Critical factors in drawing cold-drawn tubes

Selection of material

Cold-drawn cylinder is made of hot-rolled pipe, the material, specification and quality of hot-rolled pipe directly affect the quality of drawing and finished products.
Selection of materials should pay attention to the following points:
(1) in the selection of materials generally in the case of strength guarantee, select the low hardness, good plasticity of the material;
(2) steel pipe specifications should be selected according to the specifications of the finished product to ensure that its elongation in twenty to forty per cent; elongation is too small, the strength of the finished product surface can not be guaranteed, too large, making it difficult to pull system;
(3) The surface of the material must not have serious defects such as pits, cracks, fissures, folding, scars, ovals, etc.;
(4) It is best to select the steel pipe placed 0.5~2a after hot rolling, too short a time, the steel pipe surface corrosion shallow, too long a time, the steel pipe surface corrosion is too deep, all of these will lead to inadequate pretreatment of the steel pipe surface, thus affecting the finished product surface quality.

Pre-treatment

Without pre-treatment of the steel pipe, cold drawing due to the friction coefficient between the surface of the steel pipe and the mould is too large to make the pulling system can not be carried out; only after the pre-treatment process, so that the steel pipe rust removal, and through phosphating, saponification and other treatments, so that its internal and external surfaces to form a dense film of metal soap to reduce the friction between the steel pipe and the mould to ensure the smooth progress of the pulling system. At the same time, through the pre-treatment can also reduce the loss rate of the mould, improve the rate of finished products and work efficiency, and make the surface of the finished product after processing smooth and uniform, rust effect.
Steel pipe pretreatment should pay attention to the following points:
(1) Pickling and rust removal should be thorough, once the rust is found to be not removed, it is necessary to pickle again.
(2) In the production, should often test the phosphate solution and saponification solution composition concentration, to ensure that the phosphate solution and saponification solution production indicators, found to be unable to meet the indicators, should be promptly deployed.
(3) To strictly control the temperature of the treatment solution and operating time.

Design of mould

Cold-drawn tube is under the action of force, through a certain shape, size of the mould drawn into the mould size accuracy, surface quality directly affects the dimensional accuracy and quality of the finished product.
Mould design should pay attention to the following aspects:
(1) inside and outside the mould sizing size should be considered after the cold drawing of the finished product rebound, general low hardness, deformation of the material, its rebound is small, high hardness, deformation of the material, its rebound is large;
(2) The surface of the mould should have low roughness requirements, generally take the value of one or two levels lower than the finished product;
(3) Mould material selection of high-strength wear-resistant materials.