The China Foundry Association recently organized a scientific and technological achievement evaluation meeting on “Application Research of New Carbon-Free Clay Green Sand Casting Technology” in Weifang City, Shandong Province. An evaluation committee composed of well-known domestic experts such as Li Peigen and Ding Wenjiang, academicians of the Chinese Academy of Engineering, and researcher Zhang Libo, president of the China Foundry Association, listened to the work report and technical report of the project team and reviewed the applications provided by the project unit. Certificates and other scientific and technological achievements evaluation materials.
After detailed inquiries and discussions, the expert evaluation committee unanimously agreed to appraise the scientific and technological achievements of the project, and believed that the new carbon-free clay green sand casting technology was an original technological achievement, reaching the international leading level, and cracking down on the pulverized clay wet sand foundry industry. Sand casting technology has a long-term global problem of pollution and has very important application value. It can provide strong technical support for the transformation and upgrading of the foundry industry’s green development.
Traditional sand casting technology faces three major problems
As we all know, the foundry industry is the foundation of the equipment manufacturing industry and is closely related to people’s lives and industrial production. From daily necessities to high-end equipment, casting is inseparable. Among them, castings produced by sand casting methods account for more than 80% of the total castings. Molding sand is the main modeling material in foundry production, and it occupies an important position in foundry production.
The reporter learned that the existing foundry sand mainly includes three types: pulverized clay green sand, sodium silicate sand, and resin sand. At present, most foundry companies at home and abroad are using pulverized clay green sand. This type of sand is added with coal powder and other organic matter and carbonaceous additives to the clay green sand. It is mainly used for anti-sticking sand and sand inclusion. The casting quality and environmental pollution problems caused by the inherent defects of pulverized clay green sand have never been solved.
Sodium silicate sand is prepared by mixing quartz sand, sodium silicate and additives. The sand mould made can be chemically hardened by blowing CO2, or it can be hardened by heating or hardened by itself under the action of a hardener. This kind of molding sand does not contain toxic substances and is more environmentally friendly. However, sodium silicate sand has the insurmountable shortcomings such as difficulty in falling sand, difficult regeneration of old sand, and serious sand sticking, which make it unable to be fully promoted.
Resin sand is prepared by mixing quartz sand, resin and hardener. Commonly used resins include furan resin, resole phenolic resin and urethane resin. The sand mould made of this kind of sand has high strength, accurate size, good collapsibility and low energy consumption. However, a large amount of toxic gas is produced during the production process, which causes a large amount of emissions and a high cost.
“Sand casting technology has three major global problems: high pollution, high energy consumption, and low casting quality. Exhaust gas pollution, dust pollution and solid waste pollution will occur during the casting process. The serious dust and gas pollution in the foundry will cause the workers to work in a very harsh environment. , The dust and gas discharged to the outside of the workshop are also one of the important sources of smog.” said Zhu Shigen, a professor at Donghua University. At present, the resin sand and sodium silicate sand used in production can only be used once. Although the pulverized clay green sand can be partially reused, the total amount of discharge is very large, and the solid waste pollution is very serious.
In addition, the foundry industry is a major energy consumer in the machinery industry, and its energy consumption accounts for about 45% of the total energy consumption of the machinery industry, of which the consumption of pulverized coal is considerable. Castings produced by traditional casting technology have many pores, china sand casting inclusions and sand washing phenomenon from time to time, resulting in problems such as unsmooth surface, large cleaning workload, and large machining allowance, which seriously reduces production efficiency and has a high rejection rate. Among them, the waste rate caused by molding sand accounts for about half.
School-enterprise cooperation to develop new carbon-free clay green sand
In recent years, with the promulgation of the new “Environmental Protection Law”, “Air Pollution Prevention Law”, “Three-Year Action Plan to Win the Blue Sky Defense” and other legal documents, pollutant discharge standards have also been continuously improved. As a traditional industry with high energy consumption and high pollution, solid waste and air pollutants are the most emitted during the production process of the foundry industry. How to reduce environmental pollution while ensuring the quality of castings is an important issue faced by traditional foundry enterprises.
