In rolling production, due to uneven temperature, uneven deformation, uneven cooling after rolling, and other factors, rolled products often have defects such as bending.
For this reason, the rolled steel must be straightened to meet the specified quality standards. The steel leveling equipment required to straighten the steel is called a leveler.
A Leveler machine is a device for straightening metal profiles, bars, pipes, wires, etc. The roller leveler uses the leveling roller to squeeze the plate, bar, and other materials to change the straightness.
5 major types of leveling machines
The so-called leveling simply means to make the curved part of the steel material undergo considerable reverse bending or stretching, causing a certain elastic-plastic deformation in this part. When the external force is removed, the steel material undergoes elastic recovery and then reaches straightness.
There are different types of levelers due to differences in the way in which reverse bending or stretching of the steel is applied, as well as structural differences.
Mainly divided into pressure leveling machines, roller leveling machines, pipe, and bar leveling machines, stretch leveling machines (stretch leveling machines) stretch forming leveling machines, and other types.
Pressure leveler
- Pressure leveling machines are divided into two types: vertical and horizontal
- Working principle: The steel is located between the movable indenter and the fixed fulcrum, and is leveled by a single reverse bending method. The correction process of the pressure leveler is to make the steel located on the two fixed fulcrums bear the external force exerted by the pressure head, produce reverse bending deformation, and obtain straightness after elastic recovery.
- Disadvantages: The main disadvantages of this leveler are its complex operation and low productivity, so it is rarely used.
- How to use: This leveling machine is located in a large rail beam workshop, placed after the roller leveling machine, to supplement the correction of large steel materials or rails.
Roller leveler
- Structural composition: The roller leveler is composed of upper and lower rows of straightening rollers, frames, transmission devices, and other components that are staggered with each other.
- Working principle: The steel to be straightened passes through the arranged rollers and is leveled by repeated bending.
- Application: The roller leveling machine is mainly used for straightening plate strip steel (plate leveling machine) and section steel.
- Advantages: Roller levelers have high productivity and are easy to mechanize, so they are widely used.
Pipe and rod leveling machine
Working principle: The pipe and rod leveling machine also uses repeated bending to make the steel straightened straight.
Stretch leveler
When thinner plates are difficult to straighten on a roller leveler, a stretch leveler is often used for correction. This type of leveler is also called a stretch leveler.
Working principle: During correction, two jaws are fixed and the other jaw is movable. By moving the jaws, a tensile force exceeding the yield limit of the material is exerted on the metal, causing it to produce plastic extension, thereby straightening the plate. This method is single-sheet correction and has low productivity. In addition, the end will cause a larger scrap head, so the metal loss will be larger.
Stretch bending leveler
The stretch leveling machine is also called the continuous stretch forming leveler. It is developed based on the continuous stretch leveling machine and the roller leveling machine. It combines the characteristics of the two to form a new type. Leveler.
- Composition: It is mainly composed of two sets of stretch rollers and the bending roller and leveling roller in the middle.
- Working principle: When the metal to be straightened passes through the leveling machine, the combined stress formed by the stretch formed by the stretch roller and the bending stress formed by the bending roller causes the strip to have a certain plastic extension and is leveled by the leveling roller. Thereby eliminating the unevenness defects of the strip.
- Advantages: This form of leveler consumes less energy than a stretch leveler and has higher correction quality. This leveling unit is generally used on continuous operating lines and can straighten various metal strips including high-strength and extremely thin strips.
It can also be set up on the pickling unit to break phosphorus to improve the pickling speed and phosphorus removal effect. Therefore, it is a straightening machine with a promising future.
Roller leveler
The size and direction of the original bending curvature of the metal are different. The roller leveler bends the metal repeatedly many times to eliminate the uneven curvature, thereby making the curvature change from large to small and make it straight.
In a roller leveler, there are two possible correction schemes based on the amount of deformation (reduction amount) produced by each roller in the metal: a small deformation correction scheme and a large deformation correction scheme.
Two leveling options plan
- Small deformation correction plan: The so-called small deformation correction plan assumes that each roll of the upper row of work rolls of the straightening machine can be adjusted independently, and the adjustment principle for the reduction of each roll is: the metal entering the roll undergoes reverse bending and After rebounding, its maximum original curvature should be completely eliminated, that is, the part should be straightened.
