Technologist of unit head recovery

Contents

Introduction

1. Peculiarities of cylinder liners design

2. Main defects and causes

2.1.Delivery of inner surface of cylinders

2.2.Cavitational wear

2.3.Inclusion of sleeve collar

2.4. Cracks on the sleeve surface

2.5.Delivery of sleeve landing belts

3. Selection of the sleeve recovery method

3.1.Development for repair size

3.2.Inward surface grinding

3.3.Electropulse coating application

3.4.Recoveries with electrolytic coatings

3.5.Halvanomechanical method of reduction

3.6. Reduction by thermoplastic deformation

3.7. Method of repair bushings installation

4. Development of Job Instruction

4.1.Determination of monthly batch of parts

4.2.Selecting bases

4.3.Development of process of recovery of cylinder liners of SiL- engine

4.4. Calculation of processing allowances

4.5.Process plan

4.6. Calculation of processing mode and time standards

4.7.Selecting Equipment

4.8. Calculation of the number of repair workers, workplaces, time fund and equipment quantity

5. Protection of labor

5.1.Safe measures during repair of ICE sleeves

5.2.Assuring fire safety in case of shell restoration

Conclusion

List of information sources

Introduction.

The reliability and durability of the machine is usually judged by the stability of the performance inherent in it during manufacture. Under operating conditions, stability of engine performance can be impaired due to many causes of failure of its mechanisms and systems. Malfunctions can occur as a result of disturbing adjustments that are eliminated during operation, or due to natural wear of the mating parts, which is not eliminated by simple adjustment.

Durability, as a rule, is determined by the natural wear of the mating parts, mainly the wear resistance of such mates as the cylinder liner - piston, piston ring - piston groove, piston pin - piston butt, piston pin - connecting rod sleeve, crankshaft journals - bearings, valve - valve seat in the cylinder head.

Maintaining a high level of technical readiness is largely determined by the extent to which their spare parts requirements are met.

Maintenance and repair of equipment in spare parts is ensured by manufacturing and restoration of parts. Under these conditions, great attention should be paid to the economical use of material resources, the development of work on the restoration of parts. At the same time, the volume of technological operations is reduced by 5-8 times compared to the production of new products of the same name. The cost of restoration is usually 30-50% lower than the cost of producing new similar products.

At various types of enterprises, technological processes and equipment have been developed and improved, which make it possible to restore many parts of cars by progressive methods that provide their post-repair resources at a level close to pre-repair.

Research and training institutes carry out various studies in the field of improving the organization of repair and restoration of parts.

The connection of the cylinder liner - piston is one of the connections undergoing the greatest wear in internal combustion engines. Therefore, the development of sleeve repair technology is an important task for improving the quality of repair of engines.

The purpose of our work is to describe in detail the methods of restoring the ICE cylinder liner mirror and choose the optimal one.

To achieve this goal, the following objectives must be achieved:

- Determine that there is an ICE cylinder, their features;

- Identify types of cylinder/liner defects;

- Characterize each method of restoring the cylinder mirror;

- Review in detail the optimal recovery method;

- Determine the methods of labor protection during works on cylinder mirror restoration.

2.4. Cracks on the sleeve surface.

The reason for the occurrence of cracks in the parts are primarily abnormal operating conditions, namely, strong overheating, rapid cooling, impact loads, etc. Cracks can also occur due to a violation of repair technology. Pulling the block head bolts on some engines can cause cracks on the surface of the sleeves. Operation of the engine in the cold season on water in the cooling system is also a common reason for cracks in the block and cylinder liners after water freezing.

A crack that occurs in a particular part is rarely localized, that is, it remains unchanged for a long time. In most cases, experiencing cyclic workloads and cooling cycles, the crack develops further to the breakage of the part. The consequences and rate of crack development depend on the type of part, material and cross section through which the crack passes. For critical parts of KSM and piston group, including crankshaft, connecting rods and piston pins, crack, regardless of the place of its formation, almost always leads to destruction of the part and failure of the engine.

In housing parts such as cylinder block and block head, as well as crack liners, cracks, as a rule, pass into the cavity of the cooling system, connecting it with channels of lubrication systems, crankcase ventilation, cylinders, or with the environment, causing leaks and/or mixing of working liquids. In addition, through cracks in the wall of the cylinder or combustion chamber, exhaust gases are supplied to the cooling system during engine operation, which displace the cooling liquid, drastically reducing the cooling efficiency of the engine.

Cracks in the lower part of the sleeve are usually associated with impacts of a broken connecting rod and, as a rule, are located vertically.

Installation of a part with a crack on the engine usually leads to its inoperability (failure) immediately after the first start or after a certain time, that is, to the need for repeated repair. In addition, traditional types of repair of work surfaces of a part with a crack (grinding, honing, etc.) sometimes cause losses to the repair enterprise, since a part with a crack is obviously non-repairable and requires replacement. Considering this, the detection of cracks in the parts before repair should be given the most serious attention.

2.5.Delivery of sleeve landing belts.

