The application of carbide tool grinding fluid-tungsten carbide tool and characteristics
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Update time : 2017-09-04 16:21:43
Carbide tools and their characteristics
In all kinds of tools,carbide tool is the most widely used.
The so-called cemented carbide, refers to the carbide (mainly tungsten carbide WC, titanium carbide TiC, tantalum carbide TaC and niobium carbide NbC) with metal bonding cobalt made by powder metallurgy alloy. The main features of the cemented carbide are:
High hardness, HV hardness of 1300 ~ 1800 kg / mm2;
Yield strength is high, reaching 4600-6000 MPa, good resistance to plastic deformation;
Thermal conductivity is small, 0.07-0.19 W / (m • k), how to reduce the heat generated during processing and take away heat is a big difficulty;
Thermal expansion coefficient is low, 5 X 10-6 ~ 6.5x10-6 ° C, about 1/3 of steel;
Brittle.
As the carbide tool material itself high hardness, brittleness, thermal conductivity is small, and thus to the tool grinding, especially the grinding of the overall balance of the overall carbide cutting tool grinding is very difficult. among them:
Tool material hardness is high, requires a greater grinding pressure;
Tool material thermal conductivity is low, does not allow excessive grinding heat;
The material of the tool is brittle and the possibility of cracking is increased.
Therefore, the carbide cutting tool requires both the grinding wheel has a good self-sharpening, but also requires a reasonable grinding technology and good cooling.
When grinding carbide cutting tools, if the grinding temperature is higher than 6000C, the tool surface will produce oxidative discoloration, resulting in varying degrees of grinding burns; serious, will make carbide cutting tool cracks. These cracks are generally relatively small, near the crack surface grinding often blue, purple, brown, yellow and other different tungsten oxide color.
The grinding fluid used in the manufacture of carbide cutting tools
For the tool manufacturer, in the tool manufacturing process, in addition to the need to consider the equipment, grinding wheel and other factors, a problem can not be ignored is a reasonable choice of grinding fluid and grinding oil.
Grinding fluid selection
Carbide material itself is higher hardness, brittle, grinding processing temperature up to 1000 ° C or so, but only a large amount of heat generated by 15% with the debris away, 8% with the workpiece away. For the grinding fluid used in the manufacture of carbide cutting tools, it should have the following performance characteristics:
Better lubrication performance, extreme pressure performance;
Excellent cooling performance, can be washed away in time grinding grinding and grinding wheel wear sand;
Better anti-foam, to ensure that the grinding fluid in the large flow and high-speed grinding state does not produce foam, effectively ensure the cooling and cleaning;
Effectively prevent the precipitation of cobalt.
Grinding oil selection
In contrast to grinding fluids, the primary purpose of using grinding oil is not to cool the cutting area, but to reduce heat generation by providing high lubricity. The requirements for grinding oils used in the manufacture of cemented carbide tools are generally as follows:
The use of higher flash point and lower evaporation of the better quality base oil, such as hydrogenated cracking base oil or synthetic base oil, so that under the same viscosity conditions, can greatly reduce oil consumption and improve the cleanliness of the working environment.
Grinding oil has a suitable viscosity, to ensure that the oil has excellent flushing performance and settling performance.
Grinding oil with a reasonable formula system, such as to avoid the use of sulfur and chlorine extreme pressure additives to prevent grinding oil on the machine non-ferrous metal parts corrosion.
Other precautions
The traditional silicon carbide grinding wheel due to the existence of low grinding efficiency, grinding force and grinding contact area surface temperature (1100 ° C or so) and other shortcomings, resulting in the existence of poor cutting tool edge, poor surface roughness and waste High rate of defects, has been gradually eliminated.
The current widely used tool manufacturing is diamond grinding wheel (Figure 9). Diamond grinding wheel grinding efficiency, grinding force is small, good self-sharpening, sharp edges, easy to passivation, and grinding contact area surface temperature is low (400 ° C or so).
For the grinding wheel binder, there are two main options:
Metal bonding agent: its good thermal conductivity, grinding force, grinding efficiency, mainly for rough slotting process (grinding groove) coarse grinding and grinding, particle size can choose 120 to 140 mesh (screen size 0.106 ~ 0.125 mm).
Resin binder: good lubricity, low grinding force, good self-sharpening, mainly used for tooth grinding process (front and rear flank, end tooth groove, partial back to the margin and other processes) (Mesh size: 0.125 to 0.180 mm) and 200 to 240 mesh (mesh size 0.061 to 0.075 mm) were selected for the grinding and grinding.
