What is a Wire Rod Mill Laying Head?

What is a Wire Rod Mill Laying Head?

The laying head of wire rod mill is the key equipment in high-speed wire production to spin rolled wires into coils for collection.

Wire rod mill laying head is one of the key equipment in high-speed wire production and an important bottleneck restricting further speed-up of high-speed rolling mill. The quality of wire spinning directly affects the physical quality of high-speed wire. With its special shape structure and certain speed, the laying head changes the straight current wire moving at high speed into coils with stable ring shape and uniform spacing. With the increase of wire rolling speed and output, the requirement for wire rod mill laying head is getting higher and higher. Therefore, many high-speed wire production enterprises will have unstable coils in production, which will affect product quality and smooth production.

With the development of wire production technology, horizontal wire rod mill laying head has become the throat part of the production line as a coiling equipment matching with the uncoiled cooling line. Its function is to guide the wire rolled from the finishing mill K1 or pinched in a straight line into a horizontal laying head machine. The wire slips relatively without twist in the tapping tube with rotation. Under the action of centrifugal force, Coriolis force, inertia force and friction force, it bends and deforms gradually along with the shape of the tapping tube, reaches the required curvature at the outlet, forms the spiral coil and realizes its working purpose.

The high-speed wire rod mill laying head is a horizontal structure, which is located between the water-cooled box and the cold-controlled roll track of the controlled cooling line after the finishing mill. Horizontal laying head machine is composed of transmission device, shield, tapping disc, hollow shaft, tapping tube, bearing seat, motor, bevel gear pulley and other components. The threading machine is driven by a motor and driven by a pair of bevel gears meshing in the gear box to rotate the hollow shaft. The threading tube is installed on the threading disc, which is connected with the hollow shaft by bolts. 

Development of Wire Rod Mill

    At present, Asia is the fastest-growing economy in the world. However, China is the focus of Asia. Under such a rapid development situation, China's infrastructure has developed rapidly, and various types of wires have been in short supply. The original old-fashioned horizontal rolling mill and double-rolling mill are far from meeting the needs of today's market development in terms of accuracy and quality, as well as in terms of output and control level.

    Therefore, in the late 1960s, with the continuous improvement of the technical level, various new types of high-speed twistless finishing mills were developed in the world, and the wire weight was increased from tens of kilograms to two and a half tons. The final exit speed of the rolling is increased from the original 20m/s to 30m/s to the current 130m/s, and the finished product tolerance is ±011mm.

Due to the smooth surface quality of the wire, the head-to-tail tolerance value is small, and the metallographic structure is more uniform after the water-cooling and the loose-rolling control are cooled, so that the wire can be drawn without heat treatment, thereby greatly reducing the cost and receiving a large number of users. Praise and welcome.

At present, representative finishing mills include internal drive 45-degree wire rod mill, external mesh drive 45-degree finishing mill, X type 45 degree centralized drive finishing mill, Y type three-roll finishing mill, flat roll drive finishing mill, 75 degrees. ×15 degree concentrated transmission finishing mill six types.

Compared with the old-fashioned rolling mill, these rolling mills have the following characteristics:
1. Single-line continuous rolling, convenient and safe operation;
2. High rolling speed, currently up to 130m/s;
3. Convenient for changing rolls;
4. Convenient for changing guides;
5. High, low cost;
6. Wire rod tolerance is small, the surface is smooth;
7. Wire rod has high internal quality;
8. High level of automation control.

In recent years, China's wire rod mill equipment has developed very rapidly.

What is Wire Rod Mill?

Wire Rod Mill Brief Introduction

Wire rod mill consists of roughing mill, intermediate rolling mill, and finishing rolling mill. Roughing mill, intermediate rolling mill and finishing mill are arranged in horizontal, semi-continuous and continuous forms. Continuous finishing mills include horizontal two-roll mill, horizontal-vertical alternating mill, 45-degree non-twist mill, and Y-type mill. A new type of closed roughing and an intermediate rolling mill with the alternating horizontal and vertical arrangement, cantilever non-torsional pre-finishing mill, super heavy top-crossing 45-degree non-torsional finishing mill should be adopted. Non-torsional rolling, tension-free and micro-tension rolling technology should be adopted throughout the line. Start-stop flying shears should be set before rough rolling, medium rolling and finishing rolling to ensure that the rolling speed is not less than 100 m/s and the maximum coil is reached. The single 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 behind the finishing mill. Temperature control rolling and cooling control are carried out. Precision rolling is carried out by the sizing and reducing mill, and on-line diameter gauge and flaw detector are equipped. In the production of high-speed wire rod mill, the key equipment of rolling wire into coils for collection is adopted. The speed of the new laying head is over 100 m/s.

