A. Direct rolling method
The direct rolling method is a more common method for the production of metal composite plates, which can be divided into hot rolling composite method, cold rolling composite method, asynchronous rolling composite method and vacuum rolling composite method.
1. Hot rolling composite method
The hot rolling composite method is a method in which the composite material and the substrate are overlapped, welded around, and the composite material and the substrate are combined by hot rolling. Under the action of shear deformation force, the contact surface between the two metals is very similar to a viscous fluid, and tends to be more fluid characteristics. Once the surface of the new metal appears, they produce adhesive friction behavior, which is conducive to the fixation of the metal on the contact surface, and forms a stable thermal diffusion based on the fixing point (or core) under high temperature thermal activation conditions, thereby realizing the welding bond between the metals.
2. Cold rolling composite method
Usually, people refer to the equal roll diameter and equal roll speed cold rolling composite method as the cold rolling composite method. In the 50s of the 20th century, the United States first began to study, and proposed a three-step production process of "surface treatment + cold rolling composite + diffusion annealing". Compared with the hot rolling composite method, the first pass deformation during cold rolling composite is larger, generally reaching 60%~70%, or even higher. Cold-rolled lamination, with a large amount of pression, cold-rolled overlapping two or more layers of metal, causing them to produce atomic bonding or mortion mating, and then strengthening them by diffusion annealing.
3. Asynchronous rolling composite method
Asynchronous rolling is a strip rolling production technology that began to rise in the 60s of the 20th century, which rolls metal by changing the upper and lower roll rolling speeds to make the roll line speed different. In the 70s, asynchronous rolling was used as the production of composite plates, called asynchronous rolling composite method, and many countries, including China, have invested considerable efforts in basic research and industrialization. The asynchronous rolling composite method generally corresponds the harder metal to the fast roll, and the softer metal to the slow roll. Asynchronous rolling lamination takes full advantage of relative slippage within the "rolling zone". On the one hand, the frictional friction of the relatively sliding interface generates heat to provide energy for the combination of the interface; On the other hand, relative sliding is conducive to the crushing and extrusion of the contaminated layer and oxide film of the contact surface, and promotes the formation of fresh surfaces. Therefore, relative sliding is beneficial to improve the interfacial bonding strength and reduce the average rolling pressure.
4. Vacuum rolling composite method
Usually in the atmosphere, the metal surface is covered with an oxide film, an adsorption layer, and the surface is convex, which hinders the bonding between metals. In view of these circumstances, in 1953, the Soviet Union first began to test vacuum rolling, and then the United States, China, and Japan also began to study. The vacuum rolling composite method is divided into two cases: hot rolling in vacuum and cold rolling. The biggest feature of hot rolling in vacuum is that, due to the absence of oxidizing atmosphere, oxides and nitrides are not formed on the metal surface, making it easy to process metals that are oxidized in the atmosphere and difficult to process, and the original characteristics of the metal surface generated by plastic processing can be fully utilized, and because the vacuum helps to degasse, a clean finished metal surface can be obtained.
B. Explosion billet rolling method
The explosion billet rolling method is a production method in which the required base and composite materials are welded by explosion, and then rolled to the required specifications and sizes of composite strips by a hot rolling mill. This method is a new joint technology developed by combining the advantages of explosive composite technology and rolling technology, and its advantages are:
(1) The explosion composite method billet ensures the quality of the two-layer or three-layer metal composite plate bonding zone;
(2) The product has high dimensional accuracy and good surface quality;
(3) It increases the flexibility of production and is convenient for promotion.
C. Sintering method
The sintering method is a composite method in which powder particles and composite substrates are combined with each other by heating under a protective atmosphere. Protective gases mainly use hydrogen and nitrogen. The composite substrate needs to be pretreated through processes such as degreasing, rust removal and wooling. There are two main methods of powder preparation:
(1) Uniform mixing of the powder of dissimilar pure metal;
(2) Direct preparation of powder of cladding alloy. The basic principle of the sintering method is that at high temperatures, the amplitude of the atoms increases and diffusion occurs, so that dissimilar metal atoms form a bond. It is mainly used in the composite substrate and alloy cladding. Since the sintering temperature is lower than that of the high melting point pure metal component during the sintering process, the microstructure properties of the alloy cladding are very uniform, which is a useful supplement to the rolling method.
D. Casting and rolling composite method
The process of casting and rolling complex is: the two steel plates are superimposed, the inner layer is coated with stripping agent, the surrounding sides are welded and placed in the casting mold containing molten metal, and the liquid metal is solidified for the first rolling, and finally the edge of the weld is cut off, that is, the composite plate is obtained. High composite strength can be achieved at the right temperature and pressure. This method is simple and low-cost, and can be used for mass production.
E. Reverse solidification method
The reverse solidification process is a thin strip continuous casting process developed by German metallurgists in 1989. The process is to let a certain thickness of the base band pass through the molten steel in the reverse solidifier, so that the molten steel near the surface of the base band is rapidly cooled, solidifies on the surface of the base band to form a new phase, and rolls when the new phase is still in a semi-solidified state to obtain a hot rolled thin strip with a flat surface and uniform thickness. This method is a new fusion technology for the production of bimetallic composites. However, it is different from the mold casting method, and its substrate is ordinary carbon steel (solid phase), and the composite layer is stainless steel (molten steel). It has the characteristics of high efficiency and low energy consumption, and can produce composite panels with stainless steel composite layer less than 1mm, which can realize the continuous and short process of the production process, simple process, high product quality, and environmental protection.
