Appearance and size inspection

　　After the head is cooled, the appearance and dimensions shall be inspected according to the relevant requirements in GB/T25198-2010 "Pressure Vessel Head" and GB150-2011 "Pressure Vessel". After inspection, there were no defects such as scratches and knocks on the inner and outer surfaces of the head. The inner diameter, circumference, thickness, height, etc. were measured, and the dimensional tolerances were controlled within the standard range.

　　Overlay ultrasound

　　A 100% UT inspection was performed on the inner surface of the composite layer of the head. After inspection, the coating did not peel off, and the molding process did not affect the bonding quality of the composite board.

　　Test board mechanical performance test and physical and chemical analysis

　　Mechanical performance test

　　Perform tensile, bending, impact test and hardness test on the furnace test panel (base layer), and all properties must be qualified.

　　Test plate intergranular corrosion test

　　The intergranular corrosion of the coated duplex stainless steel was carried out in accordance with ASTM A923-03 (Method C). Two samples, numbered A and B, were weighed and the surface area was calculated. Then put it into the ferric chloride solution for corrosion. After the sample is soaked for 24 hours, observe whether there is obvious adhesion of corrosion products on the surface, and check whether the corrosion test is qualified.

　　Test plate metallographic detection and determination of α-phase area content

　　The microstructure observation and ferrite content test of the coated duplex stainless steel are carried out according to ASTM A923-03 (A method) standard. The measured magnification is 500 times. The microstructure of the sample is a dual-phase structure, the black stripe part is the ferrite phase, and the white part is the austenite phase. After observation, there is no second phase precipitation or segregation phase at the grain boundary. Compared with the standard series of drawings, the area percentage of the α-phase of the duplex stainless steel sample is 40%, which is greater than the minimum content required in the standard. 30%.

　　Test plate grain size determination

　　The grain size measurement of the base layer is carried out in accordance with GB/T6394-2002 "Metal Average Grain Size Measurement Method". After the sample is etched with a chemical etchant, the microstructure is observed under a 100x microscope and compared with the standard series of rating charts. It is determined that the grain size grade is 9 and the grains become coarser, but the mechanical properties of the material are All meet the standard requirements. In addition, there is generally a deviation when using the comparison method to evaluate the grain size.

　　In view of the particularity of the design material of the duplex stainless steel composite plate head, strict requirements are put forward for the base layer, cladding and composite plate during material procurement, and the steel plate is sampled for re-inspection during the acceptance of the steel plate. The performance of the material meets the standard requirements. Strictly control the heating temperature, heat preservation time and final pressure temperature when the head is hot-pressed, and spray the inner and outer surfaces of the head immediately after pressing to speed up its cooling, so normalizing treatment is not required after forming. After pressing, the physical and chemical analysis and mechanical performance test of the head hot-pressed test plate verified that the original performance of the duplex stainless steel composite plate head did not decrease during the hot pressing process, and the composite plate head pressing scheme was determined The feasibility of this method will provide reference experience for making composite plate heads of similar materials in the future.