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Are stainless steel CNC parts difficult to machine?

CNC machining solutions for stainless steel parts

Compared with parts of other materials, stainless steel will have more problems, causing some CNC factories to be reluctant to process stainless steel precision parts. Shenzhen Xiehe has rich experience in the processing of stainless steel precision parts, and has achieved excellent results in terms of product accuracy, stability and production efficiency. The stainless steel parts produced by our factory are usually made of conventional grades such as SS201, SS301, SS303, SS304, SS316, SS316L and SS420. Due to its good formability, compatibility, corrosion resistance and rigidity, stainless steel parts are widely used in automobile, electric power, aviation, medical, automation equipment, petroleum, food and other industries.

The following is a detailed introduction to the CNC machining difficulties and solutions of stainless steel parts.

1. Severe work hardening

Among the stainless steels, austenitic and austenitic-ferritic stainless steels have the most prominent work hardening phenomena. Due to the high plasticity of stainless steel, the material is distorted during plastic deformation, and the enhancement coefficient is large. Austenite is not stable enough, and under the action of cutting stress, part of austenite is transformed into martensite. In addition, under the action of cutting heat, the composite impurities are easily decomposed and dispersed, forming a hardened layer during the cutting process. The work hardening caused by the previous feeding or the previous process seriously affects the smooth progress of the subsequent process.

2. Lathes that require large cutting force

The cutting force of machining stainless steel is large, and the plastic deformation of stainless steel is large during the cutting process. The work hardening of stainless steel is severe, and the high thermal strength further increases the cutting resistance. The curling and breaking of chips is difficult.

3. High cutting temperature

During the cutting process, the friction between the plastic deformation and the tool is large, which generates cutting heat. In addition, the thermal conductivity of stainless steel is low, and a large amount of cutting heat is concentrated on the interface between the cutting zone and the chip, resulting in poor heat dissipation conditions.

4. Not easy to break and stick

The plasticity and toughness of stainless steel are particularly large. Continuous chipping during turning not only interferes with the smooth operation of the operation, but also crushes the machined surface. Under high temperature and high pressure, stainless steel has a strong affinity with other metals, and it is easy to stick to form a built-up edge. It increases tool wear and thus deteriorates the machined surface. This characteristic is particularly prominent in low carbon martensitic stainless steels.

5. The tool is easy to wear

The affinity in the cutting process of stainless steel leads to the bonding and diffusion of chips, resulting in bonding wear and diffusion wear on the tool. The result is a crescent crater on the rake face of the tool, as well as tiny flaking and crevices on the cutting edge. In addition, the hardness of carbide particles in stainless steel is high, and direct contact with the tool during cutting will rub the tool. The phenomenon of work hardening increases tool wear.

6. Large coefficient of linear expansion

The linear expansion coefficient of stainless steel is about 1.5 times that of carbon steel. The workpiece is prone to thermal deformation under the action of cutting temperature, and it is difficult to control the dimensional accuracy of the workpiece.

Although stainless steel precision parts are difficult to process, Shenzhen Tuofa Technology Co., Ltd. has 17 years of experience in stainless steel parts processing. Considering many factors, the solution to the problem of difficult machining of stainless steel is as follows:

A. Selection of tool material

Due to the large cutting force and high cutting temperature when machining stainless steel parts, cubic boron nitride inserts that are second only to diamond in hardness and can withstand high temperatures can be used. In addition, its chemical inertness is large, and it has no chemical interaction with iron group metals at 1200-1300 ° C, which is very suitable for the processing of stainless steel materials.

B. Tool geometry

The geometric parameters of the tool play a key role in its cutting performance. To make cutting light and smooth, carbide tools should use a larger rake angle to improve tool life. This is beneficial to strengthen the blade and give full play to the superiority of the high compressive strength of the ceramic tool. Both tool wear and insert strength are affected by the size of the relief angle. Changes in the entering angle will affect the changes in radial and axial cutting forces, as well as the size of the cutting width and cutting thickness.

C. The roughness value should be smaller when the rake face is sharpened

Chip sticking can be avoided by thoroughly sharpening the front and sides of the tool to ensure low roughness values, thereby reducing chip flow resistance and preventing chips from sticking to the knife.

D. The blade should be kept sharp

The cutting edge of the tool should be kept sharp to reduce work hardening, and the feed rate and post-cut amount should not be too small, so as to prevent the tool from cutting into the hardened layer and affecting the service life of the tool.

E. Pay attention to the grinding of the chip breaker

Due to the strong and tough characteristics of stainless steel chips, the grinding of the chip breaker on the rake face of the tool should be appropriate, so that the cutting process is convenient for chip breaking, chip holding and chip removal.

F. The choice of cutting oil should be appropriate

Since stainless steel has the characteristics of easy adhesion and poor heat dissipation, it is very important to choose a special stainless steel cutting oil with good anti-adhesion and heat dissipation performance when cutting.

G. Select the cutting amount

According to the characteristics of stainless steel materials, low speed and large feed should be used for cutting.