In order to solve the problems of pulverized clay green sand, Donghua University, Shandong Xuanhe New Material Technology Co., Ltd., and Yiwu Yunxi New Material Technology Co., Ltd. have developed a new type of carbon-free clay green sand after several years, using pure inorganic materials as raw materials. , No pulverized coal and any substitutes for pulverized coal, no carbonaceous materials and organic materials.
“The new carbon-free clay green sand has the characteristics of green environmental protection, low carbon and energy saving, circular economy, and high-quality castings. It breaks through the anti-sticking and sand inclusion mechanism of traditional coal silt and other organic matter, and has mastered the effective control of the interface between the sand and the metal. The principle has realized the substantial transformation from accidental experimental phenomenon to reproducible and repeatable, forming a new technology of pure inorganic anti-sticking sand, which is the first at home and abroad and has successfully applied for a national patent.” New carbon-free clay wet Said Zhu Shigen, a professor of Donghua University, the inventor of molding sand technology.
It is understood that the new carbon-free clay green sand is khaki-colored, and its raw materials are all non-toxic inorganic substances. Its conventional indicators are equivalent to those of coal pulverized clay sand. The wet compressive strength, fluidity and compaction rate at room temperature are adjustable, and the air permeability is good. The hot and wet tensile strength is high, which can guarantee the basic modeling operation and pouring requirements.
In addition, the new carbon-free clay green sand has high high-temperature hot pressing strength, low high-temperature thermal expansion rate, better reusability, no exhaust gas during the casting process, and a small amount of waste sand produced without any toxicity, and it can even be used for farming. The surface roughness and dimensional accuracy of castings produced by using this sand are improved, the subsequent mechanical processing is easier, and the energy consumption of processing and cleaning is reduced.
Good feedback from new sand production test
Laboratory research has laid the foundation for the practical production and application of the new carbon-free clay green sand. However, the production conditions of the foundry industry vary greatly. Whether it is the size, shape and cnc operating material of the parts, the molding method and the degree of automation used, or the molten iron pouring temperature, head height and pouring speed, etc., different requirements will be placed on the molding sand. Whether the new carbon-free clay green sand casting technology can withstand the test of actual production conditions requires further actual production tests.
Since 2014, the new type of carbon-free clay green sand has been tested in large-scale production and application in foundries in Zhejiang, Jiangsu, Fujian, Shandong and other places. The production products include automobile castings, valve castings, engine block and cylinder head castings, fire-fighting pipe fittings, motor housings, water pump castings, road accessories and other products. The casting materials involve ductile iron, gray iron, aluminum alloy, etc. Modeling methods include manual modeling, shock-pressure molding machine modeling, and vertical parting extrusion modeling.
After testing, the new carbon-free clay green sand is completely suitable for the production of castings of various materials and sizes, such as gray iron, ductile iron, and non-ferrous metals. No toxic waste gas is produced during the pouring process, and it does not pollute the air. The dust floating in the workshop was greatly reduced, and the air quality was significantly improved. A small amount of waste sand scrapped during the casting process is non-toxic and harmless, similar in color to the soil, and compatible with the environment. The surface of the production castings has less sand sticking, low sand inclusion and sand washing defects, seldom found pore defects in the castings, the quality of the castings is improved, and the product yield can be increased by 3% to 5%.
In September of this year, Weifang Deere Foundry Co., Ltd. cooperated with Shandong Xuanhe New Material Technology Co., Ltd. to use a new type of carbon-free clay green sand casting technology to conduct production trials of six-cylinder block castings for Steyr engines. “This kind of cylinder water cavity consists of a water jacket core, which has strict requirements on the casting process and is a very difficult casting to produce. For the convenience of comparison, the same pressure, pouring temperature and speed as ordinary sand are used in the production process. After comparison, it is found that the air permeability, anti-sticking sand and sand inclusion properties of the new sand are better than that of clay sand, and the quality and precision of the castings fully meet the requirements.” said Zhao Fahai, chief engineer of Weifang Dier Casting Co., Ltd.
