Paper on the manufacture of hollow steel ball moul

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The expansion project of Urumqi diwobao International Airport is the structural characteristics and working principle of the national bending testing machine and the key construction project of the autonomous region, of which 101 maintenance hangar is an important part. The hangar roof is composed of two structural forms: long-span steel truss and welded hollow spherical joint frame, which are designed by China Aviation Industry Planning and Design Institute. With a plane size of 86m in depth and 115m in span, it can park two IL 86 large passenger planes for maintenance at the same time, which can be called the first span in the northwest; The total weight of the frame is more than 800 t, of which the total number of hollow steel balls is 200t. The frame is installed by Shaanxi mechanized construction company, and the hollow steel ball is made by Xinjiang industrial equipment installation company φ 500mm × At that time, there was no manufacturer in Xinjiang to produce 25mm hollow steel balls with material pressure decreasing by 16Mn in sequence. Our company had to develop and design a set of molds to meet the needs of the project

2 structure and service performance of hollow steel ball mold

the original design scheme of the ball mold of the stamping die is an integral steel casting, which has the characteristics of compact structure and good service stability. However, due to the high cost, it is instead welded with 860mm steel plate (Fig. 1). In order to ensure the welding quality and the safety performance requirements of the mold, the welding between all main vertical plates, auxiliary vertical plates and stiffener plates requires the processing of double-sided grooves, which must be smooth and flat, and the iron filings and oxide scales on the surface. Oil, rust and water pollution must be cleaned up. Welders must work with certificates and have welding qualifications. All welds shall be fully welded, and the appearance inspection shall be carried out. There shall be no cracks, incomplete penetration, slag inclusion, pores and weld beading, and they shall comply with the standard of code for welding of building steel structures (jgj81 - 91). After passing the inspection, the use accuracy shall be achieved after eliminating deformation and machining

before processing, in order to simplify the process, reduce the cost and facilitate the machine tool processing operation, it is necessary to process in pieces. The flat surface of the ball tyre is first processed by the gantry planer, and the ball tyre tray is processed by the vertical lathe to the specified size (900mm × 80mm) and drill M16 screw holes with lines, then fix them with the base with a special fixture and weld them. In order to reduce welding deformation, cross symmetric welding method is adopted. After all welding is completed, remove the special fixture after cooling, and the mold will not deform. The base of the ball tyre consists of a base plate (1200mm × 1200mm), ball tyre tray φ 900mm × 80mm), 2 main vertical plates (1200mm × 500mm), 2 auxiliary vertical plates and 6 stiffener plates. The clearance between the lower mold of the ball tyre and the tray of the ball tyre adopts the following standards: φ 80mh11h11, connected with Mg bolts, and the ball tire can be replaced according to the needs of the project. The replacement range is φ 400mm- φ The hollow steel balls of various specifications between 600 mm have expanded the scope of use of the mold, played the role of the first mock examination with multiple uses, and reduced the production cost. The lower mold material of the ball tyre is 45# steel, which reaches hrc52-56 after heat treatment; The upper mold of the ball tyre is made of ductile iron (QT). In order to strengthen the strength of the mold head, cross rib plates are used inside, which not only increases the compressive strength but also reduces the quality of the mold. The blanking method is adopted for die pressing. After forming, the hemisphere is directly taken out from between the two main vertical plates, and the die does not need the compression ring, because according to the empirical formula T/D × When 100> 2, the hemispherical blank will not wrinkle during pressing, so the blank positioning is accurate and the operation is convenient when using the mold. It is worth noting that when pressing hemispherical wool embryo, the embryo material must be heated to more than 720 ℃, which has two functions: one is to reduce the working pressure, the other is to reduce the rebound of steel plate and maintain the accuracy of forming. Because the size of the ball subcutaneous material is large( φ 700mm), so the weight saved by using steel is helpful to improve the fuel economy and reduce emissions. A coke heating furnace is welded to heat hemispherical blanks, heating more than 10 pieces at a time for about 30 minutes

3 test results and analysis

the mold test equipment is a 1000t four column hydraulic press, and the hemisphere is formed by stamping at one time. After assembly, check the steel ball diameter ① 5 plus, roundness. 2mm, meeting the requirements of mold design and the standard of "standard for quality inspection and evaluation of frame structure engineering" (jgj78 - 91). In the process of pressing, the ball skin thinned under the action of stretching, and the thinning amount exceeded the standard. After special processing, the thinning amount was controlled within the specification, which also accumulated the experience of tightening the upper and lower jaws. After hemispherical assembly, the carbon dioxide gas shielded welding is used for backing, and the submerged arc automatic welding of the cover surface is shown in Figure 2. This method is at the leading level among peers in the country. Through nondestructive testing, its welding quality meets the H-2 welding schematic level standard specified in the code for construction and acceptance of steel structures (gb50205-95). The finished products were subjected to destructive tests (6 tensile tests and 6 compressive tests) by the engineering structure laboratory of the general Architectural Research Institute of the Ministry of metallurgy, and all properties were qualified according to the (metallurgical quality inspection (final test) Zi (96) No. 24 inspection report). The design and manufacture of the whole set of molds are based on the principle of simplifying the process and reducing the cost, and the quality is guaranteed from processing, assembly, trial production, production, inspection and test. Therefore, it can meet the needs of the project faster and better. At the same time, it adds a new variety to Xinjiang, expands the market and increases the enterprise benefits

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