- Introduction
With steel industry overcapacity reaching critical levels, steel plants are under intense pressure to upgrade, improve quality, and increase efficiency. Developing and producing high-end specialty steel has become a key strategy for steel plants to break out of difficult situations. The No. 1 slab caster at a steel plant, commissioned in September 2007 with an annual capacity of 1.2 million tons, has gradually revealed insufficient capability to produce specialty steel as the proportion of specialty steel production continues to rise. In particular, the short online service life of caster segments—especially severe water leakage issues—has severely restricted the R&D and production of specialty steel. Addressing these challenges requires a systematic approach combining precision assembly, equipment modification, and strict quality control. For more technical insights on steel manufacturing equipment, visit our technical blogLMM Group technical blog.
- Root Cause Analysis
Non-compliant Offline Assembly
During offline assembly of segments, if the roller splash plates, columns, and shims are not thoroughly cleaned, small particulate debris can cause slight wear on the splash plate surface and the O-ring seal on the column during installation. After a period of online operation, the O-ring damage intensifies, leading to water leakage from the rollers. Inadequate shim cleaning directly affects arc adjustment accuracy, causing some rollers to be overloaded during operation and reducing roller service life. Regular cleaning with kerosene and multi-point measurement with feeler gauges are essential preventive measures.
Poor Water Quality & Improper Waterway Design
The caster segment equipment water is supplied by a comprehensive pump station with relatively poor water quality and high debris content. The roller core shaft cooling water and bearing housing cooling water are designed in a series waterway arrangement. Once a water hole becomes blocked, rollers and core shafts downstream of the blockage cannot receive cooling water. During production, lack of cooling water causes bearing housing O-ring carbonization and high-temperature deterioration of bearing grease, resulting in bearing housing water leakage, bearing oil starvation, and roller rotation failure. Installing Y-type filters on inlet water lines and cleaning them at least twice weekly is critical for preventing debris buildup and O-ring degradation.
- Improvement Measures
Precision Assembly of Caster Segments(rolling mill rolls)
Through analysis of recent segment replacement reasons, a series of targeted improvement measures have been implemented to extend the online service life of caster segments. During precision assembly, after each old roller is removed from a segment, the segment bench must be thoroughly cleaned—all accumulated dust and oil sludge removed. Remove the splash plate and clean the arc adjustment shims, columns, and splash plates with kerosene before reinstallation. When adjusting the arc line, to ensure accuracy, each measurement point on every roller must be measured three times with a feeler gauge to minimize measurement error. During each calibration process, wipe both the handheld roll gap instrument and the roller measurement surface clean, take measurements at multiple points, and readjust shims for any values with significant deviations to ensure calibration accuracy.
Roller Equipment Modifications
Roller bearing cages are changed from copper to steel, improving cage strength and reducing bearing damage. Ten heat dissipation holes of 5 mm diameter and 15 mm depth are machined around each roller bearing housing water inlet and the splash plate. The bearing housing water inlet is enlarged from original φ10 mm to φ12 mm to increase cooling water flow. Triangular supports are machined inside the bearing housing water tank to prevent water tank cover collapse causing poor water flow. A cleaning hole of φ10 mm is added at the center of the rotary joint to prevent rotary joint blockage. A threaded Y-type filter is added on the inlet water line of each caster segment equipment, and cleaned at least twice weekly to prevent debris from blocking roller water passages and causing O-ring carbonization.
Caster Segment Waterway Redesign
The original series arrangement of roller bearing housing and core shaft waterway—where bearing housing return water serves as core shaft inlet water—has been changed to a parallel arrangement. Rollers and core shafts now have separate inlet and return water lines with individual water tanks. This prevents situations where a single blocked water hole causes reduced cooling water flow to downstream components, leading to seal carbonization and bearing oil starvation. The redesign ensures continuous cooling even when individual passages become restricted.
Roller Repair Quality Acceptance
Roller repair quality acceptance is strictly enforced. Eleven inspection items including bearing housing water tank deformation, excessive bearing housing looseness, and uneven base surface are checked. Any items failing acceptance are sent back to the manufacturer for repair. Roller repair manufacturers must use a polisher to thoroughly clean scale from inside the bearing housing water tank and re-drill bearing housing water holes to reduce scale buildup. Roller hardness, concentricity, and outer diameter dimensions are measured individually—only rollers meeting all specifications are accepted for use in production. This rigorous quality control process ensures repaired rollers perform consistently and extend segment service life. Quality assurance for rolling mill rolls is essential for maintaining production efficiency.
- Application Results
After implementation of improvements, segment water leakage issues have been brought under control and online service life has been extended. Average service life has been extended by approximately 250,000 tons of casting throughput. Stable segment operation ensures stable production of the slab caster and improves the steel plant’s specialty steel production capacity. The combined approach—precision assembly, roller modification, waterway redesign, and strict quality acceptance—delivers measurable improvements in caster segment longevity and overall production reliability. Plants implementing these practices can expect reduced unplanned downtime, lower maintenance costs, and improved product quality for specialty steel grades. For related equipment solutions, explore our range of rolling mill rolls and graphite electrodes.
- Frequently Asked Questions (FAQ)
Q1. What is a slab caster segment?
A slab caster segment is a key component of a continuous casting machine that supports and guides the solidified steel slab as it moves through the casting line. Each segment contains multiple rollers and a water cooling system that maintains operational temperature and prevents steel from sticking to the mold wall. The cooling system includes components such as the copper mold tube in crystallizer, which requires proper water cooling to prevent overheating issues.
Q2. How does water leakage affect caster segment life?
Ans: Water leakage from roller bearings and seals causes O-ring carbonization, bearing grease deterioration, and loss of lubrication. This leads to accelerated wear, increased roller resistance, and ultimately premature segment failure—severely reducing the online service life of the caster segment.
Q3. What is the difference between series and parallel waterway design?
In a series design, bearing housing return water becomes the core shaft inlet water—if any water hole blocks, all downstream components lose cooling. A parallel design gives each roller and core shaft its own dedicated inlet and return lines, so a single blockage does not cascade into widespread component damage. This principle is fundamental to understanding steel properties and material behavior in continuous casting processes.
Q4. Why is precision assembly important for segment life?
Ans: Precision assembly ensures correct roller positioning, proper O-ring sealing, and accurate arc alignment. Debris or misaligned components cause uneven roller loading, accelerated wear, and water leakage—directly shortening segment service life and increasing unplanned downtime.
Q5. How often should Y-type filters be cleaned on caster segments?
Ans: Y-type filters on caster segment water inlet lines should be cleaned at least twice per week to prevent debris accumulation that can block roller water passages and cause O-ring carbonization and bearing damage.
Q6. What quality checks are required for roller repair?
Ans: Roller repair quality acceptance covers 11 inspection items including bearing housing water tank deformation, bearing housing looseness, base surface flatness, roller hardness, concentricity, and outer diameter dimensions. Only rollers passing all checks are accepted for reinstallation.
Q7. How much can segment service life be extended?
Ans: With combined improvements in precision assembly, roller modification, waterway redesign, and quality acceptance, the average segment service life can be extended by approximately 250,000 tons of casting throughput—a significant improvement in production capacity and cost efficiency.
