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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History of the use of turbo technology
The supercharging technology of automobile engines can be divided into mechanical supercharging and exhaust turbocharging, among which exhaust turbocharging technology is most widely used due to higher energy efficiency ratio.
When it comes to turbo technology, it has been around for more than 100 years. In 1905 Dr. Alfred Buchi applied for the patented-powered axial supercharger of the first turbocharger. By 1961, the car began to tentatively install the supercharger, but because of the tremendous pressure and heat generated in an instant, the effect after installation was not satisfactory. Saab, from Northern Europe, is the first car manufacturer to apply turbochargers to automotive products. The Saab 99 car, which was introduced in 1977, makes the car engine use turbo technology. It began to mature, and its arrival also announced the birth of a new era in the automotive industry. Turbocharging technology rewrites the traditional concept of "displacement size determines power."
Turbocharged engine performance
A car equipped with a turbocharged engine not only has a digital performance in terms of power and power, but also far exceeds the same-displacement car product. In actual use, it can be compared with its own previous class. Competing. For example, Saab's 2.0-liter turbocharged engine on the latest Saab 9-3 Vector 2.0TS can output an amazing 155 kW of power at 5,300 rpm, an indicator that has almost caught up with the regular car's 3.0 displacement. Engine. That is to say, to some extent, the power produced by this four-cylinder engine is equivalent to that of a conventional six-cylinder engine. This brings obvious advantages, not only does it need to spend more in pursuit of high speed. The cost of buying a large displacement car, and the engine is less noisy when working, and the use of a lighter engine is more beneficial to reduce the weight of the vehicle and reduce fuel consumption.
Environmentally friendly, lower emission standards are also an important advantage of turbochargers. Because today's pollution is getting worse, a car manufacturer with a high sense of responsibility must not only satisfy the customer's desire to drive the car, but also ensure that the product has enough driving pleasure, and it is also necessary to protect the environment and create a good living space. The turbocharger is just enough to meet the comprehensive requirements of improving fuel economy and reducing emissions without sacrificing driving pleasure. Because the boost will provide more air to the combustion chamber, making the combustion more thorough and the emissions more clean. Especially in high-altitude air thin areas and cold regions, turbine engines can also work effectively. At present, only Saab Saab is the only car brand in the whole series that uses turbo technology.
Performance principle of turbocharged engines
Compared to the turbo engine's superior advantages, its core components can be as simple as an air pump. The exhaust gas discharged from the engine drives the impeller on the turbocharger side. As it turns faster and faster, the impeller on the other side also accelerates synchronously, increasing the amount of intake air entering the combustion chamber. Although the principle is simple, but in fact it is very complicated and precise, not only the tight fit of the internal components, but also the turbocharger should be closely matched with the engine, otherwise it will reduce the efficiency of the engine and even cause damage. In this regard, Saab's advantages are obvious. Saab's original power split technology and their newly developed engine management system Trionic8 are designed according to the needs of turbocharged engines. It can accurately understand the driver's intentions. And in this way to control the engine start process and the temperature response of various parts, while improving the response sensitivity of the torque and throttle.
Turbo technology tomorrow
As technology advances, turbochargers have become smaller, smaller, higher speeds, and have better air compression ratios. Today, in Europe, turbochargers have accounted for 50%, and turbocharged engines have become the mainstream of improving power performance. With the new high-temperature materials, new balancing technology and the use of a small oil bearing system and new electronic controls, turbochargers are also playing an important role in future cars.
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.
Talking about the Technology and Prospect of Automotive Turbocharged Engine
In general, the displacement and power of an automobile engine are directly proportional. To increase the output power of the engine, the most direct method is to increase the displacement of the engine. However, while the displacement is increased, the precision, weight and energy consumption of the engine manufacturing are also increased indefinitely, and the disadvantages are also obvious. In order to resolve this contradiction, the ingenious automotive engineers have used the engine boost technology in an innovative way, which makes it possible for the car engine to obtain additional high-power power output.