High-manganese steel frog is one of the key wearing parts in the railway ballast installation and is the bearer of the powerful impact load of the train from one rail to another rail. The transition zone between the rail top and the rail lug intersects if there is a shrinkage shrinkage zone in the casting process. Under the repeated action of the heavy fork impact load on the wheel, fatigue cracks originating from shrinkage cavity shrinkage defects will be generated. The outer part gradually extends to the working side and the non-working side and breaks or/exfoliates off (see Figure 1). It has a direct impact on the safety of railway transportation and the requirement of constant speeding of railways.
Baoji Bridge Factory is a large-scale professional manufacturer of domestic and foreign high-manganese steel frogs. It is smelted using 5 t and 6 t electric arc furnaces. The DV4 direct-reading spectrometer imported from the United States is used in front of the furnace to match real-time steel samples. The hardened sand type is produced in the process of production process and casting inspection in the VRH (vacuum, displacement, hardening) molding line introduced in Japan. Since 1992, a series of optimizations and improvements have been made to the molding process, eliminating shrinkage and shrinkage defects and achieving good results.
1 The main features of the optimization of the molding process The basic structure and optimization process of the high-manganese steel splitter are shown in Fig. 2. The main features of the process are: the three-wall intersection of the splitter and the upper part of the runner. 2? 180 mm 200 mm insulated riser with upper jaws on both sides? 25 mm 60 mm round bar cold iron.
2 Anatomical section before and after the process optimization compares the anatomical section of the posterior frog, it can be seen that after the improvement, the frog cross section is dense and the defect is completely eliminated.
3 Analysis High-manganese steel frogs are thin-walled but complex structures with long castings, each mass ranging from 400 to 500 kg. Under the condition of inclined pouring, most of the toe end, wing rails and heart rails will be poured. The realization of the process sequence solidification is fully supplemented. Due to the slow cooling of the heel end, if the follow-up metal supply is insufficient, the amount of replenishment is insufficient, and shrinkage shrinkage and shrinkage defects are likely to occur.
5 Casting Technology 64/2001 Analysis of Factors Affecting the Rheological Properties of Molding Materials by Optimizing the Process of Shrinkage Reduction of High-manganese Steel Frog Shrinkage Chai Zengtian 1, Zhou Tietao 2, Han Changren ( 1. Chengde Petroleum College, Chengde 067000, Hebei, China 21 Beijing University of Aeronautics and Astronautics, Beijing 100083) Determination of the number.
Article identification code: A quality of investment castings is closely related to the rheological properties of the investment itself, and the process of manufacturing the investment mold is the process of filling the press-type molding material. Therefore, the flow deformation property of the molding material itself will transfer the pressure, the flow state of the molding material in the press-type cavity, the working performance requirements of the wax injector, the design of the press-type runner, and the quality of the investment itself (eg, the size Accuracy, surface roughness, deformation, etc.), press-type structure, mold release ability, casting quality, etc. all have important influences. In addition, the process of manufacturing the mold material, the composition of the mold material, the state of the mold material when the investment mold is pressed, and the flow deformation property of the mold material also have a certain relationship. Therefore, in order to be able to use the best process, choose the most reasonable wax injection equipment, design a suitable pressure type structure, make high quality investment molds and obtain high quality castings, it is necessary to make the flow deformation properties of the mold materials for investment molding. Influencing factors for research 1 rheological properties) rheological curves describe the rheological behavior of mold materials generally using rheological curves of mold materials. The rheological curve of the mold material is the relationship between the shear rate and shear stress and viscosity. For Newtonian fluids, the shear rate is proportional to the shear stress, see Figure 1 (Line 1): Most fluids are non-Newtonian fluids, and the shear rate is not proportional to shear stress. Several common fluids The rheological curve is shown in Figure 1.
Using Instrall's 3 variable pressure capillary rheometer, rheological properties were measured and the rheological curves obtained are shown in Figure 2 and Figure 3.
From the rheological plot, it can be seen that the mold material is a pseudoplastic fluid with shear thinning.
At the same time that the riser is set at the intersection with the three walls, two insulated feeders are installed at the upper part of the runner to increase the feeding strength and the amount of feeding. Because the feeder and the cold iron are used at the same time, the two complement each other, which not only facilitates the feeding of the frog along the length of the working edge, but also facilitates obtaining a better austenite crystal structure.
4 Effect Optimization After the optimization of the process plan, no shrinkage porosity and shrinkage defects were found in the section anatomy. X-ray radiographs all achieved good results. From the results of track-by-line observations, the fractures produced by this process have never been found to have been broken or uncovered in recent years. The service life of the speed fork of Jinpu and Beijing-Guangzhou Line was generally improved. The average throughput was over 150 million tons, the longest use was 681 days, and the throughput reached 2.388 billion tons.
5 Casting Technology 64/2001 Factors Affecting Rheological Properties of Molding Materials
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