Causes of "edge cracks" and coils "tower shape" in the production of copper strips and how to avoid them

Defect 1: the edge crack of the strip rolling

Edge cracks can be generated in both hot rolling and cold rolling.

Hot rolled edge crack:

cause:

1, the ingot heating temperature is low

2. Poor metal plasticity

3, there are organizational defects in the edge of the ingot

4, hot rolling cooling strength is large

5, the time of the roller stick is not appropriate

6, the roller type control is not good, there is additional tensile stress on the edge to produce crack

7, the final rolling temperature is low

Elimination measures:

1. Change the heating and hot rolling process parameters according to the characteristics of the alloy, and appropriately increase the temperature of the ingot

2, reduce the amount of cooling lubrication

3, use the roller roll side by side one or two times in advance

4, appropriate increase in finishing temperature

02

Cold rolled edge crack:

cause:

1. There is a crack in the edge of the incoming material.

2, the incoming grain is coarse

3, the processing rate of the pass is large

4, the total processing rate is large

5, rolling tension is large

Elimination measures:

1. Cut the crack existing in the edge of the incoming material

2, reduce the processing rate of the pass, according to different equipment, the general pass processing rate does not exceed 30%

3, cold rolling to a certain degree should be annealed in time, the total processing rate of copper and H90 and above low zinc alloy can exceed 90%, the total processing rate of other alloys generally does not exceed 80%, especially not more than 60%, such as HPb59- 1 and so on.

4. Reasonably control the rolling tension to avoid cracks due to the presence of edge defects when the tension is too large.

Defect 2: Belt "tower shape"

cause:

When the strip is coiled, the coil is not tight, the coil is not aligned, and the winding tension is unstable, and the coil "tower shape" is produced.

1. The lateral tolerance of the incoming material is obviously too large, which causes the strip to deviate from the center line when rolling.

2. The material of the material is wide and skewed, causing deviation when the head is loose.

3, the roll gap or roll type adjustment is unreasonable, causing the strip to run off

4, the tension is not suitable for the size, fluctuations, causing the strip to run off

Elimination measures:

1. Hot rolling should be centered as much as possible to ensure the uniformity (symmetry) of the head and tail (tongue) and avoid sideways

2. Adjust the roll gap and roll shape during hot rolling to ensure good lateral tolerance control of the strip.

3, the tension should be appropriate and uniform when taking up

4. When there is a slight deviation in the rolling process, adjust the pressure on both sides in time to correct and ensure the uniformity of the roll.

5. Reasonably select the stripping tension of the strip in the process of cleaning and shearing, and control the strip tension by the strip to meet the requirements of the roll uniformity and constant tension coiling of the coil.

Defect 3: Surface bonding of strip and strip

cause:

Some copper and copper alloy ribbons have defects that stick together between the coil layer and the layer produced by the annealing process.

1, the strip surface is too rough

2, the take-up tension is too large, too tightly wrapped

3, the annealing temperature is too high or the holding time is too long

4. Heating is uneven during heating, and the amount of thermal expansion between layers is different.

5. The cooling rate is faster during the cooling process, which causes the coefficient of contraction between the cooled outer and inner rolls to be different.

Elimination measures:

1. When the coiling is taken, especially when the final coiling is performed before annealing, the tension should be moderate.

2. Strictly control the heating and cooling rate in the annealing process

3. Properly reduce the annealing temperature or shorten the holding time

4. Appropriately increase the smoothness of the roll