Posted 14 Mar 2011 19:38
Cold rolling process is a small, no cutting of the new technology, the precision cold rolling to maximize the accuracy of the workpiece shape and the shape is close to finished parts and precision, and can significantly improve the intrinsic quality of the workpiece, all countries in the world dedicated to the development of cold rolling technology research and practical application in mass production. Such as the UK FORMFIO's cold rolling production line, the German company's EMB-based SKF reaming closed molding machine cold rolling production line, Profiroll (Bade Du this) the URWA automatic bearing ring of cold rolling machine, the Japanese co-prosperity CRF-type cold rolling machines, of which Germany and Japan, equipment in the domestic bearing industry has a small introduction. Although many domestic enterprises cold rolling technology of growing concern, but subject to raw material quality, weight and precision rough, cold rolling process and the lack of cost-effective equipment and other reasons, cold rolling bearing ring has not been widely used technology, so understand the working principle of cold rolling, process, and the advantages and disadvantages that exist to help business applications for the cold rolling to make the right choice. First, the working principle of cold rolling 1, precision cold rolling technology is at room temperature, the ring for rotational parts using extrusion and then be finished pieces of plastic deformation of a cold forming method. Cold rolling work of the main reasons is driven by the shape of a rolling wheel to shape the outer surface of the shape forming mandrel of a slave to the inner surface of the shape forming, mandrel and workpiece supported by the supporting wheels, rolling part, the rolling wheel drive the workpiece rotation, mandrel in conjunction with the feeding device the supporting solid round extrusion parts, driven to achieve workpiece rolling. 2, the cold rolling stage of the cold rolling process, the rolling pressure is not a constant, and its schedule with the change of feed, there is a clear stage, cold rolling the general relationship between pressure and stroke can be divided into three phases: the first Stage \u2160 - pinched deformation stage. Rolling start, bearing wheel institutions began to feed, metal rolling pressure to overcome internal resistance and the deformation of the friction between billet and mold, so that all of the metal lattice is completely compressed, the metal material begins to produce plastic deformation, rolling pressure sharply increased. Section \u2161 stage - stable deformation stage. Institutions to continue supporting the feed wheel, forcing the metal continues to flow. At this stage, the only change the billet height, deformation zone remained stable, a high degree of plastic deformation zone does not change over time, the pressure does not change with the stroke, it is known at this stage a high degree of plastic deformation zone within the plastic deformation zone as a high degree of stability . The height can be achieved under the pressure when rolling a minimum, be produced to determine the principle of stable deformation. Stage \u2162 - when the stock's residual thickness of more than a high degree of stability after the deformation zone, such as round bodies to continue to support the forward movement, the rolling pressure has increased dramatically. From the above analysis we can see the end of the second stage, if it continues rolling, the pressure to rapidly increase. Therefore, at this time to end rolling, or mold or rolling machine to more easily damaged. When the second phase is completed to the end of the rolling process, then, when rolling over the thickness of material equal to a high degree of stability of deformation zone. If you continue to the end of the second stage of rolling, this time the pressure will rapidly increase. If the increase in value does not exceed the limit allowable unit pressure die, and in this principle more than material obtained the thickness of rolling, so you can give full play to the ability of mold material, but also savings on raw materials consumption. Rolling more than expected at this time should be less than the thickness of a high degree of stability of deformation zone. Under normal circumstances, the second phase of rolling ends. Second, the primary cold rolling application process 1, by application of sophisticated methods are generally divided into two kinds of cold rolling and coarse rolling. Most of foreign crude is used in rolling. General complex shape and small size of the ring rolling process with more precision, the larger size (usually 308 or more) basic coarse rolling, SKF does not recommend the use of fine crushed. Advantage of precision cold rolling channel, chamfering without cars, disadvantage is the mold with high requirements, large deformation of the grinding rate. Rough rolling advantage is easy to control, does not affect the grinding efficiency, production layout simple. Disadvantage is the lack of precision, a larger follow-up vehicle processing workload. 2, according to rough types before rolling into the cold forging and cold rolling steel ring forming two cold rolling forming the above process should be based on actual user conditions, economy, product requirements to choose, but whatever the process, the blank material requirements, rough hardness, rough weight control are the same. 3, the general need for cold rolling after forming the whole track, to ensure that rings accuracy. Third, the cold rolling of the advantages and disadvantages of 1 advantage 1) can reduce the consumption of raw materials, turning the traditional way of comparison, precision cold rolling process allows material savings rate increased by 10% to 15% or more; 2) can be a complex surface of the molding process, improve labor productivity; 3) can improve the mechanical properties of components, cold rolling deformation, the grains of metal material is more compact, the metal flow lines remain unchanged, there is no cut, the material fatigue strength ; 4) cold rolling to reduce material consumption and shorten the processing time, reduce production costs. 2, inadequate 1) abrasive machining difficult and abrasive use of high cost; 2) process control difficulties, the use of more difficult; 3) Ring prone to the phenomenon of micro-cracks; 4) shape error is relatively large (size more large error greater), large deformation effects due to the follow-up grinding efficiency; 5) on the rough high quality requirements: cold rolling should be used with a certain precision rough, rough weight of error should not exceed 0.5%, the hardness required uniform rough, not cracks and significant decarbonization and so on. 6) The lack of experience in domestic technology, operation and maintenance personnel, companies need to explore their own experience, so the introduction to the sophisticated application from the device generally takes a very long period.