In all kinds of tools,carbide tool is the most widely used.
The so-called cemented carbide, refers to the carbide (mainly tungsten carbide WC, titanium carbide TiC, tantalum carbide TaC and niobium carbide NbC) with metal bonding cobalt made by powder metallurgy alloy. The main features of the cemented carbide are:
High hardness, HV hardness of 1300 ~ 1800 kg / mm2;
Yield strength is high, reaching 4600-6000 MPa, good resistance to plastic deformation;
Thermal conductivity is small, 0.07-0.19 W / (m • k), how to reduce the heat generated during processing and take away heat is a big difficulty;
Thermal expansion coefficient is low, 5 X 10-6 ~ 6.5x10-6 ° C, about 1/3 of steel;
Brittle.
As the carbide tool material itself high hardness, brittleness, thermal conductivity is small, and thus to the tool grinding, especially the grinding of the overall balance of the overall carbide cutting tool grinding is very difficult. among them:
Tool material hardness is high, requires a greater grinding pressure;
Tool material thermal conductivity is low, does not allow excessive grinding heat;
The material of the tool is brittle and the possibility of cracking is increased.
Therefore, the carbide cutting tool requires both the grinding wheel has a good self-sharpening, but also requires a reasonable grinding technology and good cooling.
When grinding carbide cutting tools, if the grinding temperature is higher than 6000C, the tool surface will produce oxidative discoloration, resulting in varying degrees of grinding burns; serious, will make carbide cutting tool cracks. These cracks are generally relatively small, near the crack surface grinding often blue, purple, brown, yellow and other different tungsten oxide color.
The grinding fluid used in the manufacture of carbide cutting tools
For the tool manufacturer, in the tool manufacturing process, in addition to the need to consider the equipment, grinding wheel and other factors, a problem can not be ignored is a reasonable choice of grinding fluid and grinding oil.
Grinding fluid selection
Carbide material itself is higher hardness, brittle, grinding processing temperature up to 1000 ° C or so, but only a large amount of heat generated by 15% with the debris away, 8% with the workpiece away. For the grinding fluid used in the manufacture of carbide cutting tools, it should have the following performance characteristics:
Better lubrication performance, extreme pressure performance;
Excellent cooling performance, can be washed away in time grinding grinding and grinding wheel wear sand;
Better anti-foam, to ensure that the grinding fluid in the large flow and high-speed grinding state does not produce foam, effectively ensure the cooling and cleaning;
Effectively prevent the precipitation of cobalt.
Grinding oil selection
In contrast to grinding fluids, the primary purpose of using grinding oil is not to cool the cutting area, but to reduce heat generation by providing high lubricity. The requirements for grinding oils used in the manufacture of cemented carbide tools are generally as follows:
The use of higher flash point and lower evaporation of the better quality base oil, such as hydrogenated cracking base oil or synthetic base oil, so that under the same viscosity conditions, can greatly reduce oil consumption and improve the cleanliness of the working environment.
Grinding oil has a suitable viscosity, to ensure that the oil has excellent flushing performance and settling performance.
Grinding oil with a reasonable formula system, such as to avoid the use of sulfur and chlorine extreme pressure additives to prevent grinding oil on the machine non-ferrous metal parts corrosion.
Other precautions
The traditional silicon carbide grinding wheel due to the existence of low grinding efficiency, grinding force and grinding contact area surface temperature (1100 ° C or so) and other shortcomings, resulting in the existence of poor cutting tool edge, poor surface roughness and waste High rate of defects, has been gradually eliminated.
The current widely used tool manufacturing is diamond grinding wheel (Figure 9). Diamond grinding wheel grinding efficiency, grinding force is small, good self-sharpening, sharp edges, easy to passivation, and grinding contact area surface temperature is low (400 ° C or so).
For the grinding wheel binder, there are two main options:
Metal bonding agent: its good thermal conductivity, grinding force, grinding efficiency, mainly for rough slotting process (grinding groove) coarse grinding and grinding, particle size can choose 120 to 140 mesh (screen size 0.106 ~ 0.125 mm).
Resin binder: good lubricity, low grinding force, good self-sharpening, mainly used for tooth grinding process (front and rear flank, end tooth groove, partial back to the margin and other processes) (Mesh size: 0.125 to 0.180 mm) and 200 to 240 mesh (mesh size 0.061 to 0.075 mm) were selected for the grinding and grinding.