Rolling mill AGC oil cylinder piston rod end gasket and design method thereof

Abstract

The invention provides a rolling mill AGC oil cylinder piston rod end gasket and a design method of the rolling mill AGC oil cylinder piston rod end gasket, and belongs to the technical field of strip steel rolling. And after internal gaps are eliminated and integral design is adopted, spare parts are unified, and the temperature of the backup roller bearing is prevented from rising under the action of long-term super-strong rolling force, so that the service life of the backup roller is prolonged, the uniformity of the spare parts is improved, the cost is reduced, and the production requirements are met under the action of the long-term super-strong rolling force.

Description

Technical Field

[0001] This invention belongs to the field of strip steel rolling technology and is mainly used in industries such as heavy machinery manufacturing and metallurgy. In particular, it relates to the end gasket of the piston rod of the AGC cylinder of the rolling mill and its design method. Background Technology

[0002] The AGC system (Automatic Thickness Control system) is a core control technology of modern rolling mills. Its basic working principle is to adjust the roll gap by controlling the displacement of hydraulic cylinders through electro-hydraulic servo valves, thereby achieving precise control of the plate thickness. This system continuously measures relevant parameters using thickness gauges, displacement sensors, and pressure sensors to continuously adjust the hydraulic cylinder displacement and rolling pressure, ultimately achieving precise control of the steel plate thickness difference.

[0003] In hot strip mill finishing mills, the most commonly used equipment is the four-high mill, which consists of upper and lower work rolls and upper and lower support rolls. During rolling, the work rolls are subjected to rolling force, which is transmitted to the support rolls. The upper and lower support rolls are supported by bearing housings on both sides. The upper support roll bearing housing is supported by the piston rod of the AGC (Automatic Gauge Control) cylinder. The hydraulic cylinder base is mounted on the mill stand. The rolling force is ultimately transmitted to the mill stand through the work rolls, support rolls, support roll bearing housings, and AGC cylinders. During rolling, the support rolls of the four-high mill are subjected to rolling force, causing the roll body to bend. Consequently, the support roll bearing housings also tilt inwards towards the mill, resulting in the stress point of the upper support roll bearing housing and the cylinder piston rod deviating from the cylinder center. To avoid this undesirable phenomenon, shims are installed at the end of the cylinder piston rod to alter the stress state.

[0004] In the prior art, such as the patent with publication number CN210510256U, entitled "A Gasket Structure for the End of the Piston Rod of a Rolling Mill AGC Cylinder with Uniform Force Distribution", the gasket at the end of the piston rod of the cylinder is a split design, consisting of a concave surface and a convex surface. The convex surface is fixed to the cylinder by bolt connection, and the concave surface is fixed to the cylinder by pressure ring, so that the two gaskets fit tightly together.

[0005] However, after the support roller bearing housing is tilted under stress, the contact point between it and the cylinder piston rod will change. Under the long-term action of ultra-strong rolling force, the gap of the split gasket structure will increase or local deformation will cause the outer ring of the support roller bearing to shift, and the outer ring of the bearing will also deform. The bearing bushing will wear unevenly, so the temperature will rise, which will easily cause damage and shorten the service life. Summary of the Invention

[0006] In view of this, the present invention provides a gasket for the piston rod end of a rolling mill AGC cylinder and its design method. Based on actual on-site surveying and calculation, the existing split gasket structure is changed to an integrated gasket structure. After eliminating internal gaps and changing to an integrated design, the support roll pads are standardized, the temperature of the support roll bearings is suppressed under long-term ultra-strong rolling force, so as to improve the service life of the support rolls, improve the uniformity of spare parts, reduce costs, and meet production requirements under long-term ultra-strong rolling force.

[0007] Therefore, the present invention provides the following technical solution: On one hand, the present invention provides a piston rod end gasket for a rolling mill AGC cylinder, comprising: an integral spherical pad body; the spherical pad body is fixedly connected to the end of the cylinder piston rod by bolts; the spherical surface of the spherical pad body matches the contact surface of the support roller bearing housing.

[0008] Furthermore, the spherical pad body is integrally formed using a forging process.

