Slowly heating hi carbon steel

[Burak]

My teacher has always told me to slowly heat hi carbon steels by resting steel near heat to a black height with slight red glow before putting steel withing heat source, for coke forges. Alternatively, you can put steel within the gas forge while starting the gas forge.

My question is with regards to gas forges, is there risk of micro fractures if inserting the hi carbon steel immeaditly within the forge that is already at desired temp?

[Steve Sells]

many tool steels need a pre heat

[ThomasPowers]

Ambient can be an issue too. for instance -20 degF and 112 degF. (I've forged in each before.)

[jlpservicesinc]

Yes.  Ideally heat shock can happen to any of the higher carbon steels and alloys.   the outer skin expanding way faster than the inner colder core.

Just lay it on the side of the forge while working on something else. 

[arkie]

Burak, Steve, Thomas and Jennifer...thanks for pointing out the preheat on hi carbon steels.  I was not aware of that, good to know!!

[basher]

This is not a practice I have ever seen a profesional smith working with carbon steel do? or heard of one doing in the modern world...I have come across it in old machenery manuals but assume it is redundant apart from very specific instances (complex crosssectional changes come to mind.)

[jlpservicesinc]

Alloys are particularly susceptible to heat shock so should be treated accordingly.  Ideally, its best to heat all high carbon or alloy steels this way as what percentage actually suffers a problem for the blacksmith is probably fairly small but knowing it can be a problem is key. 

[Burak]

Thanks for answering, it was strange when I took a 2 day knife making class with 1084 and there was no preheat in the has forge.

[jlpservicesinc]

I think there is a lot of things that get done that are not by the book.  It's one of the most amazing things about working metals by hand or blacksmithing. 

 

It's a very archaic process yet the results can be quite amazing. 

 

The human factor plays in all over it and while in Industry the accountability is linked to the process, at each individual shop every smith has their own take on any facet and if the item looks decent and functions as intended the "home" smith won't ever see a real difference unless there is a failure. 

So, the simple answer is there is a " BEST practice" but many do whatever they want as it's what they do and have done the process a hundred times with good success. 

[JHCC]

Remember also that many "by the book" methods are calculated for thicker sections than one finds in most blades.

[Steve Sells]

which is the big reason we have a separate section for knifes in heat treating