Since December 2017, Gaomi Zhicheng Machinery Co., Ltd. has purchased a total of 503 tons of new carbon-free clay green sand for vertical parting injection molding casting production. It has been used for 10 months to produce and export various agricultural machinery parts and other castings. More than 2500 tons. “After using new molding sand, the black visual pollution of traditional green sand is eliminated, no toxic waste gas is produced during the casting process, the dust floating in the workshop is greatly reduced, and the air quality is significantly improved; waste sand emissions are reduced, and the produced castings are not sand-sticky. , It is easy to clean, the yield rate is improved, and the cost of castings is relatively reduced.” said Sun Shensheng, general manager of the company.
In addition, Zhu Shigen led the project team to compare the pollutants emitted by different molding sands during the production process. The data shows that the hourly average concentration increase of particulate matter (PM2.5, PM10, PM100), formaldehyde, and carbon dioxide after pouring pulverized coal green sand exceeds the limit specified in GBZ2.1-2007 “Occupational Exposure Limits for Hazardous Factors in Workplaces” , The hourly average concentration increase of sulfur dioxide and nitrogen dioxide exceeds the limit specified in GB3095-2012 “Ambient Air Quality Standard”. The new carbon-free clay green sand after pouring, particulate matter (PM2.5, PM10, PM100), particulate matter, formaldehyde, nitrogen dioxide, and carbon dioxide did not exceed the limit specified in GB2.1-2007 “Occupational Exposure Limits for Hazardous Factors in Workplaces” , Carbon monoxide and sulfur dioxide do not exceed the limit specified in GB3095-2012 “Ambient Air Quality Standard”.
“Casting itself is a traditional industry of material regeneration. What we have to do is how to produce castings in a more environmentally friendly and energy-saving manner. The emergence of new carbon-free clay green sand makes us more confident to put into production as soon as possible. Zhonggo, do its part to protect the ecological environment.” said Yan Xueli, director of the foundry department of Qinwei (Tianjin) Industrial Co., Ltd., Qin Meida International Holdings Co., Ltd.
Technological breakthroughs help industry transformation and upgrading
In recent years, the conversion of old and new kinetic energy has become a national strategy, and the driving force for the conversion of old and new kinetic energy lies in innovation. The research and development of new carbon-free clay green sand is of great significance to change the situation of high pollution and high energy consumption in the foundry industry and promote the transformation and upgrading of the industry.
The reporter sees from the evaluation opinions formed by the expert evaluation committee that the project team led by Zhu Shigen has systematically researched and developed a new type of carbon-free clay green sand for the first time at home and abroad. It has excellent conventional casting performance and does not contain carbonaceous materials such as coal powder and organic materials. Materials, energy saving, low exhaust gas, dust and solid waste emissions, good reusability, low sand consumption, and cost reduction are new breakthroughs in the development of green sand casting technology. Relevant technical standards should be formulated as soon as possible to further increase the scale of application.
Lu Xinmin, council member of the Foundry Branch of the Chinese Mechanical Engineering Society, said: “Whether it is application effect or originality, the emergence of new carbon-free clay green sand casting technology plays an important role in the foundry industry across the country, especially in the country. Under the background that it will take three years to win the blue sky defense war, this technology will have more opportunities to promote.”
Ren Xingwu, Chairman of Weichai Power (Weifang) Casting and Forging Co., Ltd., said that Weichai Group has been seeking more environmentally friendly and energy-saving casting technologies and solutions. The new carbon-free clay green sand casting technology is a significant improvement to the traditional coal powder clay sand technology. For breakthroughs, we will actively contact and continue to pay attention to the product, and consider applying it to the Weichai production line under the premise of mature conditions.
Weifang Yuchuan Machinery Co., Ltd. General Manager Liu Wei said at the evaluation meeting: “As an advanced unit of green casting in the country, we are the first to use the new carbon-free clay green sand casting technology to take the lead in demonstrating the transformation, upgrading and green development of local foundry enterprises. .”
Link：The world's leading environmentally friendly sand new material solves the problem of casting pollutionREF: Hearing amplifier, Hearing Loss, Hearing Aids Types
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