Different Cutting Process Requirements For Cutting Fluid

Metal cutting fluid is abbreviated as cutting fluid; the lubrication effect in the cutting process can reduce the friction between the rake face and chips, and the flank face and the machined surface, forming part of the lubricating film, thereby reducing cutting force, friction and power consumption, reduce the surface temperature and tool wear of the friction part between the tool and the workpiece blank, and improve the cutting performance of the workpiece material.

Different cutting processes have different requirements for cutting fluid. The correct selection of suitable cutting fluid is very important to the quality of the workpiece.

Rough Turning

When rough turning, the machining allowance is large, so the cutting depth and feed are large, the cutting resistance is large, a large amount of cutting heat is generated, and the tool wear is also serious. It should be mainly used for cooling and with certain cleaning, lubrication and rust prevention. The effective water-based cutting fluid removes the cutting heat in time, reduces the cutting temperature, and improves the tool durability. Generally, it is better to use extreme pressure emulsion. In addition to good cooling performance, extreme pressure emulsions also have good extreme pressure lubricity. When using water-based cutting fluid, pay attention to the maintenance of the guide rail surface of the machine tool. Dry the cutting fluid on the workbench and apply lubricant before leaving work.

Finishing Turning

When finishing turning, the cutting allowance is small, the cutting depth is generally only 0.05-0.8mm, and the feed rate is also small. It is required to ensure the accuracy and surface roughness of the workpiece. Due to the low cutting force and low temperature during finishing turning, cutting fluids with low friction coefficient and good lubricating performance should be used. Generally, high-concentration (mass fraction above 10%) emulsions and cutting fluids with oily additives should be used. For turning with high precision requirements, such as fine threading, rapeseed oil, soybean oil or other products must be used as lubricating fluid to meet the precision requirements. As mentioned above, due to the poor stability of vegetable oils and easy oxidation, some factories use (mass fraction) JQ-1 precision cutting lubricant 15% and L-AN32 total loss system oil 85% as precision cutting oils, with good results .

Boring

The mechanism of boring is the same as that of turning, but it is internal hole machining, the cutting amount and cutting speed are not large, but the heat dissipation conditions are poor, the emulsion can be used as the cutting fluid, and the flow and pressure of the cutting fluid should be appropriately increased when applicable.

Milling

Milling is intermittent cutting. The cutting depth of each tooth changes from time to time, which is prone to vibration and a certain impact, so the milling conditions are worse than turning. When using high-speed steel tools for high-speed flat milling or high-speed end milling, cutting fluids with good cooling properties and certain lubricating properties are required, such as extreme pressure emulsions. In low-speed milling, cutting oil with good lubricity is required, such as precision cutting oil and inactive extreme pressure cutting oil. For stainless steel and heat-resistant alloy steel, cutting oil containing sulfur and chlorine extreme pressure additives can be used.

Reaming

Reaming is the finishing of holes and requires high precision. Reaming is a low-speed and small-feed cutting, mainly because the tool and the hole wall are squeezed and cut, and the chip fragments are easy to stay in the groove or stick to the edge of the blade, which affects the squeezing effect of the land. Destroy machining accuracy and surface roughness, increase cutting torque, but also generate built-up edge and increase tool wear. Reaming basically belongs to the state of boundary lubrication. Generally, high-concentration extreme pressure emulsion or extreme pressure cutting oil with good lubricity and certain fluidity can be used to obtain good results. For stainless steel and heat-resistant steel, a compound cutting fluid with high extreme pressure can be used. For deep hole reaming, deep hole drilling cutting oil with good lubrication performance can meet the technological requirements.

Broaching

The broach is a processing tool in which a large number of teeth are arranged along the axial direction according to the teeth of the blade. The characteristic of broaching is that it can process workpieces with complex shapes with high precision. Because the broach is a valuable tool, the durability of the tool has a greater impact on production costs. In addition, broaching is finishing, which has strict requirements on the surface roughness of the workpiece. When broaching, the cutting resistance is large, the chip removal is difficult, the cooling condition is poor, and the surface of the workpiece is easily scratched, so the lubricity and chip removal performance of the cutting fluid are required. There are special broaching oils containing sulfur extreme pressure additives in China.

