Adjusting Roll Gap in 6Hi Reversing Cold Rolling Mill for Thin Strip

In the production of automobile steel, thin strip, and coil—critical materials for automotive electronics, precision components, and lightweight body parts—roll gap adjustment is a core technical link that directly determines thickness accuracy and product quality. 6 hi reversing cold rolling mill and 4hi reversible cold rolling mill are the main equipment for thin strip production, and Yang Wang Li Xin (YWLX), a leader in advanced steel rolling technology, has matured four/six hi reversing cold rolling mill products widely used in Chinese steel enterprises. Among them, the 6 hi reversing cold rolling mill (with 900mm, 1150mm, 1380mm width specifications) excels in thin strip rolling, capable of reducing carbon steel strip thickness from 3.0mm to 0.2mm in six passes (without intermediate annealing) and silicon steel strip from 0.63mm to 0.26mm in 2-3 passes.

YWLX Four/Six Hi Reversing Cold Rolling Mill Product Specifications Table

Core Principles of Roll Gap Adjustment in 6 Hi Reversing Cold Rolling Mill for Thin Strip

• 6 Hi Reversing Cold Rolling Mill adopts a multi-roll structure (work roll, intermediate roll, backup roll) that provides stronger roll bending control, which is the key to precise roll gap adjustment for thin strip. Unlike the 4hi reversible cold rolling mill (only work roll and backup roll), the 6hi mill’s intermediate roll can move axially (adjustment range ±50mm) and apply bending force, enabling fine-tuning of the roll gap profile. When rolling thin carbon steel strip (e.g., 0.2-0.5mm thick SPHC for automobile interior parts), YWLX’s 6hi mill first calculates the initial roll gap based on the target thickness (e.g., 0.3mm target requires 0.32mm initial gap, accounting for elastic deformation) and then uses the intermediate roll axial shift to eliminate edge thinning. For example, if the strip edge thickness is 0.003mm thinner than the center, the intermediate roll shifts toward the edge by 20mm, increasing the edge roll gap pressure and balancing the thickness. This principle ensures that the thin strip’s full-width thickness tolerance is controlled within ±0.002mm, meeting automotive precision component requirements.

• Elastic Deformation Compensation is a critical principle for roll gap adjustment in 6 hi reversing cold rolling mill thin strip production. During rolling, the work roll and backup roll undergo elastic deformation under rolling force, which expands the actual roll gap and causes thickness deviation. YWLX’s 6hi mill integrates a “roll elastic deformation model” into the control system: based on the strip material (e.g., carbon steel’s elastic modulus 200GPa), rolling force (e.g., 800kN for 0.3mm thin strip), and roll diameter (work roll diameter 120mm), the system calculates the deformation amount (typically 0.01-0.02mm) and pre-compensates by reducing the set roll gap. For example, if the target thickness is 0.2mm and the calculated elastic deformation is 0.015mm, the set roll gap is adjusted to 0.185mm. This compensation avoids over-thickness caused by roll deformation, which is particularly important for thin strips (≤0.5mm), where even 0.005mm deformation can lead to 2.5% thickness deviation. Wholesalers can emphasize this technical advantage to clients producing high-precision automotive thin strips, as it reduces post-rolling thickness correction processes.

Key Factors Influencing Roll Gap Adjustment in 4hi Reversible Cold Rolling Mill for Thin Strip

• Rolling Force Stability is a core factor affecting roll gap adjustment accuracy in 4hi reversible cold rolling mill thin strip production. Compared with the 6 hi reversing cold rolling mill, the 4hi mill has fewer roll layers, so the work roll is more sensitive to rolling force fluctuations. When rolling 0.3-0.8mm automobile thin steel strips (e.g., door hinge substrates), if the rolling force fluctuates by ±50kN (based on a nominal force of 600kN), the work roll elastic deformation changes by ±0.004mm, directly leading to ±0.004mm thickness deviation. YWLX’s 4hi reversible cold rolling mill solves this by adopting a dual hydraulic cylinder drive system (left and right cylinders with pressure synchronization error ≤1%) and real-time force monitoring (sampling frequency 100Hz). If force deviation exceeds 3%, the system adjusts the hydraulic valve opening to stabilize the force, ensuring the roll gap remains consistent. For wholesalers, this factor reminds clients to prioritize rolling force stability when using 4hi mills for thin strip production, especially for materials with low yield strength (e.g., IF steel), which are more prone to thickness changes due to force fluctuations.

