Assembly technology - welding of apparatus housing 1-4-2.5-3 (09G2S)

Contents

CONTENTS

PAPER

SUMMARY

Z AND D AND N AND E

INTRODUCTION

1.TECHNOLOGICAL SECTION

1.1 Description and purpose of the structure

1.2 Selection and justification of materials

1.3 Selection of welding method

1.4 Selection of welding equipment

1.5 Preparation of edges for welding

1.6 Calculation of welding modes

1.7 Measures for removal of welding stresses and elimination of residual deformations

2. DESIGN SECTION

2.1 Assembly and welding equipment

2.2 Calculation of rollers

3. ORGANIZATIONAL AND ECONOMIC PART

4. SAFETY OF PROCESS OF ASSEMBLY-WELDING OF APPARATUS HOUSING 1-4-2, 5-

4.1 Decomposition of hazardous and harmful factors

4.2 Engineering Safety Solutions

4.3 Recommendations for reducing harmful effects

CONCLUSION

LIST OF LITERATURE

APPLICATION

Paper

Explanatory note contains: pages -; drawings -; tables -; drawings and posters -.

KEYWORDS: WELDING, APPARATUS, HOUSING, WELDING MODES, WELDING APPARATUS, PROTECTIVE GAS.

Object of development: process of assembly and welding of apparatus housing 1-4-2.5-3 (container) for storage of liquids with length 3700 mm and diameter 1200 mm.

The purpose of the development is to develop the technology of assembly and welding of the housing, to develop a method of welding the product, which is the most profitable from a technical and economic point of view.

The design analysis was carried out, the welding methods were analyzed and selected, the design of the welding bench was selected, the process documentation in the form of operational maps was developed, the welding operations were rationed, the economic calculation of the welding technologies used was carried out, the safety of welding processes was considered.

The basic technology for manufacturing the case involves automatic welding and semi-automatic welding in the environment of protective gases (CO2) for both tacks and for welding the main parts of the case.

The following results were obtained: The technology of semi-automatic welding in protective gas was developed when manufacturing the vessel body 1-4-2.5-3 for storage of liquids of the chemical industry. Welding equipment and tooling for works are selected.

Summary

In this output work, the choice of the method of assembling and welding the body of the vessel 1-4-2.5-3 for storing liquids of the chemical industry is justified, the welding modes are calculated, the process of manufacturing the body using semiautomatic welding in a CO2 medium is developed, and suitable equipment for performing welding work and the assembly process is selected.

The economic section contains analysis and calculation of the accepted welding method, the economic efficiency of implementation of the developed technology is evaluated.

Occupational safety and fire safety measures have been developed.

Z A D A N I E for qualification work (VKR)

T E M A VKR

_ _ Assembly-welding technology of apparatus housing 1-4-2.5-3 ______________

Target installation and source data:

This process envisages welding of apparatus housing 1-4-2.5-3 by mechanized welding in carbon dioxide medium.

This paper discusses the process of assembly-welding of the body of the apparatus 1-4-2.5-3. When performing the process, special attention should be paid to the observance of welding modes. The process consists of the following operations and transitions: - install the shells on the rollers of the rotators; - weld with the shells tacks; then weld the shells with mechanized welding in CO2 medium; - weld with bottom tacks to the shells; then welded by mechanized welding in CO2 medium. Welding works shall be performed by welding semi-automatic AIS 500PT of ELITECH company. After welding, the weld quality shall be checked.

Introduction

In the second half of the twentieth century. there was a transition from a machine-technical revolution to a scientific-technical one, which is characterized by the widespread use of science-intensive technologies. At the beginning of the third millennium, welding is one of the leading technological processes for creating the material basis of modern civilization.

More than half of the gross national product of industrialized countries is generated through welding and related technologies. Up to 2/3 of the world's steel consumption goes to the production of welded structures and structures. In many cases, welding is the only possible or most effective way to create integral joints of structural materials and to obtain resource-saving blanks that are as close in geometry to the optimal shape of the finished part or structure as possible. The continuous growth of welding capacity sciences contributes to the improvement of product quality, efficiency and competitiveness.

Today, welding is used for the integral connection of the widest range of metal, non-metallic and composite structural materials in the conditions of the Earth's atmosphere, oceans and space. Despite the continuously increasing use of light alloys, polymeric materials and composites in welded structures and products, steel remains the main structural material. That is why the global market for welding equipment and services is growing in proportion to the growth of global steel consumption. By the beginning of the XXI century. It is estimated at about $40 billion, of which about 70% comes from welding materials and about 30% from welding equipment.

Arc and contact welding will remain the dominant method of metal bonding. It is expected that the share of manual arc welding with coated electrodes by 2010 will be 20-25% of the total welding volume.

The share of mechanized and automatic welding methods in protective gases replacing manual arc will in the future be 50-55% of its total volume.

