The article which is about using wear-resistant treatment technology and written by relevant personnel in Jianzhuang Coalmine was published in the 31^st issue of 2012 of Heilongjiang Science and Technology Information.

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• Application of Plasma Cladding to Middle Trough of Scraper Conveyor and Transfer Machine

  Miao Yongxin, Gong Guoqing

  (Shaanxi Coal Group Huangling JianZhuang Mining Industry Co., Ltd.)

   

  Abstracts: as the middle trough of our scraper conveyer and loader get worn easily, the plasma cladding technology is put forward to make the middle trough of scraper conveyer more wear-resisting so as to prolong its life and the life of the whole set of scraper conveyer. And more importantly, this technology can reduce maintenance and equipment transportation times meanwhile, it enables the process of installation and construction safer and the equipment more efficient.

   

  Key words: middle trough; plasma cladding; wear-resistance; economical efficiency

   

  The scraper conveyer and loader used by Shaanxi coal group Huangling JianZhuang Mining Industry coal face 4-2101 are type SGB800/1050 and type SZZ1000/400 respectively. They both are produced by Shandong Mining Machinery Group Co., Ltd. The trough of scraper conveyer is 1.75 meters long and 0.8 meters wide; the trough of loader is 1.5 meters long and 1meter wide. This type of scraper conveyer was put into use in July 2010 and by far, it has been used in one coal face with 2.6 million tons coal conveyed. The middle trough is badly worn. There have been 2 chain ditches about 2-4 mm deep and 5-6 mm wear. The ends of rump pan sides and its upper edges are worn worse with 4-6 mm wear in slippery boots passage. The middle board of loader is worn even more severely with 6-8 mm wear and two chain ditches with 3-5 mm deep.

  In order to ensure the coal face in a sound operation, we should apply the plasma cladding coating technology to deal with the wear problem of the middle trough of scraper conveyer and loader.

  1.    The analysis of wear mechanisms in middle trough

  There are mainly 3 types of wear in middle trough, namely, abrasive wear, corrosive wear and adhesive wear with heavy load.

  1.1               Abrasive wear. This type of wear is caused by micro cutting force from bulges in scraper, chains and particles between middle boards.

  1.2               Corrosive wear. Due to the damp environment under the mine well and regional high temperature and corrosive mediums in mineral water of the well, the equipment are easily exposed to corrosion, which will contribute to wear. The new surface of wear continues to corrode, thus, it forms a vicious recycle.

  1.3               Adhesive wear. As the contact type is point contact between scrapers, chains and middle board, when the link is loaded, a large stress will come into being, which leads to a high contact stress in chain. This stress makes surface temperature of contact points between middle board and chain rise sharply, which will soften the surface of material and even make it melt regionally, in so doing, cold welding will occur under the action of stress. Therefore, these points get snipped when the chain move continuously and then adhesive wear will be caused

  2.    The basic theory of plasma cladding technology

  Under the action of the flexible high temperature plasma beam, the alloy powder or a ceramic powder and the substrate surface are rapidly heated and melted, together and then mix, diffuse, react and solidify. When plasma beam leaves and becomes self cooling which forms a wear-resistant alloy layer so as to strengthen and harden its surface.

  3.    Parts of wear resistant treatment and its methods

  Cladding improved parts: upper surface of middle board of middle trough of scraper, two ends of iron rump pan, upper edges of rump pan, upper surface of middle board of middle trough of loader.

  The plasma cladding equipment independently researched and developed by Shandong Haina Plasma Science and Technology Co., Ltd., will heat the alloy powder and the substrate surface rapidly and make them melt, mix, diffuse, react and solidify together, under the action of the flexible high temperature plasma beam. When plasma beam leaves and becomes self cooling which will form a wear resistant alloy layer so as to strengthen and harden its surface. The chain ditches of middle board of middle trough are applied conventional build-up welding method to fill the later cladding wear-resistant layer whose shapes are like diamonds with 6-8 mm wide and 2-3 mm high and there are 2-3 mm deep melted into substrate (details refer to pictures attached behind); the upper edge cladding of rump pan is a line of 6-8 mm wide; two ends of iron rump pan are applied hand-held device cladding 150-200 mm. The middle chain ditches of middle board of loader are applied conventional build-up welding method to fill the later cladding wear resistant layer whose shapes are like diamonds with 6-8 mm width and 2-3 mm height and 2-3 mm deep melted into substrate (details refer to diagrams attached behind)

  The micro-hardness of ceramic cladding can reach HRC55.

  4.    Process, purpose and requirement of wear-resistant treatment

  Wear-resistant treatment process: wear-resistant treatment technology adopts -8 nm metal ceramic powder and autonomous robot arms. The special type DRD-3 plasma equipment can achieve 150 mm clearance between two passes and 0.5 m per minute Servo Gun velocity.

  Purpose of wear-resistant treatment: the middle trough will become more wear-resistant after treatment and prolong its life to save cost and reduce maintenance and equipment transportation times, meanwhile; it enables the process of installation and construction much safer.

  Requirements for middle trough before treatment: middle trough must be clean, neat, without deformation and has little strength.

  5.    Anticipated effects and economic benefits achieved

  The middle trough treated through wear resistance can fit perfectly with technology. Cladding layer is of strong adhesion and doesn’t drop and its hardness can reach higher than HRC55. When the surface of wear-resistant alloy layer reacts with chains of scraper board, a smooth surface will come into being. This can reduce the friction of conveying coal, saving 10% energy consumption of the motor. The total purchase price of scraper conveyer and loader is RMB 27.83 million Yuan. The life of scraper conveyer will be prolonged by 4-5 years on the base of its original life of 3 years, or about 1.5 times longer than before. In other words, RMB 12.2 million Yuan will be saved through this sophisticated technology (apart from the expense of plasma cladding treatment RMB 740,000 Yuan). At the same time, 1500 working hours for installation and movement and the electricity charge of RMB 150,000 Yuan will be saved.

  The diagram is omitted here.