-Key technologies of ACR copper pipe horizontal continuous casting and rolling process
1. Horizontal continuous casting of acr type copper tube
Horizontal continuous casting equipment is the lowest height casting machine, and its process center line is completely horizontal. The horizontal continuous casting device is mainly composed of a tundish, a crystallizer, a blank casting machine, a cutting machine, a cooling bed, a traction system and a microcomputer control system. In addition, auxiliary equipment also includes melting furnaces, temperature control equipment, etc. Among them, the separation ring, graphite sleeve, crystallizer, blank casting machine and automatic control system are the key equipment of the horizontal continuous casting machine.
The crystallizer consists of a graphite mold and a water-cooled copper sleeve. One end of it is fixed on the front wall of the intermediate insulation bag, and the other end is fixed on the cooling system. During the melting and casting process, the electrolytic copper is melted by the intermediate frequency melting furnace and then kept warm in the holding furnace. When the temperature of the molten copper reaches 1250°C, billet casting begins. The solidification process of molten copper in horizontal continuous casting is that the molten copper enters the mold cavity through the entrance of the crystallizer. After entering the crystallizer, it forms a cylindrical solidified shell through the chilling action of the cooling water. It is pulled from the crystallizer at a certain speed in the billet drawing mode. Cast it out and get the billet.
The ingot structure of acr type copper pipe includes grain size, shape and orientation, and the shape, size and orientation of grains in pure metal cast structure.
The typical ingot structure can be divided into three layers:
(1) The quench layer is located at the outermost layer of the ingot and is composed of fine equiaxed grains;
(2) The columnar crystal layer, located inside the quenching zone, is composed of columnar grains that are perpendicular to the mold wall and parallel to each other;
(3) Coarse equiaxed crystal layer, located in the center of the ingot.
There are many factors that affect the structure of the ingot, such as casting temperature, wall thickness and shape of the mold, mold temperature, ingot size, casting method and whether a grain refiner is added, etc.
2. If you want to obtain the required solidification structure of acr type copper tube, you can choose according to the following methods:
1. Using a metal mold and increasing the wall thickness can allow the liquid metal to obtain a greater cooling rate, resulting in a larger temperature difference between the inside and outside, which is conducive to the development of columnar crystals. Sometimes the columnar crystals have developed before nucleation in the central area. There is therefore no central equiaxed crystal zone in the center of the ingot, only two zones: chilled and columnar crystals.
2. The higher the casting temperature, the greater the temperature difference between inside and outside, and the longer the condensation time, which will be beneficial to the development of columnar crystals.
3. Adding a certain grain refiner can promote non-uniform nucleation and help obtain fine equiaxed grains. However, if the liquid metal is overheated too much, the number of non-spontaneous cores will be reduced, and thicker columnar crystals will easily be obtained.
4. Mechanical vibration, magnetic field stirring, ultrasonic treatment, etc. can promote nucleation and weaken the development of columnar crystals.
