The protruding bead of the HSS longitudinal seam weld, on the inside of the HSS, needs to be considered if using interior splice plates. With splice plates just on the outside of the HSS the bolts will be in single shear, but if splice plates are used on the inside of the HSS as well the bolts will be in double shear the number of bolts will then be halved and the connection length will be substantially less. A hand (or access) hole may be necessary in order to position the nuts on the inside of the HSS (Figure 1). The familiar steel construction maxim of “weld in the shop, bolt in the field”, naturally applies.ĭue to the closed shape of the cross section, bolting directly into the walls of a hollow section is difficult with regular high-strength bolts. Identical, or similar-sized, HSS members frequently need to be joined end-to-end, or spliced, particularly in long-span construction and in tall columns. Heat the same piece of steel the th4e same temperature and let it down slowly in an oven and you'll have a nicely annealed piece of HSS when you're done.Bahen/Tanenbaum Professor of Civil Engineering, University of Toronto, Ontario, Canada You can heat that HSS to a nice orange and let it cool on a rack and it'll be almost as hard as it was when you got it even though it went above the annealing temperature and passed through it on the way back down. HSS, unless cooled *very* slowly, will harden. Some simple steels can be heated and left in still air and they will be annealed, more complex alloys will harden in the same conditions. The point remains - what hardens a steel (that can be hardened) is the rate of cooling. I managed to confuse the hardening temp with the annealing temp (which are generally the same in a high carbon steel) but the hardening temp listed for M2 on your reference is 2200 degF.

RobertSteel does not melt at 1350 to 1500, you're confusing the melting point with the critical point. Steel melts between 13° F, and the TIG tip temperature is considerably higher than that, so the HSS in the heat affected zone should be well within the annealing temperature. If you look at the M2 datasheets, the critical temperature (when the steel changes its structure to austenite) is 1500☏, and the annealing temperature is 1600☏: You won't notice it until using the tool and you get some cratering behind and on the edge. If you get the edge really hot and dunk it in water the rapid quench can cause microcracking. The one thing you want to be careful about with HSS is in grinding. For the most part a HSS isn't really quenched as much as 'allowed/encouraged to cool rapidly', using in what we would normally consider a hot oil. It's made to cut at a dull red without too much loss in hardness, and that loss is regained on cooling. To anneal HSS you usually have to take it up to something like 2200 degF + and cool it at some really slow rate, 50 degF/hr or so. I've welded HSS toolbits together and used them as-in afterwards with no effects from the welding. A high carbon steel will likely have lost its hardness when you have surface colors (the temper will certainly have changed) but a HSS will not change much at all. If you weld it, you run the risk of losing the temper on the tool, especially if it's a small bit.īasically, if the HSS tool bit gets discolored (rainbow colors) from the weld, it's lost its temper.I think that you have that exactly backwards.

Welding of hss square