1. Введение
This article introduces the structural composition and performance advantages of the horizontal and vertical short stress line bar mill. Compared with traditional housing rolling mills, this optimized mill type effectively reduces equipment weight, plant area and foundation engineering volume. It serves as an ideal model for new-built and renovated bar rolling production lines.
Fully continuous rolling production lines have become the mainstream for domestic small-sized bar steel projects. Considering technical performance and economic efficiency, the HV arranged housing-free short stress line bar mill is the preferred equipment for modern full-continuous bar rolling lines.
2. Technical Advantages of Horizontal and Vertical Short Stress Line Bar Mill
2.1 Structural Characteristics of Horizontal and Vertical Short Stress Line Bar Mill
The two-roll short stress line mill consists of a roll gap adjusting device, tension rod assembly, roll unit, mill base device and on-site piping system. Each component is compactly arranged to ensure high rigidity and stable rolling performance.
2.1.1 Roll Gap Adjusting Device
Manual or hydraulic motor driving systems power two worm gear boxes, which drive four tension rods connected with bevel gear boxes. This structure realizes synchronous and symmetrical roll gap adjustment for upper and lower rolls, ensuring precise rolling line alignment.
2.1.2 Tension Rod Device
Tension rods are manufactured from high-quality alloy steel and copper alloy materials. Integrated with the roll assembly, four elastic damping absorbers eliminate assembly gaps between tension rods and copper nuts, improving overall mill stability and reducing vibration during high-speed rolling.
2.1.3 Roll Assembly Device
Four-row cylindrical roller bearings bear radial rolling force. Thrust bearings installed on the operation side undertake axial force, matched with an axial adjustment mechanism to realize accurate upper roll axial displacement control. This configuration guarantees stable roll operation and high dimensional precision of finished bars.
2.1.4 Drum Gear Universal Spindle
Roll end sleeves are equipped with rolling bearing support seats. The design keeps upper and lower roll end sleeves horizontal at all times, greatly simplifying roll disassembly, assembly and replacement procedures for daily maintenance.
2.1.5 Self-Balancing Universal Spindle Bracket
The lever-supported self-balancing spindle bracket is fitted with a hydraulic latch cylinder. It enables automatic separation and combination between the spindle bracket and mill base, improving the efficiency of mill replacement and equipment maintenance.
2.1.6 Mill Base Assembly
The mill base adopts four hydraulic clamping cylinders for reliable mill fixation. Equipped with horizontal shifting cylinders, the device supports fast roll replacement and pass changing, reducing production downtime and improving operational efficiency.
2.1.7 Hardened Gear Combined Gearbox
The gearbox features a steel plate welded box body. Cylindrical gears adopt 6-grade precision helical gears with grinding finish. Spiral bevel gears apply Klingelnberg equal-height tooth technology with 6-grade precision. Made of high-quality carburized and quenched alloy steel, the gears reach hardness of HRC 58~62. Gear modification technology optimizes meshing performance, reducing noise and wear during long-term operation.
2.1.8 Vertical Mill Rack Changing Trolley
Hydraulically driven trolleys assist vertical two-roll short stress line mills to enter and exit rolling stations quickly. The mechanism realizes rapid vertical mill replacement and improves production line flexibility.
2.1.9 HV Convertible Mill Frame and Clutch
The mill and gearbox are installed on a rotary frame with four rollers sliding along the arc guide rail of the fixed frame. Two hydraulic locking cylinders fix the rotary frame stably, while two driving cylinders realize horizontal and vertical mill state conversion. Manual or hydraulic clutches control connection and disconnection between the main motor and transmission gearbox for flexible production switching.
2.2 Core Technical Features
The horizontal and vertical short stress line bar mill possesses outstanding comprehensive performance suitable for high-speed and high-precision bar production. Its main advantages are summarized as follows:
- High mill rigidity effectively reduces elastic deformation and improves dimensional accuracy of rolled bars;
- Floating bearing seat structure ensures uniform load distribution and stable operation;
- Four-row cylindrical bearings feature large stress angle, high load capacity and long service life;
- Independent thrust bearing device bears axial force and supports precise axial adjustment;
- Elastic damping balancers eliminate assembly gaps and simplify on-site piping layout;
- Universal horizontal and vertical rack structure reduces spare part types and procurement costs;
- Symmetrical roll gap adjustment fixes the rolling line position, bringing convenient operation and high equipment availability;
- Advanced oil-air lubrication technology greatly extends roll bearing service life;
- Top-drive vertical mill structure prevents cooling water and iron oxide scale from entering the transmission system;
- Local pass adjustment and single roll replacement are simple and efficient;
- Integral rack replacement shortens roll changing time, and roll disassembly is completed in the roll workshop;
- Reasonable HV layout realizes full-line no-twist rolling and improves finished product quality.
3. Economic Advantages of Horizontal and Vertical Short Stress Line Bar Mill
The horizontal and vertical arranged short stress line mill significantly reduces overall investment. It cuts direct equipment costs, plant construction area and foundation engineering volume, bringing remarkable economic benefits for steel rolling enterprises.
3.1 Reduced Plant and Foundation Construction Costs
3.1.1 Shortened Rolling Line Length
Compact equipment layout minimizes the spacing of mill stands. The full line of 18 HV mills (including two flying shears and seven vertical loopers) only occupies 60 метры, 15 к 20 meters shorter than traditional rolling lines.
3.1.2 Narrower Main Rolling Span
The optimized structural design shortens the overall unit length. The total length of the Φ610mm mill stand is less than 7.5 метры. The distance from the rolling line to the transmission column line is 1.0~1.5 meters shorter than conventional mills, effectively narrowing the main workshop span.
3.1.3 Lower Plant Height
The maximum height of the Φ610mm vertical mill with main motor cooling equipment is only 6.1m (rolling line elevation +0.8m), о 2 meters lower than traditional models. The crane rail elevation can be controlled at 7.2m to 7.8m on the ground floor and 12.6m with a 5m platform, greatly reducing plant construction costs.
3.1.4 Suitable for Old Workshop Renovation
Most old rolling workshops feature narrow spans, low crane rails and limited floor length. Traditional closed housing mills cannot adapt to these conditions, while horizontal and vertical short stress line mills with compact structure can perfectly match old workshop reconstruction requirements, realizing production upgrading without large-scale plant renovation.
3.2 Reduced Equipment Procurement Costs
The short stress line mill effectively reduces equipment weight and investment compared with closed housing mills. The larger the mill specification, the more obvious the cost advantage.
Для 6 sets of Φ610/Φ520mm mills with 6 spare racks, the total equipment cost is about 1.2 million RMB lower than traditional housing mills. For Φ420/Φ350mm units, the cost saving reaches 700,000 RMB.
In practical project comparison, one bar plant adopting 18 traditional housing mills has a total equipment weight of 687 тонны. Another plant equipped with 18 sets of optimized HV short stress line mills (plus 11 spare racks) has a total weight of only 577 тонны, reducing 110 tons of steel consumption and saving about 600,000 RMB in equipment investment.
4. Заключение
Horizontal and vertical short stress line bar rolling mills feature compact structure, high rigidity, convenient maintenance and significant economic advantages. The full-line no-twist rolling capacity ensures stable product quality, while the lightweight design reduces plant and equipment investment. It is the most cost-effective and reliable equipment for new construction and upgrading of modern bar rolling production lines.