Failure Analysis and Surface Modification of Precision Seamless Steel Tube Cold Drawing Die

Seamless steel tube cold drawing die is a kind of precision tool made of high-hardness hard alloys. It has high cutting properties, wear resistance, and bending properties. With the development of modern industry, more and more high-precision seamless steel tube cold drawing dies have been used in the production process, increasing the requirements for their Density performance, fatigue performance, and fracture toughness.
    
Therefore, for the production of high-precision seamless steel tube cold drawing dies, it is necessary to carry out failure analysis and surface modification and other measures to ensure the stability and accuracy of their performance.
    
Failure Analysis
The failure of the seamless steel tube cold drawing die is mainly caused by the working environment such as long working hours and frequent start-stop operation, and its working surface is easily worn and scratched.
    
The failure can be divided into four aspects: steels die surface deformation, steel die cracking and spalling, damage to die cutting edge and rust corrosion of the subsurface.
    
1. Steels die surface deformation
The surface deformations of cold-drawn seamless steel tube die are mostly due to improper selection of working parameters, such as die feed speed, feed pressure, and cutting depth. In addition, the composition of the material, crystallographic orientation, and other microstructure factors also have an impact on the surface quality of the die.
    
2. Steel die cracking and spalling
Cracking and spalling defects often occur in the die cavity under the action of high pressure, resulting in chip wear, cracking, and corrosion of the die. The main reason for the fracture is due to mechanical fatigue caused by too many start-stop operations and more than one machining process.
    
3. Damage to the die cutting edge
The damage to the cutting edge is caused by high contact stress between the workpiece material and the inner and outer faces of the die. The contact stress will cause static fatigue, leading to the deformation and deformation of the cutting edge, resulting in the cutting edge being worn and becoming blunt. This can increase the working resistance and even cause the die blade to be unable to cut.
    
4. Rust corrosion of the subsurface
The subsurface of the steel tube die is prone to rust corrosion due to the humid and corrosive working environment, leading to serious rust, which makes the appearance of the die dull, reduces the appearance quality, and even affects the internal precision of the die.
    
Surface Modification
    
After the failure analysis, the surface modification should be carried out to improve the performance of the cold-drawn seamless steel tube die. The surface modification process generally includes cleaning, polishing, grinding and coating.
    
1. Cleaning
Before surface modification, the surface of cold drawn seamless steel tube die needs to be cleaned, which can remove dust and oxides on the surface and improve the performance and accuracy of the die.
    
2. Polishing
After cleaning, the surface of the die should be polished, which can improve the surface finish of the die and reduce the contact stresses between the workpiece material and the die surface.
    
3. Grinding
Grinding is used to improve the cutting performance of the seamless steel tube die. Grinding can make the cold drawn seamless steel tube die reach a mirror-like finish, reduce the friction between the workpiece material and the die surface, and reduce the wear and tear of the die.
    
4. Coating
Coating the cold drawn seamless steel tube die with a wear-resistant coating can prevent corrosion of the subsurface and protect the die from wear and tear. In addition, the coating can also improve the lubrication performance of the die and reduce the contact stresses between the workpiece material and the die surface.
    
Seamless steel tube cold drawing dies play an important role in the production process, so it is necessary to carry out failure analysis and surface modification measures to ensure the accuracy and stability of their performance. The failure analysis of the die can be divided into four aspects: steels die surface deformation, steel die cracking and spalling, damage to die cutting edge and rust corrosion of the subsurface. The surface modification of the die generally includes cleaning, polishing, grinding and coating. These steps can improve the performance and accuracy of the seamless steel tube die and ensure the stability of the production process.

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