[0009] Furthermore, the ratio of the height of the spherical pad body to the width of the ring does not exceed 1.5.

[0010] Furthermore, the surface roughness Ra of the core contact surface of the spherical pad body is ≤0.8μm; the surface roughness Ra of the non-contact surface of the spherical pad body is ≤1.6μm.

[0011] Furthermore, the spherical pad body is made of 45# steel with a heat treatment process.

[0012] In another aspect, the present invention also provides a design method for a gasket at the end of the piston rod of a rolling mill AGC cylinder, comprising the following steps: S1. Disassemble the split spherical pad at the end of the piston rod of the AGC cylinder of the rolling mill, and measure its structural parameters and processing data. The structural parameters include inner diameter, thickness, spherical radius and roundness, and the processing data includes surface roughness and hardness. S2. Based on the measured structural parameters of the split spherical pad and the rolling force data during the operation of the hydraulic cylinder, determine the processing parameters and accuracy requirements of the integrated spherical pad. S3. The integrated spherical pad is machined as a whole using a CNC lathe with forging technology, and the surface is heat treated to ensure that the hardness and other parameters meet the requirements for use.

[0013] Furthermore, the precision parameters of the integrated spherical pad include: inner diameter deviation ≤ 0.02 mm; thickness tolerance controlled within ± 0.03 mm; spherical radius tolerance ± 0.05 mm; and roundness error ≤ 0.01 mm.

[0014] Furthermore, the ratio of the height to the width of the integrated spherical pad does not exceed 1.5.

[0015] Furthermore, the surface quality parameters of the integrated spherical pad include: the surface roughness of the core contact surface is controlled at Ra≤0.8μm; the surface roughness of the non-contact surface is controlled at Ra≤1.6μm.

[0016] Furthermore, the integrated spherical pad is made of 45# steel with a tempering treatment and a hardness of HB220-250.

[0017] The above technical solution has the following beneficial effects: In this invention, the AGC cylinder spherical pad, after redesign and installation, has an overall quality improvement of about 10% in terms of precision, hardness, etc., compared with the original split spherical pad. The contact surface matching contact rate reaches more than 95% (originally about 92%), reducing contact stress by 10%-15%. It successfully solves the stress concentration problem under high load conditions, enabling the system to maintain good surface contact when the support roller is bent and deformed, protecting the bearing hole from damage, eliminating displacement and point contact phenomena between the pad and the support roller, extending the life of the support roller bearing and standardizing spare parts under full load production. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the end gasket of the piston rod of the AGC cylinder in a rolling mill in the prior art; Figure 2 This is a schematic diagram of the structure of the end gasket of the piston rod of the rolling mill AGC cylinder in an embodiment of the present invention. Detailed Implementation

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Spherical pads and their connectors are key pressure-bearing and guiding components in hot rolling equipment (such as rolling mill stands, pressing mechanisms, universal joints, etc.). Their core function is to adapt to deviations, resolve angular deviations caused by installation tilt, deformation, or vibration of connecting components, avoid damage caused by hard contact, ensure fitting accuracy, and provide precise support and positioning for rotating and swinging components. This ensures both freedom of movement and fixes the core position to prevent offset. Pressure dispersion evenly transfers concentrated loads to the contact surface, reduces excessive local stress, and extends the service life of related components.

[0022] Under normal conditions, the spherical pads and their connectors automatically adjust coaxiality through spherical contact, preventing uneven loads on the mill stand and rolls, ensuring the straightness of the strip (reducing waviness and camber), ensuring thickness uniformity, absorbing vibration, buffering impact loads, reducing fatigue damage to mill components (stands, roll bearings, lead screws), lowering equipment failure rates, extending maintenance cycles, ensuring high reliability, guaranteeing continuous rolling, and reducing downtime for adjustments. However, if the spherical pads and their connectors fail, frequent downtime for replacement or repair is required, increasing maintenance costs (spare parts + labor). Furthermore, product quality issues lead to increased rework rates, directly reducing production efficiency.

