Overview
A wire rod mill is a rolling mill dedicated to rolling wire rod. The wire rod is the product with the smallest section size of the profile. It is rolled from the billet to the finished product, and the total elongation coefficient is large. The rolling stock is often rolled only once on each rolling mill. Therefore, the wire rod rolling mill has the largest number of stands and the smallest division of labor in hot-rolled profiles. rolling mill. Modern continuous wire rod rolling mills are generally composed of 21 to 28 rolling mills, which are divided into rough rolling mills, intermediate rolling mills and finishing mills. The intermediate rolling mills are sometimes divided into two groups. The structure and arrangement of wire rod mills have been developing in the direction of high speed, continuous, no twist, single line, combined structure, mechanization and automation.
Wire rolling mills have rough rolling, intermediate rolling and finishing rolling. The layout forms include row type, semi-continuous type and continuous type; continuous finishing mills include horizontal two-roll type, horizontal and vertical alternating type, 45° non-twist rolling mill and Y-type rolling mill.
Roughing mill
Rough rolling mills play the role of billeting, and are often arranged in horizontal, in-line, continuous and other layout forms. Among them, the continuous rough rolling mills are mostly composed of 6 to 8 two-high horizontal rolling mills, which are arranged in close proximity to each other. At the outlet of the heating furnace, the frame is turned over by twisting rollers. A feeder and a counting device are installed at the entrance of the rough rolling unit to realize multi-groove rolling; a flying shear is installed at the exit to remove the possible split ends after rolling and prevent the steel from being stuck when entering the next unit. accident, and when a production failure occurs in the next unit, the rolling stock is continuously sheared.
Intermediate rolling mill
The role of the intermediate rolling mill is to link the above, which can not only produce the finished wire rod with thick diameter, but also adjust the section size of the rolling stock entering the finishing mill, so as to ensure the stable rolling of the finishing mill. The layout forms of the intermediate rolling mill are in the form of row type, double type, continuous type, etc., and the continuous type layout is divided into two forms: full tandem rolling and semi-tandem rolling. Except for full continuous rolling, rolling pieces generally form more than one looper during rolling to facilitate adjustment. The intermediate rolling mill can be a two-high horizontal rolling mill, a horizontal-vertical alternately arranged rolling mill, or a Y-shaped rolling mill. Generally, the length of the looper is controlled by photoelectricity. When the looper is picked from the bottom, the length of the looper can also be controlled by the principle of capacitance or inductance. Flying shears are generally installed between the intermediate rolling unit and the finishing rolling unit to perform head cutting and accident shearing.
Finishing mill
The role of the finishing mill is to ensure the production of qualified products. Its layout forms include duplex, semi-tandem and full-tandem rolling. The full tandem rolling mill is divided into several types: full horizontal mill, horizontal and vertical alternating mill, Y type finishing mill and 45° finishing mill. Among them, the semi-continuous rolling is a two-high horizontal rolling mill, which uses shroud operation and torsional turning for 1-2 grooves side-by-side rolling. The rolling speed is generally about 25-30m/s. Rolling bearings, high precision rolling products, DC motor drive, loopers between each stand, easy adjustment, flexible production, each intermediate stand can roll out products of different specifications, suitable for small batches, multi-variety wire production. The horizontal full tandem rolling is collective drive, multi-line rolling, and the rolling speed is 20~30m/s; the straight tandem finishing mills are alternately arranged horizontally and vertically. The vertical and horizontal rolling mills are alternately arranged to carry out multi-pass single-line rolling, the rolling speed can reach about 35m/s, and the disc weight can reach 800kg. The rolling speed of Y-type finishing mill can reach 50m/s.
Layout
Modern production should adopt a new type of closed-type roughing and intermediate rolling mills alternately arranged horizontally and vertically, cantilever non-twisting pre-finishing rolling mills, super-heavy top-cross 45° non-twisting finishing rolling mills, and the whole line adopts non-twisting rolling, tension-free and micro-tension rolling. Rolling technology, start-stop flying shears are installed after rough rolling, intermediate rolling and before finishing rolling, to ensure that the rolling speed is not less than 100m/s, and the maximum coil weight is not less than 1.8t. Water cooling devices are installed in front of the finishing mill, between the stands of the finishing mill, and after the finishing mill, to implement temperature-controlled rolling and controlled cooling, and use a sizing and reducing mill for precision rolling, equipped with online diameter gauges and online flaw detectors. In the production of high-speed wire rod, the key equipment for laying the rolled wire rod into coils for collection is adopted, and the speed of the new laying machine is above 100m/s.
The length of the roller-type air-cooled conveying line with large air volume delay is not less than 90m, and the blowing direction and air volume of the fan can be adjusted automatically. For uniform cooling, there are several drops in the air-cooling line. The heating furnace of the wire rod rolling mill adopts a walking beam heating furnace, which has the functions of automatic steel burning and optimal combustion control. There is a high-pressure water descaling device in front of the rolling mill, and the pressure is not less than 18MPa. In addition, there is a complete collection and transportation system such as automatic collection, transportation, baling, and weighing. The main drive motor of the wire rod rolling mill is all-digital AC variable frequency speed regulation.