- Large deformation correction scheme: Due to the change in the original curvature of the metal being corrected and the difficulty in determining it accurately, large deformation correction schemes are often used in production.
Two force energy parameters of roller leveler
- Pressure of the straightening roller: The pressure acting on the straightening roller during straightening can be calculated using the bending moment required for the metal to be straightened, considering the metal as a continuous beam subject to many concentrated loads.
- Transmission power of roller straightener: Transmission power is related to torque and curvature.
5 basic parameters of roller leveler
The basic parameters of the roller leveler include roller distance t, roller diameter D, number of rollers n, roller body length L, and straightening speed v, among which the most important parameters are D and t.
Roller distance t
The choice of roller distance t has an important impact on the correction quality. When determining the roller diameter t, both the correction quality of the steel and the strength condition of the roller must be considered.
The minimum allowable roller distance t is limited by the strength, and the maximum allowable roller distance t is limited by the correction quality. Determination of the minimum allowable roller distance t: When the roller diameter D is constant, the smaller the roller distance t, the higher the correction quality. However, it can be seen from the calculation of the roller pressure: the smaller the roller distance t, the greater the correction pressure P, that is, the roller surface The greater the contact stress with the metal, which accelerates the wear of the roller and damages the metal surface.
Therefore, the minimum allowable roller distance t is limited by the contact stress on the roller body surface and the torsional strength of the straightening roller.
Roller diameter D
The roller diameter D is usually selected according to the table according to the determined roller distance, and its value should also comply with the data in the straightening machine parameter series.
Number of rollers n
Increasing the number of rollers means increasing the number of reverse bends of the metal. Therefore, increasing the number of rollers is conducive to improving the quality of correction, but it also increases the degree of work hardening and correction power of the metal. Therefore, the principle of determining the number of rollers should be to ensure the quality of correction. Under the premise of reducing the number of rollers as much as possible.
Roller body length L
The length L of the roller body should be determined by considering the number of grooves arranged on the roller body.
Correction speed v
The correction speed is mainly determined based on productivity, and factors such as the type and temperature of the product to be corrected should also be taken into consideration.
Structure of roller leveler
According to different uses and structures, roller levelers can be divided into: plate roller levelers, profile steel roller levelers and inclined roller levelers for pipes and bars.
The roller leveler is mainly composed of a motor, a reducer, a gear seat, a connecting shaft, a straightening roller working base, and other components.
Plate leveling machine
According to the arrangement and adjustment method of the straightening rollers, the plate leveling machine types include parallel roller row leveling machines, adjustable straightening roller deflection leveling machines, inclined roller row leveling machines, etc.
- Parallel roller row plate leveling machine: The upper and lower rows of straightening rollers of the parallel roller row leveling machine are arranged in parallel. The lower row of rollers is fixed, while the upper row of rollers can be adjusted individually.
- Inclined roller row plate leveling machine: The lower row of rollers of this leveling machine is fixed, and the upper row of rollers is installed in the adjustable upper frame. The upper row of rollers can be adjusted to form an inclination with the lower row of rollers.
- Adjustable correction roller deflection plate leveler: The support roller of this leveler is segmented.
Structural steel leveling machine
When producing section steel, steel with complex cross-sections such as I-beams, channel steels, and rails are cooled and then straightened.
In order to adapt to the characteristics of many types and specifications of profiles, the straightening roller in the profile steel leveling machine is composed of a roller and a detachable roller sleeve with holes and grooves.
Correction roller sleeves are available in integral and combined types. The combined type is composed of several roller rings and washers, so using a set of roller rings with different washers can correct the same type of steel with different specifications. Combined bushings are mostly used to straighten large steel materials such as I-beams, channel steels, and rails.
Two types of steel leveling machines
According to the different positions of the straightening roller sleeves placed on the roller shaft, the steel straightening machine is structurally divided into a cantilever straightening machine and a closed straightening machine.
Cantilever (also called open) leveler
The cantilever leveler has the straightening roller placed on one side of the frame, and the roller is cantilevered on the roller. The straightening machine is characterized by its convenience in operation, adjustment, maintenance, and replacement of bushings. However, because the rollers are cantilevered, the two support bearings of the rollers receive uneven forces, so in the past, this kind of type leveler was mostly used to straighten small and medium-sized steel products.
