forgemaster Posted September 29, 2011 Share Posted September 29, 2011 Yeh I agree for 2" thickness or less I would recomend oil. Years ago I spent ages on making some fully forged axe heads from 4140, had a bright idea to harden them in water, still got 25 axe heads here years later, all with cracks running all over the blades. xxxx. I'll find a use for them one day. We also make a forged ring from 4140 normally 60 off at a time 185mm od x 120mm id x 75mm thick (or long depend on how you want to call it) gives about a 32.5mm wall thickness, we always harden them in oil from 870 deg C and temper to 580 deg C holding for a couple of hours, I can almost guarantee to get a minimum of 277HB every time. Quote Link to comment Share on other sites More sharing options...
HWooldridge Posted September 29, 2011 Share Posted September 29, 2011 Try the salt based "superquench" formula. Even mild steel (A36) will get in the 35-40 range with a fast quench. Quote Link to comment Share on other sites More sharing options...
Awalker Posted October 2, 2011 Share Posted October 2, 2011 I don't think it would matter if it was decarb steel, as he has heated it and forged it, hence you have reworked the surface and likely lost the decarb layer. I think he just doesn't have 4140, just mild steel. Also, there is no need at all to soak a 3/4" thick piece of steel in the forge at that high a temperature. Here is the data for that material. Thermal Treatments. Annealing: 1550F (840C), hold 2 hours, slow cool 50F(30C)/hr. max. to 1200F (650C), then air or furnace cool. Hardness BHN 185/200. Stress Relieving: Annealed Material: 1100-1300F (595-740C), hold 2 hrs, air cool. Hardened Material: 50-100F (30-55C) below last tempering temperature, hold 2 hrs, air cool. Straightening: Best done warm 400-800F (205-425C) Hardening: (Atmosphere or Vacuum Furnace) Preheat: 1250-1300F (675-705C), equalize High Heat: 1550-1600F (840-870C), soak 10 to 30 minutes. For vacuum hardening, use the high side of the high heat range and soak times. Quench: Oil quench to hand warm, 150F (650C). Temper immediately. Water quenching from 1550F (840C) may be used for simple shapes and larger sections. Note vacuum furnaces must have oil quench capability to achieve comparable results. Temper: Tempering at 400-1200F (205-650C) for 1 hour per inch (25mm) of thickness at temperature is recommended (2 hrs min). Air cool to room temperature. Quote Link to comment Share on other sites More sharing options...
LongShadows Posted October 4, 2011 Share Posted October 4, 2011 There are already many good responses to your original question, but I thought I'd share an URL that is loaded with good info about many steels, including heat treat procedures. www.suppliersonline.com Quote Link to comment Share on other sites More sharing options...
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