annealed wire, recommended Rc, prior to heading process 3

[daal]

In the cold heading process, from the annealed process prior to the headed process , are there recommened Rockwell specs to use as a guide for different grades of wire used to form metal fasteners (not stainless)? If so,where can this be found?

 

[CoryPad]

ASTM F 2282 Standard Specification for
Quality Assurance Requirements for Carbon and Alloy Steel
Wire, Rods, and Bars for Mechanical Fasteners is a good one for your needs, although it does not list hardness.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[TVP]

There are some general guidelines that you can use, depending on the grade and the exact type of wire processing (annealing and cold drawing) prior to cold heading. ASTM F 2282 is an excellent reference document, and you should obtain it as soon as possible. Table 11 lists the maximum tensile strength requirements for the various grades and annealing processes. As an example, 4140 in the annealed in process condition (highest strength/hardness) should have a maximum tensile strength of 102 ksi (703 MPa) which is equivalent to a maximum of ~ 95 Rockwell B. I converted the tensile strength to hardness using ISO 18265. 4140 that has been spheroidize annealed at finish size (SAFS) will be the softest condition, and the tensile strength requirement is 82 ksi (565 MPa) or ~ 87 HRB. Steels that have been annealed should be measured using Rockwell B (HRB) or Vickers (HV) not Rockwell C (HRC). HRC is for hardened steels.

 

[Screwman]

It is also very dependent on what type of heading that you are going to do: a trimmed hex head can be formed from much harder wire than can a Torx round washer head. Also, upsetting processes generally take a lower hardness wire compared to the extruding type heading progressions. Also keep in mind the number of heading blows that you will be performing on the wire; an alloy steel that has a high strain hardening rate might get so hard that it cracksif you try to use 5 blows to form a part with it.
This is another area where there are some rules of thumb, but then there are so many exceptions to those rules that they are almost useless. Spend some talking to an experienced header tooling engineer and you will learn a huge amount. A lot of this information is kept in private notebooks and not given out freely...I have some tooling people here who won't show me their private 'black book' of upsetting ratios for different materials and head styles and first blow designs.

Dick