Cold rolling process knowledge Q&A –part I

1. What is reversing cold rolling? What are the advantages of cold rolled strip steel?

Answer: Rolling deformation of metal below recrystallization temperature is called cold rolling.

Cold rolling production can provide a large number of steel plates and strips with high accuracy and superior performance. Its main feature is low processing temperature. Compared with hot rolling, it has the following advantages:

① Cold rolled strip products are accurate in size and uniform in thickness;

② Extremely thin materials that cannot be produced by hot rolling can be obtained;

③ The surface quality is superior, and there are no such defects as pitting, pressed scale and so on that often occur in hot rolled strip steel.

④ Good mechanical and technological performance;

⑤ High speed rolling and full continuous rolling can be realized with high productivity.

2. What characteristics does the motor meet in the cold tandem rolling process?

Answer: ① The rolling mill is required to have a large speed regulation range and be continuously adjustable.

② The rolling mill speed of each stand can be separately started, braked, operated in forward and reverse directions, and can be jointly started and braked.

③ In order to ensure smooth threading, the motor characteristics should be hard enough, and the dynamic speed of the motor should not be greater than 25%. In order to ensure smooth threading and establish tension, a speed trimming device must be provided.

④ During threading, acceleration, steady speed rolling and deceleration operations, the required strip steel tension shall be ensured and tension fluctuation shall be reduced.

3. What is the minimum rolling thickness of cold rolling machine?

Answer: When a certain product is cold rolled on a certain rolling mill, the rolling down becomes more and more difficult as the strip steel gets thinner. When the strip steel thickness reaches a certain limit, no matter how much rolling down, no matter how many rolling passes, it is impossible to make the strip steel thinner. At this time, the limit thickness of the strip steel is called the minimum rolling thickness.

4. What is rolling mill plant variable stiffness?

Answer: The stiffness of the rolling mill refers to the ratio of rolling pressure and elastic deformation of the rolling mill. It is a major parameter in the design of the rolling mill and the calculation of rolling parameters. After the manufacturing and installation of the rolling mill, its stiffness is a fixed value. By special means, manually changing the stiffness of the rolling mill is called variable stiffness. The high rigidity of the rolling mill is conducive to reducing the fluctuation of incoming material thickness, while the low rigidity of the rolling mill is conducive to reducing the fluctuation of finished product thickness caused by the rolling mill itself.

5. How does work hardening affect the cold rolling mill process?

Answer: The strip steel has different degrees of work hardening during rolling. After the work hardening exceeds a certain degree, the strip steel is too hard and brittle to continue rolling. Therefore, if the strip steel wants to continue rolling thin after a certain pass of cold rolling, that is, after a certain total cold rolling reduction is completed, softening heat treatment (recrystallization annealing, etc.) is often required to restore the plasticity of the rolled piece and reduce the deformation resistance.

6. What are the components of the cold strip rolling machine train?

Answer: ① Main drive motor

② Main motor drive shaft

③ (Flange type) safety spindle

④ Belt reducer (gearbox)

⑤ Main drive shaft

⑥ Working base

7. What effect will the roll diameter have on the rolling process?

Answer: ① The roll diameter is too small, which reduces the adjustment effect of bending roll and makes it difficult to control the plate shape.

② The roll diameter is too small, exceeding the depth of the hardening layer on the roll surface, and the surface hardness of the roll is small. On the one hand, there are many soft spots, which affect the surface quality; On the other hand, the contact arc area in the deformation zone increases, and the rolling force increases.