Tribology Applied Research and Development of Metal Processing Oils
1. INTRODUCTION Metal processing oils are used to refer to lubricants, water-based lubricating fluids and ointments (including greases) used in metal cutting or metal forming after stamping, extruding or the like after mechanical cutting or electric discharge cutting. Unlike the three major oils (engine oil, hydraulic oil, and gear oil), metal processing oils only account for 1 to 2% of the lubricating oil consumption, but they vary widely due to friction conditions, requiring a wide variety of metalworking oils. The three major oils are used in large amounts, and the engine oil consumption accounts for half of the total amount of lubricants. It is estimated that by 2005, the total number of vehicles in China will reach 30 million, and the annual consumption of engine oil will reach 1.7 million tons. However, the cost of developing engine oil is very high, and rig tests required for the development of a formula abroad cost up to several million US dollars. Multinational companies seize the high-end engine oil market in China with their strong economic strength and patented technology. Although the level of engine oil developed by China itself is not low compared with foreign countries, Sinopec and CNPC's high-end products only account for 3% of the market due to unreasonable sales channels. Apart from a few types, metal processing oils are generally small in quantity and variety, and it is difficult for multinational companies to monopolize the Chinese market. Another feature is high added value, especially in scarce varieties, with a profit rate of 100% or more. Another feature is that Jinyou Oil does not generally have very strict and standardized bench test procedures like the three major oils, and it lacks an effective unified simulation test method. It mainly relies on field tests to evaluate its quality. Under this circumstance, it is of positive significance to carry out research on the application of tribology to improve the quality of metalworking oil, to solve the various lubrication problems faced, and to develop an effective simulation test method. This paper discusses the tribological issues of several major types of metalworking oils and presents its own perspective on future research directions.
2. Metal cutting lubricant
2.1 Overview Cutting lubricants account for about half of the metalworking oil consumption. The cutting oils are mainly used for difficult processing of low-speed, small-feed processing conditions, while the large-scale use of environmentally friendly, non-smoke and fire water Basic cutting fluids, water-based cutting fluids in developed countries accounted for more than 90% of total cutting lubricants in the 1980s. Water-based cutting fluid is divided into emulsion, synthetic liquid and microemulsion. Although these water-based cutting fluids all have a cooling effect, a cleaning effect, a rust prevention effect, and a lubricating effect, the overall performance of the microemulsion is superior, and the microemulsion is not easy to mold, and the waste liquid is easy to handle, but it has become the development direction in the future.
2.2 Friction and wear in cutting In addition to EDM, pulse discharge is used to partially melt the metal to achieve the purpose of cutting metal. Other cutting uses metal tools (including carbide cutting tools and ceramic cutting tools) and abrasives for metal processing.
2.2.1 Friction mechanism in cutting The cutting force during cutting is derived from the rake face and flank face. One is the elastic and plastic deformation resistance of the metal on the surface of the metal being cut, the chip and the workpiece, and the other is the frictional resistance between the knife-chip and the knife-workpiece, and the proportion of the cutting force source varies with the cutting system. Cutting heat is generated by cutting and passes through the tool, workpiece, chips, and cutting fluid. Because cutting force and cutting temperature are easier to achieve on-line inspection, it is often used as an indirect physical quantity for tool friction and breakage.
2.2.2 Wear Mechanism in Cutting Cutting is a severe friction and wear process. Tool wear not only shortens the tool life but also directly affects the precision and surface roughness of the machined part. The wear mechanism of the tool includes thermal wear and mechanical wear. The former is a special wear mechanism not encountered in engine gears and hydraulic systems, while the latter has common features.
2.2.2.1 Thermal wear includes diffuse wear, thermoelectric wear, and oxidative wear.
In the diffusion wear cutting process, the cutting pressure of the cutter is up to 2~3GPa and the cutting temperature is up to 900~1100°C. Under the conditions of cutting high temperature and high speed, the diffusion wear of the tool is much larger than that of general mechanical parts. It not only causes the tool to spread and loses material, but also increases the adhesion between the tool and the chip and increases the adhesive wear of the tool. The outward diffusion of the tool binder and the hard phase (WC and TiC) and the diffusion of the workpiece components to the tool also cause the embrittlement and softening of the tool, reducing the surface strength, increasing the adhesive wear and abrasive wear of the tool, making the front knife The surface is crescent-shaped.
