3.1.11 slag analysis and testing
The gases in the molten iron are mainly oxygen, nitrogen and hydrogen, which are only less than 0.05% by weight, but have a considerable influence on the microstructure and mechanical properties of the cast iron. Oxygen and nitrogen were tested in the molten iron. Hydrogen has certain difficulties, and it is difficult to determine the index as pre-furnace control. Therefore, in order to obtain high-quality molten iron, the content of Feo in the slag is increased as a control item. By measuring the content of Feo in the cupola slag, the degree of burning of si and Mn in the charge can be judged. This kind of detection is not difficult, only chemical analysis can be used. For domestic automotive foundry factories should be carried out.
3.1.12 pre-furnace thermal analysis method
The domestic automotive foundry industry should continue to conduct research and development of the “thermal analysis methodâ€. It is probably the best choice for future quality testing methods for cast iron furnaces. Because it can not only quickly report the spheroidization rate, but also can simultaneously detect the C, Si content and the inoculation effect of cast iron, matrix structure and mechanical properties. However, due to the influence of many factors such as the accuracy of domestic thermocouple materials, thermal analysis is not very satisfactory in terms of test accuracy.
3.2 Casting quality control aspects
The high level of modern casting lies in. It is not only to achieve high-level inspection of finished castings, but also to realize intermediate quality inspection and intermediate quality control in the whole casting process; not only to achieve the closed loop of “pre-testâ€, “measured†and “post-tested†in the intermediate process of casting Control, but also to achieve automation and computerization of the closed-loop control of the intermediate process. In terms of improving and stabilizing the quality of castings, the application of microelectronics to control the smelting process and the quality of the sand is particularly important for larger foundries. For multi-variety and small batch production, the microcomputer can be conveniently used for counting, template replacement, selective casting, cooling program conversion, etc., which has the special advantages of flexible manufacturing units. High-efficiency molding machines are no longer possible to control manually, and microelectronics technology can adapt to a variety of changes. From the current situation of the domestic automobile casting industry, the two processes of sand treatment and melting have not only been more backward than foreign casting, and these two processes are also the greatest potential for improving the quality and cost economic benefits of domestic foundry factories.
3.2.1 Sand treatment quality control
Microcomputers have long been used in the management of sand properties. For a sand treatment system, simply controlling moisture, temperature, and constant ratio is not enough. For this purpose, Dietert has established 15 procedures for sand quality diagnostic analysis for each foundry and for automatic quality control of sand. The micro-computer-controlled sand treatment department that has been developed by the German company Eirich has added sand and auxiliary materials to the sand mixer. After dry mixing and then adding water to the wet mixing, the computer continuously controls the moisture, temperature and tightness of the mixture. Some can also automatically change the ratio and other performance parameters in time according to the requirements of the molding department. These are one of the efforts of our automobile foundry industry in the early 21st century.
3.2.2 Quality control of the melting process
At present, foreign countries have reached a high level in the automatic detection and control technology of cupola. The furnace is controlled by an electronic computer. According to the iron grade, the charge composition and the price, the linearization method is used to optimize the ingredients, which not only meets the melting quality requirements, but also ensures the lowest cost. In front of the furnace is mainly engaged in automated recording and control adjustment. It can not only detect the main variables such as molten iron temperature, melting speed, air volume and coke consumption during the smelting process, but also comprehensively adjust the melting speed, air supply intensity, molten iron temperature and coke according to the changes of process parameters such as composition and temperature of molten iron. Consumption, according to the principle of automatic adjustment, the output is feedback-adjusted to the input quantity, and the cupola is stabilized in the optimal working state (automatic finding and constant value control of the optimized working point such as air volume and coke consumption). Whether it is the cupola furnace smelting or the computer automatic adjustment control of the power frequency furnace smelting, especially the automatic adjustment and control of the composition of the molten iron and the temperature of the molten iron, the gap in China is very large. This aspect is also the direction that our automotive foundry industry should strive to improve in the early 21st century.
