What is the Production Process of Cold Drawn Steel

1. What is cold drawing of steel

Cold drawing is to forcibly stretch the steel bar under normal temperature conditions to exceed the tensile stress of the original steel yield point strength, so that the steel bar produces plastic deformation to improve the strength of the steel yield point and save steel for the purpose.

Cold drawing refers to the process of using tensile mechanical equipment to stretch steel at room temperature. Cold drawing produces cold tensile strengthening effect: the tensile stress exceeds the yield strength of the steel after unloading. The yield strength of the steel will be increased to the unloading stress water.

Cold drawing effect: The process of drawing steel with tensile mechanical equipment under constant temperature. Cold drawing produces cold tensile strengthening effect: the tensile stress exceeds the yield strength of the steel after unloading. The yield strength of the steel will be increased to the unloading stress level.

The process of plastic deformation after neck formation in tensile test. At this time, the elongation of the sample is manifested as a neck segment with a stable cross-section size expanding along the sample until the entire sample becomes a neck state. Neck formation occurs in the stage of sharp stress reduction at yield point. In the process of cold drawing, the tensile force of the sample remains basically constant.

In order to save steel and improve the yield strength of steel bars, the practice of stretching steel bars to exceed the yield strength but less than the ultimate strength is called cold drawing steel bars.

2. Cold drawing equipment:

Electric winch: the general traction force of electric winch is 29–49kN, the drum diameter is 350–450㎜, and the drum speed is 6–8r/min.

Block and return block: the number of doors and tonnage of cold drawn block, generally 3 ~ 8 doors, 150 ~ 500kW. The number of doors and tonnage of the return block, when the cold pull and the return use the same hoist, with the reverse and reverse rotation of the drum to achieve the return, the number of doors and the cold pull block are the same. When the special hoist is used to achieve the return journey, it is generally used 2 ~ 3 doors, 30 ~ 50kN.

Cold drawing jig: cold drawing jig is a clamping steel equipment, requiring strong clamping force, safe and reliable, durable, easy to operate. Commonly used clips have:

Wedge fixture: The fixture is made of high-quality carbon steel, which is suitable for cold drawing steel bars with a diameter of 14㎜ or less

Eccentric fixture: made of high quality carbon steel, suitable for cold drawing I level disc round bar.

Slot fixture: there is no fixed form and specifications, depending on the site situation. It is suitable for cold drawing steel bar with screw or upsetting head at both ends. In addition, there are crescent fixture and conical tooth plate clamp and other forms.

When cold drawing, only the cold drawing rate or cold drawing stress control is called single control, and when cold drawing, the cold drawing rate and cold drawing stress are applied simultaneously, which is called double control. Using single control, the construction is simple and convenient. However, for steel bars with uneven materials, it is impossible to test root by root (root by root test, labor and material costs, it is impossible to do so, and some of the same steel bar cold drawing rate is not the same) cold drawing quality is not guaranteed. Dual control method can avoid the above problems. When cold drawing, if the control stress has been reached and the cold drawing rate has not exceeded the allowable value, it can be considered qualified. However, if the cold tensile rate has been reached, and the cold tensile stress has not reached the control stress, the steel bar should be used to reduce the strength. Dual control method must be adopted for prestressed reinforcement.

3. Cold drawing steel process

(1) Selection of materials: First of all, select the appropriate material according to the requirements of the physical, chemical and mechanical properties of the required products.

(2) Lean feed: The selected material is put into the lean feed system in batch form, and the feed rate and length are controlled by the computer.

(3) Processing blank: the selected material is mixed first, and then the long blank silver bag, wire rod or secondary deoxidation treatment. For the production of bar or wire, lean feed and then open rolled into round steel blank.

(4) Cold rolling: the treated blank is cold processed in the cold rolling machine for multiple passes, gradually reducing the section diameter, and ensuring the internal texture of the material is uniform.

(5) Stretching: put the cold-processed billet into the drawing machine, gradually increase the strength of the tensile material, so that it gradually becomes thinner, but also improve the strength and hardness of the material.

(6) Straightening: the steel after stretching may have some bending and tortuous, so it needs to be straightened to restore it to a straight state.

(7) Cutting: The steel after stretching and straightening is cut into segments according to the required size, usually by cutting or sawing, so that it gets the finished product size.

(8) Surface disposal: Finally, the surface is treated with oxidation, cleaning, etc., and the specified surface effect can be achieved before packaging, storage and transportation.

Glory Rail Main Productions: cold drawn square steel, flat steel, rail, lifting rail, stainless steel, spring steel, steel chamfer and so on.

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