Thermo-electric wear Another type of thermal wear is thermo-electric wear. Under the effect of high temperature in the cutting zone, contact between two different materials of the tool and the workpiece will generate thermo-electric and thermal currents, which will increase tool wear.
Oxidation wear When the cutting temperature is high, the tool material oxidizes violently to form a series of loose oxides, which are cut away and cause “oxidative wearâ€, causing the tool to “burn†and cause the tool to become grooved.
2.2.2.2 Mechanical wear includes abrasive wear, adhesive wear, and fatigue wear, which have in common with common wear mechanisms in machinery.
2.2.2.3 The relative importance of various wear mechanisms
figure 1
1 Abrasive wear 2 Fatigue wear 3 Adhesion wear 4 Oxidation wear 5 Thermo-electric wear 6 Diffusion wear
figure 2
(a) High-speed steel (b) Cemented carbide (c) Ceramics At low temperatures, tool wear is dominated by mechanical wear. At high temperatures, the amount of thermal wear increases with cutting temperature faster than mechanical wear. Predominantly, various types of wear contribute differently to the tool's wear strength (the amount of wear per unit of cutting process) at various temperatures (Fig. 1), and different materials have different wear characteristics (Fig. 2).
2.3 cutting lubricant anti-wear mechanism
2.3.1 Infiltration Mechanism Due to the geometry of the friction pair during cutting and the characteristics of high temperature, high pressure and high speed, the cutting fluid is inherently difficult to enter into the knives-swarf and knives-work friction contact zone. It has been speculated that cutting is powerful on the friction interface. The micro-crack under the action of the extrusion and shear stress acts as a capillary and brings the cutting fluid to the friction surface, acting as a lubricant friction surface.
2.3.2 Cooling The cooling depends on the thermal conductivity, specific heat, heat of vaporization, and lubricity of the metal surface. Therefore, the cooling capacity decreases in the following order: Synthetic fluid> Microemulsion> Emulsion> Cutting oil, cooling plays a key role in reducing the severity of cutting friction conditions.
2.3.3 Lubrication Mechanism Under extremely high temperatures and pressures in the cutting zone, it is difficult to form fluid lubrication and elastohydrodynamic lubrication conditions for a mechanical part, usually working under boundary lubrication conditions. Therefore, the cutting fluid is usually added with extreme pressure antiwear agent to form a low shear strength boundary lubricating film on the friction surface to prevent knife-chip and knife-tool adhesion, and reduce cutting force and cutting strength. For the cutting of light load during finishing, fatty acid is generally added to form a semi-solid film of fatty acid soap on the friction surface, which has a certain load-bearing capacity at 90 to 150°C. In the case of high-speed heavy-duty cutting, S, P, and Cl are added. Pressure agent, forming a high melting point solid lubricant film (FeS melting point up to 980 °C or more) under the harsh conditions of lubrication.
For a good cutting lubricant, not only good heat dissipation is required, but also good cutting performance is required. It is expected that the workpiece to be cut has large wear, the cutter used for cutting and the grinding wheel wear less, the cutting force is saved, and the tool and the grinding wheel have a long life. This is very different from the usual mechanical parts that require friction reduction and wear resistance. It also leaves a lot of room for research on cutting oil formulations with excellent cutting performance. According to reports, cutting fluids developed using new technologies can increase grinding performance by up to 130 times. Over the past few decades, research papers have focused heavily on the study of friction wear and lubrication behavior of steel-steel friction pairs, but the number of papers on the mechanism of additives for steel-grit lubrication has been limited. Yamanaka et al. studied in detail the effects of various additives in the grinding fluid used for the CBN grinding wheel, indicating that the extreme pressure agent has the best effect, especially the sulfur extreme pressure agent and the acid phosphate ester, followed by the oiliness agent, and the friction modifier is the most Poor, oily agents have the highest cutting efficiency of saturated fatty acids above C14.
2.3.4 Material Dependence of Lubrication Mechanism Two types of different materials are used for cutting tools and abrasives. The lubrication mechanism of the two is very different. Because of the brittleness of the ceramic material, it is not as easy to produce plastic deformation as the metal material in the process of friction and wear, which means that it is not easy to produce adhesive wear. The ceramic is resistant to high temperature, corrosion and wear, and it also reduces the extreme pressure antiwear agent. Chemically active, it is not easy to produce an extreme pressure solid film containing S, P, and Cl as metallic materials, which makes it difficult to lubricate.
