Common problems of rolling rolls

 Roller is a tool for plastic deformation of (rolled material) metal, and it is an important consumable part for the efficiency of the rolling mill and the quality of the rolled material. Rolls are important parts of rolling mills in rolling mills. They use the pressure generated by a pair or a set of rolls to roll steel. It mainly bears the influence of dynamic and static load, abrasion and temperature change during rolling.

There are two types of rolling we usually use, cold rolling rolls and hot rolling rolls.

There are many types of materials made of cold rolling rolls, such as 9Cr, 9Cr2, 9Cv8 Crmov and so on. There are two requirements for this type of rolling:

1: The rolled surface must be quenched

2: The hardness of the surface must be HS45105

The materials manufactured by hot rolling generally include 60 Crmnmo, 55Mn2 and so on. The field of use of this type is very wide. It can be used in some processing such as section steel, bar, rebar, high, non-steel, and open, etc. It bears strong rolling force, severe wear and thermal influence, Moreover, it works at high temperatures and allows diameter wear per unit of work, so it does not require surface hardness, but only requires high strength, initial properties and heat resistance. Hot rolling only uses overall normalizing or fire, and the surface hardness requires HB190-270 hardness.

The common failure forms and reasons of rolls are as follows:

1. Cracks.

Roll cracks are mainly caused by excessive local pressure of the roll and rapid heat and cold of the roll. On the rolling mill, if the emulsion nozzle is blocked, causing poor local cooling conditions of the roll, cracks will occur. Due to the low temperature in winter, cracks are prone to occur compared to the season

2. Peeling.

If the cracks continue to develop, it will form lump or flake peeling. Those with light peeling can be re-ground and continue to be used. Rolls with severe peeling will be scrapped.

3. Make pits.

The pitting is mainly due to the welding seam or other debris entering the rolling mill, so that the roll surface is marked with pits of different shapes. Generally, rolls with pits must be changed. When the quality of the welding seam of the steel is not good, the rolling operation should be lifted and pressed down to prevent the pits from being scratched.

4. Sticking roller.

The reason for the sticking of the roll is that during the cold rolling process, broken chips, wave breaks and broken edges appear, and due to the high pressure and high temperature, it is very easy to form a bond between the steel band and the roll, resulting in a small area of ​​damage to the roll. Through grinding, the roll can be used continuously after the cracks on the surface of the roll are eliminated, but its service life is significantly reduced, and it is prone to spalling accidents in future use.

5. Le roller.

Rolling is mainly caused by the excessive reduction of the steel which causes heavy leather or slight folds and the deviation of the steel to produce heavy leather. When the roll is severely struck, sticky rolls will occur and the steel will be cracked. When the roll is slightly stretched, both the steel and the roll will be stamped.

6. Broken roller.

The main causes of roll breakage are overpressure (that is, excessive rolling pressure), defects in the roll (non-metallic inclusions, bubbles, etc.), and stress field caused by uneven roll temperature.