Tough to grind material
1. Type
- l Materials with high brittleness, toughness and ductility
- l High hardness material
- l Material with high chemical activity - titanium alloy
- l High temperature and high strength materials
2. Characteristic
- l Large grinding force;
- l High cutting temperature;
- l Material hardening in grinding;
- l High wear of abrasive tool;
- l Low grinding efficiency.
3. Machining of typical tough to grind materials
3.1 Stainless steel material
Stainless steel grinding features:
- l Large grinding force and high grinding temperature;
- l Material hardening in grinding;
- l The debris easy to stick with grinding wheel, so that the gap between the abrasives is blocked;
- l The debris is difficult to clean, the abrasive particles are easy to blunt, and the grinding wheel is rapidly worn;
- l The machined surface is easy to burn;
- l The workpiece surface is easy to scratch;
- l The workpiece is easy to deform.
Abrasive type: CBN > SA / MA > WA.
Particle size: coarse grinding B251 or B301; Finish grinding B151 or B126.
Bond: Vitrfied bond can be recommended, with good waterproof, heat resistance and corrosion resistance; Resin bond can be recommended for cutting, slotting and centerless grinding.
Grinding parameters: if the grinding depth is too small, the abrasive particles can not cut into the workpiece material, but slide and squeeze on the surface, resulting in the increase of grinding force and grinding heat, the abrasive debris is easy to adhere and block the surface of the grinding wheel, which reduces the cutting performance of the grinding wheel and causes the surface burn of the workpiece;
When the grinding depth is too large, the total grinding force and grinding heat will increase, and it is also easy to burn.
3.2 Superalloy steel material
Grinding characteristics of Superalloy steel:
Large plastic deformation;
Large grinding and cutting force;
Severe work hardening;
High grinding temperature;
The service life of abrasive tools is short.
Abrasive type: CBN > SA / WA / PA.
3.3 Titanium alloy material
Material characteristics: High specific strength; Good heat resistance; Good corrosion resistance; Low thermal conductivity; Small elastic modulus.
Grinding characteristics:
The exothermic phenomenon in the grinding area is the main cause of burns. The exothermic result changes the metallographic structure of the surface of the workpiece and greatly changes its mechanical and service properties.
Large grinding force and high grinding temperature;
The deformation during grinding is complex;
The adhesion of the grinding wheel is serious, and the falling off of the adhesion can lead to the breakage and falling off of the grinding particles of the grinding wheel;
Titanium alloy has strong chemical activity. Under the action of high temperature, it is easy for Al, C, O, N and other elements to form a variety of compounds, which makes the surface of titanium alloy change α Phase strengthening.
Abrasive type: Diamond / CBN > SiC.
3.4 Other difficult grinding materials (thermal spraying alloy; new high speed steel; steel-based cemented carbide; ball milled cast iron; copper and aluminum alloy; engineering ceramics)
Thermal spraying alloy
Including nickel base alloy, cobalt base alloy and iron base alloy spraying materials.
Grinding features: low durability of grinding wheel, easy to blunt, and reduced grinding force; It is easy to produce vibration. Due to the uneven surface and uneven hardness of the coating, the uneven force during grinding will produce vibration and impact; High grinding temperature.
New high speed steel
It refers to the steel that changes other components on the basis of ordinary high-speed steel to improve the strength, toughness, red hardness and other physical and mechanical properties of the material. It is widely used as tool material.
Grinding features: High hardness; Large grinding force; Poor thermal conductivity, high grinding temperature and easy blockage, resulting in workpiece burn.
Steel base cemented carbide
It refers to the material made by powder metallurgy with tool steel or alloy steel as bonding phase and metal carbide as hard phase.
Grinding features: high hardness and high strength. Resin bonded diamond grinding wheel is usually used.
Ball milled cast iron material
It has the dual properties of steel and cast iron, and the properties of steel are more obvious. Vitrified bond diamond wheel / resin / Vitrified bond CBN wheel can be selected.
Copper and aluminum alloy materials
Grinding characteristics:
Grinding debris is easy to block the grinding wheel;
The workpiece surface is easy to scratch and has low roughness;
The workpiece is easy to deform;
Low grinding efficiency.
Engineering ceramic materials
Features: high hardness, heat resistance, corrosion resistance, wear resistance, light weight and great brittleness.
Types of ceramics: alumina system, zirconia system, silicon nitride system and silicon carbide system.
Commonly used diamond grinding wheel processing, generally through rough grinding → semi fine grinding → fine grinding → mirror grinding and other processes to achieve mirror effect.
