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LMM GROUP main products focus on the cold and hot plate & wide strip mill rolls and heavy section mill rolls and big casting & forging pieces.

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Navigating the Crucial Roles of backup Rolls and Work Rolls in Cold Rolling


Cold rolling machinery and equipment

Due to the needs of thinning and shape control, various cold strip mills have emerged. The rolling mill is mainly composed of two parts: the working stand and the main transmission system. The rotation, steering and speed of the roll are realized by the drive and control of the main transmission system. The working machine base is a system that supports and fixes the rolls and guides, and adjusts the position of the roll gap (rolling line), the size of the roll gap, and the shape of the roll gap. It includes a rolling hydraulic roll bending device, a roll axial movement adjustment device, a frame, Upper roller balancing device, guide device, etc.

Navigating the Crucial Roles of backup Rolls and Work Rolls in Cold Rolling

The power transmission sequence of roller rotation:
Main motor – Reducer – Herringbone gearbox machine – Shaft – Roller

The main motor used for steel rolling has a large capacity and volume. Currently, most AC motors are used, relying on frequency conversion speed regulation systems to obtain the changing roll speed required by the steel rolling process.

Roll types and composition

In multi-roll mills, such as six-high mills, the rolls are divided into work rolls, intermediate rolls and backup rolls. The work rolls are in direct contact with the rolled product. The back-up roll supports the work roll. By contacting the work roll with the workpiece, the diameter of the work roll can be reduced and the stiffness of the work roll can be enhanced.

Cold rolling rolls are the main components of cold rolling mills. The roll consists of three parts: roll body, roll neck and shaft head. The roll neck is installed in the bearing and transmits the rolling force to the frame through the bearing seat and the pressing device. The shaft head is connected to the connecting shaft to transmit rolling torque. In addition, there are some auxiliary surfaces required for manufacturing and installation, such as center holes, grooves for fastening and lifting, screw holes, and grooved shaft extensions for turning the rolls before the rolling mill is commissioned.

Cold rolling work rolls can be divided into two types: integral work rolls and nested rolls. Among them, the overall work rolls are divided into solid rolls and hollow rolls.

When the diameter of the cold rolling roll exceeds 400mm, a center hole of 170 to 250mm is usually bored in the center of the roll after forging. In this way, when the work roll is surface quenched, cold water can be passed through the center hole of the roll to improve the quenching effect and ensure the hardness and thickness of the quenched layer. The metal in the center part of the roll often has looseness, pores and other defects, which are factors that cause stress concentration during quenching. After boring the center hole, the internal stress distribution of the roll can be relatively uniform after heat treatment. The center hole can also be used to preheat the roll and cool the roll during production.

Navigating the Crucial Roles of backup Rolls and Work Rolls in Cold Rolling

1-Transmission end;
2-Roller neck;
3-Roller body;
4-Conical transition zone;
5-fastener groove;
7-Roller neck lubricating oil groove;
8-flat mouth;
9-inner hole;
lO-biconical transition zone;
12-Carbide sleeve;
14-Axis tightening nut

There are also two types of support rollers: solid rollers and hollow rollers. There are two types of support roller necks: cylindrical (for installing rolling bearings) and conical. The tapered roll neck is used to facilitate the disassembly and assembly of the oil film bearing. The taper is generally 1:5. The hollow roll has center hole plugs at both ends to facilitate centering when turning the roll. The hoisting grooves arranged symmetrically on both sides of the support roller are specially designed for hanging steel ropes during hoisting. The turning grooves at both ends can be connected to special sleeves so that a crane can be used to turn the rolls before the trial operation of the rolling mill.

During the cold rolling process, the roll surface is subjected to great extrusion stress and intense wear. During high-speed rolling, steel jamming, overburning, etc. will cause cracks on the roll surface. Therefore, cold rolling work rolls should have extremely high and uniform hardness, a certain depth of hardened layer, and good wear resistance and crack resistance. The roll’s good resistance to overburning and cracking are the main factors that extend the life of the roll. Reducing the hardness of the roll can improve the crack resistance, but the wear resistance is reduced. Therefore, the surface hardness of the roll must be selected correctly.