Selecting a Welding Method

Welding semiautomata for working in the environment of protective gas is a relatively new type of welding, which has become widespread over the past 20 years. In this welding method, two versions of the work are used:

MIG (Metal Inert Gas) - the welding process proceeds under the influence of an inert gas (argon or another mixture of gases).

MAG (Metal Active Gas) - welding of metal in active gas (carbon dioxide).

The peculiar binding to the gas cylinder reduces the possibility of using this type of welding in the open space, but with a stationary method of welding, there are no analogues to this welding.

The welding process takes place with the participation of an electrode wire containing silicon and manganese, which is supplied to the welding region. Carbon dioxide is also supplied there to protect the electrode and welded metal from environmental influences.

During semi-automatic welding in the gas environment, the welder is able to control the whole process. The advantages of semi-automatic welding in the gas medium include the fact of saving time that could be spent on changing electrodes and grinding seams from slag, which in this case are not produced.

The quality of semi-automatic welding in the gas environment is much better than without it, but there are also their own nuances. For example, a welding seam made in an active gas (CO2) medium will have a flaky relief or grat (sticking balls), and a welding seam made in a mixture of argon and carbon dioxide gases (80% and 20%, respectively) is smooth and even, practically without additional treatment.

Recently, inverter power supplies have been used for the operation of welding semi-machines, which have many advantages over an AC source:

low weight;

smooth voltage adjustment;

low load on the electric network.

Preparation of edges for welding

The edge preparation angle is performed at a metal thickness of more than 3 mm, since this absence (edge preparation) can lead to non-penetration along the section of the welded joint, as well as to overheating and burnout of the metal; In the absence of edge preparation to provide a wire, the electric welder must increase the welding current.

Edge preparation allows you to weld in separate layers of a small section, which improves the structure of the weld joint and reduces the occurrence of welding stresses and deformations.

The clearance correctly set prior to welding allows for complete penetration of the joint section when the first (root) layer of the weld is applied, if the appropriate welding mode is selected.

The length of the sheet bevel is controlled by a smooth transition from a thick welded part to a thinner one, stress concentrators in welded structures are eliminated.

Edge blunting is performed to ensure a stable welding process when the root layer of the weld is performed. The absence of blunting contributes to the formation of burns during welding.

The offset of the edges creates additional welding strains and stresses, thereby deteriorating the strength properties of the weld joint. Edge displacement is regulated by either GOST or specification. In addition, the edge offset does not allow a monolithic weld to be obtained along the section of the edges to be welded.

Preparation of edges for welding is carried out on mechanical machines - turning (processing of pipe ends), milling, strict - processing of sheets, etc., as well as using thermal cutting. Sheets, pipes made of carbonaceous steels are treated with gas-oxygen cutting. As combustible gases can be acetylene, propane, coke gas, etc. Non-ferrous metals as well as stainless steels are treated with plasma cutting.

Before welding of particularly critical structures, the ends of pipes or sheets after gas-oxygen cutting are additionally machined; this is done in order to avoid any inclusions in the metal.

Measures for removal of welding stresses and elimination of residual deformations

If the measures to prevent the formation of welding stresses and deformations are insufficient, it becomes necessary to eliminate (remove) the resulting stresses and deformations.

Vacation. To relieve stress, welded joints are heat treated. For this purpose, when welding carbonaceous structural steels, a general high tempering of the structure is carried out (heating up to 630-650 C with holding at this temperature for 2-3 minutes per 1 mm of metal thickness). Cooling must be slow so that no voltage is generated again. The cooling mode mainly depends on the chemical composition of the steel. The higher the content of the quenching elements, the lower the cooling rate. In many cases, the part is cooled to a temperature of 300 ° C with a furnace, and then in calm air.

At high tempering, welding stresses are relieved due to the fact that at a temperature of 600 ° C the yield stress of the metal is close to zero and the material has practically no resistance to plastic deformation, during which the welding stresses decrease (relaxation).

In some cases, you can limit yourself to the high release of individual subassemblies. Thus, in the manufacture of spherical storage tanks for various products, they are limited only to the release of petals with welded hatches. The release of individual units is also used in the manufacture of welded frames of trolleys of cars and locomotives. Such operations are much simpler than the release of the entire structure, and, as experience has shown, provide the required operational reliability.

High tempering is an expensive operation that lengthens the manufacturing process of the structure and should be used in truly necessary cases. If machining is carried out on a part that has not passed the release, then due to stress redistribution, its dimensions may change. In most cases, when welding articles made of steel with high carbon content and alloying elements, it is possible to limit only to preliminary local or general heating and not to carry out subsequent heat treatment. Argonoarch processing. Melting of the transition section from the seam to the base metal by the non-consumable electrode in argon disturbs the equilibrium of the internal forces of the stress field due to the transition of part of the metal to a liquid and plastic state. Naturally, during crystallization of the molten metal, stresses will again occur, but they are relatively small, since the amount of this metal is many times less than the amount of the weld metal. Melting a small amount of base metal and weld metal results in a 60-70% reduction in stress. The smooth transition from the seam to the base metal thus obtained contributes to a significant increase in the strength of the welded joints, especially at variable loads.

