Steel Joining Process of Tungsten Carbide Roller (2/2)

Tungsten carbide consists of refractory metal carbide as the matrix and binder metal fabricated by powder metallurgy, which has many differences in mechanical properties with common steel (cast iron, cast steel, carbon steel, etc.). Especially the difference in linear expansion coefficient is the key factor of affecting the connecting property directly, which is easy to produce internal stress in the joints. If the stress exceeds the tensile strength of the cemented carbide, carbide will lead to cracking. In addition, due to the particularity of cemented carbide, the common methods are hot charging, casting, hot isostatic pressing, welding and cementing method in which the WC composite cast iron and soldering processes and solder wettability is poor.

Hot charging method uses the inner interference to thermal inner and outer layers together. The process requires tungsten carbide must have a certain thickness of the outer ring to avoid ring cracking under tension effect. So the biggest defect of the process is the consumption of tungsten carbide, which can not save the cost. The cementation method, as the name suggests is to use an epoxy resin adhesive polymer inner and outer ring are bonded together. But since he adhesive properties of the physical and chemical limits such composite roll through the process of the preparation can not be used at high temperature and pressure environment, under the alternating stress and mechanical stress joint action, is extremely prone to surface cracking phenomenon.

Thus, the three methods currently used mainly casting, hot isostatic pressing and welding. Casting is a method of pre-plating the outer layer of metal carbide as a buffer layer, using the casting method in conjunction with the iron carbide into a composite outer roll. CIC (cast in carbide) can casting carbide ring and ductile iron and form a strong metallurgical connection, so that the stress distribution can be dispersed cemented carbide. Tungsten carbide outer ring can with high hardness and excellent wear resistance withstand pure rolling force, and ductile iron with good toughness can deliver the rolling moment by the connection with tungsten carbide ring. But there are also casting some technical problems, such as the casting process is difficult to obtain precise control, so that will cause the quality of the composite roll stability can not be guaranteed.