Thickness offset above 0.5 mm is not acceptable. At 0.25 mm and 0.5 mm thickness offset tubes can safely expand up to 9.5% and 7.8%WR, respectively. Thickness offset of 0.125 mm tubes does not severely affect joint strength when expanded to 12%WR. There are evident severe plastic strain and grain rotation at the thinner sections. Thickness offset tubes' reduction in pull-out force was observed compared to uniform thickness tubes at higher %WR. The result shows that the hardness value has a linear relationship with pull-out force up to 12%WR for uniform thickness tubes. This paper focuses on tube thickness offsets of 0.125, 0.25, and 0.5 mm, microstructure and hardness values of expanded tubes and pull-out force at various %WR. Hydraulic expansion pressure of 190 MPa, and roller expansion pressure corresponding to 6, 8, 10, and 12%WR were used. Hybrid expansion of hydraulic and roller expansion was considered for this study. Apparent wall reduction (%WR) is used to evaluate the expansion joint strength. Thickness offset at the swaged ends of tubes reduces the joint strength and leak-proof characteristics of joints. Process improvement, preventing intermediate pull thin wall thickness and increase Haou exceeds the control range of the occurrence and improve the thickness accuracy.Uniform wall thickness all around the circumference is significant to get the right tube-to-tube sheet expansion joint pull-out strength. When welding, the mandrel is inserted between the two sections of a positioning pin of finishing, in order to prevent total straightness tolerances from welding too large. Mandrel outer precision control ± 0.1mm, straight mandrel deviation of not more than 5mm. Slenderness mandrel is relatively large, generally use the first car to break the outer diameter of the mouth and then welding, or using a long material directly Turning molding. Uniform thickness of the thick-walled tubes and solid blanks, you can make the probability of a significant reduction in the mandrel bending deformation, can effectively improve the precision of the thickness of steel pipe. Cross section is a 75 mm × 125 mm rectangle with a 51 mm × 101 mm rectangular cutout. For the loading given, determine (a) the stress at points A and B, (b) the point where the neutral axis intersects line ABD. To choose the mandrel and the thick walled tube processing, the smaller size of the mandrel can be used instead of a solid billet. The tube shown has a uniform wall thickness of 12 mm. Perforation jack usually selected outer diameter Φ108mm-Φ114mm, wall thickness and wall thickness requirements ≥25mm uniform thick-walled tube. Guarantee from the centerline of the guide rollers and in piercing and rolling from the center line, ie upper and lower rollers from equal distance about equal to the guide. Roll from the center of the guide must be from the rolling line. Each heating and cooling to maintain a slow and steady, the maximum temperature does not exceed the lift 30 ℃.ĭetermine whether the centering roller is mounted in place, adjust the roll core holding center, the opening angle of the opening movement and all the same size, hold the center of the core roll to the rolling line.Įnsure a consistent rolling piercer piercing car center line and the center line, to avoid "rolled on" or "rolling down" so that the tube holding force even when the perforation.įor wear head, guide and roller rolling tool must be promptly replaced. Heat uniformly prohibit rapidly elevating temperature. Seamless steel pipe wall thickness control is a difficult steel pipe production, measures to improve the production of seamless steel pipe wall thickness accuracy mainly includes the following aspects:
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