• Strip Tension Control indirectly affects roll gap adjustment in 4hi reversible cold rolling mill thin strip rolling. Appropriate tension (e.g., 15-25kN for 0.5mm carbon steel strip) can reduce the required rolling force, thereby reducing roll elastic deformation and simplifying roll gap adjustment. However, excessive tension (＞30kN) causes strip stretching, leading to under-thickness, while insufficient tension (＜10kN) results in strip slippage, increasing rolling force and expanding the roll gap. YWLX’s 4hi mill uses a “tension-roll gap cooperative control” strategy: when the strip tension increases by 5kN, the system automatically reduces the rolling force by 50kN and adjusts the roll gap by +0.003mm to avoid under-thickness. This cooperation ensures that even if tension fluctuates slightly, the roll gap can be adjusted in real time to maintain thickness accuracy. For example, when rolling 0.4mm automobile thin strip, if the tension suddenly increases from 20kN to 23kN, the roll gap is adjusted from 0.39mm to 0.393mm, and the rolling force is reduced from 550kN to 500kN, keeping the final thickness at 0.4mm ±0.002mm.

6 hi reversing cold rolling mill FAQS

What is the difference in roll gap adjustment between YWLX’s 6 hi reversing cold rolling mill and 4hi reversible cold rolling mill for thin strip?

The core difference lies in the roll structure and control precision: 1. Roll layers: 6 hi reversing cold rolling mill has intermediate rolls, enabling axial shift (±50mm) and intermediate roll bending force control to fine-tune the roll gap profile, suitable for ≤0.5mm high-precision thin strips (e.g., silicon steel for automotive motors) with thickness tolerance ±0.002mm; 4hi reversible cold rolling mill lacks intermediate rolls, so roll gap adjustment relies only on work roll bending, suitable for 0.3-0.8mm general thin strips (e.g., automobile interior substrates) with tolerance ±0.005mm. 2. Deformation compensation: 6hi mill’s multi-roll structure reduces work roll deformation, requiring less elastic deformation compensation (0.01mm vs. 0.015mm for 4hi mill under the same force). Wholesalers can guide clients to select mills based on thin strip precision requirements: 6hi for high-precision silicon steel/stainless steel, 4hi for cost-sensitive carbon steel thin strips.

How does YWLX’s 6 hi reversing cold rolling mill adjust the roll gap to handle thin strip edge thinning?

YWLX’s 6 hi reversing cold rolling mill uses “intermediate roll axial shift + edge roll bending” combined adjustment to solve thin strip edge thinning: 1. Intermediate roll shift: When edge thinning (e.g., 0.003mm thinner than center) occurs, the intermediate roll shifts toward the edge by 15-30mm (based on strip width, e.g., 20mm shift for 1150mm width), increasing the edge work roll contact pressure and reducing edge roll gap expansion. 2. Edge roll bending: The mill’s work roll is equipped with edge bending cylinders (independent of the middle bending cylinder) that apply 5-10% higher bending force to the edge area, compressing the work roll edge to reduce the gap. For example, when rolling 0.26mm non-oriented silicon steel strip, if edge thinning is detected at 10mm from the strip edge, the intermediate roll shifts 25mm, and the edge bending force increases by 8%, reducing edge thickness deviation to ≤0.001mm. This method is more effective than the 4hi reversible cold rolling mill (which only uses work roll bending) and is critical for automotive thin strips requiring full-width uniformity (e.g., battery shell stainless steel strips).