There are still many other microcomputer controls in other countries. For example, the new generation of molding line products are controlled by microcomputer, the molding machine adopts quick change template device; the core of the microcomputer controls the core making, hardening, purification and environmental protection; the special line for cleaning uses the microcomputer to control the shot blasting machine, with CNC The machine tool performs pouring riser cutting and deburring burrs; some companies use simulated follow-up robots for sand falling, slag slag and pouring operations. Due to space limitations, it will not be detailed.
3.3 Casting measurement and environmental testing
Metrology and testing is the most basic, most important and most important task of casting enterprises in quality, cost reduction, efficiency increase and accurate calculation of input and output. It is also the premise of quality control in casting process. However, the current automobile foundry has not paid enough attention to the metering rate, integrity rate and update development of measurement methods. For example: the accurate measurement of the feed material of the train into the factory (using the "train in the train", the "interface" between the workshops), the accurate counting or measurement of the input and output and the logistics, especially the feeding of the melting workshop. Work, etc. are lack of means or means of low level and unreliable. This is an urgent problem to be solved in the future. It should also adopt electronic weighing instruments that are intelligent and capable of continuous metering and development to “remote monitoring†and computer management. Environmental testing is the inevitable path of the foundry industry in the 21st century. Casting abroad has long been valued and brought to justice. However, the environmental pollution inside and outside the factory of China's foundry industry has become a major public hazard. At the beginning of the 21st century, it is necessary to combine environmental testing and self-inspection. China is very backward in environmental testing equipment, and some basic and necessary instruments should be introduced.
3.4 Casting Inspection and Control Technology Management
Automobile foundry factories should pay special attention to the improvement and development of casting quality inspection and quality control methods, and they must be willing to invest in this quality cost, because an effective detection means that the economic benefits are not much larger than their own value investment. It is necessary to grasp the "two heads" of the whole process of casting, and also to bring "the middle"; it is necessary to grasp the means and manage. At present, many of China's automobile foundry factories have "common problems" in the detection and control technology management: either the measurement detection and quality inspection methods are incomplete; or only the detection but no feedback control; or the process parameter detection without parameter evaluation; Or although there are detection and control means, but their cycle maintenance, metrological verification, planned repair and spare parts supply can not keep up. These problems are all issues that China's automobile foundry enterprises must urgently solve.
3.5 Casting quality management technology plus “five technologies combinedâ€
Since the founding of the People's Republic of China, China's automobile foundry enterprises have carried out many years of "quality month" activities, and have undergone comprehensive quality management training for all staff members. Although they have received certain results, they have not really gone. The road to standard specifications for casting quality management. The author believes that modern casting companies can only truly study and implement the ISO9000 family standard management in order to truly embark on the norm of casting quality management. Because only by implementing the "standard", can we truly implement quality inspection, quality control, quality improvement, quality prediction, quality prevention and various quality management techniques; in order to enable the quality inspection department to be busy all day from the current production problems The liberation of passive checks and emergency "firefighting" can be carried out from "low-level stage of passively shutting down firefighting" to "advanced stage of active prevention", thus realizing the transformation from "necessary kingdom" to "freedom kingdom". It should also be pointed out that many years of practice have shown that in order to give full play to the power and role of casting quality inspection and quality control, it is necessary to achieve the "five technologies combined". That is, the combination of detection technology (including metrological verification technology), control technology (including automatic adjustment technology), assessment technology, maintenance technology (including maintenance), and measurement technology (including batching, continuous feeding, and input and output measurement). The author is convinced that the ISO9000 family standard technology and the "five technologies combined" will surely produce tremendous material strength in China's automobile foundry enterprises! Automotive casting engineering and technical personnel not only need to study the casting process and detection control technology, but also study the "total quality management" technology, but also the "comprehensive cost management" technology. Like the machinery manufacturing industry, China's foundry industry must take the modernization of quality inspection, quality control and cost measurement technology as the leader, and promote the modernization of information and the modernization of enterprise management in the whole process of production, in order to fully promote the modernization of the foundry industry!
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