The tungsten steel end mill for stainless steel is a general-purpose carbide high-speed cutting tool with high precision and long life. It has excellent comprehensive properties such as wear resistance, thermal shock resistance and corrosion resistance. It is characterized by high hardness, high strength, good thermal stability, stable chemical properties and low price. This product is widely used in rough processing and semi-finishing of various metal materials.
Difficulties in Processing Stainless Steel
Stainless steel is a high-strength and high-corrosion-resistant alloy material, which often brings some problems when used as a processing material. Because stainless steel often contains metal elements such as chromium and nickel, its hardness and toughness are relatively high. At the same time, it also has certain adhesion, low thermal expansion rate, poor thermal conductivity and other characteristics, which increase the difficulty of stainless steel processing.
Severe Work Hardening
Stainless steel has severe work hardening. The first choice is a mixture of austenite and ferrite. The hardness of the hardened layer is 1.4~2.2 times higher than the original matrix hardness, and the strength R=1470~1960MPa. This type of stainless steel has high plasticity and a large strengthening coefficient. Moreover, austenite is unstable and easily transforms into martensite under the action of cutting force.
Large Cutting Force
Stainless steel has high plasticity, especially austenitic stainless steel, whose depth-to-length ratio is 2.5 times that of 45# steel. The plastic deformation during milling is large, which increases its cutting force, causes severe work hardening, high thermal strength, and makes cutting curling and breaking difficult.
High Cutting Temperature
Stainless steel has large plastic deformation, aggravated friction, and its thermal conductivity is relatively low. Therefore, under the same conditions, the temperature of milling stainless steel is about 200 degrees higher than that of 45# steel.
Cutting is Not Easy to Break
When processing stainless steel, it is easy to bond and produce built-up edge. Stainless steel has relatively large plasticity and toughness, and it is not easy to break when milling. Under high temperature and high pressure, the tool is prone to bonding wear and built-up edge.
The Tool is Easy to Wear
Of course, stainless steel milling cutters must be used to process stainless steel, because the TiC hard points of stainless steel are easy to cause severe grinding wear of the tool. Under high speed, high temperature and high pressure conditions, the cutting and tool are prone to bonding, diffusion and crescent wear.
Easy to Stick to the Tool
Stainless steel has poor thermal conductivity. The heat generated during the cutting process is difficult to dissipate and easily accumulates between the tool and the workpiece, causing the chips to adhere to the blade and form nodules. Nodules will further aggravate tool wear and increase cutting temperature, forming a vicious cycle.
How to choose an end mill
Choose the Appropriate Hardness According to the Hardness of the Stainless Steel Plate
The hardness of stainless steel plates is usually between HV150-200, which puts high requirements on the selection and hardness of carbide milling cutters. In order to ensure that the tool can withstand the cutting force and impact load of the stainless steel plate during processing and maintain sharpness and wear resistance, it is very important to choose the appropriate carbide milling cutter hardness. Therefore, the hardness of the selected carbide milling cutter should be controlled above HV1600, so as to ensure that the tool has sufficient hardness and toughness to overcome the difficulties of stainless steel processing and improve processing quality and efficiency.
Choose the Appropriate Tool Shape
Different processing technologies have different requirements for tool shape, and the appropriate tool shape should be selected according to the specific processing technology. For example, rough machining requires a tool shape with high strength and strong cutting ability, while fine machining requires a tool shape with high precision and smooth surface. Different stainless steel materials have different requirements for tool shapes, and the appropriate tool shape should be selected according to the specific stainless steel material. For example, for stainless steel with higher hardness, a tool shape with high strength and good wear resistance should be selected.
Select Tool Coatings According to Different Milling Workpieces
For different stainless steel materials, different tool coatings need to be selected. Generally, TiN-coated drill end mills are suitable for milling stainless steel materials. The drill end mills used in stainless steel milling are treated with special coatings to improve wear resistance and corrosion resistance, so that they have a longer service life and better processing effects during the milling of stainless steel materials.
Commonly used milling cutter types for processing stainless steel
High Speed Steel End Mill
High-speed steel end mill is a type of end mill made of high-speed steel. It has high hardness, strength and wear resistance and is widely used in various cutting and processing fields. However, for stainless steel processing, high-speed steel milling cutters are not always the best choice. However, the cost of high-speed steel milling cutters is much lower than that of carbide milling cutters. Therefore, for occasions where the processing accuracy requirements are not high, the use of high-speed steel milling cutters can reduce the processing cost. The material of high-speed steel milling cutters is relatively soft and easy to sharpen, which can extend the service life of the tool. For stainless steel with higher toughness, high-speed steel milling cutters are less likely to produce edge chipping, which is more advantageous.
