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Roll introduction

Author: Publications:2018-3-13 14:48:07 Click:

      Rolls are tools for plastically deforming metals and are important consumables for determining mill efficiency and quality of rolled products. Rolls are an important part of a rolling mill's rolling mill, and the steel is rolled by the pressure generated by rolling a pair or a set of rolls. It is mainly subjected to dynamic and static loads during rolling, wear and temperature changes.

    轧辊介绍



    Roll introduction


    Roll classification

    There are many types of rolls. There are three types of rolls commonly used: cast steel rolls, cast iron rolls and forged rolls. There are also a small number of hard alloy rolls on the profile rolling mills (high boron high speed steel rolls, vanadium nitrogen high speed steel rolls, high tungsten high speed steel). Roll).


    Roll forming method

    Casting rolls and forging rolls;

    Casting rolls refer to the types of rolls produced by the direct casting of smelting molten steel or molten iron.

    According to the material, the casting rolls can be divided into two types: cast steel rolls and cast iron rolls; according to the manufacturing method, they can be divided into two types: integral casting rolls and composite casting rolls.


    Forging rolls are classified by material as follows:

    (1) Forged alloy steel rolls;

    (2) forging a semi-steel roll;

    (3) Forging a semi-high speed steel roll;

    (4) Forging white cast iron rolls.


    Roll damage cause

    The working conditions of the rolls in the mill components are the most complicated. Residual stresses and thermal stresses are generated in the preparation process of the rolls prior to manufacture and use. It is further affected by various cyclic stresses, including bending, torsion, shear, contact stress and thermal stress. The distribution of these stresses along the roll body is uneven and constantly changing, not only because of design factors, but also by the wear, temperature and roll shape of the rolls during use. In addition, rolling conditions often have abnormalities. Rolls that are improperly cooled after use can also be damaged by thermal stress. Therefore, in addition to wear, the rolls often have various local damages and surface damage such as cracks, breaks, peeling, and indentation. A good roll should have a good match between strength, wear resistance and various other performance indicators. In this way, not only is it durable under normal rolling conditions, but it can also be less damaged in the event of some abnormal rolling. Therefore, in the manufacture of rolls, the metallurgical quality of the rolls should be strictly controlled or external measures should be taken to enhance the load carrying capacity of the rolls. Reasonable roll shape, hole shape, deformation system and rolling conditions can also reduce roll work load, avoid local peak stress and prolong roll life.


    Roll repair method

    Polymer composite material repair method: It has super strong adhesion, excellent compressive strength, wear resistance and corrosion resistance.


    Cold welding repair method: The cold welding machine uses the principle of electric spark high-frequency discharge to perform non-thermal surfacing on the metal surface, so it does not deform, no annealing, no undercut and residual stress during repairing defects such as roll blisters and scratches. Does not change the state of the metal structure. High repair accuracy, coating thickness from a few microns to a few millimeters, can be used for metal workpiece wear, scratch, pinhole, crack, defect deformation, hardness reduction, trachoma, damage and other defects deposition, sealing, and equal repair function It only needs to be polished and polished, and can also be used for various machining such as turning, milling, planing, grinding, etc., as well as post-processing such as electroplating.


    Roller prevention method

    Preventing roll breakage should be carried out in terms of reducing manufacturing residual stress, mechanical stress, tissue stress and thermal stress.

    Under normal circumstances, most of the manufacturing residual stress will be eliminated during the heat treatment process, and will gradually disappear as the roll storage time is extended. Therefore, the new roll can be used for a period of time and can reduce the risk of breakage. The main method of avoiding large mechanical stress is to avoid overcooled steel. The method of reducing the tissue stress is to control the residual austenite content of the working layer of the roll body to less than 5% by heat treatment. The way to reduce the thermal stress is to cool the rolls well during the rolling process.

    Residual stress, mechanical stress, microstructure stress and thermal stress are the main reasons for the fracture of high chromium steel rolls. Good heat treatment, rolling conditions and cooling can effectively prevent high chromium steel roll breakage.



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