American bow shackles have been on the market for many years. The common bow shackles are G209 and G2130. At present, the production processes of most domestic manufacturers are as follows:

Blanking → heating → forging drilling → tapping → quenching → tempering → surface treatment. However, there are certain problems in this production process (1) The concentricity of the optical hole and the screw hole is out of tolerance due to the overall deformation of the heat treatment, which affects the assembly of the pin shaft. (2) Quenching cracks are prone to occur when the thread part is quenched.

In order to solve the problems existing in the above production process, and according to the existing equipment conditions and product characteristics of the shackle company, the production process is changed to: blanking → heating → forging → quenching after forging → tempering → drilling → tapping → surface deal with.

A 300kw medium frequency induction furnace is used for heating, and the temperature of the billet is controlled at 1150-1180°C when it comes out of the furnace. Because the diameter of the minimum section of the shackle is 22.4-52,8~ (see Table 1), and there is no thin wall, no quenching cracks will occur, so no pre-cooling is required, and it can be directly quenched. For the conveyor chain for quenching, the running speed of the chain should be consistent with the forging production rhythm. When the shackle is running on the chain to cool, the spacing should not be less than 10cm, otherwise it is easy to cause uneven quenching hardness or soft spots. The quenching medium is 5%-8% CaCl2 aqueous solution, the temperature is 20-40 ℃, and the water temperature of the shackle is 100-150 ℃. Well-type resistance furnace for tempering, according to the American bow shackle product standard, the tempering hardness is 22-29HRC. In order to facilitate drilling and tapping, the hardness should be controlled at 22-26HRC. Use low speed and large feed amount when drilling. Tapping and post-processing are performed after drilling.