2.3.5 Simulation Test for Evaluating the Effectiveness of Cutting Lubricants
image 3
In addition to direct testing on lathes, the following testing machines are often used:
Four-ball machine domestic evaluation Lubrication of cutting lubricant is the most commonly used four-ball machine, cutting oil to determine PB and PD, and water-based cutting fluid measured according to GB/T 6144 PB value. However, there is no plastic flow of metal in the four-ball test. The experience of the factory shows that the level of PB does not have a certain relationship with the cutting performance of the emulsion. Some emulsions with high PB values ​​tend to have relatively high soap content and high viscosity. It is easy to clog the grinding wheel. Yang Wenqing et al. proposed using PD/PB ratio as an index to evaluate lubricity, and pointed out that using a higher PD value and an appropriately low PB worth of cutting fluid can significantly reduce wheel wear and improve grinding efficiency.
It is worth noting that the use of surfactants to increase the oil film strength PB value of water-based cutting fluid is very effective, but the conventional S, P, Cl extreme pressure agent added to the water-based lubricant, the effect of improving the sintering load is very poor Perhaps the presence of water reduces the effect of these traditional extreme pressure agents. For example, the PB value of Imperial-1070 mother liquor is 85Kg, the PD value is as high as 620Kg, when it is diluted to 5% emulsion, the PB value only drops 5Kg to 80Kg, while the PD value is only 160Kg, and the sintering load of water (100-126Kg) ) The difference is not large. To effectively increase the PD value of the cutting fluid, one must rely on nanotechnology. Nanoclays can increase the PD of water by 2 levels. Add 1% 40 ~ 60nm oleic acid modified TiO2 particles, and then use tea saponin as a surfactant to disperse it evenly in water, the PD value up to 4400N.
In addition to the four-ball machine, the tapping torque tester evaluates the most of the cutting fluid lubrication using a tapping torque tester. It can directly measure the tapping torque and calculate the tapping efficiency. It can also perform a squeeze test for simulation. Drawing and rolling.
The modified Timken tester and Falex tester used electroplating or the like to change the material of the friction surface of the pin of the Timken ring block tester or the Falex pin block tester to evaluate the abrasive and additive abrasives. One of these forms is shown in Figure 3.
3. Metal plastic forming processing lubricant
3.1 Stamping and drawing technology Lubricant stamping and deep drawing is a kind of plastic deformation processing technology in mechanical manufacturing. It is difficult to spread out in a short time through the die due to the slippage of the lattice and the large amount of heat generated by the intense friction. If there is no good solution to the lubrication problems in the stamping and drawing process, when the friction reaches a certain level, the workpiece will be pulled and scrapped, which will not only directly affect the quality of the product, but also affect the life of the mold. Many large and sophisticated molds are imported and worth millions of dollars, which can cause great losses.
The part that is required for lubrication in the stamping process is the interface where the mold and the processed plate actually rub against each other. In the stamping process, it is difficult for the entire friction surface to form a continuous fluid lubricating film, and boundary lubrication and dry friction exist. At present, the quality of stamping oil in our country is not closed, resulting in wrinkling of stamping parts and a large number of scraps. The scrap rate reaches 7 to 10%. In addition, many precision molds rely on imports, each up to several million dollars. Considering the cost of repairing and scrapping the molds is much greater than the cost of oil, many manufacturers prefer to use imported stamping oils.
3.2 Cold Extrusion Process The cold extrusion of a lubricant is a processing process that does not cause the recrystallization and softening of the billet and is plastically deformed by the extrusion force. It is characterized by large deformation resistance and high mold temperature (300°C). In the past, the phosphating process was used to produce solid phosphate films on the surface of steel materials, but the film formation was slow and was not suitable for rapid processing. The lubricants using solid lubricants and high molecular polymers had better effects.
3.3 Die Casting Process Lubricants require high lubricant lubricity and adhesion, excellent lubricity, and heat dissipation. The trend is to develop non-graphite polymer water-based lubricants.
3.4 Drawing Process Lubricants A large number of rods, wires, and tubes are produced using a drawing process. Friction plays a key role in the drawing process. Different from drawing and rolling, no friction is needed. It is hoped that the lubricant can minimize the frictional wear of the drawing. Oil-based and water-based lubricants can be used, based on tribological properties and cooling capacity. The mixed lubrication condition is often encountered during drawing, but the contact geometry during the high-speed drawing plus drawing process is appropriate, and it is also possible to form plastic hydrodynamic lubrication. Fluid lubrication is the most ideal lubrication state in drawing. It can greatly reduce the friction coefficient, friction surface temperature, no wear and adhesive damage, and greatly increase the life of the mold and the surface quality of the product. Drawing requires good adhesion of the lubricant, temperature, pressure, can form a stable lubricating film, wire, wire and mold cooling and lubrication, easy to remove the lubricant film after drawing.
