How to choose cutting fluid under different metal cutting conditions?
Jan 16, 2024
Regarding different cutting methods, the cutting characteristics of the same metal are different, and the changes in machining difficulty are also different and significant. For example, when using Q235 carbon steel data, in order to ensure the quality policy of surface roughness, it is difficult to cut other surfaces when machining threads. Fine machining is difficult to rough machining. Difficult machining requires higher cutting fluid. The correct use of cutting fluid can ensure machining quality, extend the service life of cutting tools, and improve machining ability.
Rough machining
When CNC machine tools require rough and precision machining, or when the workpiece is not completed on the same machine, cutting fluid can be selected based on the characteristics of rough and precision machining. In rough machining, both the back cutting amount and feed rate are large, resulting in high cutting resistance, which generates a large amount of cutting heat. The heat transferred to the workpiece and tool increases accordingly, causing thermal deformation of the workpiece and increased tool wear. A water-based cutting fluid with cooling as the main method and certain smooth cleaning and rust prevention functions should be selected, and continuous pouring should be carried out under high flow rate. When turning is attributed to continuous machining or uniform rough machining allowance, cutting heat is the key issue to consider, and the cooling effect of cutting fluid is the primary measure.
In milling or machining with irregular shapes, uneven allowances, and intermittent machining, the cutting speed is lower than that of continuous uniform machining, and the impact of cutting heat on the tool and workpiece is less than that of impact and vibration. The smoothness and cooling effect of the cutting fluid should be balanced. If the machine tool conditions permit, the internal hole lathe, boring cutter and slotting cutter with internal liquid supply hole can be used for hole processing and blocking, and pressure liquid supply can also be used. The spray liquid supply can be used for rough machining of difficult machining data, which can play a good role.
Rough machining workpieces generally have machining allowances. In addition, when processing difficult to process data and non-ferrous metal data, the policy requirements for surface roughness accuracy are not high. So when processing difficult to process data and non-ferrous metal data, the chemical composition of the cutting fluid is not high during rough machining, and water-based emulsions can be used.
When rough machining cast iron and brittle non-ferrous metals, the common feature of these data is that the chips are breaking and fine chips are moving under the impact of cutting fluid. When the cutting fluid circulates, most of it will accumulate as it flows through the cutting fluid tank, and some will move with the cutting fluid, blocking the cooling nozzle and causing chips to adhere to the moving parts of the machine tool (such as the guide rail motion pair). Chemical reactions occur between cutting fluid and some components in cast iron, leading to the disintegration of cutting fluid and a decrease in its function. Because cutting fluid can cause these problems, cutting fluid is generally not used. In order to reduce the impact of dust and cutting heat, if conditions permit, vacuum equipment can be considered to absorb dust, small debris, and some heat. Assuming the use of cutting fluid, it is easy to use water-based cutting fluid, and it is necessary to do a good job in filtering and purifying the cutting fluid to avoid the disintegration and concentration reduction of the cutting fluid. In rough machining, the concentration of cutting fluid is lower than that in precision machining.
finish machining
According to the different cutting speeds, precision machining can be divided into high-speed precision machining and low-speed precision machining. In high-speed precision machining, oil-based cutting fluid can ensure the appearance quality of the workpiece and extend the service life of the tool. However, the viscosity and flash point of the mineral oil contained in it are low, and oil fumes, oil mist, and oil vapor often appear, distinguishing toxic components together, affecting the production environment, and endangering the physical and mental health of operators. Therefore, when finishing high-speed cutting, try to use lotion or micro lotion containing extreme pressure additives in water-based cutting fluid, whose concentration should be higher than that during rough machining. When low-speed precision machining, the cutting temperature is low and the above problems are not easy to occur. To ensure the machining accuracy of the workpiece, oil-based cutting fluid should be used.
