Decarburization depth if HT semi high alloy steel in gas oven without protection?

S

shqxk

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Mar 26, 2012
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I gonna get some Calmax sheet soon. I don't want to send it to commercial HT since they trend to oversoak most of the time.

This is the spec of steel.

http://www.uddeholm.com/files/PB_Uddeholm_calmax_english.pdf

All I have is digital control gas oven and low temp molten salt for quenching.



What is the decarb depth should I expected if HT with 1380F Preheat with 15 min soak then ramp up to 1780F and soak for 30 min?

I never do high alloy steel without ss foil protection before but I don't have any foil left at this time and this steel seems to require significantly lower austenitizing than D2 or XHP.

I going to quench in 400F molten salt then straight forward to subzero. Do you think some thin refractory mortar clay coat going to help with decarb?


Thanks in advance!
 
IME + wild guess with your setup.

naked blade would decarb .2-.3mm deep and .3-.4mm with less than 0.6%C. Carbon diffusion (high to low <=> core to surface) is fairly fast at this temperature.

I would sandwich the blade with 2 high carbon steel(e.g. 1095) rectangle pieces (25+% bigger than blade). Put edge down. Most carbon burn will be from these 2 sacrificial pieces. I would expect almost no decarb and ~0.1mm-0.2mm spine to end up with lower hrc (due to a little bit lower carbon).
 
Thanks you bluntcut. I have refractory mortar clay do you think some thin coat with it gonna help?
 
SS foil is PIB for me - always seem fumbling around cut & pull 1900+F blade out quickly.

I've tried (thin & thick) satanite & itc100, they worked but not 100%. Ceramic coating invariably crack when the blade is thermally expanded, those hairline cracks = here & there decarbs = aggravation (well at least for me, especially for steels has less than 0.8%C). Re-apply clay after the coated blade reached ~1000F eliminate most crack lines but still not 100%.

In electrical oven, I place a small slab of satanite + 5% coal powder (I just crush a lump of charcoal) near the door to burn incoming O2. Burnt gas is low O2 compare to electric but negate (rate depend on fuel/air mixing ratio) by moving air.
 
If I use SS foil I would quench with the foil without any problem but I just can't wait to buy the 309 foil from USA so clay properly an option.
 
You don't even have an old ss foil envelope?


Pablo
 
Sure - most air hardening steels would quench fine in foil. My ht involves direct contact with blade, especially high cr% (mainly stainless) steels.
shqxk said:
If I use SS foil I would quench with the foil without any problem but I just can't wait to buy the 309 foil from USA so clay properly an option.
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Direct contact through clay or other coating? Is there really a difference between that and foil?
 
An upfront apology for my ambigous answer. Yes (with my ht) coat vs foil differences: coating can easily knock/shed away; spine & edge are accessible with coat; envelope cooling is slower (in temp range I care anyway). At any rate, cutting foil works fine with practice - I did 12 blades that way a couple hrs ago.

kuraki said:
Direct contact through clay or other coating? Is there really a difference between that and foil?
Click to expand...
 
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