1, Definition and classification of difficult to process materials
Difficult to machine materials usually refer to those materials that have low processing efficiency, severe tool wear, poor surface quality, and high processing costs due to their high hardness, toughness, poor thermal conductivity, and high chemical activity during mechanical processing such as cutting and grinding. These materials have a wide range of applications in high-tech industries such as aerospace, petroleum, chemical, weapons, and atomic energy. Therefore, improving their processing efficiency and quality has always been an important direction for the development of CNC machining technology.
Difficult to process materials can be roughly divided into the following categories:
High hardness materials, such as quenched steel, hard alloys, ceramics, etc., have much higher hardness than conventional cutting tools, resulting in severe tool wear, high cutting force, and high cutting temperature during the cutting process.
High toughness materials, such as stainless steel, titanium alloys, etc., are prone to plastic deformation during the cutting process, resulting in increased cutting force, difficulty in dissipating cutting heat, and the formation of chip deposits, which affect the surface quality of the processed material.
Low thermal conductivity materials, such as titanium alloys and certain high-temperature alloys, have poor thermal conductivity and are difficult to dissipate cutting heat during the cutting process, leading to a sharp increase in cutting temperature and accelerating tool wear.
Materials with high chemical activity or strong affinity, such as titanium alloys, aluminum alloys, etc., are prone to chemical reactions or affinity interactions with tool materials during cutting, resulting in tool adhesion, diffusion wear, and shortened tool service life.
2, Specific analysis of difficult to process materials
stainless steel
Stainless steel has a wide range of applications in kitchenware, medical equipment, chemical containers, and other fields due to its excellent corrosion resistance and high temperature strength. However, stainless steel has high work hardening properties and is prone to plastic deformation during cutting, resulting in increased cutting force, higher cutting temperature, and shorter tool life. Meanwhile, stainless steel has low thermal conductivity, making it difficult for cutting heat to dissipate, further exacerbating tool wear. In addition, stainless steel has a high affinity, which can easily cause chip deposits on the cutting edge and attachments on the back cutting surface, affecting the quality of the machined surface.
titanium alloy
Titanium alloys have the advantages of low density, high strength, and good corrosion resistance, and are widely used in fields such as aerospace, automotive, and medical equipment manufacturing. However, the cutting machinability of titanium alloys is poor, mainly manifested by poor thermal conductivity and difficulty in spreading cutting heat, resulting in a short tool life. At the same time, titanium alloy has a high affinity and chemical activity, which makes it easy to bond and diffuse with metals in contact, resulting in severe tool wear. In addition, titanium alloys have low elastic modulus and large elastic deformation, which can result in a large contact area between the machined surface and the back cutting surface, leading to severe wear.
Quenched steel
Hardened steel is a type of steel that has undergone quenching treatment. It has high hardness and strength, and is commonly used in the manufacture of components that require high loads and impacts. However, the hardness of quenched steel is much higher than that of conventional cutting tools, resulting in severe tool wear, high cutting force, and high cutting temperature during the cutting process. In addition, quenched steel has high toughness and is prone to cracking and chipping during cutting, which affects the quality of the machined surface and tool life.
Hard alloy
Hard alloy is a composite material made by powder metallurgy of metal carbides (such as WC, TiC, etc.) and metal binders (such as Co, Ni, etc.). It has extremely high hardness and wear resistance, and is commonly used in the manufacture of cutting tools and wear-resistant parts. However, the high hardness and toughness of hard alloys make their processing very difficult. During the cutting process, hard alloys are prone to high temperatures and pressures, leading to severe tool wear and high cutting forces. At the same time, the brittleness of hard alloys is also high, and cracks and fractures are prone to occur during processing.
3, Processing strategies for difficult to process materials
For the above-mentioned difficult to machine materials, a series of strategies need to be adopted in the CNC machining process to improve machining efficiency and quality, and reduce machining costs. These strategies include:
Choosing the appropriate tool material: Based on the characteristics of different difficult to machine materials, selecting the appropriate tool material is the key to improving machining efficiency and quality. For difficult to machine materials such as stainless steel and titanium alloys, hard alloy cutting tools or cubic boron nitride (CBN) cutting tools can be used; For materials with extremely high hardness such as quenched steel, ceramic or diamond cutting tools can be used.
Optimizing cutting parameters: Reasonable cutting parameter settings can significantly improve machining efficiency and quality. For difficult to machine materials, cutting speed and feed rate should be appropriately reduced, cutting depth should be increased to reduce cutting force and cutting heat, and tool wear should be reduced. At the same time, appropriate cutting fluid should be selected to reduce cutting temperature and minimize tool wear.
By adopting advanced processing technologies such as high-speed cutting, ultrasonic assisted cutting, laser assisted cutting, etc., the processing efficiency and quality of difficult to machine materials can be significantly improved. These technologies effectively reduce tool wear and machining costs by increasing cutting speed, reducing cutting force and cutting temperature, and improving cutting conditions.
Strengthen tool management and maintenance: For difficult to machine materials, the wear rate of tools is relatively fast, so it is necessary to strengthen the management and maintenance of tools. This includes regular replacement of tools, inspection of tool wear, timely cleaning and lubrication of tools to ensure their good condition and machining efficiency.
