In the past, when casting exhaust pipe, the main forming mode was wet sand gravity casting, and the materials were traditional gray iron, vermicular iron and. Because of the use of automatic production line, therefore, the production efficiency is very high, the production speed can reach more than 200 models per hour. However, with the development of globalization, the temperature of molten steel in automobile reached 1600 ℃ at the end of 20th century The traditional casting mode has been unable to meet the temperature requirements, so the new resin sand core preparation technology for exhaust pipe cavity is adopted, which not only greatly improves the work efficiency, but also meets the temperature requirements, and with the continuous development of core technology, large-scale production has been achieved. In addition to the resin process, there was a lost wax investment at that time. The parts produced by this process were not only of high accuracy, but also very durable. However, due to the high production cost and low productivity, it is difficult to put into use on a large scale. It is generally used to produce parts with small quantity and complex process. This lost wax investment casting process is a combination of various processes. It can not only achieve the minimum error and the highest precision, but also produce products with high complexity and demanding thin wall, which solves many problems.
Later, a new process appeared. The process was first developed by two foreign automobile companies. It is a great integration of various casting processes. The traditional cold box technology is used in the manufacturing of sand core; the high-temperature inorganic binder is used in the core assembly, and the wax loss casting process is used in the casting of ceramic mold. This process is named Kaidi turnover mold process CCM process for short. It is difficult for the traditional casting process to reach the temperature of liquid steel when pouring, which can not meet the filling performance of liquid steel. However, CCM process can fully meet the needs of temperature when pouring liquid steel, and will not form stimulation to liquid steel, so it can well meet the filling performance of liquid steel. In addition, the CCM casting process not only has small gas defects, but also has small shrinkage. The final product has high success rate and high accuracy. In addition, CCM process in the manufacturing of materials is not high, many poor materials can also be cast through CCM process to produce good finished products, which greatly reduces the cost, improves the success rate and improves the work efficiency. It can not only produce in large quantities, but also produce high-precision castings, which has epoch-making significance.