What is a guide wheel?
In the steel mill, the guide wheel is a component that plays a guiding and supporting role. It is usually installed in many links such as the rolling production line and conveying equipment. For example, in the rolling process of strip steel, the guide wheel is located at the entrance and exit of the rolling mill, guiding the strip steel accurately into and out of the rolling mill. On a continuous conveying device, the guide wheel can guide the steel to run along a predetermined track, ensuring that the steel does not deviate during the production process.
The structure of the guide wheel generally includes parts such as the wheel body, shaft, bearing, and bracket. The wheel body is the part that directly contacts the steel, and its surface is usually smooth to reduce friction with the steel. The material of the wheel body varies according to the usage environment and requirements, commonly including cast iron, cast steel, and alloy steel. The shaft is used to connect the wheel body and the bearing, transmitting the rotational motion of the wheel body to the bearing. The bearing ensures that the wheel body can rotate flexibly and reduce frictional resistance. The bracket is used to fix the position of the guide wheel, ensuring its stability during operation.
Why do guide wheels need to be repaired frequently?
1.Poor working environment
High temperature influence: In the hot rolling process of steel mills, the guide wheel needs to work in a high temperature environment. For example, in the hot-rolled strip production line, the temperature of the steel billet after passing through the heating furnace can reach more than 1000 ℃. This high temperature environment will cause changes in the properties of the guide wheel material, such as a decrease in material strength and hardness, which is prone to deformation and increased wear. Moreover, repeated temperature changes can also cause thermal fatigue of the guide wheel and defects such as cracks.
Friction effect: The movement of steel on the guide wheel produces huge friction. Whether it is in the conveying link or the rolling link, the weight of the steel combined with its movement speed makes the friction between the guide wheel and the steel very large.
2.High work intensity
Continuous working hours: The production of steel mills is usually continuous and uninterrupted, and the guide wheel needs to run for a long time. Long-term continuous work makes the wear of the guide wheel a continuous accumulation process. Even under normal working conditions, the surface material of the guide wheel will gradually wear out due to continuous contact and friction with the steel.
3.It has a great impact on the quality of steel
Dimensional accuracy control: The wear of the guide wheel will affect the dimensional accuracy of the steel. In order to ensure the dimensional accuracy of the steel, it is necessary to repair the guide wheel in time so that it can accurately guide and support the steel.
Surface quality assurance: Damage to the surface of the guide wheel, such as scratches and corrosion pits caused by wear and tear, will be transmitted to the surface of the steel. In the production of high-quality steel, such as automotive steel, household appliance steel, etc., the surface quality of the steel is highly required. Even small scratches or pits may cause quality problems in the subsequent processing or use of the steel.
Advantages of laser cladding equipment
The advantages of laser cladding repair guide wheel are as follows:
1.Good repair effect
Good bonding strength: During the laser cladding process, the cladding material and the guide wheel substrate can form a good metallurgical bond, with high bonding strength and less prone to coating peeling, ensuring that the repaired guide wheel coating can firmly adhere to the substrate during use and withstand various stresses and frictions.
Excellent microstructure performance: The rapid solidification characteristics of laser cladding make the microstructure of the cladding layer dense and the grains small, which helps to improve the hardness, wear resistance, corrosion resistance and other properties of the guide wheel.
2.Strong customizability
Flexible material selection: Different cladding materials can be selected according to the specific usage requirements and working conditions of the guide wheel, such as nickel-based alloys, cobalt-based alloys, iron-based alloys, etc., to meet the different performance requirements of the guide wheel.
Precise control of the repair area: The energy and position of the laser beam can be precisely controlled, which can achieve precise repair of the worn parts of the guide wheel and avoid affecting other intact parts of the guide wheel. For complex-shaped guide wheels, accurate repair can also be performed.
3.Low thermal impact on the substrate
Laser cladding is a local heating repair technology with relatively small heat input and small thermal impact area on the guide wheel substrate, which will not cause excessive deformation and residual stress on the guide wheel substrate. This is very important for ensuring the dimensional accuracy and shape accuracy of the guide wheel. The repaired guide wheel can be directly put into use without additional processing and correction.
4.High efficiency and energy saving
Fast repair speed: The energy concentration of laser cladding can complete the repair work in a short time and improve production efficiency. Compared with traditional repair methods, laser cladding can greatly shorten the repair cycle of the guide wheel, reduce equipment downtime, and bring higher economic benefits to the enterprise.
High material utilization rate: During the laser cladding process, the amount of cladding material used can be precisely controlled, reducing material waste and reducing repair costs.
5.Wide application range
Laser cladding technology can be applied to the repair of guide wheels of various materials, including steel, cast iron, alloy steel, etc. Whether it is a small guide wheel or a large guide wheel, laser cladding technology can be used for repair.
Disadvantages of laser cladding equipment
However, there are also some disadvantages to laser cladding repair guide wheels.
- High equipment cost: The price of laser cladding equipment is relatively expensive, and enterprises need to invest a large amount of money to purchase equipment. In addition, the maintenance and upkeep cost of laser cladding equipment is also high, and professional technicians are needed to operate and maintain it.
- High process requirements: The process parameters in the laser cladding process have a great impact on the repair effect, and it is necessary to precisely control the parameters such as laser power, scanning speed, and powder feeding speed of the cladding material. If the process parameters are selected improperly, it may cause defects such as pores, cracks, inclusions, etc. in the cladding layer, affecting the repair quality.
