Restoration of the cross of the driveshaft VAZ 2109

Introduction

The constant lack of maintenance of spare parts is a serious factor in the decrease in technical readiness of the automobile fleet. The expansion of their production, new spare parts is associated with an increase in material and labor costs. However, about 75% of parts are discarded during the first overhaul of cars, are repairable, or can be used at all without restoration. Therefore, a reasonable alternative to expanding the production of spare parts is the secondary use of worn-out parts restored during the repair of the car and its units.

It is known from repair practice that most parts rejected for wear lose no more than 12% of the initial mass. moreover, the strength of the parts is practically preserved.

From the point of view of reproduction of machines, the economic feasibility of repair is due to the possibility of reusing most parts both suitable and extremely worn out after restoration. This makes it possible to carry out repairs in a shorter time with lower metal costs compared to the costs of manufacturing new parts.

The high quality of repaired cars and units makes an increase in the requirement for the resource of restored parts. It is known that in cars and units after overhaul, the parts work, as a rule, in significantly worse conditions than in new ones, which is associated with a change in basic dimensions, displacement of the axes in the body parts, a change in the conditions of the lubrication task, etc. In this regard, the technology of restoring parts should be based on such methods of coating and post-processing, which would allow not only to preserve, but also to increase the life of repaired parts.

Task

Option # 1.

- cross-piece cardan shaft of VAZ2106 car;

- annual program of 2500 pieces;

- repair factor 0.75

Working conditions and requirements for the part

Recoverable defects

Spider material - structural steel (Steel 20X GOST 105088)

Hardness of the cross - HB 50;

Krestovina works with a constantly operating twisting load;

Part class - 4;

Choose a rational recovery method

The choice of the method of restoring the part depends on the structural and technological features and working conditions of the parts, their wear, technological properties, the restoration methods themselves, which determine the durability of the repaired parts and the cost of restoring them.

Assessment of the recovery method is given according to three criteria: technological, durability criterion and economy criterion.

4.1. Technological criterion

Considering the properties of the part material, heat treatment, the quality of the working surfaces, the design is taken (based on the characteristics of the decision methods) that in order to restore the functional capacity of the part it is necessary:

Dents from needle rollers on the working surface of the spike and wear of the spikes are restored using the plasma surfacing method, such a method is more productive (13 minutes) compared to the vibration surfacing (17.3 minutes). The allowance for mechanical treatment is reduced by 1.52 times, which allows saving surfacing metal, the recovery life of plasma surfacing crosses corresponds to the resource of new ones.

Wear of the ends of the opposite spikes is not repaired, and when 89.84 mm is reached, the cross is married.

Worn or damaged threads (more than two threads) in the holes of the flywheel are brewed and drilled. After grinding of the built-up metal to the level of the main metal, the hole is drilled, the chamfer is countersunk and the holes are countersunk to a certain depth and the thread is cut in accordance with the dimensions in the working drawing.

Development of the process of restoration of the cross

5.1 Procedure of vibration-medium surfacing

During development of vibration-fluid surfacing it is necessary to:

1. Prepare part for build-up;

2. Select the type and grade of the wire;

3. Select the thickness of the layer to be melted.

4. Select the position of the electrode wire relative to the part to be welded;

5. Select welding current value;

6. Select the coolant flow rate;

7. Select a current source;

8. Select the head to build up.

Steel of which the detail 20X is made temperature of preliminary heating of 100 wasps has an udovlitvaritelny provarivayemost.

When heating the part to the surfacing, it is necessary to carefully clean the surface from lubrication and other contaminants.

The part is cleaned of oiled film and mechanical contaminants. Therefore, immersion cleaning is possible. To this end, a synthetic detergent MS11 is used. To achieve the required surface frequency, the solution concentration should be 2030 g/l, the solution temperature 80100 ° C, and the cleaning time 2 minutes.

The electrode wire is selected depending on the required hardness of the weld layer (surface hardness of splines 50 HRC), therefore the selected wire Nl65G according to GOST 1054363. It has hardness when built up in a liquid of 3652 HRC.

To achieve the highest productivity and the highest stability of the process, welding is carried out with a wire with a diameter of 1.62.5 mm. We accept 2mm.

The thickness of the layer to be laid is determined by the amount of wear, and the allowance for mechanical treatment of the built-up layer is also taken into account (the thickness of the layer is taken as 0.5 mm).

The feed rate of the electrode wire to obtain the optimum welding current and the required amount of molten electrode metal is 0.017 m/s.

The build-up speed for the best formation and required thickness of the build-up layer is 1.6 m/h.

The position of the electrode relative to the part is determined by the following parameters: the departure of the electrode, the angle of approach of the electrode to the part, the angle of inclination of the electrode to the part, the angle of approach of the electrode to the part, the frequency and amplitude of vibration.

The discharge of the electrode wire shall be 812 mm to prevent the wire from being welded to the mouthpiece at low departure and poor guide of the wire relative to the part at high departure.

The angle of approach of the electrode to the part, for the best formation of the build-up layer and its quality, this angle must be approximately perpendicular to the tangent plane to the build-up surface.

The angle of inclination of the electrode of the part to improve adhesion with the base metal and the roller between each other is the optimal value of this angle of 70 ° - 80 °

Amplitude of electrode vibration. With a small amplitude, roughness increases and strains are formed, with an increase in amplitude, the intensity of melting and spraying of the electrode wire increases. Optimum amplitude of wire oscillations 1.82.0 mm.

The welding current is 100110 A, since the welding voltage is 1819 V and the feed speed is 0.017 m/s.

The frequency of wire oscillations affects the amount of idle current. The lowest idling value is obtained at a frequency of 50100 Hz.

The coolant flow rate affects the amount of deformation of the part, the rate of metal cooling, the degree of metal protection from oxidation and nitriding, and the stability of the build-up process. The optimum flow rate is 0.70.2 l/min. The cooling liquid used is 4% aqueous soda ash solution. Liquid is supplied at a distance of 15 mm from the surfacing point.

Current source. To obtain the best result of vibration surfacing, a DC reverse polarity current source is used, three removable rectifiers are connected in series.

The head for vibration surfacing shall ensure constant wire feed speed, stability of vibration process, maintaining constant setting. Surfacing is performed by head with mechanical vibration of MMVK1.

Selection of equipment, cutting and measuring tools

The quality of part recovery is determined by the set of properties of its recovery process, the compliance of this process and its results with the established requirements. The main production factors are technically sound selection of cutting and measuring tool equipment.

Conclusion

In the course work, the development of technological processes for the defect, restoration and treatment of the crosspiece of the VAZ2106 cardan shaft was carried out, as well as the justification for the selection of the most rational operations included in these technological processes.

In this work, the technique was mastered and the skills of independently solving specific problems related to the processes of manufacturing and repair of automotive equipment were obtained.

Крестовина 1..cdw