Carbide End Mills
Compared with high-speed steel end mills, carbide end mills have higher hardness and toughness, and can better cope with the problem of high hardness of stainless steel. The hardness of carbide milling cutters is much higher than that of high-speed steel milling cutters. The tool materials are usually tungsten carbide, titanium carbide, etc., and the hardness can reach HV9000 or above. The high hardness ensures that carbide milling cutters can easily cut stainless steel without the occurrence of edge chipping, wear and other phenomena, effectively extending the service life of the tool. A lot of heat will be generated during the processing of stainless steel. Carbide milling cutters have good heat resistance and can maintain the sharpness and strength of the tool at high temperatures, avoiding tool softening and edge chipping caused by high temperatures.
Diamond Coated End Mills
Diamond coated end mills have extremely high hardness and wear resistance and can be used to process the hardest stainless steel. They are also very resistant to high temperatures and can be used for high-speed processing. The blades of diamond coated end mills are composed of diamond particles, so they have extremely high hardness and wear resistance, can withstand the high cutting loads and high temperatures generated during stainless steel processing, are not easy to wear, and the tool life is significantly extended. Diamond has excellent thermal conductivity and high temperature resistance, and can still maintain its hardness and strength at high temperatures. Therefore, diamond coated milling cutters can be used for high-speed processing of stainless steel without worrying about the tool softening or failure due to high temperature. However, diamond coated end mills are expensive, and the hardness of diamond coated end mills is too high. For stainless steel with lower hardness, it is easy to cause tool wear and chipping.
Appropriate Cutting Parameters
When milling stainless steel, a smaller cutting amount or feed amount should be used because the thermal expansion coefficient of stainless steel is small and it is easy to convert into thermal deformation. At the same time, the number of lateral movements of the tool should be reduced to maintain the stability of the tool and avoid tool shaking and swinging, which affects the milling quality. At the same time, the tool should use sharp teeth, and control the milling speed and feed rate to ensure the best milling effect and processing quality.
Cutting Speed
- High-speed steel milling cutter: For austenitic stainless steel (such as 304, 316), the cutting speed of high-speed steel milling cutter is usually between 20 and 40 m/min. For martensitic stainless steel (such as 416, 420), the cutting speed should be reduced to 15 to 25 m/min.
- Carbide milling cutter: For austenitic stainless steel, the cutting speed of carbide milling cutter is usually between 60 and 80 m/min. For martensitic stainless steel, the cutting speed should be reduced to 40 to 60 m/min.
- Diamond coated milling cutter: Diamond coated milling cutter is very wear-resistant and can be used for high-speed milling of stainless steel. For austenitic stainless steel, the cutting speed of diamond coated milling cutter is usually between 120 and 150 m/min. For martensitic stainless steel, the cutting speed should be reduced to 80 to 100 m/min.
Feed Rate
- A smaller feed rate results in a smoother surface finish, but the cutting force will also increase. This is because a smaller feed rate results in an increased cutting load on each cutting edge. If the feed rate is too small, the cutting force may be too large, causing tool breakage or vibration.
- A larger feed rate results in a rougher surface finish, but the cutting force will also decrease. This is because a larger feed rate results in a reduced cutting load on each cutting edge. However, if the feed rate is too large, the cutting edge may not be able to effectively remove the material, resulting in a decrease in machining quality.
- For stainless steel, a feed rate of 0.01 to 0.2 mm/tooth is generally recommended. The specific value should be adjusted according to the material hardness, tool material, cutting speed, and machining requirements.
Axial Depth of Cut
- A larger axial depth of cut improves machining efficiency because more material can be removed per cut. However, it also results in an increase in cutting force. This is because a larger axial depth of cut results in an increased cutting load on each cutting edge. If the axial depth of cut is too large, the cutting force may be too large, causing tool breakage or vibration.
- A smaller axial depth of cut will result in lower processing efficiency, but the cutting force will also be reduced. This is because a smaller axial depth of cut will result in a smaller cutting load on each cutting edge. However, if the axial depth of cut is too small, the cutting edge may not be able to effectively remove the material, resulting in longer processing time.
- For stainless steel, an axial depth of cut of 0.1 to 0.5 mm is generally recommended. The specific value should be adjusted according to the material hardness, tool material, cutting speed, feed rate and processing requirements.
Commonly used tools for stainless steel milling mainly include high-speed steel end mills, carbide end mills, and alloy drill coated end mills. When selecting tools, factors such as the hardness of the stainless steel plate, tool shape, and tool coating need to be considered. At the same time, when performing milling, attention should be paid to various factors such as cutting volume, feed volume, tool stability, milling speed and feed rate to ensure milling quality and processing efficiency.
