1. Material problems in pressure vessel manufacturing mainly include material substitution, substituting good for bad and substituting thick for thin. This situation is common in the actual production process. Material quality control is the precondition to ensure the safe use of pressure vessels. The quality of materials should be strictly controlled from the whole process of design, purchase, acceptance, storage, distribution and use. The national standards and specifications must be strictly implemented in the selection of materials. When choosing and purchasing materials, it is necessary to ensure that the materials produced by the material manufacturing enterprises conform to the relevant standards and norms. Before entering the field, materials need to be checked and accepted. The first is to check the qualifications of material suppliers. If the main pressure components of pressure vessels are used in modern times, they need to be put on record with the original unit. Material labeling transplantation is an effective means to prevent the misuse and misremembering of materials, and to establish a sound material labeling transplantation management procedure to ensure the traceability of pressure components in the process of storage, distribution, cutting and production and circulation. The parameters of raw materials should be inspected and checked strictly in accordance with relevant standards and norms. After the material enters the field, the person in charge of the material shall carry out the acceptance number of the material. The management of welding materials must be carried out in accordance with special specifications in order to avoid potential safety hazards. The storage of welding materials in the production process of pressure vessel quality cannot be guaranteed. Secondary storehouses must be set up. The storage should be classified according to different categories, clearly marked according to the grades, specifications and material inspection numbers, and special welding materials should be specially kept.
2. Deformation of pressure vessel seriously affects the tightness and reliability of use, and further affects the safety of pressure vessel in operation. It is necessary to carefully formulate and strictly abide by manufacturing technology and standards to ensure that the quality of pressure vessel meets the requirements of national standards and regulations. The deformation of pressure vessel in manufacturing process is mainly caused by the error of blanking size, die shape and assembly process. To solve this problem, we also need to start from these three aspects: first, to improve the cutting level and strictly calculate the required materials, we can use computer software to calculate the cutting and management [1]; secondly, to strictly control the shape of the die, fully consider the changes in the process of pressure vessel forming and after forming; in addition, in the process of assembling pressure vessel, we should use positioning clamp. Line positioning to prevent pressure vessel from deforming, and use theodolite to detect straightness. In the actual operation process, symmetrical cutting or mechanical processing are adopted to avoid flame cutting deformation after slab slab cutting and flattening correction. For instability deformation, the stiffened plate can be used to strengthen the opening area, and the stiffened plate can be removed when the back shell of the welded pipe is in the overall stable state. In order to avoid heat treatment deformation, a fire wall is set up at the flame nozzle of the furnace wall. If necessary, the pressure vessel parts which are easy to lose temperature at high temperature are strengthened.
3 During the manufacture of pressure vessel with welding seam problem, many parts are connected by welding. The arrangement of welding seam and the quality of welding directly affect the quality of pressure vessel. Particular attention should be paid to the defect of welding seam and the phenomenon of stress concentration. In the process of welding, attention should be paid to the layout of the welds, and the overlap and intersection of the welds are unavoidable. Therefore, stress analysis of pressure vessel is needed before operation, and computer software can be used to assist calculation. The key to affect the welding quality is the professional level of the operators. Therefore, we should pay attention to the management of the welding staff, review their qualifications and related qualifications, and ensure that they are certified on duty.
4. Stress corrosion cracking is caused by the interaction of stress and corrosion environment. In the actual operation process, it is unavoidable to produce stress, and the corrosive environment is also unable to get rid of. Therefore, the problem needs to be solved from the material itself. In the design of pressure vessel, it is necessary to take stress corrosion into full consideration and select suitable materials. In addition, the structure can be treated, heat treatment, anti-corrosion treatment, etc., to minimize stress corrosion; the possibility of cracks.
5. Hydrogen embrittlement is the hydrogen dissolved in steel and polymerized into hydrogen molecule, resulting in stress concentration, exceeding the strength limit of steel, and forming tiny cracks in steel, also known as white spots. Hydrogen embrittlement can only be prevented but not cured. Once hydrogen embrittlement occurs, it cannot be eliminated. The higher the temperature, the deeper the degree of hydrogen embrittlement, and the higher the carbon content of steel, the more serious the phenomenon of hydrogen embrittlement. To prevent the occurrence of hydrogen embrittlement, metal elements such as chromium, titanium and vanadium can be added to steel, corrosion inhibitors can also be added, electroplating, sand blowing and rust removal can reduce the occurrence of hydrogen embrittlement to a certain extent.
Above is the main content of this issue, I hope that the above content can arouse enough attention.
