With that volume of parts to be made I'd like to know I went the extra step to ensure a repeatable process. When it's all said and done I'm going to make a duplicate die set for the Oops factor.
It will get bad really quick. Without a spare set and about 1 week of downtime we're over 1, parts behind IMO, your boss didn't do a great job of steel pickin'. One problem with 41xx steels for this part is that they lack nickel, which promotes deep hardenability. The severity of the quench necessary to avoid the pearlite nose on the TT plot is much higher than with a Cr-Ni-Mo steel like , and that's not meant to imply that is a good die steel.
All it means is that the likelihood of warpage is directly related to the severity of the quench. Obviously you've got quite a chunk of money tied up in this part already, so saving it would be a good thing [img]smile. I'd investigate the suitability of salt bath nitrocarburizing if it was my part.
You end up with a surface that's in the low to mid 60's, and that surface has good lube retention properties which can be desirable in a process like you describe. If you do a search for Kolene, it should bring up some good info on the SBN process. Kolene is one of the owners of a proprietary SBN process, and they license it to heat treaters around the country. I've had it done to some parts in the past, and found it will do everything they say it will do.
I dont think you can get the hard enough to have any appreciable wear resistance without some type of surface hardness treatment.
I've made a lot of cold flanging dies in the past from similarly heavy sections of , and after a minimal temper they were seldom above Rc My guess is that your part will likely be under Rc50 after tempering. That's probably not nearly hard enough for resisting the wear that wants to happen when your Ti slides under high pressure during forming.
SBN will give you a surface hardness and friction coefficient close to that of hard chrome, so it should do well for resisting wear.
A treater who does the process should be able to look at your part and tell you whether there are certain features that would make the process unsuitable, such as thin highly loaded sections, etc.
If it'll work, it should be about the safest process out there for getting the hardness with minimal danger of distortion. I agree A2 cuts like butter for the most part, Even M42 and H13 do not present any real problems to machine in the annealed state, the only thing I did on H13 was cheat on the tap drill size a touch and run it one letter size bigger H13 will make you think a sharp new tap is a dull old one Bill.
As John and others have said, anything that big and thin is going to move around. We buy the heat treated and drawn material. It's usually a little less than 35Rc which makes is tough, but not impossible to machine. It can be drilled and tapped with HSS. If we have wear spots, those usually get inserted with A-2 or D If the inserts are kept small, say the size of your fist or less, we just make them to size and don't bother to grind.
We heat treat in a vacuum furnace and have very little less than 0. Bright heat treat and annealing is sure nice JR isnt it?? If accurate dimensioned parts are what your after, I would stay away from series steel and use a good air hardening series, like A5 or A7 properly hardened and tempered to desired hardness. Always discuss a project with a heat treater before selecting a material. It makes life way easier. Best regards, Mark in Buffalo. Bookmarks Bookmarks Digg del.
Thread Tools Show Printable Version. Machining prehard or Annealed? We are attempting to machine annealed and have had significant tool life issues? Has anyone done this successfully? We have the option to machine after hardening to 38 rc. Has anyone tried machining hardened with success?
Any input or ideas would be greatly appreciated. I usually rough to about. You might be experiencing a phenomenon where the chips harden as they are cut. If they come off red hot that's OK, they will stay soft that way.
I've also had experience with carbide microcracking because of the amount of heat generated at the cutting interface and quenching with coolant, which causes premature failure. HSS actually works well, use cobalt and lots of coolant. You can buy HT bar and skip the outside service.
I'm in MN also so if you need more help send a PM. Turning or milling? Turn: Rough: - sfm,. What kind of tool life are you getting now? Prehard is actually very workable. We typically work with Stavax, H13, and other materials in the HRC range if that makes you feel any better.
The coating won't reach it's oxidizing temp if you flood it, so if chip evacuation isn't an issue, just run it dry. Tell us more about the operations you need to perform. It has excellent ductility when annealed and is a through-hardening alloy.
Table 1, below, provides some important mechanical properties of steel. Type steel has a modulus of elasticity of GPa ksi , which is higher than some high strength spring steels such a steel read more in our article on steel. This means that steel does not easily bend and can withstand large stresses and still return to its original form. This is a great characteristic in structural steel, as its main goal is to remain rigidly in place. The ultimate and yield tensile strengths provide the maximum stress a material can withstand before permanent changes in geometry occur.
Yield stress describes the onset of permanent or plastic deformation, and the ultimate strength is the stress value before fracture. Both are important measures for designers, but yield strength is a vital component in structural applications where this value can never be exceeded. This is not to say that steel is weak; in fact, it far surpasses most aluminum alloys.
Hardness is a qualitative, comparative parameter that describes the response of a material to local surface deformation. There are many hardness scales that depend on standard hardness testing machines; for most alloys, the Rockwell indenter machine is used and each material is graded on the Rockwell hardness scales. For reference, the Rockwell B hardness of copper, a relatively soft metal, is Type steel has a Rockwell hardness of 92, which is high for steel and shows why this material is so tough.
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