Closed leveler
The straightening roller of the closed leveler is placed between the two bearings of the roller shaft. The structural feature of this leveler is that the straightening roller is located in the middle position. Therefore, the bearings at both ends are evenly stressed and the machine base has good rigidity. It is mostly used for straightening large steel materials. The disadvantage is that the operator cannot see the correction of the steel during production, which makes adjustment difficult. In addition, it is inconvenient to disassemble and assemble when replacing the roller sleeve, which affects the operation rate of the straightener.
Pipe and bar leveling machine
Roller levelers used to straighten tubes and bars are often called inclined roller levelers. The straightening roller of the inclined roller leveler is placed at an angle. When the pipe and bar enter the leveler, they not only move forward but also rotate at the same time. During the straightening process, pipes and bars are subjected to repeated bending and deformation through several rollers to become straight. Inclined roller levelers are divided into three-roller, five-roller, six-roller, and seven-roller types according to the number of rollers.
Stretch bending leveler
Due to the limitations of its structure and correction process, the roller leveler is difficult to correct the ternary shape defects of high-strength alloy steel strips, because in order to eliminate the ternary shape defects, the strips must be sufficiently shaped during correction. Stretch deformation, that is to say, the original short fiber part of the strip is elongated.
For this purpose, stretch levelers and continuous stretch levelers have appeared. However, these levelers have many shortcomings. In order to overcome the shortcomings of roller levelers and continuous stretch levelers and absorb Due to their advantages, a new type of strip leveler, stretch bending leveler, has been developed in recent years.
Work characteristics
It adapts to the requirements of a strip high leveling system, can comprehensively embody the advantages of roller type and stretch leveling machines, and can eliminate three-dimensional errors.
Composition: machine base, leveling roller group, bending roller group, tension roller group
The main features of stretch bending leveler
It can eliminate three-dimensional shape defects such as buckling, edge waves, and sickle bends of the strip, thereby improving the correction quality.
After the annealed strip is stretched and bent, its mechanical properties are improved.
Both the bending roller and the leveling roller are driven rollers, so they can move synchronously with the strip and will not scratch the surface of the strip due to slippage.
It is suitable for strip processing lines and straightening various metal materials.
It can be used as a mechanical phosphorus-breaking device in the pickling unit.
Straightening principle of stretch bending leveling machine
When the strip is corrected, it bears a certain tension and undergoes repeated bending by the bending roller. Under the action of superimposed tensile and bending stress, elastic-plastic extension deformation occurs, so that the original fiber part is elongated and the ternary shape defect is eliminated.
The structure and driving method of the stretch bending and leveling machine
The stretch bending and leveling machine is composed of a tension roller set and a stretch bending machine base. According to different process requirements and site conditions, the layout of these two units can be in various forms.
- Stretch bending machine base: The stretch bending machine base is a unit that causes the strip to bend and deform. It consists of two basic units (bending roller unit and leveling roller).
- Tension roller group: The function of the tension roller group is to produce a certain tension on the strip. It is composed of two sets of tension rollers at the front and rear. Both tension roller sets are driven. The linear speed of the rear tension roller group is higher than that of the front tension roller group, and the tension of the strip is generated by the linear speed difference. The number and arrangement of tension rollers are determined by the maximum tensile force required by the strip and the site conditions.
- Driving mode: The driving modes of the tension roller mainly include: DC motor driving alone, motor collective driving with differential mechanism, hydraulic motor driving alone, and hydraulic circuit closed-loop connection driving mode.
Summary
In the world of rolling production, various factors like uneven temperature, deformation, and cooling can lead to defects in rolled products, such as bending. To meet quality standards, rolled steel needs to be straightened using a machine called a leveler. This article introduces the concept of steel leveling machines and outlines five major types:
The article discusses the importance of key parameters like roller distance, diameter, number of rollers, roller body length, and correction speed in roller levelers. It also explores different structures of roller levelers based on their applications, including plate leveling machines, structural steel leveling machines, and inclined roller levelers for pipes and bars.
Additionally, it introduces the stretch bending leveler, which can eliminate three-dimensional shape defects in strips and improve correction quality. This machine is suitable for strip processing lines and various metal materials.
The article concludes by mentioning the driving methods for tension roller groups in stretch bending and leveling machines, which play a crucial role in the straightening process.