The larger the diameter of the cold rolling roll, the deeper the hardened layer is required and the higher the hardenability requirements of the steel.

The huge rolling pressure exerted by the rolled piece on the cold rolling work roll is mostly transmitted to the support roll. The support roller must not only be able to withstand large bending stress, but also have great rigidity to limit the elastic deformation of the work roller to ensure uniform thickness of the steel plate.

The surface Shore hardness of the rolling mill support roll is generally around HS45. At present, in order to improve the plate thickness accuracy and extend the life of the roll, the hardness of the backup roll has a tendency to increase.

backup Rolls

The requirements for roll manufacturing are to ensure the mechanical strength of the roll, the surface quality of the strip and the installation accuracy of the roll.

(1) The technical requirements specified to ensure the mechanical strength of the roll. Ensure the chemical composition and mechanical properties of the roll material. During roll casting, casting defects are not allowed. Such as pores, blisters, cracks, slag inclusions and segregation, etc.; the blank of the forged roll must be evenly forged from multiple sides, and the forging ratio should not be less than 3; the residual stress after heat treatment should be minimal; the surface hardness required to ensure the contact strength of the roll.

(2) The technical requirements specified to ensure the surface quality of strip steel. During the rolling process, the surface of the roll is in direct contact with the surface of the strip, so the roll surface must have high wear resistance to ensure the surface quality of the strip. The wear resistance of the roll depends on the surface hardness of the roll.

(3) Ensure the roll matching dimensions and geometric tolerance requirements specified in the installation and rolling accuracy. The matching dimensions of the roll include the diameter of the roll neck, the size of the positioning sleeve for installing the bearing and the size of the bearing fastening screw, the matching size of the work roll and the coupling, and the size of the flat head of the work roll transmission.

(4) The stipulated geometric tolerances of the roll include: the ovality and cylindrical tolerance of the roll neck, the coaxiality of the roll body relative to the roll neck, and the perpendicularity of each end surface relative to the roll axis centerline. The symmetry of the two parallel planes of the work roll drive flat head relative to the work roll axis, the radial runout of each step on the roll neck relative to the roll neck, the symmetry of each keyway surface relative to the roll axis, etc.

Cold rolling mill rolls

Generally it is 5-10 days if the goods are in stock. or it is 15-20 days if the goods are not in stock, it is according to quantity.

A: Payment<=1000USD, 100% in advance. Payment>=1000USD, 30% T/T in advance ,balance before shippment.

Always a pre-production sample before mass production;
Always final Inspection before shipment;
During the epidemic, provide remote detection technical support

Tell us a little about your application and we’ll get back to you to finalize a quotation to meet your needs as quickly as possible.

Rolling mill rolls product

Classification by roll material:

Cast iron mill rolls

  • Alloy indefinite chilled cast iron rolls
  • Alloy chilled cast iron rolls
  • Alloy SG ductile cast iron roll
  • Pearlitic ductile cast iron roll
  • Bainite ductile cast iron roll
  • Centrifugal cast iron roll

Cast steel mill rolls   

  • Alloy cast steel rolls
  • Semi-steel roller
  • Graphite steel rolls
  • High-chromium steel roll
  • High-speed steel roll

Forging mill rolls

Sort by position on the rolling mill:

Work rolls
backup rolls

Intermediate roll

Product advantage

The world No. 1 in crude steel production steel plant, over 70% of the HSS for bar and wire are from us.

LMM high-speed steel rolls have higher steel passing per groove (times) due to their good wear resistance, which saves roll changing time, improves rolling mill operation rate, reduces roll consumption, and improve the overall efficiency of the factory.
Generally, the amount of steel passing in a single groove (times) is 3 to 5 times that of cast iron rolls.

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