Abstract: This paper introduces in detail how to use laser cladding technology to repair the gate arch of a steel plant, including the preparation work before repair, the selection of laser cladding process parameters, the key points of operation during the repair process, and the quality inspection after repair, etc., to provide reference for relevant engineering and technical personnel.

1. Introduction
In the steel production process, the gate arch, as an important equipment component, has been subjected to harsh working conditions such as high temperature, heavy load and friction for a long time, and is prone to problems such as wear, cracks and corrosion, which seriously affect the normal operation and service life of the equipment. Traditional repair methods such as surfacing and thermal spraying have the disadvantages of large heat-affected zone, low bonding strength and poor repair accuracy. As an advanced surface modification and repair technology, laser cladding technology has the advantages of small heat-affected zone, high bonding strength and high repair accuracy, providing a new solution for the repair of gate arches.

2. Preparation before repair
2.1 Equipment inspection
Carry out a comprehensive inspection of the gate arch that needs to be repaired, including appearance inspection, dimensional measurement and non-destructive testing, etc., to determine the damaged part, degree of damage and repair scope.
2.2 Surface pretreatment
Pretreat the surface of the repaired part to remove pollutants such as oil, rust and oxide layer, and use mechanical grinding, sandblasting or pickling to make the surface reveal metallic luster and the roughness reach Ra3.2 – Ra6.3μm.
2.3 Material selection
Select suitable laser cladding materials according to the material and working conditions of the gate arch. Generally, alloy powders with good compatibility with the base material, wear resistance and corrosion resistance are selected, such as cobalt-based, nickel-based and iron-based alloy powders.
2.4 Tooling fixture design
Design special tooling fixtures according to the shape and size of the gate arch to ensure the positioning and fixation of the workpiece during the repair process and ensure the repair accuracy.
3. Selection of laser cladding process parameters
3.1 Laser power
Laser power is one of the important parameters affecting the quality of laser cladding. Generally speaking, the greater the laser power, the greater the depth and width of the cladding layer, but too high laser power will cause defects such as cracks and pores in the cladding layer. According to the material, thickness and repair requirements of the gate arch, select the appropriate laser power, generally between 1-5kW.
3.2 Scanning speed
The scanning speed determines the action time of the laser on the workpiece surface and the forming speed of the cladding layer. If the scanning speed is too fast, the thickness and width of the cladding layer will decrease, and the bonding strength will decrease; if the scanning speed is too slow, the cladding layer is prone to overheating, ablation and other problems. According to the laser power and repair requirements, select the appropriate scanning speed, generally between 2-10mm/s.
3.3 Powder feeding rate
The powder feeding rate affects the composition and thickness of the cladding layer. If the powder feeding rate is too large, the unmelted powder in the cladding layer will increase and the structure will be uneven; if the powder feeding rate is too small, the thickness of the cladding layer is insufficient and cannot meet the repair requirements. According to the laser power and scanning speed, select the appropriate powder feeding rate, generally between 5-30g/min.
3.4 Overlap rate
In order to ensure the continuity and uniformity of the repaired parts, there needs to be a certain overlap between adjacent cladding paths. The overlap rate is generally between 30% and 50%, and the specific value is determined according to the repair requirements and process parameters.

4. Key points of operation during the repair process
4.1 Equipment debugging
Before the formal repair, debug the laser cladding equipment to ensure that the parameters of the equipment are stable and reliable, the optical path system is clean and unobstructed, and the powder feeding system is smooth and unblocked.
4.2 Cladding operation
Install the pre-treated gate arch on the fixture, adjust the distance and angle between the laser head and the workpiece surface, and perform laser cladding operation according to the preset process parameters. During the cladding process, pay attention to the formation of the cladding layer, adjust the process parameters in time, and ensure the quality of the cladding layer.
4.3 Multi-layer cladding
For deep damaged parts, multi-layer cladding is required. After each layer of cladding is completed, the surface of the cladding layer should be cleaned and polished to remove the oxide layer and unmelted powder on the surface, and then the next layer of cladding is performed until the size and performance required for the repair are achieved.

5. Quality inspection after repair
5.1 Appearance inspection
Carry out appearance inspection on the repaired gate arch to check the surface quality of the cladding layer, such as whether there are defects such as cracks, pores, slag inclusions, and whether the surface flatness and roughness meet the requirements.
5.2 Dimension measurement
Use measuring tools to measure the dimensions of the repaired parts to check whether the dimensions after repair meet the design requirements.
5.3 Nondestructive testing
Use nondestructive testing methods such as ultrasonic testing, magnetic particle testing, and penetration testing to test the internal quality of the cladding layer and check whether there are internal defects.
5.4 Mechanical property test
Perform mechanical property tests on the repaired cladding layer, such as hardness test, tensile test, impact test, etc., to check whether the mechanical properties of the cladding layer meet the working requirements.

Conclusion
As an advanced repair technology, laser cladding technology has broad application prospects in the repair of gate arches in steel plants. Through reasonable process parameter selection and strict operation control, the damaged parts of the gate arches can be effectively repaired, the service life and reliability of the equipment can be improved, and strong support can be provided for the safe production and cost reduction and efficiency improvement of steel enterprises. In practical applications, it is necessary to continuously optimize the process parameters and operation methods according to the specific situation to further improve the repair quality and efficiency of laser cladding technology.