Pushing and transforming into a lathe machine

The high-temperature cracking tube used in petrochemical plants is centrifugally cast and made of Cr25Ni35Nb with a length of more than 4m and an outer diameter of 56mm. It is required that the outer surface of the pipe is not machined and the inner surface must be machined. After processing, the inner diameter is Ø43±0.1mm and the surface roughness Ra is 3.2μm. For tubes with inner diameters greater than 50 mm, it is usually pushed. The advantages of this method are: simple structure, convenient feeding and processing. However, when the inner diameter of the pipe is less than 50mm, the mast is long and slender. If push-pull method is adopted, the rigidity of the boring bar is too small to cause vibration, chip removal is difficult, the tool is easy to be cut, the tool life is short, the machining accuracy is difficult to ensure, and the pipe wall thickness is Uneven even penetrates the wall. Therefore, when the slender tube is processed, the ramming process should be changed to a ramming process. The original push-pull machine was transformed into a Lathe Machine. The spindle speed was controlled by a frequency converter to achieve stepless speed control. The machine's guide rails and precision all meet the boring and machining requirements. Fig. 1 is a schematic diagram of a modified lathe machine. The specific process of evasive change is as follows: 1. Cooling hose 2. Box 3. Guide bush 4. Workpiece 5. Center frame 6. Mast support 7. Bracket Fig. 1 Drawing machine diagram

Cooling and lubrication of the boring tool The cooling and lubrication of the boring tool guarantee the service life of the tool. In this structure, we used the high-pressure cooling system in the original machine tool to cool and lubricate the cutting edge through a slanted hole in the tool shank. At the same time, the high-pressure liquid was used to wash away the iron from the tool head. One of the key technologies. The reamer and floating reamer in the pull rake are an important part of the machining quality. The reamer cuts the blank to the basic dimensions and leaves a certain amount of hinge. The reamer is used for dimensional correction and the surface roughness is reduced. Degrees, to meet the drawing requirements. Figure 2 shows the structure of the pull tab. Chip removal For slender tube boring, evacuation is both difficult and important. If the chips cannot be discharged smoothly, the tool life will be greatly reduced, the quality of the machining surface will be deteriorated, and the chip removal channel will be blocked, resulting in inability to be processed. Since the inner diameter of the tube is small, the space for chip removal is very limited. Therefore, we design the mast as a structure with a spiral groove (Fig. 2). In this way, both the rigidity of the mast and the large evacuation channel are ensured. In the actual processing, the iron scrap is smoothly discharged under the double action of the spiral groove spiral pushing and the high pressure oil scouring. The direction of rotation of the spiral groove is opposite to the direction of rotation of the tube. 

1. Guide sleeve 2. Nut 3. Cap 4. Floating bearing 5. Arbor 6. Floating reamer 7. Reamer cutter 8. Compression nut 9. Workpiece 10. Pull rod Fig. 2 Tensioner structure work drawing

The viscosity of the guillotine chip breaking Cr25Ni35Nb material is large. The boring of the Cr25Ni35Nb material with a common tool will result in a small space for chip evacuation. Therefore, a trowel with a chip breaker must be used (Figure 2). The guiding sleeve and the floating support of the boring bar To ensure that the boring bar is smoothly introduced into the pipe, a guiding sleeve must be added at the front end of the feeding knife. The inner diameter of the guiding sleeve is the same as the diameter required for machining. In order to increase the rigidity of the mast and ensure the machining accuracy, a floating support is added to the rear end of the cutter head of the mast, and the material of the floating support is a soft bakelite. The accuracy of the workpiece after machining is ensured by the precision of the floating support. When soft bakelite is worn out, it must be replaced. The actual processing effect after changing from push to pull is very good. The diameter error of the slender tube processed is not more than ±0.1mm, and the surface roughness Ra is 3.2μm, which meets the specified technical requirements.