Car air quality standards will be introduced
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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Since the beginning of this year, the problem of air quality in cars has begun to attract more and more people's attention. People have a basic understanding of the universality and harm of their existence. At the same time, under the appeal of the industry, the mandatory standards for air quality in cars have been issued. In 2015, the country will issue mandatory air quality standards for cars.
In this context, the Gasgoo Automotive Research Institute's Roundtable Forum event was held in Beijing on December 5th. The event was organized around the industry's hot topics: "The Harmful Situation of the Air Quality in the Vehicle and the Future Trend of the Automotive Industry."
At the forum, the experts in the relevant fields in the industry, the representatives of the OEMs, the representatives of the material suppliers, and the mainstream media reporters from all over the country gathered to discuss the air quality hazards in China from multiple perspectives, including theoretical discussions, case studies, and information sharing. The status quo and the future trend of the automotive industry, together explore the future prospects of green materials and the response of the relevant OEMs and parts companies.
Song Guangsheng, director of the National Indoor Vehicle Environment and Environmental Product Quality Supervision and Inspection Center, delivered a speech explaining the implementation and development of China's air quality standards in a comprehensive and detailed manner. In his opinion, the problem of air quality in the car has begun to suffer from the entire society. Concern that the introduction and implementation of mandatory standards for air quality in cars need to rely on the joint efforts of vehicle manufacturers and raw material manufacturers. It also requires the supervision of the entire society.
Guo Yanheng, a professor of respiratory diseases at Chaoyang Hospital in Beijing, shared what harm harmful substances in the car will cause to the human body. It said that in recent years, the disease caused by indoor air pollution has caused a significant upward trend, which has become one of the greatest threats to modern humans. According to reports, car volatiles, such as benzene and formaldehyde, people inhaled after a short time, there may be central nervous system anesthetic effect, light people have dizziness, headache, nausea, chest tightness, fatigue, confusion, severe can cause Coma causes death due to breathing and circulatory failure. If the long-term exposure to toluene, xylene, a certain degree of solubility will cause chronic poisoning, there may be headaches, insomnia, listlessness, memory loss and other symptoms of neurasthenia.
At the meeting, Chen Wenkai, director of Gasgoo Automotive Research Institute, released a survey on more than 1,500 people in the industry. The survey results showed that the root cause of frequent air quality problems in the car was the lack of laws and regulations. At the same time, due to the complexity of the air pollution problem in the car and the industry’s concerns about poor enforcement, policy makers should formulate supporting policies as soon as possible and improve the monitoring and supervision system. From the automotive industry's point of view, the most important thing to be solved is the vehicle manufacturer's attention to the air quality in the vehicle and the environmental protection materials, especially the research and development of low emission materials.
In fact, some environmental protection raw material manufacturers already have solutions, and international low-spreading material company Kumho has launched a series of innovative materials for “car air pollution†in recent years. The tripartite authority has rated chemical materials as the lowest-distribution automotive interior plastics. This material has been reduced by more than 60% compared to conventional interior plastics, which is far lower than the VOC (volatile organic compound) emission standard of major host plants. Volvo Cars has always been one of its selling points in the interior of the car and has achieved good market response.
The influence of the air in the car on the human body runs through the entire life cycle of the car. With increasing attention from consumers, and the gradual improvement of laws and regulations, the automobile industry should pay more attention to the air quality in the car, and strict selection of materials from the source. To control and widely use environmentally friendly materials with low emissions to completely change the current state of air pollution in domestic vehicles.
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.