- High working environment requirements: Smoke and dust will be generated during the laser cladding process. If the working environment is poorly ventilated, it may pose a health hazard to the operator. In addition, the laser cladding equipment also has certain requirements for the temperature and humidity of the working environment, and it needs to be operated under appropriate environmental conditions.
How to choose materials suitable for laser cladding repair guide wheels?
Environments with high wear resistance requirements
If the guide wheel works in a highly frictional environment, such as in a high-speed steel rolling production line, high-hardness and high-wear-resistant cladding materials need to be selected. Common materials include tungsten carbide nickel-based alloy powder, in which WC particles are dispersed and distributed in the nickel-based alloy matrix, with extremely high hardness, which can significantly improve the wear resistance of the guide wheel. Its Rockwell hardness (HRC) can reach about 60-70, which can effectively reduce wear when withstanding long-term friction of steel.
Iron-based alloy powders can also be selected, such as iron-based alloys containing boron (B), chromium (Cr), molybdenum (Mo) and other alloying elements. These alloying elements can form hard phases and enhance the wear resistance of the material. For example, the hardness of iron-based alloy powders containing Cr-Mo-B after cladding can reach HRC 50-60, and the cost is relatively low, suitable for repairing guide wheels with certain requirements for wear resistance but limited budgets.
Corrosive environmental resistance
When the guide wheel works in a humid or chemically corrosive environment, such as in a pickling workshop or a steel mill near the sea, a cladding material with good corrosion resistance should be selected. Nickel-based alloys are a good choice, containing elements such as nickel (Ni), chromium (Cr), and molybdenum (Mo), which can form a dense passivation film on the surface and effectively resist the corrosion of chemical media such as acid and alkali.
Cobalt-based alloys are also a type of corrosion-resistant cladding material. They have good resistance to thermal corrosion and chemical corrosion, especially suitable for high-temperature and corrosion-prone working environments. For example, in some steel transportation links after heat treatment, the guide wheel may come into contact with high-temperature and corrosive oxide scales and other substances. Cobalt-based alloys can effectively cope with this situation.
High temperature environment
For guide wheels working in high-temperature environments, such as some guide wheels in hot rolling production lines, the high-temperature performance of the material is crucial. Ceramic materials (such as aluminum oxide (Al2), zirconia (ZrO)) and metal composite cladding materials are good choices. Ceramic materials have excellent high-temperature resistance and can withstand thermal stress at high temperatures. At the same time, the metal phase can improve the toughness of the material and make the cladding layer less prone to cracking.
Some high-temperature alloys, such as nickel-based high-temperature alloys (such as the Haynes series), have good high-temperature strength and oxidation resistance. These alloys can maintain high hardness and strength at high temperatures, ensuring stable operation of the guide wheel in high-temperature environments.
Our customer cases
Case 1. Steel plant hot-rolled guide wheel repair
Background
In the hot rolling production line of a large steel plant, the guide wheel experienced severe wear under high temperature and high friction working environment. The original material of the guide wheel is cast steel, and the surface wear depth reaches 2-3mm, which leads to deviation during steel transportation and affects production quality and efficiency.
Solution
Using laser cladding technology, nickel-based alloy powder is selected as the cladding material. Nickel-based alloy has good high temperature resistance and wear resistance, and can adapt to hot rolling environment. By accurately controlling the parameters of the laser cladding equipment, such as setting the laser power to 3-4kW, scanning speed to 8-10mm/s, and powder feeding amount to 10-15g/min, a uniform and dense cladding layer is formed on the wear surface of the guide wheel, with a thickness of 3-4mm, completely covering the wear area and reserving a certain margin for subsequent processing.
Result
The repaired guide wheel was put back into use after processing and debugging, effectively solving the problem of steel deviation. After long-term operation monitoring, it was found that the wear resistance of the guide wheel was significantly improved, and the service life was extended by about 2-3 times compared to the original. In the subsequent production process, the replacement frequency of the guide wheel was reduced, the equipment maintenance cost was reduced, and the quality of hot-rolled products was improved.
Case 2: Repair of corrosion-resistant guide wheels in cold rolling plants
Background
The guide wheel of a cold rolling mill works in the pickling workshop and is corroded by acid for a long time, resulting in large corrosion pits and local corrosion penetration on the surface. The guide wheel is made of stainless steel, and its normal operation is crucial for controlling the surface quality and dimensional accuracy of the steel.
Solution
Using laser cladding technology, choose cobalt-based alloy as the cladding material. Cobalt-based alloy has excellent corrosion resistance and can resist the acidic environment of the pickling workshop. During the laser cladding process, adjust the laser power to 2-3kW, control the scanning speed at 6-8mm/s, and feed the powder at 8-12g/min. Layered cladding repair was carried out for corrosion pits. First, fill the deeper corrosion pits, and then clad a uniform cladding layer as a whole, with a thickness of about 2-3mm, to restore the smoothness of the guide wheel surface.
Result
The repaired guide wheel can resist acid corrosion well after being put back into use in the pickling workshop. After one year of use, there are only slight signs of corrosion on the surface of the guide wheel, while the unrepaired guide wheel will experience severe corrosion after a few months of use in the same environment. This case not only extends the service life of the guide wheel, but also ensures the surface quality of cold-rolled steel and reduces surface defects caused by guide wheel corrosion.