[0023] like Figure 1 The existing split-type spherical pad and its connector shown consist of two parts: a concave surface 11 and a convex surface 22. The convex surface 22 is fixed to the hydraulic cylinder by bolts, while the concave surface 11 is fixed to the hydraulic cylinder by a pressure ring, ensuring a tight fit between the two pads. This structure cannot precisely fit the related components, and installation deviations and vibration-induced offsets cannot be offset, leading to loose fit, inaccurate positioning, and gaps that concentrate loads locally, making components prone to deformation and wear. During operation, it generates impact vibrations and increased noise, and also shortens the service life of the spherical pad and related components. Gaps can cause loose connections between components, potentially leading to movement and offset, which in severe cases affects the operating accuracy of the entire equipment and may even cause safety hazards.

[0024] This invention is based on rolling balance and uses an integrated spherical pad to compensate for misalignment of the connection surface caused by installation deviation, component deformation or vibration, avoid stress concentration due to hard contact, improve the life of spare parts to meet production needs, and solve problems such as slow rolling rhythm caused by short service life of support rollers and spherical pads, thereby extending the service life of spare parts and meeting the needs of normal production.

[0025] like Figure 2As shown, a piston rod end gasket for a rolling mill AGC cylinder includes: an integral spherical gasket body 1; the spherical gasket body 1 is fixedly connected to the end of the cylinder piston rod by bolts; the spherical surface of the spherical gasket body 1 matches the contact surface of the support roller bearing housing. The spherical gasket body 1 has a cylindrical outer contour and includes: multiple fixing bolt holes 2 penetrating the entire spherical gasket body, a locating pin hole 3 located at the bottom of the spherical gasket body, and a mating step 4 between the spherical gasket and the cylinder head.

[0026] The design method for the piston rod end gasket of the AGC cylinder in the above-mentioned rolling mill specifically includes the following steps: S1. Disassemble the split spherical pad at the end of the piston rod of the existing rolling mill AGC cylinder, and measure its structural parameters and processing data. The structural parameters include inner diameter, thickness, spherical radius and roundness, and the processing data includes surface roughness and hardness. S2. Based on the measured structural parameters of the split spherical pad and the rolling force data during the operation of the hydraulic cylinder, determine the processing parameters and accuracy requirements of the integrated spherical pad. The gasket precision parameters include: inner diameter deviation ≤ 0.02mm, thickness tolerance controlled within ±0.03mm; spherical radius tolerance approximately ±0.05mm to ensure fitting accuracy; roundness error ≤ 0.01mm to avoid affecting the stability of the fit when the component rotates or swings. Adapting to the existing bolt connection method with the existing equipment also requires the height-to-ring width ratio not to exceed 1.5 to meet the sealing requirements of high-pressure operating conditions.

[0027] Surface quality parameters include: the surface roughness of the core contact surface must be controlled within Ra≤0.8μm, and the surface roughness of the non-contact surface must be Ra≤1.6μm; the material section is 45# steel with quenching and tempering treatment HB220-250 to avoid poor bonding or accelerated wear due to surface roughness.

[0028] S3. The integrated spherical pad is machined as a whole using a CNC lathe with forging technology, and the surface is heat treated to ensure that the hardness and other parameters meet the requirements for use.

[0029] Using the existing split-type spherical pads, the support roller temperature at full load production reached 81℃ (15% above normal). On-site analysis revealed uneven gaps of 0.08-0.1mm between the existing spherical pads (normal gaps are 0.03-0.05mm). By redesigning and replacing the existing connection with an integrated pad, the gaps were eliminated. On-site observation and measurement showed the highest support roller temperature was 70℃, meeting production requirements.

[0030] Compared with the prior art, the above embodiments have the following technical advantages and beneficial effects: After redesign and installation, the AGC hydraulic cylinder spherical pad has improved overall quality by about 10% compared to the original split spherical pad, including precision and hardness. The contact surface mating contact rate has reached over 95% (compared to about 92% previously), reducing contact stress by 10%-15%. This successfully solves the stress concentration problem under high load conditions, enabling the system to maintain good surface contact when the support roller bends and deforms, protecting the bearing bore from damage.

