Tungsten carbide roller has characteristics of good wear resistance, high temperature red hardness, thermal fatigue resistance and thermal conductivity and high strength , have been widely used in high-speed wire rod, bar, rebar, seamless steel tubes, etc. Domestic production of tungsten carbide roller materials mostly WC- Co, WC- Co- Ni- Cr two series, and the content of Co, Co- Ni - Cr is in the range of 6wt% ~ 30wt%. From the use of perspective, tungsten carbide rollers has good mechanical properties, its flexural strength up to 2200 MPa or more, shock toughness up (4 ~ 6) × 10^6 J/ m^2, Rockwell hardness (HRA) is up to 78 to 90, widely in the high-speed wire rod rolling process, which is much higher than single-slot chilled cast steel or high speed steel rolls.Tungsten carbide is made of Tungsten Carbide Powder and binder phase (such as drilling, nickel, etc.), and then pressing and sintering, regardless of the conditions under cold rolled or hot rolled has excellent wear resistance, tungsten carbide rollers has been widely used in pre-finishing mill and finishing of high-speed wire rod currently. On the performance of tungsten carbide roller in hot-rolling wire rod , the material must meet the following requirements:
Tungsten carbide roller material design
Tungsten carbide roller category
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This project is an important part of the "Gasification Shaanxi Project." In a recent interview, the reporter learned that in the Huimin project, which has invested 5.9 billion yuan to achieve "gasification" in Shaanxi province within four years, and reached 4 billion cubic meters of natural gas by 2012, the chemical industry is hard to win. More natural gas.
Shaanxi is an important natural gas resource in the country, with a reserve of 4.18 trillion cubic meters and a proven reserve of 1.02 trillion cubic meters, ranking third in the country. The main natural gas production area in the Ordos Basin at Yulin Energy and Chemical Base is China's land. Proven largest integrated gas field.
The application of natural gas industrialization in Shaanxi began in the early 1990s. In 1994, Shaanxi Yulin Natural Gas Chemical Industry Co., Ltd. built the first 30,000-ton/year methanol plant, which is both a demonstration project for the application of natural gas chemical industry and an official start for the province's large-scale use of natural gas. In 1997, Shaanxi completed the Jingbian-Xi'an natural gas transmission pipeline, which brought natural gas from northern Shaanxi to Guanzhong, and natural gas transmission and distribution networks in Xi'an, Xianyang, Tongchuan and other cities were completed and put into operation in the same period. To take this opportunity, Shaanxi Xinghua Group Co., Ltd. implemented the “oil-to-gas†technology reform in 1998 and used natural gas as raw material to produce fertilizer (ammonium nitrate).
Since then, with the continuous expansion of the gas market, Shaanxi Natural Gas Company has successively established Jingxi Second Line, Xianbao Line, and Xiqiao Line, and the use of natural gas has also gradually expanded from civil and chemical industries to various applications such as power generation and automobiles. Annual gas consumption increased from the initial 100 million cubic meters to 2.05 billion cubic meters in 2007, with an average annual growth rate of 26.8%.
In 2001, Shaanxi Province issued the "Thirty-year Plan for Natural Gas Transmission Pipelines", proposing to build a gas pipeline network system that integrates three vertical, three horizontal and two ring trunk lines and branch lines that basically covers the entire province and neighboring provinces in 30 years. To achieve 100% of the city and 80% of the county's ventilation targets. Earlier this year, the Shaanxi Provincial Government accelerated the pace of “gasification in Shaanxi†and decided to achieve the goal of gasification in the province in 17 years in advance. That is, by the end of 2012, 11 urban areas, 107 counties and 10% of key towns will be fully gasified. By then, the annual natural gas consumption in Shaanxi will reach 4 billion cubic meters, the proportion of natural gas in the primary energy consumption structure will increase from the current 8% to about 12%, and more than 13 million people and more than 50% of taxis will use natural gas.
It is understood that the reason why Shaanxi proposed to achieve gasification ahead of schedule is that the development of CNPC Changqing Gas Field will be intensified and the gas production will increase at a rate of more than 3 billion cubic meters per year, plus the West-to-East Gas Pipeline II and the Sichuan-East Gas Transmission Project. The implementation of Shaanxi is facing a good situation of multiple gas supply. Second, the scope of natural gas demand and gasification continues to expand, and the people's gas demand is urgent. Third, the construction of long-distance natural gas pipeline network was accelerated. Four long-distance natural gas pipelines such as Jingxi First Line, Second Line, Xianbao Line, and Xiqiao Line have been completed, with a total mileage of 1169 kilometers, and the gas transmission capacity has been significantly enhanced.
Although the “gasification of Shaanxi†process has accelerated, the use of natural gas by the chemical industry is still more difficult.
At present, there are only two companies in Shaanxi that use natural gas as raw materials to produce chemical products. They are Lutianhua and Xinghua Group. “According to the national natural gas utilization policy, natural gas use is classified into priority, permissible, restricted, and prohibited. Among them, the production of methanol using natural gas as raw material is banned. “Gasification Shaanxi†project will not consider the chemical industry, and natural gas will not Will increase the application in the chemical industry." Shaanxi Provincial Development and Reform Commission Energy Department responsible person specifically told reporters.
