Home>Bearing knowledge>Using laser welding skills to correct the gear shaft

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Correct the gear shaft with laser welding skills

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1 Introduction A plant sulfuric acid plant I system imports SO2 fan equipment 1 pair of spare large gear; the sub gear ratio is larger than the gearbox gear ratio used; mainly considering that the future system can be replaced when the capacity is increased; Correspondingly increase the ability of the fan; ensure the normal operation of the system. However, due to the long storage time; coupled with the harsh environment; long-term exposure to corrosive SO2 flue gas; the large gear shaft journal and tooth surface are presented More severe corrosion (presented by unevenly scattered point-like pits; pit depth of 0.5 to 1 mm); on-site judgment by engineering skills personnel; recognition that it can not be used normally. If ordering from scratch or returning to foreign manufacturers to correct It is not only long-term; it is expensive (such as ordering more than 500,000 yuan from the beginning; correction is more than 300,000 yuan; cycle is about half a year); one side faces adverse effects due to normal production; it is not economical. Corrected it in the shortest time; and can reach the original function and scale requirements; after the abundant proof and careful consideration; our factory decided to entrust a domestic laser technology company to rust The etched imported SO2 fan speed increase box large gear shaft journal and tooth surface are corrected. Under the cooperation of the Institute of Metal Research, Chinese Academy of Sciences; the severely corroded journal and tooth surface are carefully analyzed and tested; and laser cladding is applied. The method was successfully corrected.
2 There are many methods for detecting and dissecting the journal; such as traditional electroplating skills, surfacing skills and thermal spraying skills; but these methods have their own advantages. The electroplating skills have coating contact strength and The problem of lack of strength, surfacing skills and thermal spraying skills have a large thermal influence surface; it is easy to form a problem of deformation of the journal and the entire part. Laser welding skills can be used to overcome the above defects; neither large heat affected zone will occur. And thermal stress; it will not affect the technical objectives such as strength and hardness; and the new alloy appearance has better wear resistance and corrosion resistance.
Through on-site careful inspection; the two supporting journals of the gearbox shaft of the speed increasing box are severely corroded; the depth is 1mm; the rusting depth of the thrust surface is 0.5mm; the rusting area is the entire journal surface. Through non-destructive testing and testing of raw materials Analyze; judged as journal corrosion failure; although the journal strength storage coefficient can still be satisfactorily used; but the rust part needs to be removed; after laser welding and finishing satisfactory scale and precision requirements, it can be used continuously.
3 laser welding correction 3. 1 laser welding skills and functions of the characteristics of the laser cladding technology is the use of high-power high-energy laser beam gathering energy is extremely high characteristics; in the case of the surface of the surface of the surface micro-melting; together make the damage appearance preset Or the metal alloy material in the same or near the base material is actively melted in synchronization with the laser beam; obtaining a fine coating arrangement in which the substrate is in metallurgical relationship; then reaching the original shape of the reconstructed workpiece; and improving the correction area against the original work Environmental corrosion and other functions.
Features of laser cladding:
(1) The laser cladding layer forms a metallurgical connection with the substrate; the connection strength is the same as the original drawing intensity; as shown in Table 1,
Table 1 Comparison of the strength of the contact between the laser cladding layer and the substrate and the strength of the original substrate

Sample variety	σ b /MPa	σ 0. 2 / MPa	δ 5 /%	A k /J
Substrate	841	676	17.6	59
50% deposited layer 50% substrate	834	665	14. 2	50. 2
percentage/%	99	98	81	85
Substrate: 2Cr13 Metal powder: DLF-202

(2) The matrix data is only micro-melted in the laser processing process; the micro-melting layer is only 0. 05~0. 1mm, and the substrate is affected by heat. 憬鑫00.1～0. 2mm; laser cladding heat effect The area is one tenth of argon arc welding.
(3) There is no coarse casting arrangement between the deposited layer and the substrate; the deposited layer and its interface are finely arranged; the grain is fine. The base of the crucible is (10) the frequency of the alkaline salt is repeated (4) the temperature rise of the substrate during the laser processing Does not exceed 80 °C; the substrate will not exhibit thermal deformation after laser processing, (5) laser welding skills controllability; easy to complete active control,
(6) The laser cladding layer arranges each characteristic gradient function data composed of the bottom layer, the middle layer and the surface layer; the bottom layer has good wettability with the substrate; the connection strength is advanced, the middle layer has a certain strength and hardness; the crack resistance In the same strength, the surface layer has the functions of erosion resistance, wear resistance and corrosion resistance; the corrected equipment is more secure in terms of safety and application.
3. 2 gear shaft laser welding correction (1) Correlation data detection of the corroded large gear together with the pinion (cavity shape public service scale, ellipticity, taper, rotor curvature, hardness, etc.); obtain raw data; Prepare for the next step.
(2) Adopt mechanical finishing methods; remove the original corrosion layer and fatigue layer of the journal by turning.
(3) Before laser welding; non-destructive testing of parts.
(4) After the test; the analysis of the shaft material is carried out.
(5) According to the process parameters of the gear shaft and working conditions, the laser cladding process is determined.
(6) Select the material of the laser cladding process alloy according to the condition of the bulk material.
(7) Set the laser welding process parameters; such as spot, speed, focal length, etc.; and carry out laser welding treatment. Increase the speed of the gearbox shaft journal laser welding direction.
(8) Mechanical finishing after welding (car, grinding); to restore the original scale and accuracy.
(9) After the laser welding process is corrected; finally, the workpiece is subjected to a non-destructive test; whether the data can be within the normal range.
(10) Issue a revised inspection and inspection statement.
4 Conclusion (1) dealt with a series of technical problems such as the inevitable thermal deformation and hot fatigue damage in the thermal processing of traditional electric welding, argon arc welding, etc.; together with the conventional electric welding, spraying and other cold processing, the coating is connected with the substrate. The opposite strength is therefore more and more important in the industry; it can also be used in other similar important parts of imported equipment.
(2) Since the laser has entered the processing category as a strong, non-touch, hygienic heat source; it has dealt with many difficult problems that cannot be processed and difficult to process; it has greatly improved the production power and processing quality; therefore, it is called future production. The processing method of the system. After the modified SO2 fan speed increase gear large gear shaft journal and tooth surface are corrected by the laser welding process; our factory will replace the gearbox gear used; replace the modified gear; The original working environment; the use of a period of time; smooth operation; the oscillation value and other targets are tested; compared with the pre-replacement; the same; the expected effect.

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