船舶 建造用 曲블록 壓縮荷重 支持臺 핀지그 性形解析에 關한 硏究

Abstract

As the casting technique developed and production of delicate casting products became available, the call for control of precise defects and for an accurate analysis of the reasons behind the defect occurrence is getting higher. it is important to estimate the position and the reasons for defects through fluid analysis to eliminate casting defects, thermal analysis and stress analysis. However, the analysis of the existing casting process does not consider the filling procedure of the mould but only consider fluidity and thermal movement when the mould is full. In addition, although extensive analysis of the mould inside is carried out relatively, the concurrent analysis with the runner and the sprue for the metallic fluid is not carried out as much. The geometric form of the runner and the sprue has an important effect on the casting procedure and hence this effect cannot be ignored. And, the normal casting process involve casting molten metal in Ingot or Slav types and after the plastic working process of the thermo-softening and cold rolling process, the final products such as metal sheets are obtained. However, in order to maintain the competitive edge in the steel and iron industry as a highly industrialized developed nations, a new process development is required to dramatically save costs in equipment installation and energy. Also, due to the reduction of skilled welding professionals, aging of the welding professionals, high remuneration of the welding professionals, the consistent quality maintenance of the welded area, there is a continuing demand for shortening time for welding large caliber pipes. The demand for pipe structures such as marine structures, pipes, iron towers and metal outfits are increasing and the productivity and precision to produce these structures are being demanded. Recently, as the overall world shipbuilding market conditions recovers, the Korean shipbuilding industry has been evaluated as reached the period of maturity. And as we enter the 21st century, despite the increase in domestic demand, the proportion of export ships will continue to be large in the Korean ship production. Hence, the building capacity will continue to expand. The small and medium shipbuilding enterprises have two concurrent problems of technology gap with the advanced countries and of labor cost increases. In order to solve these problems, it is recognized that the most effective strategy is to develop new technology. In order for the Korean shipbuilding companies to enhance competitiveness, the companies need to improve the standard of the technology and according to the fact finding survey on the industries related to shipbuilding, our firms are behind those of advanced countries in developing and applying new technology. Hence, due to the shortage of professional resources and to reduce the cost of production, the efforts are being made to reduce welding process and to produce integral structure to increase the efficiency of production cost and processes. In particular, the vertical compressive load support used in the ship block operation has a fault of crack occurrence which is common for the casting products so it is utmost important to develop marine equipments and materials with strong pulling characteristics. And in line with this development, to produce high quality casting products, the analysis of why defects occur must be carried out and hence theoretical interpretation of the physical phenomenon of the casting process must be analyzed. By analyzing the reasons for the defect occurrence, it is expected that defects occurring during casting process can be predicted so that either the mould design is amended or other process factors are controlled in order to produce high quality products. And it is also expected that the ship equipments and materials can be improved in quality and more precise products can be produced. This paper suggests that the casting process using nodular cast iron and using computer simulation for the design principles for die design and for process interpretation. In the process interpretation, the speed control of fluid in the runner and ingate is important in the cast quality. Hence, the process speed and solidification process must be analyzed on the perspective of the thermal and fluid analysis. And based on the results, the curve block pin jig for vertical compressive load support was produced and the produced parts were verified for quality. In addition, to develop the perpendicular strut curve block pin jig used in ship building and to improve its process, the flow and the solidification in the casting process must be estimated quantitatively and the cast design productivity and quality must be maximized by optimization. The results for the research as follows ; 1. As the results of design and modeling analysis of the vertical strut curved block pin jig, the stable pin jig which can withstand over 150 tons was finally designed. After the mould was designed, through the casting process vertical compressive load support made out of ductile cast iron with strong toughness characteristics was developed. 2. Based on the stress analysis on the curve block of the vertical compressive load support, out of 150 tons, the maximum yield point was estimated and the stability was achieved by spreading the stress to the wing sections and concentrating the stress under the pin jig. 3. At 100 tons, the yield strength was estimated as maximum 1.759e7 N/m2, minimum 7.577e4 N/m2 and at 150 tons, the yield strength was estimated as 4.397e7 N/m2, minimum 1.894e5 N/m2 . So few curve block pin jigs were installed at the lower end so it can withstand vertical compression in excessive of 250 tons during operations. 4. As a testing model of the vertical compressive load support for the curve block, the influencing factors for the casting process were investigated and as a result, in the casting speed and solidification process, they had effects on porosity, molten metal fluidity and solidification. 5. After analyzing the filling analysis, the possibility of defect occurring from causes such as misrun was estimated by computation, the reading results of the fluidity speed vector verified the occurrence of porosity at the lower end of the curve block and the problem was resolved by widening the runner ingate. 6. The most optimized casting requirements were selected the actual product model casting was applied, the optimized fluidity is at the molten metal temperature of 1280℃～1300℃. And, after filling, the solidification progressed quickly after 40% progress and the temperature at the time was measured at 900℃～1100℃. Below 900℃, the core of the parts were kept at a constant temperature for a set time so that thermal stability in the structure of the nodular cast iron. 7. Since additional processing costs in ensuring the produced curve block pin jig to be perpendicularly in line is required, the casting process costs were reduced. And another improvement point was made to address the large costs involved with making a hole in the pin jig. 8. As the results of the composition photos about the compressive load support pin jig, it was that the ductile cast iron was obtained as the material, the maximum HB of 200 was recorded and good test results were achieved. that is, for mechanical characteristics, tearing strength 530.7 N/mm2, yield strength 388.9 N/mm2, and elongation strength 13% were achieved.