[0031] In terms of structural design and material selection, the use of 45# steel combined with surface quenching technology results in a hardened layer thickness of over 3mm and a surface hardness of HRC48-52, which has significant advantages in avoiding piston rod wear, reducing processing difficulty, and improving installation convenience.

[0032] In terms of manufacturing processes and quality control, CNC turning combined with ultrasonic metal surface processing technology represents an advanced level of manufacturing technology, with errors controlled within 0.01mm and surface roughness reaching below Ra0.8μm. A rigorous quality inspection system, including three-dimensional morphology inspection, hardness testing, and dimensional accuracy inspection, ensures the stability and reliability of product quality.

[0033] In terms of application scenarios and performance requirements, the working frequency in a hot rolling environment is 8-15Hz, and it can withstand rolling forces of up to 45MN and impact pressures of 40MPa. (Typical working conditions refer to hot rolling mills - high-speed finishing mills such as a 1780mm production line: work roll speed 1200-1800 r / min, spherical pad working frequency 20-30 Hz; medium and low speed finishing mills such as a 1200mm production line: work roll speed 300-800 r / min, spherical pad working frequency 5-13.3 Hz; abnormal working conditions: when equipment vibrates or the roll system is misaligned, an additional impact frequency of 10-50 Hz will be added). After the gasket in this invention is put into use, the measured maximum temperature of the fully loaded support roll is 70℃ (tin-based Babbitt alloy has slightly better heat resistance, with an optimal working temperature of 15-70℃, and can withstand 80℃ for short periods; it is prone to softening and failure above 100℃).

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gasket for the end of the piston rod of a rolling mill AGC cylinder, characterized in that, include: An integrated spherical pad body; the spherical pad body is fixedly connected to the end of the piston rod of the hydraulic cylinder by bolts; the spherical surface of the spherical pad body matches the contact surface of the support roller bearing box.

2. The end gasket of the piston rod of the rolling mill AGC cylinder according to claim 1, characterized in that, The spherical pad body is integrally formed using a forging process.

3. The end gasket of the piston rod of the rolling mill AGC cylinder according to claim 1, characterized in that, The ratio of the height of the spherical pad body to the width of the ring does not exceed 1.

5.

4. The end gasket of the piston rod of the rolling mill AGC cylinder according to claim 1, characterized in that, The surface roughness Ra of the core contact surface of the spherical pad body is ≤0.8μm; the surface roughness Ra of the non-contact surface of the spherical pad body is ≤1.6μm.

5. The end gasket of the piston rod of the rolling mill AGC cylinder according to claim 1, characterized in that, The spherical pad body is made of 45# steel with heat treatment.

6. A design method for the piston rod end gasket of a rolling mill AGC cylinder as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Disassemble the split spherical pad at the end of the piston rod of the AGC cylinder of the rolling mill, and measure its structural parameters and processing data. The structural parameters include inner diameter, thickness, spherical radius and roundness, and the processing data includes surface roughness and hardness. S2. Based on the measured structural parameters of the split spherical pad and the rolling force data during the operation of the hydraulic cylinder, determine the processing parameters and accuracy requirements of the integrated spherical pad. S3. The integrated spherical pad is machined as a whole using a CNC lathe with forging technology, and the surface is heat treated to ensure that the hardness and other parameters meet the requirements for use.

7. The design method according to claim 6, characterized in that, The precision parameters of the integrated spherical pad include: inner diameter deviation ≤ 0.02 mm; thickness tolerance controlled within ± 0.03 mm; spherical radius tolerance ± 0.05 mm; and roundness error ≤ 0.01 mm.

8. The design method according to claim 6, characterized in that, The ratio of the height to the width of the one-piece spherical pad does not exceed 1.

5.

9. The design method according to claim 6, characterized in that, The surface quality parameters of the integrated spherical pad include: the surface roughness of the core contact surface is controlled at Ra≤0.8μm; the surface roughness of the non-contact surface is controlled at Ra≤1.6μm.

10. The design method according to claim 6, characterized in that, The integrated spherical pad is made of 45# steel with a tempering treatment and a hardness of HB220-250.

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