Hu Haifeng, deputy director of the Petroleum and Chemical Industry Management Office in Shaanxi Province, believes that natural gas, as a relative shortage of clean energy, uses industrial fuels, natural gas power generation, and natural gas chemical industry, but considering the combination of social and environmental benefits, natural gas should be used as a priority. City gas, which is conducive to energy conservation and emission reduction, is also in line with national industrial policies. Moreover, the current natural gas price rise is a foregone conclusion, and the use of natural gas to develop chemical industry will face severe challenges.
According to the reporter’s understanding, the National Natural Gas Utilization Policy stipulates that gas projects have been established to maintain the current status of gas supply, and in particular, the national fertilizer projects approved for construction must ensure long-term stable supply. The reporter learned from Lutianhua and Xinghua Group that at present, the company’s natural gas can only maintain its current production capacity, but it faces “shortness of breath†in the winter and it is difficult to guarantee full-load production. Under pressure, Lutianhua and Xinghua Group have invariably transformed coal chemical industry to avoid the risks caused by the shortage of natural gas supply and rising prices. The former started the project of 300,000 tons/year of coal-based synthetic ammonia, 300,000 tons/year of methanol, 300,000 tons/year of soda ash, and 324,000 tons/year of ammonium chloride at the beginning of this year; the latter also listed coal chemical industry as a key industry for development. First, the 1.4 million tons/year coal-to-methanol project is being stepped up.
The reporter noted that in previous years, Shaanxi Province had always taken natural gas chemical industry as a growth point for economic development. Since the second half of 2005, natural gas supply has been strained in various regions, and Shaanxi Province has adjusted its development plan and decided to suspend construction of natural gas chemical projects during the “11th Five-Year Plan†period. The Implementation Plan for the Adjustment and Revitalization of the Planning of the Petrochemical Industry in Shaanxi Province, which was promulgated in May this year, puts forward that relying on the advantages of resources to strengthen and strengthen the five major areas of coal chemical industry, salt chemical industry, fine chemical industry, petrochemical industry, and petroleum processing, natural gas can no longer be seen. Chemical "shadow". According to informed sources, the "Twelfth Five-Year Plan" of the Shaanxi Province that has just been initiated has no idea for the development of the natural gas chemical industry. This means that the chemical industry can no longer enjoy the benefits of the Shaanxi Gasification Project within the next 6 years.
1. Sufficient anti-fracture strength;
2. Good abrasion resistance;
3. The smooth surface finish;
4. Excellent corrosion resistance, thermal fatigue, thermal cracking performance.
Tungsten carbide roller rings can working in bad conditions , small profile rolling (especially rebar rolling) process conditions is harsher than the high-speed wire rod, and therefore corresponds to the profile rolling ,tungsten carbide rollers recommend using high binder phase carbide.
Pre-finishing all vehicles roller should ensure its high toughness, strength, rigidity and thermal conductivity, followed before considering its wear resistance. When designing each vehicles roller, pre-finishing materials should choose carbide grades of Co, Co- Ni- Cr binder content is high (greater than or equal to 25wt%) , requiring an average WC grain size of coarse (5μm ~ 6μm), to obtain a higher shock toughness, proper strength and hardness. For the finishing of the roller movements, particularly the last two rollers of the finish rolling, which suffered load is small, and high relative velocity of the material to be pressed (80 m / min ~ 120 m / min). In this case, the wear resistance of the roller to be the most important requirements, and must ensure the strength , timpact toughness and hardness of a reasonable match, so the binder of Co / Ni content ratio and the average grain WC control of particle size and other factors must have greater control in front of different pre-finishing rolling roll.
According to the structure of tungsten carbide rollers, it can be divided into solid tungsten carbide roller and composite tungsten carbide roller. Solid tungsten carbide rollers have been widely used in pre-finishing and finishing stands high speed wire rod mill (including fixed reducing the rack, pinch roller rack). Composite tungsten carbide roller is made of cemented carbide and other materials, and it can be divided into tungsten carbide composite roll rings and solid tungsten carbide composite roller. Tungsten carbide composite roll rings mounted on the roller shaft; solid tungsten carbide composite roller will be directly cast in the roll axis to form a whole, a large load is applied to the rolling mill.
Tungsten carbide rollers produced by powder metallurgy method, the key to its process control is the chemical composition of the material and the mixture was prepared, pressed molding, sintering and deep processing and other preparation process parameters.
1. Preparation of starting material (WC focus quality): As the WC raw material and quality control of the use of different levels of quality may fluctuate, resulting in adverse effects on microstructure.
2. Preparation of the mixture: Mixture preparation is the key to the production process of the roller, the roller of failure modes - trachoma, mainly generated by this procedure.
3. Pressing: roller pressing is an important process of the roller mill.
4. Sintering: roller sintering is to determine the final quality of the roller production processes, use of advanced low-pressure sintering technology, HIP sintering technology can greatly improve the performance of roller.
5. Deep processing: deep processing rollers have a greater impact on the quality and accuracy of the roller surface.
On October 10, the 154-kilometer double-track project of the Xianyang-Baoji natural gas pipeline in Shaanxi Province started construction and will be connected to the national West-East Gas Pipeline for the first time after operation, forming a natural gas ring pipe network in the central and western regions of Shaanxi Province. .