3.5 Rolling lubricant During the rolling process, the roll body undergoes plastic deformation under the pressure of the rotating roll, the shape changes, the length is extended, and the width is increased. The steel, copper, aluminum, zinc and its alloy can be processed by rolling. Production of bar, pipe, plate, sheet, and foil. In the past, only cold rolling could produce small and thin rolled bodies, but the energy consumption of cold rolling was large. In recent years, with the rapid development of hot rolling process lubrication, it has become possible to produce 1-2 mm thin steel strips that are qualified for hot rolling. Oil province (0.5% oil + 99.5% water mixed spray) is almost non-polluting and can reduce power consumption. The replacement of cold rolling is a new technology for energy saving and environmental protection in steel plants. Since the end of the last century, Baosteel and Anshan Iron and Steel have already introduced the 1780 hot rolling continuous rolling mill production line. Other steel mills have also followed suit and are ready to introduce hot rolling production lines or cold rolling into hot rolling. Hot oil has a broad market prospect. At present, the domestic hot-rolled oil market is basically occupied by foreign companies. In order to participate in market competition, our institute cooperates with Anshan Haihua Grease Company to develop hot-rolled oil for 1780 hot strip mill of Angang hot-rolled strip mill, which is currently in the industrial test stage. .
3.5.1 Severe working conditions of hot oil:
At high temperatures, the instantaneous temperature of the roll contacting the rolled material can reach 500-600°C.
High-pressure, hot-rolled metal receives unit pressure of 0.03-0.1Gpa (300-1000atm)
High shear, the oil film shear rate and rolling speed, the highest rolling speed up to 20m / s.
At high temperatures and pressures, the metal undergoes plastic deformation, continuously creating new contact surfaces and changing the contact conditions, adding to the difficulty of lubrication.
Hot-rolled oils work in very dilute concentrations. 0.5% hot-rolled oil and 99.5% water are mixed in a static mixer and sprayed onto a work roll. After being washed by cooling water, the actual working concentration of hot-rolled oil may be only 0.01% or less. Therefore, the lubrication performance of the hot rolling oil itself is very high, otherwise it will not achieve anti-friction and anti-wear effects.
3.5.2 The requirements for hot-rolled oils are high temperature viscosity, good adhesion, and water spreading.
Partially isolates or reduces the direct contact of the roll with water, reducing the generation of black skin and the resulting abrasive wear.
With a moderate coefficient of friction, it is necessary to reduce the rolling force and prevent it from slipping.
Good fluidity and diffusion prevent local roll wear.
Good thermal decomposition stability, not to burn and degenerate before entering the deformation zone, ash after combustion can reduce the chance of slippage.
It is non-toxic, has a small odor and meets environmental protection requirements. It does not harm workers' health. The increasingly stringent environmental protection requirements are also one of the biggest challenges to the company's oil.
Good storage stability, will not precipitate and block the nozzle and pipeline.
3.5.3 Wear in Hot Rolling Adhesive wear, abrasive wear, chemical wear and corrosion wear, and fatigue wear The four major types of wear are present in hot rolling. The situation is very complicated.
3.5.4 Effect of Roller Material The material of the roll is complex, including semi-steel roll, high-chromium steel roll, Ni-Cr steel roll and high-speed steel roll. It also has different requirements for oil, wide development adaptability and superior performance. A single type of hot rolling oil will bring great convenience to users. In order to reduce the impact of the black skin (Fe3O4 + Fe2O3 mixture) formed at high temperature on the roll wear, high-speed steel is currently used in place of other steels to prepare rolls. High-speed steel rolls are not sensitive to lubricants. In the future, the research on high-speed steel roll lubrication should be strengthened.
4. Conclusion As China's economy soars, the metal processing oil market becomes more and more widespread. Metal processing oil has the characteristics of small quantity, many varieties and high added value. It is difficult for foreign companies to fully occupy the market in China. It is necessary to step up the development of metalworking oil and participate in international competition.
The working conditions of metal processing oil are very complicated, but solving the problem of friction and wear is a key issue that must be solved in research and development. Environmental issues are also issues that must be carefully considered in formula research.
