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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Thirty years ago, astronomers had discovered that the only planet in our sun was here. The galaxy is full of planets with millions of human-like suns. However, it is well known that there is a blank space for understanding other star systems in the world.
According to reports, as the exploration of the planet began in 2014, astronomers not only discovered that more than a thousand "exoplanet planets" were orbiting distant stars, but also the beginning of human beings began to make accurate measurements. Ballard said that endless exoplanets are filling data, and the data can be accurate to the second decimal place. It does look amazing.
By Sarah Ballard, a NASA researcher at the University of Washington at Carl Sagan, a team of researchers at the University of Seattle in Seattle, recently measured the "Super Earth," whose diameter of 148 miles, the precision of observation accuracy is shown on the outer planets About 300 light-years of location.
First of all, from the earth's perspective, Kepler found the planet, Kepler 93 B passed directly in front of the star, causing the star to dim during transit. The dimming occurs every time this track. In Spitzer and Kepler's recording of multiple transits in the visible and infrared data consistent with the observed data, it is clear that Kepler 93B is a true planet, not an illusion of stellar variation. Ballard later calculated the size of the planet relative to the star by carefully observing the light curve. At this point, the only missing part is the diameter of the star itself.
He said that most people have heard of "earthquakes." Seismic waves have been derived from studies of Earth movements. We can learn a lot about the structure of our planetary seismic waves. Ballard’s colleague, by analyzing the stellar seismic pattern, can infer the accuracy of its radius and percentage of mass.
The new measurement confirms that Kepler 93b is a super-Earth that is about twice as large as Earth. Kepler 93B, previously measured in Hawaii, is about 3.8 times the Earth. Kepler 93B's quality derives a new radius, and density indicates that the planet is likely to be made of iron and rock.
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.
Astronomers Discover Super Earth