At present, the preparation methods of bimetallic composite roll in China mainly include inlaying and cladding, surfacing, etc. There are limitations such as complex process, high cost, poor effect, low production efficiency, etc. However, by using the connection method of centrifugal casting intermediate layer transition to improve the bonding strength of the two metals, the bimetallic composite roll with good performance can be obtained. When selecting the type of metal material, it should be noted that the linear shrinkage of the two metals should not differ too much. In addition, it should also be noted that the high melting point metal is generally selected as the outer metal and the low melting point metal as the inner metal to facilitate the formation of sequential solidification. Otherwise, the phenomenon of the inner metal solidifying first and the mixed metal at the binding layer solidifying later will occur, resulting in defects such as pores, slag inclusions, shrinkage holes, shrinkage porosity, etc. at the binding layer.
|Type of roller ring||Advantages of characteristics of different roller rings||Disadvantages of characteristics of different roller rings|
|Alloy steel||High strength and toughness, hardness,abrasion resistance||Expensive|
|Cast steel||Good strength and toughness||Low hardness and abrasion resistance|
|Nodular cast iron||Good toughness and high hardness,medium abrasion resistance and easy to process||Easy to crack and low strength|
|Bead weld||Good strength, toughness, hardness||Easy to flake off and need frequent welding overlays, insufficient resistance to hot and cold fatigue|
|High manganese steel||High strength toughness, hardness, process hardness,and medium abrasion resistance||Easy to crack and shrinkage|
|Low alloy steel||High strength toughness and impact resistant,medium hardness||Non-wear resistant and short life span|
|Spray coating||High strength and toughness,medium hardness||Low impact resistance and expensive|
|Centrifugal casting high alloy steel||High hardness, abrasion resistance of the outer layer,good strength and toughness of the inner layer||Easy to segregation|
Ye Fuming and others have studied the centrifugalof carbon steel/high chromium cast iron composite roll. The inner layer is made of carbon steel and the outer layer is made of high chromium cast iron. The cast roll ring has high outer hardness and excellent inner toughness. After heat treatment, the outer hardness of the composite roll is 45HRC~65HRC, and the thickness between the two layers is 50~130 μ The structure of the transition layer of m is pearlite with carbide particles dispersed and embedded with the inner and outer layers in the form of teeth. The service life of the composite roll prepared by centrifugal casting process is increased by more than 6 times. Compared with the traditional single-layer high chromium cast iron roll ring, the service life is increased by more than 12 times.
Zhang Zhiwen and others prepared the high alloy/nodular cast iron bimetallic composite roll ring by centrifugal casting method. Two sets of induction furnaces were used to melt the high alloy cast iron and nodular cast iron respectively. The time interval of pouring the two metals was strictly controlled. The high alloy cast iron was poured first, and then the nodular cast iron was poured. After the liquid metal was completely solidified, the heat treatment and machining processes were carried out. In the prepared high alloy/nodular cast iron bimetal composite roll ring, there is a metallurgical bonding layer in the bonding part of the two metals. Compared with the roll ring produced abroad, the cost of the composite roll ring is greatly reduced on the basis of meeting the performance requirements. The performance comparison of roller ring at home and abroad is shown in the table.