In terms of rough machining, during precision machining, the cutting speed is high, the cutting heat generated by chip deformation is lower than the cutting heat generated by tool surface conflict, and the cutting force is small. Even in high-speed cutting, the thermal deformation of the workpiece caused by cutting heat is not as obvious as in rough machining, and the main reason for using cutting fluid on the tool is to reduce the wear of the back face of the tool. During precision machining, the relative cutting speed of the tool is high, and the instantaneous temperature of the chip when it is cut off from the workpiece is very high. Even with the use of cutting fluid, if the cutting fluid does not fully penetrate the cutting area due to permeability or pressure difference, it will still make the cutting surface prone to wear. Even if the tool can still be used, the surface roughness and quality of the workpiece cannot meet the requirements, so it is still necessary to replace the tool. Therefore, in precision machining, it is necessary to use cutting fluids with obvious smoothness and good permeability to extend the service life of the tool, ensure the machining accuracy and surface roughness quality requirements of the workpiece.
When completing black metal data at low speed, active extreme pressure cutting oil can be selected; When low-speed precision machining non-ferrous metals, non active extreme pressure cutting oil should be selected; Non active extreme pressure additive lotion can be selected for high-speed finishing of non-ferrous metals.
Hole processing
In CNC machining, hole machining mainly refers to drilling, reaming, turning inner holes on a lathe, and boring holes on a boring machine. Due to difficulties in chip removal and heat dissipation, as well as poor rigidity of the tool (rod), the cutting speed of hole machining is lower than that of external induction machining, and the difficulty is higher than that of external induction machining.
When drilling, ordinary Fried Dough Twists drills are used for drilling, which is attributed to rough machining. It is difficult to remove chips during drilling and it is not easy to generate cutting heat, which often leads to annealing of the blade and affects the service life and processing power of the drill bit. Choosing a cutting fluid with good performance can significantly prolong the lifespan of the drill bit and improve productivity. Generally, extreme pressure emulsion or extreme pressure composite cutting fluid is chosen. The cutting fluid composed of extreme pressure has low surface tension, good permeability, and can cool the drill bit in a timely manner. It is very useful for extending the service life of cutting tools and improving machining ability. For difficult to cut data such as stainless steel and heat-resistant alloys, low viscosity extreme pressure cutting oil can be selected.
When drilling, whether it is ordinary drilling or deep drilling, the heat dissipation conditions are very poor, which will generate a large amount of cutting heat. The direction of chip removal is opposite to the feed direction of the drill bit. Cutting fluid needs to enter the edge of the drill bit to make it smooth, cool, and aid in chip removal. Cutting fluid must first have excellent permeability, and the supply method, flow rate, and pressure must also meet the requirements.
In terms of the life policy of floating drill bits, oil-based cutting fluid is better than water-based cutting fluid, the extreme pressure micro lotion in water-based cutting fluid is better, and the low viscosity active sulfide oil in oil-based cutting fluid is better in all cutting fluids.
Because reaming belongs to low-speed chips in precision machining, two quality policies should be emphasized when reaming, namely the standard accuracy of reaming and the accuracy of surface roughness, as well as the service life policy of reamer fitting accuracy.
In the policy of controlling pore size, oil-based cutting fluid expands pore size, mineral oil expands pore size, extreme pressure cutting oil is smaller, and active sulfurized chlorinated oil is smaller; The water-based cutting fluid reduces the pore size, the sulfur containing extreme pressure micro lotion and micro lotion reduce the pore size more, and the lotion is in the middle, making the cutting fluid smaller. In view of this, in order to control the standard of hole enlargement, water-based cutting fluid is used when using new reamers, making it difficult to enlarge the hole. When the reamer is worn to a certain extent, oil-based cutting fluid can be used to slightly enlarge the aperture.
In terms of policies to reduce the surface roughness of enlarged holes, water-based cutting fluids are superior to oil-based cutting fluids. In oil-based cutting fluids, active sulfurized chlorinated oil has a better effect, followed by chlorinated extreme pressure oil, mixed mineral oil, and pure mineral oil. In water-based cutting fluid, lotion, micro lotion and sulfur containing extreme pressure micro lotion have the same effect, but the composition of cutting fluid is worse.
In terms of controlling the service life of the reamer, the non active extreme pressure cutting oil and anti friction cutting oil in oil-based cutting fluids have better functions; In water-based cutting fluids, the composition of the cutting fluid is worse.
Except for the floating boring cutter, turning the inner hole and boring hole is a single edge cutting, and the heat dissipation conditions are worse than those of the outer circle. The use of cutting fluid is the same as drilling and reaming, so the flow rate and pressure should be appropriately increased.