Wear of landing belts is partially connected with cavitation wear. A sign of a defect in the sleeves are deep shells on the surface of the belts, which is a consequence of the phenomenon of cavitation or corrosion.

During operation, vibration of the sleeve occurs, which also causes wear of the mounting bands of the sleeve.

In real conditions of engines operation, ovality of sleeve landing belts may appear, caused by cavitation destruction or scale deposition in clearances of sleeve landing belts in the unit.

Further, in the course design, the first type of defects will be considered - wear of the inner surface of the cylinders (liners).

3. Selection of the method of sleeve restoration.

In repair practice, the restoration of worn-out car tractor parts is carried out in various ways and the choice of one or another method in specific conditions is determined either by economic considerations or the production capabilities of repair shops (the presence of appropriate technological equipment).

The following repair process diagram is adopted for the sleeves:

1) editing;

2) restoration of dimensions of landing belts;

3) troubleshooting of the support bead;

4) restoration of the internal working surface;

5) galvanizing the outer surface;

6) control.

In the course design, the restoration of the internal working surface is considered.

Restores the interior surface.

With all the variety of repair operations used in production, however, many of them can be grouped into typical groups with the same process and from the general repair technology to distinguish the most common methods of restoring parts.

The technological uniformity of repair operations is the main classification feature by which all repair methods can be divided as follows:

1). restoration of worn-out parts by means of repair dimensions;

2). restoration of worn-out parts by surfacing;

3). restoration of worn parts by metallization;

4). restoration of worn-out parts by galvanic method;

5). restoring worn parts by distributing and settling them;

6). restoring worn parts by turning them by the other non-working party;

7). restoring worn-out parts by means of additional parts having the form of bushings, sleeves or rings;

8). restoring worn parts by replacing worn parts with new parts.

3.4.Recoveries with electrolytic coatings.

The essence of the method consists in the fact that when direct electric current passes through the electrolyte solution, positively and negatively charged ions are formed in it. Positively charged ions move to the negative electric cathode, which is a metal part, and are deposited on its surface, firmly adhering to it. Negatively charged ions move to the positive electrode-anode and are released on German. As electrolytes, as a rule, aqueous solutions of salts, acids and alkalis are used.

The amount of substances released during electrolysis is proportional to the amount of electricity passed through the solution. The amount of substance in grams released from the electrolyte when passing through it current of 1 ampere for an hour is called the electrochemical equivalent of this substance (s, g/Ah). Current density (DK, A/dm2) is the ratio of current to the coated or machined surface of the part.

Metals deposited in electrolysis differ in their properties from cast metals in that their crystal lattice is distorted due to different crystallization conditions. By changing the electrolysis mode (current density, temperature and composition of the bath), the mechanical properties of the deposited metals can be significantly changed.

The formation of high quality coatings largely depends on the scattering and coating capacity of the galvanic bath. By scattering capacity is meant the degree of uniformity of the metal precipitate on different parts of the irregularly shaped part to be coated. By covering capacity is meant the ability of the bath to cover the recesses on the cathode. It is possible to improve the scattering and covering capacity of the bath by the suspension structure for parts and the shape of the anodes, as well as by using screens.

Electrolytic (galvanic) chroming and quenching processes found the greatest distribution in the restoration of parts.

Chrome plating. It is used in cases where the coating should have very high hardness and wear resistance. Electrolytic chromium has a hardness from HB 400 to HB 1200, as well as high wear resistance, low friction coefficient (0.13 with babbit friction and 0.16 with steel friction), high thermal conductivity, low linear expansion coefficient. The electrochemical equivalent of chromium is 0.324 g/A - h.

Chromium electrolytes are solutions of chromic acid H2CrO4 formed by dissolving chromic anhydride CgO3 in water. To precipitate chromium on cathodedals, sulfuric acid H2SO4 should be added to the solution. At the same time, the best precipitation quality and the highest chromium current yield are obtained at a ratio of CgO3: H2SO4 = 100. The current output of chromium is very small - only 13-15%. It has been found that a normal chroming process is provided if the trivalent chromium is in the range of 5 to 20 g/l. This can be achieved if the area of the anodes is 1.8-2 times the area of the cathode parts.

As an anode, during chromium plating, roll lead is used with the addition of 6-12% antimony. During operation of the bath, the anodes are oxidized and should be cleaned periodically.

The process of wear-resistant chrome plating of parts consists of the following operations:

1. Cleaning of parts from oil and dirt.

2. Preliminary grinding to give the parts the correct geometric shape and obtain the necessary roughness.

3. Washing. Parts are washed in hot alkaline solution, rubbed with Viennese lime, washed in running water.

4. Insulation of suspension and surfaces of parts not subject to chrome plating. It is usually isolated with zaponlac (a solution of celluloid in acetone), perchlorovinyl lacquer 9-32 or AK20 and BF adhesives, which are applied in 2-3 layers.

5. Suspension (installation) of parts on the suspension unit.

6. Degreasing. During chemical degreasing, the parts are washed in gasoline or in an aqueous solution heated to 60-70 ° C for 3-5 minutes.

