고압펌프 크랭크 케이싱 최적 주조방안에 관한 연구

Abstract

ABSTRACT

A Study on the Optimum Cast Plan of High-pressure Pump Crank Casing

By Jung, Seong-Won Advisor : Prof. Cha, Yong-Hun, Ph.D. Department of Mechanical Engineering Graduate School of Chosun University

Abstract

To produce high-quality cast in developing high-pressure water jets, the causes of defects and physical phenomenon occurring in casting have to be theoretically analysed. Defects can be predicted through analyses on causes of defects and casting plans can be changed or other processing variables can be controlled to produce high-quality cast. For effective control of casting defects, exact flow analysis, thermal analysis, and stress analysis should be conducted to predict locations and causes of defects. However, existing analyses on casting processes did not consider packing process of cast and analyse flow and thermal behaviors at full cast. There have been a number of analyses on inside the cast, but few studies which analyse gate and spruce runner. This study presents cast plan of high-pressure pump using ductile cast iron according to types and simulates die design and the principles of design for processing analyses. Fluid speed of gate and overflow must be controlled to improve quality of cast. Therefore, this study analysed cast speed and solidification in thermal and flow perspectives and based on the results, conducted a confidence test on main body of high-pressure pump. This study investigated factors of casting targeting the main body of high-pressure pumps and confirmed that locations of gates affect pores, flow and solidification of molten metal. As a result of analysing packing, defects due to mis-run were predicted through computer analyses and it was found that pores occur in thick section of the main body by gases in casting as a result of flow speed vector analysis, which can be solved through changes in size of gates. Optimal cast conditions were applied for configurations of real products and optimal flow was found at temperatures ranging from 1250℃ to 1300℃. After 40% of solidification processed after packing, rapid solidification began when temperatures were 900℃～1100℃ measured. Below 900℃, temperatures were maintained at the center of parts for certain periods for thermal stability of cast and structural stability of cast iron. Overflow recharges shrunken cast. Brinell Hardness Test was conducted on specimen from the parts where defects are predicted and hardness of the model with gates at sides was above Hв210, which indicates that part of the models used in fields may have defects. Therefore, this study discovered that defects on main bodies can be minimized according to changes in locations of gates.

Key Words : Water-Jet, Cleaning system, Moulding analysis, Utra-pressure pump, Foundry device, Gate, Overflow, Solidification, Flow temperature