Thread processing
Thread processing belongs to forming processing. When tapping, it belongs to multi edge low-speed cutting, where the cutting edge is surrounded by cutting data, the cutting torque is high, chip removal is difficult, heat cannot be carried away by the chips in time, the chips are stuck and vibrate briefly, and tool wear is simple. Especially when tapping threads, the cutting conditions are more stringent: the chip removal space is narrow, and the chips are not easy to break and flow out. Cutting and conflicting forces are generated during tapping and chip removal, which can easily lead to tap breakage. Require cutting fluid to have a low conflict coefficient and good permeability, in order to reduce the tool's conflict resistance and extend its service life.
Rough machining
When CNC machine tools require rough and precision machining, or when the workpiece is not completed on the same machine, cutting fluid can be selected based on the characteristics of rough and precision machining. In rough machining, both the back cutting amount and feed rate are large, resulting in high cutting resistance, which generates a large amount of cutting heat. The heat transferred to the workpiece and tool increases accordingly, causing thermal deformation of the workpiece and increased tool wear. A water-based cutting fluid with cooling as the main method and certain smooth cleaning and rust prevention functions should be selected, and continuous pouring should be carried out under high flow rate. When turning is attributed to continuous machining or uniform rough machining allowance, cutting heat is the key issue to consider, and the cooling effect of cutting fluid is the primary measure.
In milling or machining with irregular shapes, uneven allowances, and intermittent machining, the cutting speed is lower than that of continuous uniform machining, and the impact of cutting heat on the tool and workpiece is less than that of impact and vibration. The smoothness and cooling effect of the cutting fluid should be balanced. If the machine tool conditions permit, the internal hole lathe, boring cutter and slotting cutter with internal liquid supply hole can be used for hole processing and blocking, and pressure liquid supply can also be used. The spray liquid supply can be used for rough machining of difficult machining data, which can play a good role.
Rough machining workpieces generally have machining allowances. In addition, when processing difficult to process data and non-ferrous metal data, the policy requirements for surface roughness accuracy are not high. So when processing difficult to process data and non-ferrous metal data, the chemical composition of the cutting fluid is not high during rough machining, and water-based emulsions can be used.
When rough machining cast iron and brittle non-ferrous metals, the common feature of these data is that the chips are breaking and fine chips are moving under the impact of cutting fluid. When the cutting fluid circulates, most of it will accumulate as it flows through the cutting fluid tank, and some will move with the cutting fluid, blocking the cooling nozzle and causing chips to adhere to the moving parts of the machine tool (such as the guide rail motion pair). Chemical reactions occur between cutting fluid and some components in cast iron, leading to the disintegration of cutting fluid and a decrease in its function. Because cutting fluid can cause these problems, cutting fluid is generally not used. In order to reduce the impact of dust and cutting heat, if conditions permit, vacuum equipment can be considered to absorb dust, small debris, and some heat. Assuming the use of cutting fluid, it is easy to use water-based cutting fluid, and it is necessary to do a good job in filtering and purifying the cutting fluid to avoid the disintegration and concentration reduction of the cutting fluid. In rough machining, the concentration of cutting fluid is lower than that in precision machining.
finish machining
According to the different cutting speeds, precision machining can be divided into high-speed precision machining and low-speed precision machining. In high-speed precision machining, oil-based cutting fluid can ensure the appearance quality of the workpiece and extend the service life of the tool. However, the viscosity and flash point of the mineral oil contained in it are low, and oil fumes, oil mist, and oil vapor often appear, distinguishing toxic components together, affecting the production environment, and endangering the physical and mental health of operators. Therefore, when finishing high-speed cutting, try to use lotion or micro lotion containing extreme pressure additives in water-based cutting fluid, whose concentration should be higher than that during rough machining. When low-speed precision machining, the cutting temperature is low and the above problems are not easy to occur. To ensure the machining accuracy of the workpiece, oil-based cutting fluid should be used.