For broaching of stainless steel and heat-resistant alloys, the following formula (mass fraction) can be used: JQ-2 extreme pressure lubricant 20%, chlorinated paraffin 15%, benzene 80 used 1%, L-ANN22 total loss system oil 64 %.

Drilling

Drilling with a general twist drill is rough machining. It is difficult to remove chips during drilling and cutting heat is not easy to lead out, which often results in blade annealing, which affects the service life and processing efficiency of the drill. Choosing a cutting fluid with good performance can prolong the service life of the drill several times or more, and the production efficiency can also be significantly improved. Generally, extreme pressure emulsion or extreme pressure synthetic cutting fluid can be used. The extreme pressure synthetic cutting fluid has low surface tension and good permeability. It can cool the drill in time, which is very effective in extending tool life and improving processing efficiency. For difficult-to-cut materials such as stainless steel and heat-resistant alloys, low-viscosity extreme pressure cutting oils can be used.

The cutting fluid is required to have a lower friction coefficient and higher extreme pressure at the same time to reduce the frictional resistance of the tool and extend the use of the tool life. Generally, a composite cutting fluid containing both oily agent and extreme pressure agent should be selected. In addition, the permeability of the cutting fluid is very important when tapping the thread. Whether the cutting fluid can penetrate the cutting edge in time has a great impact on the durability of the tap. The permeability of cutting fluid is related to viscosity. Oil with low viscosity has better permeability. If necessary, a small amount of diesel or kerosene can be added to improve the permeability. In some cases, when tapping blind holes, it is difficult for cutting fluid to enter the hole. In this case, cutting fluid with high viscosity and strong adhesion will be more effective.

Here are a few formulas (mass fraction) of cutting fluids for tapping:

• Sulfated fatty oil 10%, chlorinated paraffin 10%, fatty oil 8%, L-AN15 total loss oil 72%, suitable for steel and alloy Steel tapping thread.
• JQ-2 extreme pressure lubricant 20%, JQ-1 precision cutting lubricant 10%, L-AN15 total loss system oil 70%, suitable for steel and alloy steel tapping.
• JQ-2 extreme pressure lubricant 15%, diesel engine oil 20%, L-AN15 total loss system oil 65%, suitable for aluminum and aluminum alloy tapping.
• JQ-2 extreme pressure lubricant 30%, chlorinated paraffin 10%, fatty oil 10%, L-AN32 total loss system oil 50%, suitable for stainless steel and blind hole tapping.
• Extreme pressure emulsified oil 20% + water 80%, suitable for thread processing of steel standard parts.

Grinding

Grinding machining can obtain high dimensional accuracy and low surface roughness. When grinding, the grinding speed is high, the heat generation is large, and the grinding temperature can be as high as 800-1000℃ or even higher. It is easy to cause surface burns of the workpiece and surface cracks and parts deformation due to thermal stress. The grinding wheel wears passivation and grinding Particles fall off, and abrasive debris and grinding wheel powder are easy to splash and fall on the surface of the part, which affects the processing accuracy and surface roughness. When processing tough and plastic materials, the grinding debris is easy to be stuck in the gap on the working surface of the grinding wheel or the grinding debris and the processing metal are fused on the surface of the grinding wheel, which will make the grinding wheel lose its grinding ability. Therefore, in order to reduce the grinding temperature, wash away the grinding debris and grinding wheel powder, and improve the grinding ratio and the surface quality of the workpiece, it is necessary to use a cutting fluid with good cooling performance and cleaning performance, and a certain degree of lubricity and rust resistance.

