The roll manufacturer explains the common defects of the roll and the solutions

2022-03-24 15:58

In the process of using the roll, various factors often cause various defects such as wear, crack, falling off and cracking of the roll, which has a serious impact on our production process. What is the way to deal with it? The following roll manufacturer Wuxi Taihu roll gives you a detailed summary and explanation of the common shortcomings and treatment methods of the roll:

1. Roll wear

There are three categories: mechanical wear is caused by the friction between the roll surface and the rolled piece, thermal wear is caused by the softening, melting or evaporation of the surface caused by the effect of high temperature, and corrosion wear is caused by the loss and migration of surface data caused by the chemical effect, electrochemical effect and oxidation effect of water on the roll surface.

2. Roll crack

Steel stacking, steel jamming, rear end collision and other incidents occur during rolling, resulting in a sharp rise in some of its temperatures, and the resulting thermal stress and arrangement stress exceed the limit, forming a thermal crack. The tongue is formed by rolling extension, and its temperature is lower than that of the middle rolled piece, which will produce thermal stress and sudden change of rolling stress, forming impact cracks. During rolling, cracks will also be formed due to overlapping rolling of iron oxide scale, guide scratches and other reasons.

3. Roll falling off

The composition and propagation of cracks accelerate, and will lead to falling off after reaching a certain length and depth.

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4. Roll cracking

1) Casting defects of roller shaft

In the centrifugal casting of roll, the composition and arrangement of layered segregation caused by centrifugal vibration form the rapid propagation of crack, resulting in roll cracking.

2) Disadvantages of roll arrangement

Unqualified chemical composition and improper cooling rate will lead to component segregation and too high cementite. Only the mechanical properties will be reduced and eventually lead to cracking.

3) Processing technology

When the roll is forged, the pressure is too small or the deformation is unreasonable, resulting in the roll core is not forged thoroughly, forming a transgranular crack.

Its treatment method:

1. The roll shall be made of wear-resistant and heat crack resistant materials, and the corresponding heat treatment and logistics chemical treatment methods shall be adopted to homogenize the arrangement and add the surface wear resistance. The roll shall be subject to induction inspection such as hardness and ultrasonic before being put on the rolling mill to ensure that it has no defects such as cracks.

2. During roll turning, the residual oxide layer and cracks shall be completely removed to reduce the occurrence of roll surface cracks and falling off.

3. Reasonably arrange the roll change cycle, select the roll, formulate a detailed roll repair plan, control the repair quantity within the required scale, reasonably arrange the cooling water injection scale and control the cooling water volume, and ensure that the roll cooling temperature is controlled within the normal scale.

4. Strengthen the spot inspection of equipment, prevent the accidents of steel rolling equipment, reduce the accidents such as steel jamming, steel stacking and rear end collision, strictly control the rolling temperature, prevent the low-temperature steel from passing through the rolling mill, and prevent the overload of rolling force.

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