Development of forming turning tool for machining

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Development of forming turning tool for machining double T-shaped rotor groove

0 preface

rotor is one of the most important components in steam turbine. When the rotor rotates at high speed, it must bear not only the centrifugal force generated by the moving blades, but also the dynamic stress. Therefore, the rotor groove should have very tight dimensional accuracy and low surface roughness. The rotor groove of a new unit adopts a double T-shaped structure, and the shape is shown in Figure 1

Figure 1

from Figure 1, we can see that the profile of the wheel groove is complex, with two locating surfaces, and the size of the profile is large, and the cutting length is 54mm, which puts forward higher requirements for the machining tools. Therefore, the design of the forming turning tool is the key element to ensure the machining quality of the rotor wheel groove. This paper discusses the design and manufacture of the forming turning tool for machining the double T-shaped grooves of the steam turbine rotor

1 selection of tool material

the material of rotor is 30Cr2Ni4MoV, which has high strength, toughness and viscosity; As mentioned earlier, the cutting length of the formed turning tool is large, so the cutting resistance of the formed turning tool is very large. To sum up the analysis results, the tool material is super hard high speed steel - cobalt high speed steel w2mo9cr4vco8 (M42), and its normal temperature hardness is HRC. The addition of CO improves the heat resistance and wear resistance of tool materials, and has longer durability than ordinary high-speed steel

2 determination of tool rake angle and rake angle

double T-shaped rotor groove is processed in two steps. The first step is to use the ordinary elbow turning tool to process the approximate shape of the double-T groove, with a margin of 0.2mm on one side. The second step is to use the forming fine turning tool to cut the last 0.2mm allowance to ensure the design size and surface roughness of the product drawing. Therefore, the profile size of the forming turning tool is the key to ensure the size of the wheel groove. When designing the profile precision turning tool, it has been analyzed above that the cutting resistance is very large, so the larger front angle go=10 °, and the rear angle ao=10 °, so as to ensure the smooth cutting of the tool, but the profile depth of the profile turning tool changes by 0.3mm ~ 0.5mm from the theoretical profile depth. According to the size of the front angle and rear angle, modify the profile depth dimension formula:

ctgjap=ctgj (1-tgatgg)


in the formula, j=45 °, Jap is the j dimension of the formed turning tool before grinding the rake angle, t1=16.3mm, T01 is the T dimension of the formed turning tool before grinding the rake angle. If all these plastic garbage and straw resources are reused to make wood plastic products, 1 dimension. In this way, after grinding the rake angle, the profile depth of the formed turning tool is consistent with the theoretical depth. Figure 2 shows the manufacturing details of the formed turning tool. It is necessary to have a full understanding and ideological preparation for the pain, long-term and arduous nature of structural adjustment

Figure 2

3 key points of tool manufacturing

when manufacturing forming turning tools, the key is to ensure the front and rear corners of forming turning tools. The back corner is processed by wire cutting and completed at one time. When grinding the front corner, because the two linear segments are not in the same vertical plane, if the front corner is grinded at one time, the tool tips of the two linear segments have a drop in the height direction, resulting in a 0.2mm difference between the tool profile and the product profile. Therefore, when sharpening the rake angle, it should be sharpened in two sections to ensure that the tool tips of the two straight sections are in the same horizontal plane

4 conclusion

the use of forming turning tools in processing can form a formed surface at one time, which is easy to operate. The processing accuracy is stable, and the table HR ⑴ 50A is pointer type, with high production efficiency. (end)

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