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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First, high-tech is widely used in European and American mold enterprises.
The production technology level of many die companies in Europe and America is first class in the world. The application of high and new technology to the design and manufacture of molds has become a powerful guarantee for the rapid manufacture of high-quality molds.
1. The wide application of CAD/CAE/CAM shows that the use of information technology drives and enhances the superiority of the mold industry. According to Luo Baihui, secretary-general of the International Model Association, CAD/CAE/CAM has become a commonly used technology for mold companies in Europe and the United States. In the application of CAD, it has already surpassed the initial stage of getting rid of drawing board and 2D drawing. At present, 3D design has reached 70% to 89%. The application of software such as PRO/E, UG, CIMATRON is very common. Applying these software not only can complete 2D design, but also can obtain 3D model at the same time, has offered the assurance for NC programming and CAD/CAM integration. With 3D design, assembly interference checks can also be performed during design to ensure the rationality of the design and process. The universal application of CNC machine tools ensures the precision and quality of the mold parts. 30 to 50 people's mold companies generally have more than 10 CNC machine tools. Parts processed by CNC machine tools can be assembled directly, which greatly reduces the number of fitters. CAE technology has gradually matured in Europe and the United States. The CAE analysis software was used in the injection mold design to simulate the plastic die process, analyze the cooling process, and predict possible defects in the molding process. The CAE software was used in die design to simulate the metal deformation process, analyze the distribution of stress and strain, and predict defects such as cracking, wrinkling, and spring back. CAE technology is playing an increasingly important role in the design of molds. After COMAU of Italy applied CAE technology, the test time was reduced by more than 50%.
2. In order to shorten the molding cycle and improve market competitiveness, high-speed cutting technology is commonly used. High-speed cutting is a processing technique characterized by high cutting speed, high feed rate, and high processing quality, and its machining efficiency is several times or even more than ten times higher than that of a conventional cutting process. At present, European and American mold enterprises are widely used in the production of CNC high-speed milling, more three-axis linkage, there are some five-axis linkage, the number of rotation is generally 15,000 ~ 30,000 r / min. Using high-speed milling technology, can greatly reduce the time of molding. After high-speed milling, the mold surface after finishing can be used with only a little polishing, which saves a lot of grinding and polishing time. European and American mold companies attach great importance to technological progress and equipment updates. Equipment depreciation period is generally 4 to 5 years. The increase of CNC high-speed milling machines is one of the key investments for mold and equipment enterprises.
3, rapid prototyping technology and rapid tooling technology has been widely used. Due to increasingly fierce market competition, product replacements are accelerating, rapid prototyping and rapid tooling technologies have emerged, and they have quickly gained widespread adoption. At the European mold show, rapid prototyping technology and rapid tooling technology occupy a prominent position. There are various types of rapid prototyping equipment such as SLA, SLS, FDM, and LOM, as well as agencies and companies that provide prototyping services.
Among the mold companies, many use rapid prototyping and rapid prototyping to apply to mold making, that is, using prototyping to prototype prototyping parts. The mold is then quickly made based on the prototype. Many plastic mold manufacturers use rapid prototype cast silicone rubber molds for small quantities of plastic parts, making them ideal for product trials.
Second, the management experience of European and American die companies is worth learning from.
1, personnel streamlining,
"Thin" management. Most of the mold enterprises in Europe and the United States are small, the number of employees is less than 100, and the number of mold companies is generally between 20 and 50 people. The configuration of various types of personnel in enterprises is very streamlined. There is more than one person in the enterprise, and there are more than one person. There are no idlers within the company. The ideas of lean production and "lean" management have been well reflected.
2, using professional, product positioning accurate. Most of the mold companies inspected by Luo Baihui are centered on the needs of various types of molds in the automotive and electronics industries, and determine their own product positioning and market positioning. In order to survive and develop in the market competition, each mold manufacturer has its own superior technologies and products and adopts specialized production methods. Most mold companies in Europe and the United States have a long-term cooperation with mold users, and there are also a number of cooperating mold manufacturers around the large mold companies. This reciprocal, mutually beneficial, win-win, and coexistence partnership has continued for 30 to 40 years.
3. Adopt advanced management information system to realize integrated management. Mold enterprises in Europe and the United States, especially large-scale mold companies, basically implemented computer management. From the production planning, process development, to quality inspection, inventory, statistics, etc., computers are commonly used. Various departments within the company can share information through computer networks.
4, advanced process management, a high degree of standardization. Unlike the domestic mold factories, which mostly adopt the mode of production organization based on fitters or locksmiths, the mold manufacturers in Europe and the United States rely on advanced technological equipment and process routes to ensure the accuracy of parts and production schedule. Each pair of molds has detailed design drawings, including the detailed design of each part, and they have developed detailed processing techniques.
Third, China's mold must go to the world, we must deepen reforms and expand exports.
The advanced technology and advanced management of European and American die companies have made their production of large-scale, precision and complex moulds extremely important for the promotion of the development of industries such as automobiles, electronics, telecommunications, and home appliances, and have also brought good results to mould companies. Economic benefits. American mold enterprises, per capita annual sales of about 200,000 US dollars; Italy's average annual sales of more than 100,000 US dollars. Compared with domestic mold companies, even after deducting price factors, the productivity of European and American mold companies is many times higher than ours. Luo Baihui said that to narrow the gap with the advanced industrial countries, we must accelerate technological progress, increase the degree of application of CAD/CAE/CAM, increase the proportion of numerical control processing equipment, and use information technology to further increase the level of mold design and manufacturing. At the same time, we must learn from and draw on foreign advanced management experience to further deepen enterprise reform. At present, some domestic mold factory die, plastic mold are done, large, medium and small molds are done, it is difficult to do well, must go small and specialized, small and refined, small and special road. At the same time, it is necessary to increase awareness of participation in international competition, strengthen international economic and technological cooperation and exchanges, and at the same time increase the localization of molds, further expand exports and move toward the world.
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.
The production technology level of many die companies in Europe and America is first class in the world. The application of high and new technology to the design and manufacture of molds has become a powerful guarantee for the rapid manufacture of high-quality molds.