Surface NDT methods straight seam steel selection principles: magnetic iron pipe should be used in magnetic particle testing; non-ferromagnetic steel should be used in penetration testing. Delayed cracking tendency of welded joints, the surface should be non-destructive testing after welding cooling certain time; reheat cracking tendency of welded joints, the surface should be in non-destructive testing and post-weld heat treatment once each. Surface non-destructive testing applications in accordance with the standard requirements that detects objects and applications in general as follows: (1) An outer surface of the tube material quality inspection. (2) Important butt weld surface defect detection. (3) Important fillet surface defect detection. (4) Important socket weld and jumper tee branch pipe defect detection. (5) Pipe bending surface defect detection. (6) The material tends to quench detection larger groove welded joints. (7) The design temperature is below zero or non-austenitic stainless steel pipe beveling detected 29 degrees Celsius. (8) The provisions of the double-sided weldment after weld gouging gouging detection (9) When using oxyacetylene flame cutting jig welded pipes alloy hardening tendency on when grinding parts defect detection.

How to bond the thermal expansion seamless steel pipe : 1. Thermal expansion pipe before bonding, dry cloth and the outer side of the socket socket wipe process, when the sticky surface oil to be wiped clean with acetone. 2. Thermal expansion pipe section should be flat, perpendicular to the tube axis and chamfered; inserted before bonding should be drawn markings and insert test, the test can only be inserted into the depth of the original depth of 1/3 ~ 1 / 2, prohibited the use of over-the gap is greater than the bonding method. 3. Apply adhesive should be applied inside of the socket, smear the outside of the socket, the socket should be applied along the axial direction from the inside out evenly amount, shall not apply or drain excess coating (200g / m2). 4. After the adhesive applied, the external force should be applied within 1 minute to keep the same, straight and position connectors are properly maintained. 5. After bonding is completed in a timely manner will wipe out excess adhesive in the curing time shall be subjected to force or forcibly loaded. 6. The adhesive joints or construction can not be in the rain water can not operate below 5 ℃. 7. Connect Program: Prepare → Face → try to clean up brush adhesive interposed → curing adhesive.

Seamless steel pipe cracks reasons:   First: the organization is non-uniform tube reasons. 16Mn previous steel grade Q345B already changed, and it does not matter, pay attention to choose to perform a standard tube, a certain scale manufacturers of bar line. Second: finish annealing temperature is suitable. Perforation heating temperature of 1180 ~ 1230 ℃, low carbon steel which is a temperature taken 1230-1250, it is appropriate. 35min furnace or heating time is the time? Furnace time is generally more than 60min. Third: the reason cracks, test proved that the tube (round) the reasons for the majority, the interior contains more cracks, inclusions, gas and other packages. Perforated temperature, process adjustments can not be ignored, if the temperature is low perforation, adjusted properly, can also cause tearing capillary internal organization.

1. Thermal expansion seamless pipe 16Mn material after straightening head and tail were cut early, simply cut necking and space segments and pulling the tail section cracked, no more cut; the end face to ensure smooth, not skewed;   2. Finishing classes at the test bench to be treated pipe expansion material 16Mn seamless surface inspection, the outer folding, inner folding, crack, less the number of external scarring and shallow depth of grinding to clean, as compared with outer flap multiple or deep grinding can not directly sentenced to waste, can not be used diffuser material; grinding the rear wall thickness than the negative deviation and fill with welding Shuhei;   3. Thermal expansion operatives came to power after the tubing rack, check 16Mn seamless tube inner and outer surfaces, found missed outside off, cracks and other defects with the grinding wheel clean, depending on the grinding depth with welded wire reinforcing and Shuhei ;   4. The tube wall thickness and material support by length measurement and make a record, according to the specifications 16Mn seamless tube wall thickness and length selection system expansion specification (φ273,325,377,426), to ensure that the finished product after the head and tail cut lengths not less than 6 m   5. Encountered stiff head tube to be marked in a stiff head parts, pipe expansion process, the stiff head when approaching the site to slow forward speed, an increase in temperature;   6. After completion of the pipe expansion of the inner and outer surfaces to be checked, not to eliminate defects marked on 16Mn seamless and recorded in production records; capable of grinding to go clean after grinding annealing furnace;   7. The thermal expansion of working class before the start of expanding the system to measure the thickness of the material before the three pipe, 16Mn seamless expansion of the system and then measure the wall thickness, wall thickness adjusted according to changes in velocity and temperature expansion of the system;   8. To 16Mn thermal expansion of two flat, not allowed to be expanded to the level when the system seamless docking;   9. After each expansion after a 16Mn seamless tube wall thickness to be measured after the expansion, according to standards and specifications determined to do production records.

In other conditions remain unchanged, with the different die cone angle, equivalent stress suffered tube, equivalent strain also will be changed. With the die cone angle increases, the equivalent stress increases, but the equivalent strain decreases. With the die cone angle increases, the punch load decreases. In vertical large diameter thick-walled seamless steel pipe extrusion numerical simulation, the punch load changes can be divided into three stages, filling stage extrusion, extrusion stability and end stage compression stage. When the blanks are not filled die cavity, with the extrusion load was gradually increased and reached a peak; when working with metal outflow stabilize a certain distance from the load, when extruded to a certain length later, with extruded decreasing the load continues, the end of the extrusion process.