Steel roll

Steel roll repair

Product description:

Rolls can be divided into production according to the process used. The production of medium plates, thick plates, thin plates, and strip steel production are mostly hot-rolled. Generally, the temperature of the roll during work is 700-800 degrees Celsius, and the superior rolling material temperature is as high as 1200 degrees Celsius. Under high-temperature conditions, the surface of the roll material has to withstand very large pressure, and due to the high-speed movement of the workpiece, the surface of the roll is subject to very large friction, The production process also requires continuous heating of the roll material and cooling of the cold water. Large fluctuations in temperature can easily cause thermal fatigue of the roll material. Therefore, the production process requires that the roller material must have higher surface hardness and toughness and higher wear resistance. Hot-rolled roll materials mainly include forged steel, cast steel, ductile composite cast iron, semi-steel, and high-hardness special semi-steel, high-chromium cast iron, semi-high-speed steel, and high-speed steel.

From the perspective of the production environment and the rolling force of the rolling mill, the hot roll must meet the following performance requirements:

1. Good abrasion resistance. The anti-wear performance is the main technical index of the roller, which directly restricts the production efficiency and the surface quality of the product. The surface damage of the hot roll is related to the force load of the roll material, working environment, and temperature fluctuation, and is also related to the nature, surface mechanism, and performance of the roll material.

2. The texture of the roller material is uniform, the structure of the roller surface is tight, and the hardness distribution is even.

3. It has a lower thermal expansion coefficient to have lower thermal stress accumulation.

4. Has a high heat dissipation capacity. The roller body can conduct heat away in time to reduce the accumulation of thermal stress.

5. Has a high-temperature yield strength. It can reduce the occurrence of network cracks on the surface of the roller.

6. It has high oxidation resistance and high temperature creep strength.

Main problems:

The main failure modes of hot rolls include thermal cracking and spalling caused by thermal fatigue, roll body surface wear, roll fracture, over tempering and creep, roll winding, and the failure surface covers almost the entire working surface. Among them, roll surface peeling and abrasion are the main ways of hot roll failure.

Technical plan:

Before laser cladding repair, perform dimension inspection and non-destructive inspection of the roll to check whether there are deep cracks on the conical surface. Generally, because the thickness of the laser cladding can only reach 2mm, if the thickness exceeds this thickness, the shaft will be tested Scrap, if there is no deep crack, mechanical cleaning is carried out to remove the plating layer, surface oxide layer, oil stain and fatigue layer to ensure the bonding force during cladding.

After the composite cladding powder is processed by the laser beam, it melts together with the surface metal of the roll base material and solidifies into a cladding layer with excellent performance. The surface hardness is increased, which provides a guarantee for the cladding layer to obtain excellent wear resistance. In addition to the high hardness of the cladding material itself, since the rapid heating and rapid cooling of laser cladding far deviate from the equilibrium process, the supersaturated solid solution strengthening, structure refinement, dispersion strengthening, and precipitation strengthening of laser cladding are also Plays a role that cannot be ignored. Ceramic particles strengthen the metal matrix composite laser cladding layer with metal or alloy as the matrix, ceramic particles as the second phase distribution, ceramic particles and metal matrix play their respective advantages, so that the cladding layer material can have both good properties .