Part Development Case - Course

Introduction

The purpose of this course project is to develop the most productive process of assembly and welding of the body made taking into account the modern development of welding production and welded structures.

Welding is the process of producing an undisturbed compound by establishing interatomic bonds between welded parts with their local or general heating, or plastic deformation, or the combined action of both.

Welded steel structures of today are distinguished by structural expediency, grace of engineering thought, a high degree of reliability. They are made of steels and alloys with high strength characteristics and operational properties. Non-ferrous metals and alloys are widely used in welded structures.

Modern welding processes make it possible to manufacture metal structures in a wide range of thicknesses and dimensions with high consumer properties.

In the future, today's steels will be replaced by high-strength steels with a yield strength of 6001000 MPa, which will make the structures lighter and more elegant. The active positions will be occupied by ultra-durable aluminum alloys and titanium alloys. These materials will determine the design and performance characteristics of welded vehicles, tank structures, construction and spatial structures.

Welded steel structures at the turn of the century remain the main engineering structures in almost all sectors of human economic activity.

General part

Characteristics of the specified welded structure

This housing relates to shell structures, such structures, as a rule, are overpressure and are subject to requirements for tightness of connections.

This type of structure includes various vessels, vessels and pipelines.

The case is used in the nuclear industry, operates under pressure and at high temperatures.

Body is assembled from rolled or stamped sheet blanks welded by longitudinal or annular butt seams. Corner seams are used only to strengthen the base to the lower bottom. As a rule, the bottoms are made convex with a flanging, which ensures the withdrawal of welded joints from the area of ​ ​ action of significant bending stresses. Such responsible products as nuclear reactor casings with a wall thickness of up to 200 mm and higher are made of solid-forged shells welded to each other by ring seams.

For this design, the following types of welding are used: manual arc welding, manual argon arc welding and automatic flux welding.

The product is technological, since it meets the service purpose and ensures the service life for a given resource can be manufactured with saving of time, materials and labor intensity.

The diameter of the welded shell is 2200 mm. The structure can be divided into separate units: a shell, and two bottoms welded to the body on both sides.

1.4Assembly Specifications

After the workpiece, the parts of the welded structures are delivered to the assembly.

An assembly is a process of sequentially connecting parts to each other in the order provided by the process and drawing, for subsequent welding.

The main purpose of the assembly process is to determine the most advantageous sequence of assembly of individual parts, ensuring that the technological requirements for the manufacture of this product are met with minimum labor costs, time and auxiliary materials. Prior to assembly, the worker (welder) visually checks whether the parts meet drawing and process requirements. Mating surfaces and adjacent areas of assembled parts with a width of not more than 20 mm shall be thoroughly cleaned from rust, oil, dirt, scale and moisture in order to avoid the appearance of pores and other defects in the seam material.

When assembling welded structures, parts are connected to each other by means of tacks, which are placed at the locations of future welds. The section area of the grips shall not exceed 2/3 of the section area of the future seam and shall not exceed 2530 mm2.

When assembling structures and parts, it should not be allowed to change their shape, not provided for by the technological process, but during tilting and

transportation - residual deformation.

Transfer and tilting by crane of heavy and large structures and their elements assembled only on tacks is not allowed.

The most accurate assembly with minimal labour can be achieved with assembly equipment. The main purpose of welding equipment is to fix and secure welded parts.

These the equipment distinguish on assembly and assembly and welding. The choice of equipment is determined by the process and depends primarily on the shape, dimensions and required accuracy of the products to be assembled, type of production, type of welding and other factors.

1.5 Welding Specification

For the manufacture of a steam generator, the following welding methods are allowed: manual electric arc, automatic flux welding, mechanized and manual argon arc (including with an additional protective zone for carbon dioxide welding) melting and non-melting electrode.

It is allowed to use several welding methods (among those listed above) in the process of making a single weld joint, provided that such a technology is provided for in the process documentation.

Steam generator welding shall be performed by methods specified according to the process developed and approved by the manufacturer in accordance with the established procedure.

The welding process shall ensure the required weld dimensions and mechanical properties of the weld joints.