Deepening the research on the common and different friction and wear problems encountered in cutting, stamping, drawing, extruding, die-casting and rolling several major categories of processing is the necessary basic work for the development of metalworking oils.
Focus on the development of a large number of metalworking oil varieties, can achieve better economic benefits.
Development of metalworking oil additives, including extreme pressure anti-wear agents, oil agents, antioxidants, rust inhibitors, emulsifiers, demulsifiers, defoamers, fungicides and so on. In addition to the use of existing commercial additives, it is also necessary to develop new additive varieties based on the needs of special working conditions and adopt new technologies such as nanotechnology and ceramic alloy surface repair technologies.
Given the complexity of the metalworking oil market and the high demand for after-sales services, the combination of schools, research institutes, and factories and mines will give full play to their respective advantages and will promote the localization of metallurgical oil use, which will be in an advantageous position in international competition.
2. Metal cutting lubricant
2.1 Overview Cutting lubricants account for about half of the metalworking oil consumption. The cutting oils are mainly used for difficult processing of low-speed, small-feed processing conditions, while the large-scale use of environmentally friendly, non-smoke and fire water Basic cutting fluids, water-based cutting fluids in developed countries accounted for more than 90% of total cutting lubricants in the 1980s. Water-based cutting fluid is divided into emulsion, synthetic liquid and microemulsion. Although these water-based cutting fluids all have a cooling effect, a cleaning effect, a rust prevention effect, and a lubricating effect, the overall performance of the microemulsion is superior, and the microemulsion is not easy to mold, and the waste liquid is easy to handle, but it has become the development direction in the future.
2.2 Friction and wear in cutting In addition to EDM, pulse discharge is used to partially melt the metal to achieve the purpose of cutting metal. Other cutting uses metal tools (including carbide cutting tools and ceramic cutting tools) and abrasives for metal processing.
2.2.1 Friction mechanism in cutting The cutting force during cutting is derived from the rake face and flank face. One is the elastic and plastic deformation resistance of the metal on the surface of the metal being cut, the chip and the workpiece, and the other is the frictional resistance between the knife-chip and the knife-workpiece, and the proportion of the cutting force source varies with the cutting system. Cutting heat is generated by cutting and passes through the tool, workpiece, chips, and cutting fluid. Because cutting force and cutting temperature are easier to achieve on-line inspection, it is often used as an indirect physical quantity for tool friction and breakage.
2.2.2 Wear Mechanism in Cutting Cutting is a severe friction and wear process. Tool wear not only shortens the tool life but also directly affects the precision and surface roughness of the machined part. The wear mechanism of the tool includes thermal wear and mechanical wear. The former is a special wear mechanism not encountered in engine gears and hydraulic systems, while the latter has common features.
2.2.2.1 Thermal wear includes diffuse wear, thermoelectric wear, and oxidative wear.
In the diffusion wear cutting process, the cutting pressure of the cutter is up to 2~3GPa and the cutting temperature is up to 900~1100°C. Under the conditions of cutting high temperature and high speed, the diffusion wear of the tool is much larger than that of general mechanical parts. It not only causes the tool to spread and loses material, but also increases the adhesion between the tool and the chip and increases the adhesive wear of the tool. The outward diffusion of the tool binder and the hard phase (WC and TiC) and the diffusion of the workpiece components to the tool also cause the embrittlement and softening of the tool, reducing the surface strength, increasing the adhesive wear and abrasive wear of the tool, making the front knife The surface is crescent-shaped.
Thermo-electric wear Another type of thermal wear is thermo-electric wear. Under the effect of high temperature in the cutting zone, contact between two different materials of the tool and the workpiece will generate thermo-electric and thermal currents, which will increase tool wear.
Oxidation wear When the cutting temperature is high, the tool material oxidizes violently to form a series of loose oxides, which are cut away and cause “oxidative wearâ€, causing the tool to “burn†and cause the tool to become grooved.
2.2.2.2 Mechanical wear includes abrasive wear, adhesive wear, and fatigue wear, which have in common with common wear mechanisms in machinery.
2.2.2.3 The relative importance of various wear mechanisms
figure 1
1 Abrasive wear 2 Fatigue wear 3 Adhesion wear 4 Oxidation wear 5 Thermo-electric wear 6 Diffusion wear
figure 2
(a) High-speed steel (b) Cemented carbide (c) Ceramics At low temperatures, tool wear is dominated by mechanical wear. At high temperatures, the amount of thermal wear increases with cutting temperature faster than mechanical wear. Predominantly, various types of wear contribute differently to the tool's wear strength (the amount of wear per unit of cutting process) at various temperatures (Fig. 1), and different materials have different wear characteristics (Fig. 2).