1. Ordinary grinding:

Anti-rust emulsion or soda water and synthetic cutting fluid (mass fraction) can be used, such as: anti-rust emulsion 2%, sodium nitrite 0.5%, sodium carbonate 0.2%, water 97.3%; 0.8% Sodium nitrite, 0.3% sodium carbonate, 0.5% glycerin, 98.6% water; directly use 3%-4% anti-rust emulsion or chemical synthesis liquid.

For precision grinding with high precision requirements, the use of H-1 fine grinding fluid can significantly improve the machining accuracy and grinding efficiency of the workpiece, and the use concentration is 4-5%.

2. High-speed grinding:

Grinding with a wheel speed exceeding 50m/s is usually called high-speed grinding. When the linear speed of the grinding wheel increases, the grinding temperature increases significantly. According to the test, the grinding temperature (average temperature of the workpiece) when the grinding wheel linear velocity is 60m/s is about 50-70% higher than that of 30m/s; when the grinding wheel linear velocity is 80m/s, the grinding temperature is higher than that at 60m/s. 15-20% higher. After the linear speed of the grinding wheel is increased, the number of abrasive particles participating in the grinding in a unit time increases, the friction is intensified, and the energy consumption is also increased, which increases the surface temperature of the workpiece, and increases the possibility of burns and cracks on the surface. Use coolant with efficient cooling performance to solve. Therefore, in high-speed grinding, ordinary grinding fluids cannot be used, but high-speed grinding fluids with good penetration and cooling performance should be used. For example, GMY high-speed grinding fluids can meet the high-speed grinding process with a linear speed of 60m/s Claim.

3. Power grinding:

This is an advanced high-efficiency grinding process. For example, in plunge-cutting high-speed and powerful grinding, a grinding wheel with a linear speed of 60m/s will be cut radially at a feed rate of 3.5-6mm/min. The rate can be as high as 20-40mm3/mm.s. At this time, the friction between the abrasive particles of the grinding wheel and the workpiece is very severe. Even under the cooling condition of high pressure and large flow, the temperature range of the surface layer of the workpiece in the friction zone is 700-1000℃. No, the grinding process is impossible. In plunge-force grinding, compared with emulsion, the total grinding volume is increased by 35%, the grinding ratio is increased by 30-50%, and the normal grinding time is prolonged by about 40%. The power loss is about 40%. Therefore, the performance of the coolant has a great influence on the grinding effect during strong grinding. At present, the domestically produced strong grinding fluids include QM high-speed strong grinding fluid and HM slow feed strong grinding fluid.

4. Diamond grinding wheel grinding:

This is used for the grinding of hard alloy, ceramic, glass and other materials with high hardness. It can be rough and finely ground. The ground surface generally does not produce cracks or gaps, which can achieve better Low surface roughness. In order to prevent excessive heat generation during grinding and premature wear of the grinding wheel, and to obtain a lower surface roughness, continuous and sufficient cooling is required. Due to the high hardness of the workpiece, the grinding fluid should mainly have cooling and cleaning performance to keep the grinding wheel sharp. The friction coefficient of the grinding fluid should not be too low, otherwise it will cause low grinding efficiency and surface burns. A chemical synthetic fluid based on inorganic salts is used as the grinding fluid. A small amount of polyethylene glycol can be added as a lubricant during fine grinding, which can improve the surface processing quality of the workpiece. For parts with high machining accuracy, low-viscosity oil-based grinding fluids with good lubricating properties can be used.

5. Thread, gear and screw grinding:

This type of grinding pays special attention to the quality and dimensional accuracy of the processed surface after grinding. Generally, it is advisable to use grinding oil containing extreme pressure additives. This type of oil-based grinding fluid is due to its Good lubrication performance, can reduce grinding heat, and the extreme pressure additives in it can react with the workpiece material to produce low-shear strength iron sulfide film and iron chloride film, which can reduce the wear of the cutting edge of the abrasive grain and make grinding Go smoothly. In order to obtain better cooling and cleaning properties, and to ensure fire safety, low viscosity and high flash point grinding oil should be selected.