Ethnographic Arms & Armour - View Single Post

Billman · 12th November 2010, 01:49 PM

Information on lead for hardening and tempering at http://www.7now.com/tempering_steel.htm

I think part of the problem is the use of the term tempering - in the UK it is the name of the process used after hardening to reduce brittleness and increase toughness.

In the USA it appears to be used for the process of annealing, i.e. stress relieving or softenening of the steel to allow another process to be carried out, such as drawing or cold-working:

1. The method of producing steel wire (particularly suitable for the manufacture of coiled springs) comprising forming steel rod by hot rolling, oil tempering the rod as produced in the hot rolling operation, without drawing the rod, by passing it through an austenitizing step, an oil-quenching step, and a tempering step, cold-drawing the resultant oil-tempered rod into wire, and coiling the wire

link: http://www.freepatentsonline.com/4568394.html

In this process the steel is tempered at 600 to 1000 degrees F (approx 300 to 450 degrees C). I was always taught to harden wood chisels at straw colour (230C 450F), axes at brown/purple (270C 520F) and springs at blue (300C 570F) - that is the colour of the oxide film seen on cleaned steel.

Steel starts to turn red at 400C 750F - plain carbon steels are quenched to harden at about 700C 1300F.

I cannot see how molten lead, or even a lead tin alloy, can be used for tempering of hardened carbon steel - the temparature control is too critical...

In small forges, as used commercially in Europe up to the mid 20th century, and still in use elsewhere, hardening usually took place in oil - whale oil being preferred, but fish oil and other oils also used. Today used car or lorry engine oil is often substituted... If oil was not available a strong brine solution was used, and failing that water. Some forges preferred water, but most smiths thought it cooled too quickly and could lead to cracking on small pieces, and it also vapourised on large pieces, creating an insulating barrier of steam between the work and the water, thus delaying cooling....

Much hardening and tempering was seen as a 'magical' art, and most smiths kept their methods secret, often even from their own staff and apprentices...
In the UK, the Moss family from Hampshire, when they sold their trademarks, patterns and goodwill to Elwell, an industrial manufacturer from the Birmingham area, also sold their 'secret' of hardening and tempering.

In the USA, one smith gave up making tools, and handed over the business to his son after having to learn the hardening and tempering business for a third time after his supplier (and thus the qualities and properties) of the iron and steel he used had changed yet again.... Despite years of experience, he had had enough and was not prepared to invest the required time in experimenting on how to harden and temper the new steels (sorry cannot remember the link - it was on one of the better USA collectors or clubs sites).

12th November 2010, 01:49 PM	#30
Billman Member Join Date: Nov 2010 Posts: 129	Information on lead for hardening and tempering at http://www.7now.com/tempering_steel.htm I think part of the problem is the use of the term tempering - in the UK it is the name of the process used after hardening to reduce brittleness and increase toughness. In the USA it appears to be used for the process of annealing, i.e. stress relieving or softenening of the steel to allow another process to be carried out, such as drawing or cold-working: 1. The method of producing steel wire (particularly suitable for the manufacture of coiled springs) comprising forming steel rod by hot rolling, oil tempering the rod as produced in the hot rolling operation, without drawing the rod, by passing it through an austenitizing step, an oil-quenching step, and a tempering step, cold-drawing the resultant oil-tempered rod into wire, and coiling the wire link: http://www.freepatentsonline.com/4568394.html In this process the steel is tempered at 600 to 1000 degrees F (approx 300 to 450 degrees C). I was always taught to harden wood chisels at straw colour (230C 450F), axes at brown/purple (270C 520F) and springs at blue (300C 570F) - that is the colour of the oxide film seen on cleaned steel. Steel starts to turn red at 400C 750F - plain carbon steels are quenched to harden at about 700C 1300F. I cannot see how molten lead, or even a lead tin alloy, can be used for tempering of hardened carbon steel - the temparature control is too critical... In small forges, as used commercially in Europe up to the mid 20th century, and still in use elsewhere, hardening usually took place in oil - whale oil being preferred, but fish oil and other oils also used. Today used car or lorry engine oil is often substituted... If oil was not available a strong brine solution was used, and failing that water. Some forges preferred water, but most smiths thought it cooled too quickly and could lead to cracking on small pieces, and it also vapourised on large pieces, creating an insulating barrier of steam between the work and the water, thus delaying cooling.... Much hardening and tempering was seen as a 'magical' art, and most smiths kept their methods secret, often even from their own staff and apprentices... In the UK, the Moss family from Hampshire, when they sold their trademarks, patterns and goodwill to Elwell, an industrial manufacturer from the Birmingham area, also sold their 'secret' of hardening and tempering. In the USA, one smith gave up making tools, and handed over the business to his son after having to learn the hardening and tempering business for a third time after his supplier (and thus the qualities and properties) of the iron and steel he used had changed yet again.... Despite years of experience, he had had enough and was not prepared to invest the required time in experimenting on how to harden and temper the new steels (sorry cannot remember the link - it was on one of the better USA collectors or clubs sites).