Application of composite roll
The outer layer of the roll body and the core (including the roll neck part) are made of different materials, and the two materials are metallurgically combined rolls. requirements, while ensuring the strength and toughness of the core and roll neck. The material of the outer layer and core is mainly selected according to the specific requirements of the stand where the roll is located. Commonly used outer layer materials of composite rolls are chilled cast iron, unbounded chilled cast iron, ductile iron, high chromium cast iron, alloy steel, semi-steel, high chromium steel, high-speed steel, cemented carbide, etc.; the common material for the core is gray cast iron, ductile iron, cast steel, forged steel.
Composite rolls are widely used in various rolling mills, such as finishing work rolls of hot-rolled strip mills, backup rolls of strip mills, intermediate and finishing work rolls of profiled steel pipe mills, and so on. The roll sleeves of some combined rolls are also composite, such as horizontal rolls of H-beam rolling mills, tension-reducing rolls of steel pipe rolling mills, etc.
Quality requirements for composite rolls
The composite roller should pay attention to the following aspects:
For the surface finish of the composite roller, the composite pressure should be able to be large enough (this is determined by the cylinder area and the force arm of the composite part), and the structure of the composite roller should preferably be a double-layer type (with circulating heat in the middle). Oil heating to facilitate temperature stability) and so on. The composite roller is used for the composite mold on the composite machine. Its pros and cons will play a decisive role in the quality of the composite product in the future, and it can also improve the production efficiency of the equipment.
Manufacture of composite rolls
There are many ways to manufacture composite rolls, the primary methods are as follows:
(1) Casting method. Including the centrifugal casting method in which the roll body is solidified in a high-speed rotating mold, the overflow method or flushing method in which soft and ductile metal liquid is used to replace the unsolidified hard metal liquid in the core during the solidification of the roll, and the bottom leakage method , placing a separator in the mold and pouring the roll body and the core with the corresponding metal liquid, and the roll body metal liquid was poured into the gap between the solid mandrel and the annular mold developed in the 1990s. The continuous casting compound (CPC) method (see figure) and so on.
(2) Welding method. There are mainly surfacing, electro slag, and electro slag welding methods of pouring liquid metal into a conductive mold.
(3) Powder metallurgy method. Including the hot isostatic method and self-propagating synthesis method in which powder materials and ductile mandrels are welded under high temperature and high pressure. The latter is a method of placing metal and non-metal powder raw materials that can undergo an exothermic synthesis reaction in a dry mold cavity and igniting it to cause a self-propagating synthesis reaction, and then pressurizing it to the final roll shape.
(4) Spray deposition method. It is a method of atomizing the high alloy content roll body metal liquid into liquid particles under vacuum or argon protection and depositing it on the rolling mandrel.
(5) Forging composite ingot method. The choice of composite process method depends on factors such as roll shell and core material, roll size and shape, and manufacturing cost.
