Research And Improvement On Stamping Forming Process Of Single Weld Elbow

In the process of modern industrial development,a variety of severe pipeline transportation conditions on the performance of the elbow put forward various different requirements.As a result,many elbow forming processes have been derived,among which the stamping-butt welding process as the representative of the welding elbow forming process has a wide range of applications.In order to further reduce the number of weld joints of elbow fittings and improve the safety of elbow fittings,a new stamping forming process of single weld elbow on the outer arc side is proposed.Compared with the buttwelding elbow,the forming elbow has one less weld on the inner arc side.Compared with the single-weld elbow on the inner arc side,because the stress in the inner arc area is higher than that on the outer arc side under high pressure service conditions,the welding seam in the dangerous area is moved to the outer arc side of the forming elbow by this process,which can effectively improve the safety of the elbow under high pressure service conditions.This technology has important practical significance for the development of welding elbow technology.The stamping process of single weld elbow is a new type of molding forming process.The process is as follows: firstly,the sheet metal is cut into specific shape of billet;Then use the die stamping forming the inner arc area of the elbow,the blank section is pressed into a U shape;Replace the upper die,remove the side plate of the lower die,and then press the U shaped billet into O shaped;Finally,the opening of the outer arc area of the sheet metal is welded together,and the excess billet at both ends of the elbow is removed to obtain the elbow parts that meet the requirements.The process mold is simple,easy to operate,forming quality is good;No heating,energy saving and environmental protection;No need for shaping process,high production efficiency,can achieve mass production.In this paper,the stress state of the elbow under the condition of internal high pressure was analyzed,and the finite element model of the elbow under the condition of internal high pressure was established by ABAQUS software,and the relevant conclusions of theoretical analysis were verified.Both theoretical analysis and numerical simulation prove that the stress in the inner arc zone of the elbow under internal high pressure is greater than the stress in the outer arc zone,and also directly prove that the single-weld elbow in the outer arc zone of this process is more suitable for the internal high pressure pipeline system than the singleweld elbow in the inner arc zone.One-step expansion method was used to estimate the size of the slab and analyze the formability of the elbow.The forward two-step forming process of 1.5D and 1.25 D elbow was numerically simulated by ABAQUS software,and the distribution of elbow wall thickness and the Angle of end face were quantitatively analyzed.Based on the simulation results of 1.5D elbow forming,the forming die was designed and manufactured,and the physical experiment was carried out.The factors affecting the forming quality of single weld elbow,such as blank shape,fillet at die closing and placement position,were analyzed.This research provides technical support and reference for the actual production of single weld elbow stamping process.