When welding multi-pass seams after each pass, it is necessary to carefully grind the surface of each roll from slag and splash, while the seam and the adjacent area of ​ ​ the base metal should be visually inspected to identify defects leaving the outside

In the presence of undercuts, pores, slag or tungsten inclusions exceeding the permissible dimensions, it is necessary to remove them by sandwich or other mechanical methods.

Before welding the seam and the adjacent area of the base metal shall be cleaned of slag and splash in accordance with the specified technical requirements.

Before welding, the seam and the adjacent area of the base metal shall be cleaned of slag and splash in accordance with the specified technical requirements.

Welding of corner seams, which are subject to tightness requirements, must be performed in at least 2 passages.

When welding joints from corrosion-resistant steels and multi-pass seams after each pass, welding should be stopped before the metal cools at the welding point to a temperature below 100 degrees.

1.6 Welding Material Specification

Electrodes, flux, welding wire in improper storage, can cause pores and other defects in welded joints, therefore, certain requirements are imposed on their storage.

Incoming control of the metal of the supplier for production shall be performed by the OTC of the plant or the OTC of the customer and shall include: verification of the applied materials according to certificates or passports, requirements of technical specifications standards and working drawings. Check whether there is a factory number and whether its certificate meets the data.

Metal must be sorted by grade: numbered and before

by feeding for production straightened, cleaned from scale, rust, oil, moisture

and other contaminants.

Each batch of electrodes, welding wire, flux and gas before

use must be monitored. In the absence of certificates in the case of non-conforming passport conditions and standards, a batch of materials is not allowed for use and is subject to inspection for all indicators delivered by standards or specifications.

Results of welding materials inspection shall be issued by the corresponding document and certificate.

1.7 Specification for Inspection and Acceptance of Welded Structure

After welding, the weld must be inspected externally. All welds and the adjacent surface of the base metal with a width of at least 20 mm on both sides of the weld shall be inspected and measured. The seam and the surface of the base metal shall be cleaned of slag, splashes, scale and other contaminants.

Each product at the manufacturer shall be subjected to an acceptance test that includes:

- dimensional and connection dimensions;

- strength and tightness;

- quality of welds;

- surface quality;

- coating quality;

- completeness of the article (vessel);

- completeness of accompanying documentation;

-packages.

Geometrical dimensions and shape of surfaces shall be measured by means providing errors not more than 30% of the specified manufacturing tolerance.

Overall dimensions should be determined by summing up the dimensions of the assembly units and parts included in them.

Quality control of surfaces for absence of captures, sunsets, stratification, coarse hairlines, cracks reducing quality and deteriorating commercial appearance shall be carried out by visual inspection.

Mandatory check of presence, content, location of marks on welding seams and marking on the finished vessel shall be carried out by visual inspection.

Quality control of welded joints should be carried out by the following methods:

a) visual inspection and measurements;

b) mechanical tests;

c) intercrystalline corrosion resistance test;

d) metallographic studies;

e) radiography;

e) styloscoping;

g) ultrasonic inspection;

h) color or magnetic powder flaw detection;

and) other methods of the projects envisaged;

During manufacturing of assembly units and parts, check:

- compliance of condition and quality of welded assembly units and parts and welding materials with requirements of standards (TS) and design;

- compliance of quality of edge preparation and assembly for welding with requirements of standards and design;

-observation of the process of welding heat treatment, developed in accordance with the requirements of standards and design.

Process Part

2.2 Selection of assembly method

Depending on the type of production, the design and equipment of the assembly shop, assembly can be carried out at one fixed place, to which all parts and assemblies, tools and accessories are supplied, or when the product moves from one workplace to another, a certain part or assembly is installed at each workplace.

To assemble the steam generator, a node-by-node assembly is used, which allows you to specialize workplaces, more widely use various devices, and thereby obtain greater productivity.

Assembly of ring seam No. 1 of the bottom with the housing is performed as follows.

Housing is installed on roller supports, shackle for slinging is welded to bottom. After building the bottom, bring it to the housing, assemble it butt-to-butt, withstand the dimensions as per the drawing. Maintain the clearance in the joint not more than 1 mm.

