true). As Vyv says precipitation or age hardening is a deliberate process and needs careful control it does not happen by accident.
DownWest
Well-Known Member
Copper. In WW1 the rotary engines like the Monosoupape and Bentleys had copper oil tubes. Due to work hardening cause by vibration, the had to be annealed every few hours, or they fractured. Not quite the same as age, but related..
Jamie Dundee
Well-Known Member
I remember doing this (ash tray, wouldn’t happen in schools these days). The annealing was done in acid IIRC.
I’ll get me coat now as that’s the limit of my knowledge.