Application of indexable circular edge end mill in processing of high manganese steel frogs (figure)
1. Characteristics <br> <br> high manganese steel is a single-phase high-manganese austenite steel wear. The high-manganese steel treated by water toughening treatment (heat treatment of water cooling after heating at 1000-1100 °C) has significant work hardening effect, that is, the hardness of the working surface increases from 170-220 HB W to 450 under high external impact. ~ 550 HBW or more, the heart still maintains extremely high toughness, thus achieving high impact, wear resistance and crack propagation resistance. Railway ballast casting high-manganese steel frogs (hereinafter referred to as: high-manganese steel frogs) are manufactured using the above characteristics. It has the advantages of good integrity, strong wear resistance, safety and reliability, low cost, convenient maintenance and repair.
The use of high manganese steel materials increases the hardness, strength and service life of the part, which is advantageous. However, due to its own hard work hardening, small thermal conductivity, high cutting temperature, high toughness, high elongation, difficult chip breaking, large coefficient of linear expansion, large cutting force and other physical properties, especially work hardening, high manganese Steel machining has brought great difficulties. High manganese steel is a difficult material to be processed according to the difficulty of parts removal material processing.
2. high manganese steel frog <br> <br> cutting tools with high-speed rail transport towards the development of heavy direction, and quality requirements are also increasing transport equipment. High-manganese steel frog is an over-orbiting device that makes the wheel of a rolling stock pass a rail over another rail. It is a key component of the railway ballast equipment. Material: ZGMn13, the length of the workpiece is generally 4~6m, and the thickness is generally 140-180. Mm, the width is generally in the range of 350 to 500 mm.
High manganese steel frog mechanical machining, mainly plane processing. The cutting method is end milling. The tool is generally made of carbide indexable end mill. Because it is a high-manganese steel casting, the workpiece is long and thin, and the deformation during processing is large, which has certain processing difficulty. Our factory has been developing high manganese steel frog mechanical machining for more than ten years and has accumulated certain experience.
For many years, we have used the blade grade 767 hard alloy on the high manganese steel boring tool.
The tool structure is mainly wedge clamped and axially positioned. This structure is convenient and reliable to clamp and has high positioning accuracy. As long as the positioning component and the blade geometry have higher manufacturing precision, the cutter can have higher positioning accuracy. When the cutting force is too large, the blade and the blade holder are restrained from axially swaying to prevent damage to the cutter body.
Since the milling process is interrupted cutting, each tooth has an impact when it is cut into the workpiece. In order to cut the milling cutter into the workpiece as much as possible, the rake face and the workpiece are first contacted away from the cutting edge and the cutting edge, thereby improving the knife. When the tooth is cut, the impact resistance is improved, the impact resistance is improved, the cutting edge is protected, and the chipping is reduced. The high manganese steel frog machining end milling cutter adopts the double negative rake angle form, that is, γ f and γ p are less than zero, γ f = -5°, γ p = -7°.
Domestically produced and imported translatable end mills are generally regular quadrilateral blades, and the main deflection angle κ r is mostly 75°. Our factory has been used for many years. Although it can basically meet the requirements in terms of product quality and production efficiency, due to the speciality of high manganese steel processing, the existence of edge and edge of square blade and straight cutting edge, the phenomenon of chipping in production More serious, the blade, knife pad, knife body consumption is large, the cost is too high. In recent years, we have modified the blade to be a round blade, and introduced the indexable arc-edge milling cutter into the processing of high-manganese steel frog. Since the cutting edge is arc-shaped, there is no weak tip and corner, and there is no weak zone. Therefore, no cutting edge can collapse during the cutting process. Furthermore, in the cutting process, not only the cutting pattern is changed, but also the main deflection angle κ r of the tool changes with the change of the cutting depth, and the processing conditions are improved. After testing and use, the straight cutting edge is a circular cutting edge for machining high-manganese steel frogs, which has achieved obvious results in avoiding chipping, increasing depth and feed, improving production efficiency and reducing cost. It should be noted that changing the shape of the cutting edge is a more effective way to overcome the chipping of cemented carbide blades.
The basic structure of the indexable arc edge end mill is shown in Figure 1.
3. The main features of the arc-edge face milling cutter and the analysis of the milling test (1) The main deflection angle of the arc-edge face milling cutter κ r is one of the important angles of the tool. Its size, on the one hand, affects the shape of the cutting layer, and on the other hand directly affects the length of the cutting edge and the load of the unit cutting edge, which directly affects the wear and life of the tool. When the amount of back-feeding and the amount of feed are constant, changing the angle of the main declination can make the chips thinner or thicker, affecting the heat dissipation and the change of the cutting force. That is to say, the change in the magnitude of the main declination κ r directly affects the chipping and tooling of the tool.
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