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Analysis of common failure causes and solutions for rolling guides in high-speed wire rod finishing mills

Through the analysis of the common problems of rolling guide failure, solutions are put forward in terms of water cooling, oil and gas, material type, and guide adjustment, which effectively reduces the consumption of rolling guides, reduces production costs, and improves economic benefits.

  • Failure analysis of rolling guides in finishing mills

The rolling guide is composed of guide box, guide plate, support arm, guide roller, bearing, nose cone and other components. The main reason for the failure of the rolling guide is the premature failure of the guide rollers, bearings, guide plates and other components. Among them, the failure of the guide roller is the most common, followed by the bearing, and the failure of the guide plate is rare. Therefore, the following mainly focuses on analyzing the reasons for the premature failure of the guide rollers and bearings, and proposes improvement measures to ensure that the service life of the rolling guides is greatly improved.

 

1.1 Water cooling

The guide roller is in direct contact with the rolling piece during rolling. At this time, the temperature of the rolling piece is above 1000 ℃, and the overheating of the guide roll will accelerate its wear, and the bearing in the guide roll will be heated and expanded through heat conduction, causing the bearing to burn out and cannot be used normally. The cooling of the guide rollers is very important.

 

1.1.1 Improper control of cooling water pressure

Relevant studies have shown that the cooling water pressure should generally be maintained at 0.5 MPa [1]. If the water pressure is too high, the cooling water will be ejected when it hits the surface of the guide roller, which will not achieve a good cooling effect; when the water pressure of the cooling water is less than 0.5MPa, the cooling water cannot break through the surface of the guide roller due to the small water pressure. Vapor film, resulting in poor cooling effect.

1.1.2 There is a problem with the cooling water quality

Due to the presence of oil and other impurities in the water, the guide rollers are not cooled enough, causing the guide rollers to overheat and accelerate their wear. Not only that, the bearing is thermally expanded through heat conduction, causing the bearing to burn out, making the guide unable to continue to use normally.

1.1.3 The cooling water jet is blocked

In the process of circulating cooling water, the water contains large particles of impurities, which causes the injection port to be blocked, or the iron oxide scale peeled off the surface of the rolling piece blocks the injection port, resulting in insufficient cooling of the guide roll. No matter which of the above causes the poor cooling of the guide rollers, the service life of the guides will be reduced, so we must pay attention and find solutions.

 

1.2 Oil and gas

Oil and gas is a key factor to ensure the normal operation of the guide roller bearing, which directly acts on the bearing to meet the needs of bearing lubrication. The sealing form of the guide roller bearing is realized by generating high-pressure air flow through the oil-air lubrication system, so as to generate a pressure difference between the inside and outside of the guide roller, which can prevent water or other impurities from entering the bearing. However, the premise is that the supply of oil and gas must be within a certain range. If the oil and gas is insufficient, the sealing effect cannot be achieved, and it is easy for impurities in the oil and gas to enter the bearing. Since the gap between the bearing and the ball is very small, once the impurities in the oil and gas enter the bearing, the ball will be stuck, and the bearing will not rotate flexibly, which will cause serious local wear of the guide roller and lead to the early failure of the guide.

 

1.2.1 Insufficient oil and gas wind pressure

Insufficient wind pressure results in insufficient internal and external pressure difference, which cannot effectively prevent water or other impurities from entering the bearing, resulting in the ball being stuck and the bearing rotating inflexibly.

1.2.2 Insufficient oil and gas lubrication

There are many impurities in the lubricating oil, which block the filter screen and pipeline, resulting in insufficient oil and gas and insufficient lubrication effect. Bearings are severely worn, leading to failure.

1.3 Improper control of rolling stock size

The finishing mill adopts integral drive and continuous rolling with slight tension. The size of the rolled piece not only affects the finished wire rod, but also affects the life of the guide. The role of the rolling guide is to correctly guide the rolling stock into the rolling mill. In production, the requirements for the size of the material are very strict. The rolling stock size that meets the requirements will make the guide roller wear within the normal wear range. Once the rolling stock size is not Meeting the requirements will not only accelerate the failure of the guide rollers, but also more likely to produce piles of steel, resulting in production accidents.

1.3.1 The size of the rolled piece is too large

When the guide is assembled, it is assembled according to the specified requirements, and the opening of the guide is within the required range. Therefore, when the size of the rolled piece is too large, when the rolled piece passes through the guide, the guide roller will be squeezed to make the guide support arm. If it is stretched, the clamping force of the guide roller increases, which causes excessive wear of the guide roller, which leads to the failure of the guide roller.

1.3.2 The size of the rolled piece is too small

When the size of the rolling piece is too small, the guide loses its normal guiding function, and the head of the rolling piece will hit the guide roll, which makes it difficult for the guide roll to hold the rolling piece, causing the rolling piece to vibrate between the stands, resulting in steel falling. , the rolling piece wears both sides of the guide roller along the diagonal position of the guide roller, thereby reducing the service life of the rolling guide.

1.4 Adjustment of guides

The guide base is the only support of the guide on the rolling mill, which is related to the centering of the guide. The positioning keys and sliders of the base are worn out due to long-term use. At the same time, there is also the accumulation of impurities such as iron oxide scales under the sliders, which cause the rolling guides to deviate from the rolling centerline after they are online, resulting in abnormal wear and tear of the guides.

 

  • Solutions

2.1 Improve the water quality, make the oil and other impurities in the water meet the required standard, and keep the water pressure at 0.5Mpa. Regularly clean the guide water pipes on the panel, the rolling guide cooling water pipes, and the waterway inside the guide box. In order to solve these problems, the Ergao Line has strengthened the maintenance and management of the guides, and carefully inspected the water pipes on the finishing mill panel and the waterway of the guide water pipes in the lower line, and added high-pressure air to guide the guide of the lower line. Sanitary piping is cleaned.

 

2.2 Ensure the purity of oil and gas and reduce the impurity content in oil and gas. Replace the filter regularly to improve the oil quality. When replacing the guide, check the oil and gas supply, and use high-pressure air to clean the guide oil and gas pipes on the panel, roll the guide oil and gas pipes, and the oil and gas pipelines inside the guide box in time.

 

2.3 Strictly control the incoming material of finishing rolling and the material type of each pass in the finishing rolling, and adjust the size of the material type according to the standard. During the rolling process of the rolling mill, after a period of rolling time, the material type will be changed to varying degrees due to the wear of the rollers. If it becomes larger, it requires the adjuster to check the size of the material frequently and adjust the size of the roll gap in time to ensure the standard size of the material.

 

2.4 Regularly clean the guide base, replace the deformed guide base accessories, and reposition and adjust the guide base to keep it in good condition. The adjuster installs the guides correctly so that the rolling guides are centered on the rolling centerline.

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