Introduction
High-speed bar rolling production relies heavily on the short stress line mill. Strict short stress line mill operation procedure for high-speed bar rolling ensures stable rolling rigidity, precise bar size and long equipment service life. Many workshop failures come from non-standard assembly and incorrect dismounting steps. Pour cette raison, professional operators must follow unified technical standards during daily mill maintenance and roll replacement. This article presents the complete short stress line mill operation procedure for high-speed bar rolling to standardize field operation.
1. Short Stress Line Mill Structure for High-Speed Bar Rolling
A standard short stress line mill for bar production adopts a compact high-rigidity structure. Main components include roll assembly, tension tie rod assembly, screw-down adjustment device, support de moulin, guide beam, pass replacement unit and elastic balancing system. These parts form a closed short stress loop that reduces elastic deformation during high-speed rolling.
1.1 Mill Body and Stress Line Principle
Four threaded tension tie rods constitute the main mill frame. This special structure creates the shortest stress line among traditional bar rolling mills. Operators adjust roll gaps symmetrically by rotating tie rods. All rolling force transfers through bearing seats and tie rods instead of heavy mill housings. The optimized force path greatly improves overall mill rigidity.
Radial loads act on four-row cylindrical roller bearings. Back-to-back tapered roller bearings bear all axial thrust. Workers complete fine axial positioning through worm gear and thread sleeve mechanisms. Internal elastic balance devices eliminate assembly gaps and maintain stable pre-tightening force during continuous rolling.
1.2 Screw-Down Adjustment Device Function
The screw-down device controls roll opening clearance for different bar specifications. It supports both manual and hydraulic driving modes. The clutch structure allows synchronous double-side adjustment or independent single-side fine tuning. Worm and gear sets drive four tie rods synchronously to realize accurate and symmetric roll gap correction.
2. General Disassembly & Assembly Specifications for Short Stress Line Mill
All maintenance work must follow strict technical specifications. Propreté, assembly tolerance and lubrication standards directly affect the running stability of the short stress line mill for high-speed bar rolling.
2.1 Pre-Cleaning and Sorting Rules
Clean every mill component thoroughly before disassembly. Remove all iron oxide, dust and oil contamination from mill surfaces. Adjust roll gaps to a proper position before dismantling parts. Place disassembled components neatly to avoid mixing or damage.
2.2 Bearing Disassembly and Inspection Standards
Use professional induction heaters to take out bearing inner rings. Keep qualified inner rings for reused rolls. Clean all oil holes and pipelines to ensure smooth lubricant flow. Inspect roll necks, pass surfaces and thread holes strictly. Replace any unqualified parts before installation.
2.3 Lubrication and Thermal Assembly Requirements
Lubricate main bearings with 46# anti-wear hydraulic oil before online use. Fill the screw-down device and tie rod assembly with high-quality grease. Inspect internal lubrication conditions every six months and record all data completely. Follow drawing standards strictly during thermal assembly to guarantee qualified interference tolerance.
2.4 Standard Bearing Installation Rules
Clean bearings fully and coat thin lubricant before assembly. Ensure even force during installation. Apply auxiliary tapping only with copper or wooden tools. Never strike bearing rolling bodies directly. Store bearings in dry and clean environments. Re-oil or replace long-stored bearings regularly.
2.5 Final Assembly Quality Criteria
Qualified assembly requires horizontal roll alignment, vertical centerline coincidence, firm fastening and accurate pass alignment. Check all gaps and fastening points to ensure the mill meets high-speed bar rolling requirements.
3. Standard Roll Mounting Procedure for Bar Rolling Mill
Precise roll mounting is the core step of short stress line mill operation procedure for high-speed bar rolling. Every step must follow standardized technical flow.
3.1 Pre-Assembly Cleaning and Checking
Measure component matching sizes and bearing clearances in advance. Remove burrs, dirt and oil stains completely. Blow all oil grooves and holes with compressed air. Replace worn, deformed or corroded parts immediately.
3.2 Bearing Replacement Judgment Conditions
Replace bearings with fatigue pitting, surface cracks, edge damage and excessive clearance. Remove incomplete bearings with missing rolling elements to avoid sudden failure during high-speed rolling.
3.3 Precision Installation Process
Verify roll codes, diameters and pass dimensions before assembly. Coat roll necks with lubricant for smooth fitting. Heat bearing inner rings between 90℃ and 100℃ with induction heaters. Control temperature strictly below 120℃ to prevent structural deformation.
Adjust gaskets after bearing installation to control axial clearance within 0–0.1mm. Ensure all bearings bear even load during operation.
3.4 Post-Assembly Runout Detection
Fasten the mill base tightly after assembly. Use dial indicators to test radial and axial runout. Control finishing mill radial runout within 0.15mm and axial runout within 0.25mm. Keep roughing mill radial runout below 0.5mm and axial runout below 0.4mm. Check all lubrication pipelines for leakage.
3.5 Guide Beam and Base Installation Rules
Clean and lubricate adjusting lead screws before beam assembly. Ensure flexible screw rotation without end play. Install spring washers for all fixing bolts. Clean base contact surfaces and apply dry grease. Inspect base nylon blocks frequently and replace damaged parts timely.
3.6 Final Acceptance Check
Professional inspectors check all assembled mills. Paste qualified labels and fill in mill circulation records completely before putting the mill into production.
4. Standard Roll Dismounting Procedure
Follow fixed steps during mill dismounting to protect precision components.
D'abord, remove guide beams and cooling water pipelines. Deuxième, hoist and fix the mill on the robot base. Troisième, insert roll support plates steadily. Quatrième, adjust roll gaps to compact support plates for safe subsequent disassembly.
5. Daily Operation and Maintenance Notes
Handle roll sets and bearing seats gently during hoisting. Maintain sufficient grease inside the screw-down device all the time. Complete regular inspection and written records every six months. Standard operation greatly improves the stability and service life of the short stress line mill for high-speed bar rolling.
Conclusion
Standardizing the short stress line mill operation procedure for high-speed bar rolling helps enterprises achieve high-precision, low-failure and high-efficiency bar production. Reasonable assembly, strict inspection and scientific lubrication management guarantee long-term stable operation of short stress line mills in modern long steel rolling workshops.