2.3 cutting lubricant anti-wear mechanism
2.3.1 Infiltration Mechanism Due to the geometry of the friction pair during cutting and the characteristics of high temperature, high pressure and high speed, the cutting fluid is inherently difficult to enter into the knives-swarf and knives-work friction contact zone. It has been speculated that cutting is powerful on the friction interface. The micro-crack under the action of the extrusion and shear stress acts as a capillary and brings the cutting fluid to the friction surface, acting as a lubricant friction surface.
2.3.2 Cooling The cooling depends on the thermal conductivity, specific heat, heat of vaporization, and lubricity of the metal surface. Therefore, the cooling capacity decreases in the following order: Synthetic fluid> Microemulsion> Emulsion> Cutting oil, cooling plays a key role in reducing the severity of cutting friction conditions.
2.3.3 Lubrication Mechanism Under extremely high temperatures and pressures in the cutting zone, it is difficult to form fluid lubrication and elastohydrodynamic lubrication conditions for a mechanical part, usually working under boundary lubrication conditions. Therefore, the cutting fluid is usually added with extreme pressure antiwear agent to form a low shear strength boundary lubricating film on the friction surface to prevent knife-chip and knife-tool adhesion, and reduce cutting force and cutting strength. For the cutting of light load during finishing, fatty acid is generally added to form a semi-solid film of fatty acid soap on the friction surface, which has a certain load-bearing capacity at 90 to 150°C. In the case of high-speed heavy-duty cutting, S, P, and Cl are added. Pressure agent, forming a high melting point solid lubricant film (FeS melting point up to 980 °C or more) under the harsh conditions of lubrication.
For a good cutting lubricant, not only good heat dissipation is required, but also good cutting performance is required. It is expected that the workpiece to be cut has large wear, the cutter used for cutting and the grinding wheel wear less, the cutting force is saved, and the tool and the grinding wheel have a long life. This is very different from the usual mechanical parts that require friction reduction and wear resistance. It also leaves a lot of room for research on cutting oil formulations with excellent cutting performance. According to reports, cutting fluids developed using new technologies can increase grinding performance by up to 130 times. Over the past few decades, research papers have focused heavily on the study of friction wear and lubrication behavior of steel-steel friction pairs, but the number of papers on the mechanism of additives for steel-grit lubrication has been limited. Yamanaka et al. studied in detail the effects of various additives in the grinding fluid used for the CBN grinding wheel, indicating that the extreme pressure agent has the best effect, especially the sulfur extreme pressure agent and the acid phosphate ester, followed by the oiliness agent, and the friction modifier is the most Poor, oily agents have the highest cutting efficiency of saturated fatty acids above C14.
2.3.4 Material Dependence of Lubrication Mechanism Two types of different materials are used for cutting tools and abrasives. The lubrication mechanism of the two is very different. Because of the brittleness of the ceramic material, it is not as easy to produce plastic deformation as the metal material in the process of friction and wear, which means that it is not easy to produce adhesive wear. The ceramic is resistant to high temperature, corrosion and wear, and it also reduces the extreme pressure antiwear agent. Chemically active, it is not easy to produce an extreme pressure solid film containing S, P, and Cl as metallic materials, which makes it difficult to lubricate.
2.3.5 Simulation Test for Evaluating the Effectiveness of Cutting Lubricants
image 3
In addition to direct testing on lathes, the following testing machines are often used:
Four-ball machine domestic evaluation Lubrication of cutting lubricant is the most commonly used four-ball machine, cutting oil to determine PB and PD, and water-based cutting fluid measured according to GB/T 6144 PB value. However, there is no plastic flow of metal in the four-ball test. The experience of the factory shows that the level of PB does not have a certain relationship with the cutting performance of the emulsion. Some emulsions with high PB values ​​tend to have relatively high soap content and high viscosity. It is easy to clog the grinding wheel. Yang Wenqing et al. proposed using PD/PB ratio as an index to evaluate lubricity, and pointed out that using a higher PD value and an appropriately low PB worth of cutting fluid can significantly reduce wheel wear and improve grinding efficiency.
