Dunc1 said:
If fabricated parts need subsequent machining then how would one choose the steel types?
If using 60xx or 70xx rod is the weld material itself machinable (thinking lathe or mill, not "grinder machining"?) Characteristics similar to the base metal or...?
What about machinability of the heat-affected areas?
With the exception of leaded steels, the other common steels we use in the machine shop also
happen to be steels that are readily welded.
What most people call HRS, structural steel, or mild steel in the USA is A36. It welds as good as it
gets, and it machines fair.
The other common steels we use are mainly CRS steels, like 1018, 1045, etc., and they also machine
pretty well, along with being easily welded.
The 60 and 70 series rods machine much like the majority of CRS metals. Usually, the welding
alloy and the base metal are well matched, and you won't even be able to see where a weld
starts and the base metal ends. You won't be able to tell much difference in milling a welded area
as opposed to milling the base metal, either. The main problem with milling a welded area will
usually be when you run into inclusions. Slag inclusions are very abrasive, often hard as glass, and
can be rough on cutters. The way to remedy that is to make sure you burn out your slag when
you weld.
The general purpose welding alloys are not particularly hard when it comes to milling them. They're
made for strength and toughness, but not really hardness, unless you are using an alloy that is made
specifically for that purpose.
The heat affected areas are going to depend almost completely upon the base metal. If it will get
hard from normal heat treatment, it will get hard if you weld it and quench it. Let your welds cool
naturally, and you shouldn't have problems. That's my experience, anyway.
Dean
