The grades of rivet materials used in the riveting machine are Q215, Q235, 10#, 15#, 20#, ML10, ML20 steel, etc. Due to the relatively small variety and specifications, it cannot meet the current needs of rivet production. In production practice, G3506, G3507, G4105 from the Japanese JIS standard are borrowed a lot.
The rivet surface of the riveting machine is not allowed to have cracks that affect the use; the top surface of the nail head is not allowed to have small protrusions that affect the use of the metal; If it is really flattened, it requires a higher tolerance on the coaxiality of the rivet stem. To this end, the rivet raw materials and finished products should be subjected to annealing heat treatment.
There are many types of rivet annealing heat treatment in riveting machines.
1. Spheroidizing annealing
Spheroidizing annealing is a process method to obtain fine-grained (spherical) carbide structure dispersed in the ferrite matrix. Medium carbon or medium carbon alloy steel must be spheroidized annealed, and low carbon steel for cold heading extrusion must also be spheroidized annealed, and the hardness can be 140~160HBW (82~86HRB).
2. Low temperature spheroidizing annealing
Low temperature spheroidizing annealing is the heat treatment of heating the steel to 20℃ below Ac1 for a long time (usually 4~8h) to obtain spherical pearlite. This process is suitable for cold deformation processing and cold stamping parts.
3. Isothermal spheroidizing annealing
Isothermal spheroidizing annealing is to heat the low and medium carbon alloy steel to Ac1+ (20~30℃), keep it for an appropriate time, and then cool it to a temperature slightly lower than Ar1, keep it isothermally for a certain period of time (to complete the isothermal transformation), and then Furnace-cooled or air-cooled spheroidizing annealing process.
For stress annealing, the rivets after cold deformation are heated below the recrystallization temperature, and the internal stress is removed in the past, but the cold work hardening effect is still preserved. Traditionally, the stress treatment at a higher temperature is called stress annealing, and the treatment at a lower temperature is called stress tempering, and the essence is the same.Curvedarm Type Hand Riveter-BT903