The Main Factors Affecting the Quality of the Wire Rod

In the production of high-speed wire rod mills, the quality of the coils discharged from the laying head is often not ideal, that is, the coils are oval, the coils are too large or too small, the stacking is disordered, the density is uneven, and the rolling specifications are small. This is especially noticeable with wires. Judging from the working experience of the laying head, the spinning tube and the speed of the laying head are the main influencing factors.

1. Spinning Tube

The spinning pipe is installed on the spinning disc. It is a spiral curve with a spatial cone shape. Although the curves of different manufacturers are different, they can be divided into 3 sections: First, the initial section is straight, and the wire is not plastic Bending deformation; the second is the deformation section, where the wire undergoes plastic bending deformation along with the bending shape of the spinning tube; The third is the shaping section. The wire continues to undergo plastic bending and deformation and form a stable coil. The shaping section is important for the shape of the spinning coil. The exit section of the spinning pipe is generally at an angle to the surface of the spinning disc, so that the discharged coil has a forward partial speed. Then, because the entire laying head is at a horizontal angle of 10°to 20°with the horizontal plane, the coil can be turned from the spinning tube is discharged smoothly and spread on the air-cooled roller table.

The nozzle angle of most laying head is not adjustable, so when the rolling speed changes, the horizontal forward speed of the discharged coil will be different, which will cause the situation of the coil falling on the air-cooled roller table to deviate from the setting the best condition is the appearance of suboptimal circles. For this reason, the first section of the air-cooled roller table is generally designed to be adjustable in height, so that the vertical distance from the spinning plate to the air-cooled roller can be adjusted. By adjusting the height of this roller table, the coil can be laid on the roller table correctly, but in actual production, it is often difficult to grasp because of insufficient operating experience, which causes the coil to fall obliquely.

When producing a small-scale wire rod, the front of the coil runs faster than the rear due to the large horizontal speed. When the height is not adjusted properly, the coil will be laid on the rollers in an inclined manner. Because the wire is thin and soft, the coil is very easy to form an oval shape.

        2. Speed Control of laying head

The diameter of the coil discharged from the laying head is not constant. When the size is different, it will also affect the appearance and quality of the bundle. Therefore, it is also important to ensure that the diameter of the coil discharged from the laying head is constant. When the wire passes through the spinning tube, the movement state changes from linear motion to circular motion, and the linear velocity VW. At this time, the rotating linear velocity VL of the nozzle of the spinning tube is at the same time.

If V W and V L are equal in size and opposite in direction, the composite speed of the wire at the spinning nozzle relative to the ground is 0. Because the spinning disc has a downward inclination, the wire will perform the parabolic movement in three-dimensional coordinates (the vertical direction is free fall), so that the curvature radius of the wire when it is ejected can be guaranteed. That is, the coil diameter is constant.

In order to ensure that the wires of different specifications can meet VL = VW during the entire spinning process, in order to stabilize the coil diameter, there are generally pinch rollers in front of the laying head. There are two types of pinch systems: one is full pinch, the micro tension control method is used to match the speeds of the finishing mill, pinch rolls and laying heads; the second is the tail pinch, and the small-size wire rods are used to reduce the speed of the tail pinch to prevent the phenomenon of speed increase when the tail is out of the finishing mill. The wire of the specification is clamped at the tail speed to push the wire out of the laying head to form a circle.

When V L ≠ V W, the speed of the coil relative to the ground in the disk surface direction is not 0, that is, the coil has an angular velocity relative to the ground. Therefore, a certain offset will occur during the falling process. When VL> VW, the relative angular velocity direction is consistent with the spinning direction of the spinning tube, and the coil will be deflected to the left (looking along the rolling line); when VL <VW, the relative angular velocity direction is opposite to the spinning direction of the spinning tube, and the coil will be to the right. Partial. When the coil is more severe to the left or right, it will collide with the side plate of the air-cooled wire, which will damage the surface of the wire.