Common Problems and Countermeasures of Oil Casing Pipe End Thread Turning

The processing quality of oil casing pipe end thread is not only related to the thread turning process, but also directly related to the pipe end thread material and type.

At the same time, the different formation state and chip breaking ability of iron chips in the turning process will lead to the existence of winding phenomenon in the turning process, especially in the processing details of pipe end thread skimming, thread turning, rounding, chamfering and sealing surface, there will be a large number of long or small iron chips, which will affect the quality of the pipe end threads and lead to the low machining efficiency.

1. Common problems and treatment of pipe end thread processing
   Damage of end face tool bar
   In the process of pipe end threading, the unevenness of the billet end face or the existence of accumulation of chipping tumors will cause the end face cutter to wear or hit the cutter, and if not found in time, the end face cutter bar will be damaged and accelerate the wear of the inner support expansion ring. Therefore, blanks with obvious defects at the end of the tube need to be processed offline or marked clearly during loading, so as to facilitate the identification of the tube-end turning personnel. If it is not possible to realize the offline processing operation can be installed in the tube end turning machine before the turning table frame camera, so that the post staff to find out in time to avoid unnecessary failure downtime.
   The toolholder part of the end toolholder, which is easy to wear and damage, is designed as a split inlay type. Split toolholder can effectively improve the service life of the overall toolholder, reduce troubleshooting time, and also facilitate the integration and installation of different inserts to realize different turning solutions.
   Expansion ring wear and damage
   In the process of machining, after the tube end is positioned inside the machine, the inner support extends into the tube end and relies on the expansion ring to seal the tube to prevent excessive cutting fluid from remaining inside the tube. When the tube end has uneven end surface, internal flanging, burr and excessive oxide skin, the expansion ring is easy to cause excessive wear and damage. Offline processing or marking of tube ends with obvious defects or deficiencies is the most direct way to avoid abnormal damage to the expansion ring. Reasonable choice of material and hardness of the expansion ring is helpful to avoid and reduce the wear of the expansion ring. In addition, remodeling the angle of the entrance profile of the expansion ring can effectively reduce the abnormal consumption and damage of the expansion ring.
   Processing efficiency mismatch
   The efficiency improvement program mainly relies on optimizing the program, adjusting the start-stop time of the spindle and the running speed of the clamping mechanism to achieve.
   2. Treatment of common machining defects
   Inspection and treatment of black skin buckle
   When there are more black buckles on the external thread, firstly, check the auxiliary machine stand pressure roller, roller and elevation; secondly, check whether the external centering spring is normal to ensure that when the external centering is extended, the external centering arm bar enters all the arm bar sleeve, and whether the external centering roller is normally pressed against the surface of the steel pipe; and then observe whether there is a falling phenomenon of the head of the pipe when the jaws are clamped (external centering delay adjustment can be carried out). Inner support head swing will also lead to tube end eccentricity, followed by black skin buckle, this situation can be replaced on the inner support or the inner support precision check, while checking the inner support expansion ring expansion, whether to support the tube end of the inner wall, tube end and inner support rotation is synchronized with the relative motion; incoming tube end of the outer diameter of the small, the end of the tube end of the straightness is too poor, oval degree of the black skin buckle caused by reasons such as super poor by modifying taper and other process parameters to adjust, but usually can not be fully adjusted. The black skin buckle can be adjusted by modifying the taper and other process parameters, but usually can not be completely eliminated.
   Inspection and treatment of trembling
   When trembling appears, first check whether the front and rear jaws are false clamping, when the jaws of the teeth of the nail is worn out seriously, should be replaced in time to ensure that the jaws clamping stability; steel pipe in the auxiliary machine on the table jumping seriously, the jaws clamping stability, steel pipe in the auxiliary machine on the table jumping seriously, then the table rollers, pressure rollers to check the elevation of auxiliary machines; threaded tool eating too much is also a common factor in the emergence of trembling can be resolved by reducing the amount of fine-turning Tool eating amount is also a common factor for threading tool to reduce the amount of fine-turning tool for debugging to solve the problem; due to the loosening of the tool rod, tool, screw, belt and other transmission chain there is a large gap, resulting in insufficient rigidity of the machining process, you can play the table to check the transmission error and adjust the gap elimination mechanism to solve the problem; for the incoming pipe end bending, ellipticity is too poor, the presence of local internal stress, you can increase the number of times to reduce the turning allowance to eliminate the chaffing. “White neck” inspection and treatment
   White neck” is usually due to semi-finished products thickened end of the oval degree of excessively poor or thickened outside diameter is too large, in the thickening of the oil pipe turning process, the use of integrated toolpost to complete the external threading process, the threading tool along the taper line backing out of the knife, skinning knife will still be thickened end of the outer diameter of the excess of the part of the turning, resulting in the emergence of the ” white neck” phenomenon, generally by increasing the number of times to reduce the turning allowance to eliminate chattering. White neck” phenomenon, generally can be solved by padding the threaded tool, increasing the relative position of the pick pocket knife and comb knife, or through strict control of the thickening process to solve.
   Burr and chamfer processing
   More burrs on the outer chamfer during processing, poorer outer chamfer finish, in addition to the conventional solutions such as processing parameter settings and correction of the tool patch value, can be improved by improving the strength of the blade of the burr cutting tool, coating and chip breaking groove type to improve the processing quality of the outer chamfer, and to reduce the frequency of grinding at the thread inspection post.