It is worth noting that the use of surfactants to increase the oil film strength PB value of water-based cutting fluid is very effective, but the conventional S, P, Cl extreme pressure agent added to the water-based lubricant, the effect of improving the sintering load is very poor Perhaps the presence of water reduces the effect of these traditional extreme pressure agents. For example, the PB value of Imperial-1070 mother liquor is 85Kg, the PD value is as high as 620Kg, when it is diluted to 5% emulsion, the PB value only drops 5Kg to 80Kg, while the PD value is only 160Kg, and the sintering load of water (100-126Kg) ) The difference is not large. To effectively increase the PD value of the cutting fluid, one must rely on nanotechnology. Nanoclays can increase the PD of water by 2 levels. Add 1% 40 ~ 60nm oleic acid modified TiO2 particles, and then use tea saponin as a surfactant to disperse it evenly in water, the PD value up to 4400N.
In addition to the four-ball machine, the tapping torque tester evaluates the most of the cutting fluid lubrication using a tapping torque tester. It can directly measure the tapping torque and calculate the tapping efficiency. It can also perform a squeeze test for simulation. Drawing and rolling.
The modified Timken tester and Falex tester used electroplating or the like to change the material of the friction surface of the pin of the Timken ring block tester or the Falex pin block tester to evaluate the abrasive and additive abrasives. One of these forms is shown in Figure 3.
3. Metal plastic forming processing lubricant
3.1 Stamping and drawing technology Lubricant stamping and deep drawing is a kind of plastic deformation processing technology in mechanical manufacturing. It is difficult to spread out in a short time through the die due to the slippage of the lattice and the large amount of heat generated by the intense friction. If there is no good solution to the lubrication problems in the stamping and drawing process, when the friction reaches a certain level, the workpiece will be pulled and scrapped, which will not only directly affect the quality of the product, but also affect the life of the mold. Many large and sophisticated molds are imported and worth millions of dollars, which can cause great losses.
The part that is required for lubrication in the stamping process is the interface where the mold and the processed plate actually rub against each other. In the stamping process, it is difficult for the entire friction surface to form a continuous fluid lubricating film, and boundary lubrication and dry friction exist. At present, the quality of stamping oil in our country is not closed, resulting in wrinkling of stamping parts and a large number of scraps. The scrap rate reaches 7 to 10%. In addition, many precision molds rely on imports, each up to several million dollars. Considering the cost of repairing and scrapping the molds is much greater than the cost of oil, many manufacturers prefer to use imported stamping oils.
3.2 Cold Extrusion Process The cold extrusion of a lubricant is a processing process that does not cause the recrystallization and softening of the billet and is plastically deformed by the extrusion force. It is characterized by large deformation resistance and high mold temperature (300°C). In the past, the phosphating process was used to produce solid phosphate films on the surface of steel materials, but the film formation was slow and was not suitable for rapid processing. The lubricants using solid lubricants and high molecular polymers had better effects.
3.3 Die Casting Process Lubricants require high lubricant lubricity and adhesion, excellent lubricity, and heat dissipation. The trend is to develop non-graphite polymer water-based lubricants.
3.4 Drawing Process Lubricants A large number of rods, wires, and tubes are produced using a drawing process. Friction plays a key role in the drawing process. Different from drawing and rolling, no friction is needed. It is hoped that the lubricant can minimize the frictional wear of the drawing. Oil-based and water-based lubricants can be used, based on tribological properties and cooling capacity. The mixed lubrication condition is often encountered during drawing, but the contact geometry during the high-speed drawing plus drawing process is appropriate, and it is also possible to form plastic hydrodynamic lubrication. Fluid lubrication is the most ideal lubrication state in drawing. It can greatly reduce the friction coefficient, friction surface temperature, no wear and adhesive damage, and greatly increase the life of the mold and the surface quality of the product. Drawing requires good adhesion of the lubricant, temperature, pressure, can form a stable lubricating film, wire, wire and mold cooling and lubrication, easy to remove the lubricant film after drawing.
