1010 rivet hardness

[metrat]

I have a requriement for maximum hardness of cold formed aisi 1010 rivets to be 60 HRB. Many of these rivets are very small, 0.020" diameter and 0.125" long. I am not able to consistenly get them to a hardness below 60 HRB.

I have looked at mateiral chemistry variation, tried various cooling cycles/time in my anneal process, and still not consistent success.

Any suggestions????

Thanks.

 

[Metalguy]

I had forgotten this in an earlier post for a similar question, but long exposure to around 1250 deg. F (spherodizing or spherodize-annealing) will give you the softest rivets.

 

[TVP]

As Metalguy stated, spheroidizing treatments produce very low hardness. For general information on spheroidizing, read the description I posted in the following thread:

thread330-42174

For SAE 1010, proper spheroidizing produces a tensile strength of around 300 MPa, which is low 50's HRB or around 90 HB. I would investigate the temperature uniformity of your furnace, and the duration of the annealing/spheroidizing cycle. Depending on the degree of cold working involved in forming the rivet, spheroidizing of a low carbon steel like SAE 1010 should not require a cycle as high I mentioned in the above thread. 700 C for only a couple of hours may be sufficient to produce a spheroidized structure. Can you provide details on the time and temperature settings you have used so far?