What roll gap adjustment precautions should be taken when YWLX’s 4hi reversible cold rolling mill rolls thin automobile steel strips with high strength?

When 4hi reversible cold rolling mill rolls high-strength thin automobile steel strips (DP 590, thickness 0.4-0.6mm), three roll gap adjustment precautions are key: 1. Increase pre-compensation for elastic deformation: High-strength steel requires higher rolling force (e.g., 700kN vs. 550kN for mild steel), leading to greater roll deformation (0.018mm vs. 0.012mm), so the set roll gap should be reduced by an additional 0.006mm. 2. Slow down roll gap adjustment speed: High-strength steel has poor plastic deformation, so the roll gap adjustment speed is reduced from 0.01mm/s to 0.005mm/s to avoid sudden thickness changes. 3. Strengthen rolling force monitoring: High-strength steel’s yield strength fluctuation (±30MPa) causes force changes, so the system’s force deviation alarm threshold is tightened from ±5% to ±3% to trigger roll gap adjustments in time. For example, if the target thickness is 0.5mm, the set roll gap is 0.482mm (accounting for 0.018mm deformation), and if the rolling force increases by 40kN (exceeding 3% deviation), the roll gap is adjusted to 0.485mm. These precautions ensure that high-strength thin strips meet automotive structural part thickness requirements (tolerance ±0.004mm).

How does YWLX’s 6 hi reversing cold rolling mill optimize roll gap adjustment for multi-pass thin strip rolling to improve efficiency?

YWLX’s 6 hi reversing cold rolling mill optimizes multi-pass roll gap adjustment through two strategies: 1. Pre-set roll gap based on material flow stress: Before rolling, the system inputs the strip’s flow stress curve (e.g., carbon steel SPHC’s flow stress 300MPa at 20% deformation) and calculates the required roll gap for each pass using the “slab method” (e.g., pass 1: 3.0mm→2.0mm, roll gap 2.02mm; pass 6: 0.3mm→0.2mm, roll gap 0.19mm), reducing on-site adjustment time. 2. Pass-by-pass tension-roll gap coordination: The first 2-3 passes use higher tension (25-30kN) to reduce rolling force and roll gap adjustment difficulty; the final 2 passes reduce tension to 15-20kN to avoid strip stretching, and the roll gap is fine-tuned by ±0.002mm per pass. For example, rolling 3.0mm→0.2mm carbon steel strip: pass 1 tension 28kN, roll gap 2.02mm; pass 6 tension 18kN, roll gap 0.19mm. This optimization reduces total rolling time by 15% compared to traditional adjustment methods, while ensuring thickness tolerance ≤±0.002mm. Wholesalers can promote this to clients with large-volume thin strip production needs, as it balances efficiency and quality.

What maintenance measures does YWLX recommend to ensure roll gap adjustment accuracy of 6 hi reversing cold rolling mill for long-term thin strip production?

To maintain 6 hi reversing cold rolling mill roll gap adjustment accuracy, YWLX recommends three maintenance measures: 1. Regular roll diameter measurement (monthly): Work roll wear (e.g., 0.02mm wear per 10,000 tons of thin strip) reduces the actual roll diameter, so the system’s roll diameter parameter is updated to recalculate elastic deformation and roll gap. 2. Hydraulic cylinder synchronization calibration (quarterly): The left and right hydraulic cylinders for roll gap adjustment may have synchronization errors (＞1%) due to seal wear, which is calibrated using a laser displacement sensor (calibration accuracy ±0.001mm) to ensure uniform roll gap adjustment. 3. Intermediate roll axial shift mechanism lubrication (bi-monthly): The intermediate roll shift rail is lubricated with high-temperature grease (suitable for 0-80℃) to avoid jamming, which could cause uneven roll gap profile. For example, after 3 months of thin strip production,