During electrochemical degreasing, parts are hung on suspension and immersed in bath with hot water solution. The solution is heated to 70-75 ° C and the parts are kept in it for 5-8 minutes at current density of 3-10 A/dm2 and voltage of 8-10 B.

7.Anode decapitation. It is carried out in order to remove degreased parts, oxide films from the surface and identify the structure of the part. To do this, the suspension with parts is loaded into a special bath with a weak solution of sulfuric acid in water (3-5 g/l) and held for 1-2 minutes. After that, the parts are washed in distilled water.

8. Chromium plating. To obtain hard wear-resistant coatings, the following composition of the bath and chromation regime are most often used: 150-200 g/l of chromium anhydride and 1.5-2.0 g/l of sulfuric acid; current density 35-45 A/dm2 and electrolyte temperature 56-58 ° С.

9. Washing. At the end of chromium-plating process suspension with coated parts is washed in distilled water for electrolyte collection, and then successively in running water, in 3-5% solution of alkali for neutralization, again in running water and finally in water heated to 70-80 ° C.

10. Removal (removal) of parts from suspension unit and removal of insulation.

11. Thermal processing of parts to eliminate their hydrogen fragility. Parts are usually heated in drying cabinets or in an oil bath to a temperature of 150-220 ° C and held for 1.5-2.0 hours.

Reversible chroming allows you to increase the rate of chromium deposition by 2 times, increase the purity of the coating by 1-2 classes compared to conventional chromium deposition. During reversible chroming, the current polarity is periodically changed: the duration of the cathode period is 10-15 minutes, and the anode period is 10-15 seconds. The electrolyte composition is ordinary (CgO3 - 200-250 g/l and H2SO4 - 2.0-2.5 g/l) with an increase in current density to 60-150 A/dm2.

Jet chroming of the cylindrical surfaces of the shafts and axes makes it possible to increase the efficiency of the process by 4-8 times without reducing the quality of the coating. During jet chroming of parts on special installations, the electrolyte is intensively mixed and constantly updated in the area immediately adjacent to the coated surface of the cathode.

Remaining. The current yield of the metal when remaining is 5- 7 times higher than when chroming, and is 75-95%, and the deposition rate is 10 times higher (0.4 mm per hour). When remaining, coatings up to 2 mm thick can be obtained.

For solid and wear-resistant quenching, chloride electrolytes of the following composition are usually used: ferric chloride FeC12 - 200-500 g/l, sodium chloride NaC1 - 100 g/l, hydrochloric acid HC1 - 0.5-0.9 g/l, manganese chloride MnCl2 - 10 g/l. Anodes are made of low carbon steel. The total area of the anodes should be 2 times the surface of the parts to be covered.

The hardness, toughness, and wear resistance of the coatings can be varied over a wide range by varying the electrolyte composition, temperature, and current density. At low current density and high electrolyte temperatures, fine-grained viscous coatings are obtained. As the current density increases, the hardness of the coatings increases.

The remaining process is analogous to chromium plating.

The disadvantage of reduction of sleeves with electrolytic coatings is the small thickness of the applied coating, the longer duration of coating application and the non-uniformity of the applied layer.

3.5.Halvanomechanical method of reduction.

Studies have shown that the use of the galvanomechanical method in the restoration of machine parts most fully meets the requirements of repair production. A distinctive feature of the invention is that during electrolysis the coated surface is subjected to mechanical activation (scratching) by abrasive or diamond tools in the form of ribbons or bars that move in the interelectrode space.

Mechanical activation helps to reduce overpressure of the deposited metal discharge due to reduced concentration restrictions, intensive removal of adsorbed hydrides, hydroxides and gaseous hydrogen from the cathode surface. All this makes it possible to increase working current densities tenfold when depositing chromium, nickel, cobalt, copper and significantly increase their deposition rate.

This method is a form of electrochemical honing, where an electrolyte is used as a COG for applying the corresponding metal, and is reduced to preliminary honing, electrodeposition of the metal with simultaneous honing at a low pressure of the bars and final honing to obtain the necessary geometry of the treated surface. Thus, the whole process is carried out from one plant on the same equipment.

Constant honing of the treated surface during electrodeposition, high rate of electrolyte circulation at a small interelectrode gap provides a high rate of metal deposition, which is 20-50 times higher than under stationary coating conditions.

The technological process is reduced to degreasing, washing in water, galvanomechanical process of coating application (decapitation of 15... 85 s, coating with setting to the mode during 8... 10 min, with a smooth increase of Dc and Pa to the optimal), subsequent washing of the part in running water, their neutralization and rinsing.

Technological equipment for restoring the cylinder liner mirror YaMZ238, 236, D50 (D240) was developed and manufactured. The process and installation for the restoration of the mirror of the cylinder liners D50 (D240) were tested in experimental production, as well as bench tests of three series of sleeves restored using the developed technology, which showed high operability of the parts.

The disadvantage of this method is the difficulty of acquiring

necessary equipment, relatively high cost of materials used in restoration.