In terms of rough machining, during precision machining, the cutting speed is high, the cutting heat generated by chip deformation is lower than the cutting heat generated by tool surface conflict, and the cutting force is small. Even in high-speed cutting, the thermal deformation of the workpiece caused by cutting heat is not as obvious as in rough machining, and the main reason for using cutting fluid on the tool is to reduce the wear of the back face of the tool. During precision machining, the relative cutting speed of the tool is high, and the instantaneous temperature of the chip when it is cut off from the workpiece is very high. Even with the use of cutting fluid, if the cutting fluid does not fully penetrate the cutting area due to permeability or pressure difference, it will still make the cutting surface prone to wear. Even if the tool can still be used, the surface roughness and quality of the workpiece cannot meet the requirements, so it is still necessary to replace the tool. Therefore, in precision machining, it is necessary to use cutting fluids with obvious smoothness and good permeability to extend the service life of the tool, ensure the machining accuracy and surface roughness quality requirements of the workpiece.
When completing black metal data at low speed, active extreme pressure cutting oil can be selected; When low-speed precision machining non-ferrous metals, non active extreme pressure cutting oil should be selected; Non active extreme pressure additive lotion can be selected for high-speed finishing of non-ferrous metals.
Hole processing
In CNC machining, hole machining mainly refers to drilling, reaming, turning inner holes on a lathe, and boring holes on a boring machine. Due to difficulties in chip removal and heat dissipation, as well as poor rigidity of the tool (rod), the cutting speed of hole machining is lower than that of external induction machining, and the difficulty is higher than that of external induction machining.
When drilling, ordinary Fried Dough Twists drills are used for drilling, which is attributed to rough machining. It is difficult to remove chips during drilling and it is not easy to generate cutting heat, which often leads to annealing of the blade and affects the service life and processing power of the drill bit. Choosing a cutting fluid with good performance can significantly prolong the lifespan of the drill bit and improve productivity. Generally, extreme pressure emulsion or extreme pressure composite cutting fluid is chosen. The cutting fluid composed of extreme pressure has low surface tension, good permeability, and can cool the drill bit in a timely manner. It is very useful for extending the service life of cutting tools and improving machining ability. For difficult to cut data such as stainless steel and heat-resistant alloys, low viscosity extreme pressure cutting oil can be selected.
When drilling, whether it is ordinary drilling or deep drilling, the heat dissipation conditions are very poor, which will generate a large amount of cutting heat. The direction of chip removal is opposite to the feed direction of the drill bit. Cutting fluid needs to enter the edge of the drill bit to make it smooth, cool, and aid in chip removal. Cutting fluid must first have excellent permeability, and the supply method, flow rate, and pressure must also meet the requirements.
In terms of the life policy of floating drill bits, oil-based cutting fluid is better than water-based cutting fluid, the extreme pressure micro lotion in water-based cutting fluid is better, and the low viscosity active sulfide oil in oil-based cutting fluid is better in all cutting fluids.
Because reaming belongs to low-speed chips in precision machining, two quality policies should be emphasized when reaming, namely the standard accuracy of reaming and the accuracy of surface roughness, as well as the service life policy of reamer fitting accuracy.
In the policy of controlling pore size, oil-based cutting fluid expands pore size, mineral oil expands pore size, extreme pressure cutting oil is smaller, and active sulfurized chlorinated oil is smaller; The water-based cutting fluid reduces the pore size, the sulfur containing extreme pressure micro lotion and micro lotion reduce the pore size more, and the lotion is in the middle, making the cutting fluid smaller. In view of this, in order to control the standard of hole enlargement, water-based cutting fluid is used when using new reamers, making it difficult to enlarge the hole. When the reamer is worn to a certain extent, oil-based cutting fluid can be used to slightly enlarge the aperture.
In terms of policies to reduce the surface roughness of enlarged holes, water-based cutting fluids are superior to oil-based cutting fluids. In oil-based cutting fluids, active sulfurized chlorinated oil has a better effect, followed by chlorinated extreme pressure oil, mixed mineral oil, and pure mineral oil. In water-based cutting fluid, lotion, micro lotion and sulfur containing extreme pressure micro lotion have the same effect, but the composition of cutting fluid is worse.
In terms of controlling the service life of the reamer, the non active extreme pressure cutting oil and anti friction cutting oil in oil-based cutting fluids have better functions; In water-based cutting fluids, the composition of the cutting fluid is worse.
