To start with, roll wear limits product quality and roll service life in universal rolling production. For this reason, this study uses on-site data and classic wear theories. Meanwhile, it summarizes roll wear mechanisms and uneven wear distribution rules. Besides, it analyzes key influencing factors in hot rolling. Furthermore, it also provides practical optimization and maintenance methods. Ultimately, the results guide roll selection, cycle management and stable section steel production.
1. Introduction
First of all, section steel rolling adopts special pass rolling technology. As a result, it produces complex three-dimensional metal deformation. In comparison, its friction and contact conditions are more complex than flat rolling.
In addition, roll wear accumulates continuously during mass production. Worse still, serious uneven wear causes dimensional deviation and surface defects. Moreover, it also leads to unstable rolling states. Accordingly, mastering roll wear laws helps reduce roll consumption and improve production stability.
2. Main Wear Mechanisms of Universal Mill Rolls
To begin with, workers evaluate roll conditions by cumulative steel passing tonnage. During hot rolling, continuous sliding exists between hot blanks and cooled roll surfaces. Meanwhile, forward slip and backward slip exist in every rolling pass.
Generally speaking, metal wear has seven basic types. Specifically, common forms include adhesive wear, corrosive wear, fatigue wear and abrasive wear. In fact, actual roll wear comes from multiple coupled mechanisms instead of a single cause.
In particular, rolling load, speed and cooling conditions determine the dominant wear type. Once working conditions shift, the main wear mechanism will change and accelerate roll damage.
On one hand, hot rolling forms an oxidation environment with high temperature and cooling water. On the other hand, the oxide layer weakens surface bonding strength. Consequently, micro peeling and particle loss often occur on roll surfaces.
Apart from that, cyclic load and temperature fluctuation generate contact fatigue damage. Most importantly, adhesive wear and corrosive wear dominate section steel rolling. Meanwhile, fatigue wear plays an auxiliary acceleration role.
In short, roll wear capacity refers to maximum radial wear after fixed rolling tonnage. For reference, the Archard wear model supports quantitative analysis. Therefore, wear volume increases with contact load and decreases with surface hardness.
3. Uneven Wear Distribution Law of Roll Passes
From long-term field detection, stable uneven wear features appear on section steel roll passes.
Above all, wear degree rises gradually from pass side walls to inner corners. For this reason, pass corners always form the maximum wear area. Meanwhile, wear volume drops slowly from pass bottom edges to the center.
Overall, pass bottom wear is heavier than side wall wear. Besides, the bottom surface also has better wear uniformity than side walls. Even though different rolling tonnages cause minor value differences, they never change the fixed uneven wear trend.
4. Multi-Factor Cause Analysis of Uneven Pass Wear
4.1 Differential Slip Causes Unbalanced Friction
First, special-shaped workpieces contact roll passes at different times. Thus, slip states vary greatly at the rolling outlet.
Noticeably, pass bottom corners have the smallest roll diameter and lowest linear speed. Accordingly, they produce the largest forward slip. Gradually, forward slip decreases with the rising roll diameter toward the pass center.
When roll speed matches workpiece speed, slip value becomes zero. Conversely, larger roll diameters generate backward slip. As a consequence, mixed slip states create uneven friction distribution. Naturally, corners and bottom areas suffer concentrated wear.
4.2 Chilled Layer Loss Causes Uneven Hardness
Initially, new rolls receive integral heat treatment. Hence, they form a 50–60 mm high-hardness chilled layer. At this stage, new passes have stable hardness and good wear resistance.
Nevertheless, repeated turning and grinding remove partial chilled layers. Subsequently, some pass areas enter low-hardness transition layers. Simultaneously, high rolling temperature changes surface metallographic structures.
Over long-term operation, local hardness differences keep expanding. In turn, different pass positions show inconsistent wear resistance. Eventually, obvious uneven wear appears on roll passes.
4.3 Unbalanced Temperature Changes Deformation Resistance
Mathematically, workpiece deformation resistance follows a negative exponential temperature relationship: K=Me⁻ᵐT. Simply put, lower temperature brings higher deformation resistance and larger rolling load.
In practice, section steel blanks have unbalanced temperature distribution. Specifically, web temperature is higher than flange temperature. Likewise, flange root temperature is higher than flange end temperature.
For this reason, low-temperature flange areas bear greater friction and pressure. Correspondingly, their matching pass positions wear faster. Evidently, temperature difference is a key cause of uneven pass wear.
4.4 3D Deformation Triggers Unstable Rolling Load
By definition, section steel rolling belongs to typical three-dimensional plastic deformation. As a matter of fact, web and flange have different reduction rates.
On the one hand, large-deformation zones are restricted by small-deformation zones. On the other hand, internal tension and compression change original metal flow rules. Even tiny reduction differences cause obvious rolling force fluctuation.
Due to unbalanced load distribution, each pass position bears different friction levels. In effect, this condition produces diversified wear rates on the whole pass surface.
5. Process Optimization and Scientific Maintenance Countermeasures
Based on the above wear mechanisms, this part provides targeted improvements. Broadly, it covers rolling parameters, roll processing and temperature control.
5.1 Optimize Rolling Parameters
In operation, adjust web and flange reduction ratios reasonably. In this way, metal extension and asynchronous slip can stay balanced. As a result, uniform friction distribution reduces concentrated wear on corners and bottoms.
5.2 Standardize Turning and Grinding
First and foremost, control single turning depth to protect chilled layers. Periodically, detect pass hardness regularly. Additionally, match high-hardness zones with high-load flange rolling areas.
Further, apply local strengthening on vulnerable corners and bottoms. With this method, local wear resistance can be greatly improved.
5.3 Improve Blank Heating Uniformity
To solve temperature gradient issues, optimize furnace temperature control and preheating processes. If the web-flange temperature gap shrinks, deformation resistance will stay stable. Thereby, rolling load and friction distribute evenly.
5.4 Update Roll Replacement Standards
When evaluating roll health, judge roll status by steel tonnage and actual radial wear. Throughout daily production, strengthen inspection on weak pass positions. Before defects or vibration arise, replace or regrind rolls in advance.
6. Conclusion
First, universal mill rolls show typical uneven wear features. Specifically, pass corners have the most serious wear, and pass bottom wear is heavier than side wall wear.
Second, asynchronous metal slip and complex 3D deformation form the core cause of uneven pass wear. Without eliminating these two factors, uneven wear cannot be controlled fundamentally.
Third, chilled layer attenuation, unbalanced hardness and uneven workpiece temperature jointly worsen wear differences. Altogether, these three auxiliary factors amplify local material loss on roll passes.
Fourth, parameter optimization, standardized grinding and precise temperature control effectively suppress concentrated wear. In the long run, these measures stabilize product quality and cut total roll consumption.
