1. Pipe cutting machine
The common pipe cutting machine in China generally adopts the processing method of workpiece rotation. When the pipe to be processed is not round and the wall thickness is uneven, the cutting process is prone to vibration, knife cutting and damage to the machine tool spindle.
A steel pipe company introduced a CNC special pipe cutting machine for cutting oil casing joints from abroad. The machine tool uses a spindle to drive the cutter head to rotate (ie, the tool rotates and cut), and the workpiece is stationary.
Compared with the common common pipe cutting machine, it has obvious advantages: the tool is adjusted once in one position, which ensures the continuity of the processing, is convenient and reliable, and greatly improves the production efficiency. The cutter head of the pipe cutting machine is uniformly installed with four cutting knives. When the machine is working, the spindle drives the cutter head to rotate. Under the control of the program, the four knives simultaneously feed and retract the knife, and the cutting work is completed at one time. Since the four knives are synchronously involved in the cutting, each knives bears 1/4 of the total cutting amount, the cutting load is small, the cutting speed is fast, and the quality is stable.
However, the precision and interchangeability of the arbor, blade and its accessories used in the machine tool are very high, and the structure of the arbor is complex, which is suitable for the processing range of the whole machine tool (114.3~244.5mm). Since the four knives are cut at the same time, the accuracy is very strict, and the parallelism error is in the range of 0.01 mm. The combined tooth pitch is 200mm with a combined error of ±0.01mm. The requirements for the hardness, wear resistance and mechanical properties of the shank are also very high. Therefore, since the machine tool has been cut off since the machine was put into production, it has been dependent on imports, and the price is expensive. It is difficult to ensure timely supply and it is difficult to meet the production needs. To this end, we have made research on the localization of the cutting arbor for this pipe cutting machine and achieved good results, reaching the requirements for the use of similar foreign products.
2. Cut the arbor structure and working conditions
(1) Tool structure size and adjustment range
The structure of the cutting bar is shown in Fig. 1. The machining range of the machine is 114.3~244.5mm, and there is only one type of tool (tool bar), so the tool bar is designed with a size adjustment mechanism. The adjustment of the large size is achieved by the knife bar 2, and the adjustment of the small size is achieved by the screw 8. The installation procedure is as follows: the cemented carbide insert 5 is mounted on the blade 4, and the blade is mounted on the cutter bar 2, and the clamp plate 6 is pressed by the fastening screw to fix the blade to the cutter bar. Then, the cutter bar is mounted on the cutter head of the machine tool, and the required size is adjusted by the tooth shape of the cutter bar and the toothed shape of the cutter head, and then fixed by the slider 1 and the screw, that is, the machining size is set. If the blade is worn and the dimensions are in error, the screw 8 can be used for fine adjustment.
(2) Working conditions
The cutting speed is 60-190m/min, and the spindle speed can be adjusted according to the size of the machining pipe diameter. When the spindle rotates during machining, the cutter bar makes radial movement in the cutter groove. The cutting blade is cooled by the cutting fluid.
(3) Selection of tool bar material
From the analysis of the use of imported shank, the design structure of the arbor is 324mm in total length and 84mm in width. The length of the 205mm length and the tooth thickness for adjustment are 32mm, and the thickness is only 17mm in the length of 119mm. The groove thickness of the plate is only 11mm, and there are two 15° clamping bevels on the blade mounting groove. If the material of the arbor is not properly selected, not only the hardness and wear resistance can not meet the requirements, but it is easily deformed during heat treatment, and the flatness is difficult to reach the design requirement of 0.01mm. According to these requirements and the technical requirements of the arbor, after many aspects of searching for information and years of experience in machining and the existing technical capabilities of China's heat treatment process, we finally chose high strength, high load, and nitriding. Low-alloy ultra-high-strength steel 45CrNiMoVA with small dimensional deformation and small amount of deformation after treatment.
(4) Tool bar design and manufacturing process
When designing the tool holder, firstly investigate and analyze the installation and use of the tool bar and the use of the equipment, and survey the foreign tool bar samples, determine the design plan and carry out the surveying, and finally draw the tool bar processing pattern. as shown in picture 2.
According to the design of the arbor and the high precision of the arbor, the machining process is developed. Forgings are mainly used for milling and grinding, and each process is checked to ensure the accuracy of the toolholder.
The processing flow of the arbor is: forgings→rough milling shape six sides→grinding six sides→rough milling cutter shape shape→tempering treatment 283～306H BW→finishing upper and lower shape→finishing inner groove and 15° bevel → Drilling, tapping → finishing 90° tooth shape → fine grinding inner groove. 15° bevel and 90° tooth shape to size→test→surface nitriding treatment, nitriding layer 0.3～0.4mm, hardness 766～889HV→finished product inspection→oiled packaging into storage.
3. Conclusion
After several years of on-site use, the dimensional accuracy, surface hardness, wear resistance and mechanical properties of the localized cutting shank have reached the level of similar foreign products, and completely replaced the imported arbor in production. The company's production needs are guaranteed, which greatly reduces processing costs and tool procurement costs and saves a lot of foreign exchange. Through years of practice, many tools of the steel pipe processing industry have achieved the performance of similar foreign products through localization.
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Qingdao Friend New Energy Development CO.,LTD , http://www.friendtyres.com