The length of roll air-cooled transport line with large air volume delay is not less than 90 M. The direction of the blower and air volume can be adjusted automatically. There are several drops in the air-cooled line for uniform cooling. Walking beam reheating furnace is used as the heating furnace for wire rod mill. It has the functions of automatic steel burning and optimum combustion control. High-pressure water descaling device is installed in front of the rolling mill, and the pressure is not less than 18 MPa. In addition, there are perfect collection and transportation systems, such as automatic volume collection, transportation, bundling, weighing and so on. The main drive motor of wire rod mill is fully digital AC variable frequency speed regulation.

Intermediate Mill

The function of the intermediate mill is to connect the preceding and the following. It can not only produce the finished wire rod with large diameter but also adjust the cross-section size of the rolled piece entering the finishing mill to ensure the stable rolling of the finishing mill. The layout forms of intermediate rolling mills are horizontal, double and continuous, while the continuous layout is divided into two forms: full continuous rolling and semi-continuous rolling. In addition to full continuous rolling, the rolling stock generally forms more than one looper during rolling to facilitate the adjustment. The intermediate mill can be a two-high horizontal mill, a horizontal-vertical alternating arrangement mill, and a Y-type mill. Generally, the length of the looper is controlled by photoelectricity. When the looper is lifted from the lower sleeve, the length of looper can also be controlled by the principle of capacitance or inductance. Flying shears are usually set up between intermediate rolling mill and finishing mill for cutting head and accident shearing.

Roughing Mill

The roughing mill acts as a blanking machine, often using several layout forms, such as horizontal, sequential and continuous. Roughing mills with continuous layout are mostly composed of 6-8 two-roll horizontal mills, which are arranged at the exit of the heating furnace, and twisting rolls are used to turn over steel between the stand. A distributor and a counting device are arranged at the entrance of the roughing mill to realize multi-channel rolling. Flying shears are installed at the exit to remove the splitters that may occur after rolling, to prevent the steel jamming accident when entering the next unit, and to cut the rolling piece continuously when production failure occurs in the next unit. The production of alloy steel or small-batch, multi-variety ordinary steel workshop, sometimes also uses Y-type rolling mill to form a rough rolling unit. At this time, there is no need to twist the steel between the frames, and the blank size used is also flexible, but only can roll a rolled piece.

Finishing Mill

The function of finishing mill is to ensure the production of qualified products. The layout forms are double-double finishing mill, semi-continuous rolling, and full-continuous rolling. Full tandem rolling is divided into the full horizontal mill, horizontal-vertical alternating mill, Y-type finishing mill, and 45-degree finishing mills. There are many double lines finishing mills for wire rod mills in China. They are driven by AC motors in groups and rolled by multi-groove parallel rolling with the enclosure. When rolling, the rolled parts are twisted and tipped. The rolling speed is more than 15-20 m/s and the weight of the disc is less than 160 kg.

The semi-continuous rolling is a two-roll horizontal rolling mill. The rolling operation is carried out in 1~2 trough by parallel operation and twisting steel. The rolling speed is generally about 25~30m/s. Such rolling mills generally use prestressed rolling mills and rolling bearings. The precision of the rolled products is high, the DC motor is used for transmission, and the loops are provided between the racks. Therefore, the adjustment is convenient and the production is flexible. The intermediate frames can be rolled out of different specifications and are suitable for small batches and varieties of wires produce. Horizontal full tandem rolling is a collective transmission, multi-wire rolling, rolling speed is 20-30 m/s; The vertical and horizontal roller mills are arranged alternately by the cantilever type vertical roll and horizontal roll mill. The rolling speed can reach about 35m/s and the weight of the disc can reach 800kg. The rolling speed of Y-type finishing mill can reach 50m/s.

Wire Rod Mill Types and Wire Rod Mill Layout

The production of wire rod is mainly continuous, and the number of rolling mills for the wire rod mill is generally large, which can be divided into roughing rolling, intermediate rolling mill, and finishing mills. Wire rod mill has gone through the development process from horizontal, semi-continuous, continuous to the high-speed rolling mill. Every new type of mill and every new production line arrangement has improved the rolling speed, rolling quality and caries weight of wire rod. High-speed non-twist finishing mill and controlled cooling equipment are used in wire rod production, marking the salivation of a new generation of wire rod mill. The following figure is a sketch of the layout of a Morgan type high-speed wire rod mill in a foreign factory.

The reheating furnace is a roller side-loading side-out walking beam type reheating furnace. The whole wire rod mill line consists of 6 roughing mills, 8 intermediate rolling mills, 4 pre-finishing mills, 8 finishing mills and 4 reducing and sizing mills. The small extension precision rolling is realized. The roughing mill, intermediate mill, and pre-finishing mill stands are arranged in a flat-upright arrangement, which is a double fulcrum, a long roll body, and a porous compact frame, and the rolling mill is a lower drive. The pre-finishing mill is a compact cantilever roll-ring stand with the alternating horizontal and vertical arrangement. Tungsten carbide roll-ring and roll gap are symmetrically adjusted by the eccentric sleeve. Finishing mill and reducing and sizing mill are top-crossing 45 degree super heavy non-twisting mill. Micro tension or looper control is used between the rolling mill racks.