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I would like to weld a piece of hardened steel but i don't want to ruin the treatment on the tip of the piece. Can i put some ice in the middle of the shaft so the heat generated from the welding (SMAW DCEN) doesn't temper the tip? Thanks in advance.

Tommaso Lencioni
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It will reduce the weld HAZ some , but not much. It depends on the dimensions and the heat input of the weld, the alloy , the original hardness , and the original heat treatment. The primary cooling is by conduction which is affected by the temperature difference. So the temperature difference will be 75 F / 2800 F , or 32 F /2800 F , not much of a difference. And, if the steel has much carbon ( eg. over 0.15% ) , the weld HAZ will contain some hard brittle zones with a significant chance of cracks.

blacksmith37
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    Could you please combine and edit your answers (maybe in the form of a paragraph for the general case and a paragraph for the specific case). This is useful information, but it's not clear what "is not, can not be welded" (="cannot be welded"?) means, for example. In addition, no space is used before the comma or within parentheses (e.g., "(I have seen recommended up to 600°F.)"). – Chemomechanics May 30 '18 at 17:04
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Second, more planned answer . Hard steel ( Rockwell C 35 +) is not, can not be welded. In an unfortunate situation where it must be attempted ; 1 - Soften at about 1300 F , one hour . 2 - Preheat to 400 F ( I have recommended up to 600 F) . 3 - Weld. ( maintain preheat ). 4 Inspect for cracks. 5 - Soften the weld HAZ at 1300 F. 6 Heat-treat , quench and temper, according to the alloy.

blacksmith37
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  • Thanka for your answers. The piece is a HSS 12 mm drill bit. I can't reharden it properly, so you think that preheating and welding the shank keeping the tip cold could cause cracks? – Tommaso Lencioni May 31 '18 at 16:58
  • High Speed Steel is a very different type of steel , it can maintain hardness up to 1200 F. When i worked in a drill bit heat treat lab , the shanks were clamped in tongs. Then most of the bit was put into a slot furnace at about 2150 F for a couple minutes. The shanks did not get hot enough to harden when the bit was quenched into oil. So the shank is not as hard . HSS is tempered at temperatures like 1200 F .. The point is even most commercial heat-treat shops can not harden HSS. Also , I can't guess what would happen in a weld on HSS. – blacksmith37 Jun 01 '18 at 03:21