Qingdao bolt production process

(1) Qingdao bolt process annealing

Eliminate the internal stress of steel wire processing and improve its forgeability.

Heat the steel wire to an appropriate temperature, keep it for a period of time, and then slowly cool it to adjust the crystal structure, reduce the hardness, and improve the processing of the steel wire at room temperature.

Operation process:

Feeding: Put the product to be processed into the furnace, and pay attention to the tightness of the furnace cover. Generally, one furnace can process 7 rolls (about 1.2 tons) at the same time

Heating: Slowly increase the furnace temperature (about 3-4 hours) to the desired temperature.

The insulation material 1018, 1022 wire 680c-715c is kept for 46 hours, and the material 10B21, 1039, CH38F wire 740c-760c is kept for 5.5-7.5 hours.

Cooling: Slowly reduce the temperature in the furnace (about 3-4 hours) to below 550C, and then cool to room temperature along with the furnace.

(2)Qingdao bolt quality control:

1. Hardness: The material is medium carbon wire, and the hardness after annealing is less than HRB700 (nut) and less than HRB750 (stud).

2. Appearance: No oxide film or decarburization is allowed on the surface.

3. Pickling: Reduce the oxide film on the surface of the steel wire and form a phosphate film on the metal surface to reduce the wear of the wire drawing and cold block or forming process.

Operation process:

Pickling: Soak the whole dish in three hydrochloric acid tanks for a few minutes at room temperature with a concentration of 20-25%. The purpose is to reduce the oxide film on the surface of the wire.

Clean water: remove the corrosion products of hydrochloric acid on the surface of the wire.

Oxalic acid: increase the activity of the metal and make the density of the film in the next step.

Membrane treatment: The plate is immersed in phosphate, and the steel surface is in contact with the conversion solution. Steel dissolves to form insoluble compounds (such as Zn2Fe(Po4)2·4H2O), which adhere to the steel surface to form a film.

Clean water: remove residues on the surface of the membrane.

Lubricant: Because the coefficient of friction of the phosphoric acid film is not very low, it cannot give sufficient lubricity during processing, but it reacts with metal soap (such as sodium soap) to form a hard metal soap layer to increase its lubricity.