Except for the floating boring cutter, turning the inner hole and boring hole is a single edge cutting, and the heat dissipation conditions are worse than those of the outer circle. The use of cutting fluid is the same as drilling and reaming, so the flow rate and pressure should be appropriately increased.
Thread processing
Thread processing belongs to forming processing. When tapping, it belongs to multi edge low-speed cutting, where the cutting edge is surrounded by cutting data, the cutting torque is high, chip removal is difficult, heat cannot be carried away by the chips in time, the chips are stuck and vibrate briefly, and tool wear is simple. Especially when tapping threads, the cutting conditions are more stringent: the chip removal space is narrow, and the chips are not easy to break and flow out. Cutting and conflicting forces are generated during tapping and chip removal, which can easily lead to tap breakage. Require cutting fluid to have a low conflict coefficient and good permeability, in order to reduce the tool's conflict resistance and extend its service life.
When cutting black metal materials, oil-based cutting fluids with high sulfur and chlorine additives, low viscosity, and good permeability should generally be used.
When using high-speed steel for low-speed thread turning, the cutting fluid is the same as the tapping and casing threads. Turning threads with hard alloy cutting tools has the advantages of fast cutting speed, high impact force, high cutting temperature, small cutting edge area, large acceptance of cutting force, high requirements for thread contour accuracy, and less tendency to accumulate chips and scale., This will affect the appearance quality of the threads. The service life policy of cutting tools is high, requiring the cutting fluid to have functions of cooling, smoothing, and penetration. It is recommended to choose a water-based cutting fluid containing extreme pressure additives.
Selection of different cutting tools
In many cases, to avoid damage caused by uneven heating, it is customary to choose dry cutting when cutting with hard alloy tools. However, in CNC machine tools, considering factors such as power, comprehensive cost, and machining quality, it is best to use cutting fluid. When using hard alloy cutting tools for machining, when the cutting speed is relatively high, water-based cutting fluid is generally used, which requires high flow rate continuous use. Pay attention to inquiry to ensure that the nozzle is always aligned with the cutting direction; When using high-speed steel cutting tools for cutting, when the cutting speed is low, oil-based cutting fluids with smoothness are generally used.
Ceramic cutting tools, metal ceramic cutting tools, diamond and cubic boron nitride cutting tools are mainly suitable for high-speed cutting, dry cutting, hard cutting and other machining methods, and do not use cutting fluids. Sometimes, to avoid excessive cutting temperatures, cutting fluid should be used in most cases when using these tools. Due to the fast cutting speed, it is recommended to use water-based cutting fluid.
When using high-speed steel for low-speed thread turning, the cutting fluid is the same as the tapping and casing threads. Turning threads with hard alloy cutting tools has the advantages of fast cutting speed, high impact force, high cutting temperature, small cutting edge area, large acceptance of cutting force, high requirements for thread contour accuracy, and less tendency to accumulate chips and scale., This will affect the appearance quality of the threads. The service life policy of cutting tools is high, requiring the cutting fluid to have functions of cooling, smoothing, and penetration. It is recommended to choose a water-based cutting fluid containing extreme pressure additives.
Selection of different cutting tools
In many cases, to avoid damage caused by uneven heating, it is customary to choose dry cutting when cutting with hard alloy tools. However, in CNC machine tools, considering factors such as power, comprehensive cost, and machining quality, it is best to use cutting fluid. When using hard alloy cutting tools for machining, when the cutting speed is relatively high, water-based cutting fluid is generally used, which requires high flow rate continuous use. Pay attention to inquiry to ensure that the nozzle is always aligned with the cutting direction; When using high-speed steel cutting tools for cutting, when the cutting speed is low, oil-based cutting fluids with smoothness are generally used.
Ceramic cutting tools, metal ceramic cutting tools, diamond and cubic boron nitride cutting tools are mainly suitable for high-speed cutting, dry cutting, hard cutting and other machining methods, and do not use cutting fluids. Sometimes, to avoid excessive cutting temperatures, cutting fluid should be used in most cases when using these tools. Due to the fast cutting speed, it is recommended to use water-based cutting fluid.