Forging of weld metal and near-seam zone. Welding stresses can be removed almost completely if additional plastic deformations are created in the seam and near-seam zone. This is achieved by forging the seams. Forging is carried out in the process of metal cooling at temperatures of 450 ° C and higher or from 150 ° C and lower. In the temperature range of 400-200 ° C, due to the reduced ductility of the metal during forging, it is possible to form breaks. Special heating of the weld joint is generally not required to perform the forging. Blows are applied manually with a hammer weighing 0.6-1.2 kg with a rounded striker or pneumatic hammer with a small force. In multilayer welding, each layer is forged, with the exception of the first, in which cracks can occur from the impact. This technique is used to relieve stresses when brewing cracks and closing seams in rigid structures. Forging the weld joint also increases the fatigue strength of the structure.

Thermal editing. During thermal straightening heating is carried out by gas-oxygen flame or electric arc with non-consumable electrode. The heating temperature of the deformed section during thermal straightening is 750-850 C. The heated section tends to expand, however, the cold metal surrounding it limits the possibility of expansion, as a result of which plastic compression deformations occur. After cooling, the linear dimensions of the heated section decrease, which leads to a decrease or complete elimination of deformations.

Editing weldments requires a specific skill. Therefore, if structural editing is inevitable in production conditions, then workers must be specially trained to perform thermal editing. In case of deformation of the thin sheet attached to the massive frame, straightening can be carried out by heating at symmetrically arranged points on the convex side of the sheet. Heating should start from the center of the bulge.

Mechanical editing. To eliminate deformation, mechanical straightening can be carried out on presses or at a metal thickness of up to 3 mm manually with hammer blows. This type of editing is less appropriate than thermal editing and should be restricted. During mechanical straightening, a local slope is formed that increases the yield strength of the metal. The plastic properties of the metal are sharply reduced, especially in boiling steel. The inhomogeneity of mechanical properties caused by the inclination negatively affects the static strength of the structure and during the operation of the structure under variable loads.

Recommendations for reducing harmful effects

Recommendations for protection of welder against electric shock. In order to protect the welder from electric shock when coming into contact with metal parts accidentally energized due to insulation damage, the following requirements shall be observed. The enclosures of welding converters, transformers, rectifiers, rotators, tilters, choppers, etc. shall be grounded. In addition to the grounding of the main electric welding equipment according to the "Electrical Installation Rules" during arc welding, it is necessary to ground the welded unit and the terminal of the secondary winding of the welding transformer, to which the cable going to this unit (return wire) is connected.

Recommendations to reduce dust content. Various methods (filtration, sedimentation, electrical, etc.) can be used to control the dust content of the air of the working zone. The concentration of harmful substances in the air of the working zone can also be determined using various portable gas analyzers. These protectors are divided into filtering and insulating. In filtering devices, air inhaled by a person is pre-filtered, and in insulating devices, clean air is supplied through special hoses to the human respiratory organs from autonomous sources. These devices include various respiratory devices, gas masks, etc.

Recommendations for noise reduction. The most rational way to reduce noise is to reduce the sound power at the source. This method of combating noise is called reducing noise at the source of its occurrence. Reducing mechanical noise is achieved by improving the design of machines and mechanisms, replacing parts from metal materials with plastic ones, replacing impact processes with non-impact ones (for example, riveting is recommended to be replaced by welding, stamping - by pressing), using instead of gears in machines and mechanisms of other types of gears (for example, V-belt) or using gears that do not produce loud sounds (for example, using not spur gears, but helical gears or chevron gears), applying lubricant to rubbing parts, etc.

Recommendations for reducing vibrations. Personal vibration protection equipment includes special sleeves, gloves and gaskets. To protect the legs, vibration protective shoes are used, equipped with gaskets made of elastic damping materials (plastic, rubber or felt). In order to prevent vibration sickness of personnel working with vibrating equipment, it is necessary to strictly observe working and rest modes, while alternating working operations related to vibration exposure and without it.

Overview of Section

The engineering solutions and recommendations given in the section allow: to increase labor productivity, improve the quality of work performed, reduce labor intensity, and the quality of services provided will increase, reduce the percentage of injuries to workers, increase the comfort of work .

If the above measures are carried out in good faith, the risk of adverse consequences is reduced.

Conclusion

In the course of the final qualification work, the technology of assembling and welding the body of the 1-4-2.5-3 apparatus was developed.

A more advantageous welding method was proposed, welding materials and welding equipment were selected, welding modes were calculated, devices for assembling and welding the body of the apparatus 1-4-2.5-3 were selected.

The developed new technology increases labor productivity, reduces costs of welding materials, electricity, improves working conditions of workers.