3.5 Rolling lubricant During the rolling process, the roll body undergoes plastic deformation under the pressure of the rotating roll, the shape changes, the length is extended, and the width is increased. The steel, copper, aluminum, zinc and its alloy can be processed by rolling. Production of bar, pipe, plate, sheet, and foil. In the past, only cold rolling could produce small and thin rolled bodies, but the energy consumption of cold rolling was large. In recent years, with the rapid development of hot rolling process lubrication, it has become possible to produce 1-2 mm thin steel strips that are qualified for hot rolling. Oil province (0.5% oil + 99.5% water mixed spray) is almost non-polluting and can reduce power consumption. The replacement of cold rolling is a new technology for energy saving and environmental protection in steel plants. Since the end of the last century, Baosteel and Anshan Iron and Steel have already introduced the 1780 hot rolling continuous rolling mill production line. Other steel mills have also followed suit and are ready to introduce hot rolling production lines or cold rolling into hot rolling. Hot oil has a broad market prospect. At present, the domestic hot-rolled oil market is basically occupied by foreign companies. In order to participate in market competition, our institute cooperates with Anshan Haihua Grease Company to develop hot-rolled oil for 1780 hot strip mill of Angang hot-rolled strip mill, which is currently in the industrial test stage. .
3.5.1 Severe working conditions of hot oil:
At high temperatures, the instantaneous temperature of the roll contacting the rolled material can reach 500-600°C.
High-pressure, hot-rolled metal receives unit pressure of 0.03-0.1Gpa (300-1000atm)
High shear, the oil film shear rate and rolling speed, the highest rolling speed up to 20m / s.
At high temperatures and pressures, the metal undergoes plastic deformation, continuously creating new contact surfaces and changing the contact conditions, adding to the difficulty of lubrication.
Hot-rolled oils work in very dilute concentrations. 0.5% hot-rolled oil and 99.5% water are mixed in a static mixer and sprayed onto a work roll. After being washed by cooling water, the actual working concentration of hot-rolled oil may be only 0.01% or less. Therefore, the lubrication performance of the hot rolling oil itself is very high, otherwise it will not achieve anti-friction and anti-wear effects.
3.5.2 The requirements for hot-rolled oils are high temperature viscosity, good adhesion, and water spreading.
Partially isolates or reduces the direct contact of the roll with water, reducing the generation of black skin and the resulting abrasive wear.
With a moderate coefficient of friction, it is necessary to reduce the rolling force and prevent it from slipping.
Good fluidity and diffusion prevent local roll wear.
Good thermal decomposition stability, not to burn and degenerate before entering the deformation zone, ash after combustion can reduce the chance of slippage.
It is non-toxic, has a small odor and meets environmental protection requirements. It does not harm workers' health. The increasingly stringent environmental protection requirements are also one of the biggest challenges to the company's oil.
Good storage stability, will not precipitate and block the nozzle and pipeline.
3.5.3 Wear in Hot Rolling Adhesive wear, abrasive wear, chemical wear and corrosion wear, and fatigue wear The four major types of wear are present in hot rolling. The situation is very complicated.
3.5.4 Effect of Roller Material The material of the roll is complex, including semi-steel roll, high-chromium steel roll, Ni-Cr steel roll and high-speed steel roll. It also has different requirements for oil, wide development adaptability and superior performance. A single type of hot rolling oil will bring great convenience to users. In order to reduce the impact of the black skin (Fe3O4 + Fe2O3 mixture) formed at high temperature on the roll wear, high-speed steel is currently used in place of other steels to prepare rolls. High-speed steel rolls are not sensitive to lubricants. In the future, the research on high-speed steel roll lubrication should be strengthened.
4. Conclusion As China's economy soars, the metal processing oil market becomes more and more widespread. Metal processing oil has the characteristics of small quantity, many varieties and high added value. It is difficult for foreign companies to fully occupy the market in China. It is necessary to step up the development of metalworking oil and participate in international competition.
The working conditions of metal processing oil are very complicated, but solving the problem of friction and wear is a key issue that must be solved in research and development. Environmental issues are also issues that must be carefully considered in formula research.
Deepening the research on the common and different friction and wear problems encountered in cutting, stamping, drawing, extruding, die-casting and rolling several major categories of processing is the necessary basic work for the development of metalworking oils.
Focus on the development of a large number of metalworking oil varieties, can achieve better economic benefits.
Development of metalworking oil additives, including extreme pressure anti-wear agents, oil agents, antioxidants, rust inhibitors, emulsifiers, demulsifiers, defoamers, fungicides and so on. In addition to the use of existing commercial additives, it is also necessary to develop new additive varieties based on the needs of special working conditions and adopt new technologies such as nanotechnology and ceramic alloy surface repair technologies.
Given the complexity of the metalworking oil market and the high demand for after-sales services, the combination of schools, research institutes, and factories and mines will give full play to their respective advantages and will promote the localization of metallurgical oil use, which will be in an advantageous position in international competition.
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