If edges do not match, weld wedge clamps to the shell and eliminate edge displacement, weld the joint.

2.6 Current and polarity selection

Automatic welding under flux is carried out at direct current and reverse polarity.

Direct current has the advantage. With direct current, the arc burns more stably. Welding fluxes require direct current and reverse polarity. In this case, the arc is saturated with oxygen and fluorine having a large electron affinity.

The polarity of the current affects the depth of penetration, the chemical composition of the weld and the quality of the weld.

The genus and polarity of the current also affect the shape and dimensions of the seam. With reverse polarity DC welding, the wire depth is 4050% greater than with direct polarity DC welding, which is due to the different amount of heat released at the anode and cathode. For AC welding, the wire depth is 1520% less than for reverse polarity DC welding.

2.8 Design of assembly and welding devices, equipment selection

Assembly and welding devices are selected and designed in accordance with the pre-selected methods of assembly and welding of assemblies and the overall design.

For welding of my product, I choose the installation for welding of longitudinal and annular seams "AronsonRansome." This installation allows the welding of longitudinal and annular seams, on both sides, products with a diameter of 1500 to 5500 mm, weighing up to 400 tons. The welding wire diameter during welding is from 3 to 5 mm, the supply voltage is 220/380 V, the height of the manipulator from the floor surface is 9600 mm. The product is located on a roller-bearing bench. During welding, the article rotates. The article rotation speed is from 25 to 1016 mm/min. The manipulator is located on a movable carriage, which moves vertically along the column.

The power supply shall provide specified welding modes. For automatic welding under flux, a universal rectifier, such as VDU, should be used. Such a power supply may be VDU 1250. The rectifier for arc welding of VDU1250 are intended for a complete set of automatic machines for welding and building up under a layer of gumboil and in the environment of protective gas. Rectifier is designed for operation in closed rooms at ambient temperature from minus 40 ° С to plus 40 ° С and relative humidity not more than 80% at 20 ° С. The rated welding current of this source is 1250 A, the supply voltage is 380 V, the idling voltage is not more than 55V, the operating voltage limit control is 2444 V, the welding current control is smooth, the efficiency is not less than 83 %.

2.9 Selection of methods of control of the specified welded structure

Control is necessary to prevent defects in the seams, as well as to determine the quality of finished products. Inspection is performed before, during and after welding of the article or assembly.

Before welding, the quality of the raw materials is checked, the correct selection of welding equipment, gas and electric devices is called preliminary control.

During welding, the correctness of individual operations is checked

compliance with welding modes and compliance with specified order of seams position is systematically checked for serviceability of equipment and instruments. This step is referred to as operational control during welding.

At the end of welding quality of joints and finished product is checked. This step is called final control of the welds and finished product.

Final inspection methods shall be selected in accordance with the specification for inspection and acceptance of the welded structure and the requirements of the drawing.

After completion of welding operations it is necessary to apply external inspection of the weld. The effectiveness of the external inspection depends on the qualifications of the controller. He should see undercuts, burns, craters, raids, cracks and non-roofs coming to the surface.

External inspection tool: templates, cathetomers, ruler, caliper. Visual inspection instruments:

- magnifying glass, microscopes;

- devices with fiber optics for remote observation;

- instruments for conversion of visual signal into television and telemetry information on parameters of seam and welding.

Since the steam generator is a responsible product, it is necessary to carry out ultrasonic inspection.

Ultrasonic flaw detector is used to detect surface and

internal defects, for detection of MKK zones, for control of article thickness at one-sided access. For control of chemical and physical properties and detection of zones of welding stress concentration by zones of primary metal damage at fatigue stresses.

The advantage of ultrasonic inspection is:

- high sensitivity;

- greater penetrating ability to detect internal

defects, almost instantaneous detection of defects;

- possibility of automation;

- possibility of control at one-way access to the article;

- safety of supervisors and maintenance personnel.

Disadvantages:

- surface cleanliness requirements and presence of dead zones.

Organizational Part

3.4 Key Safety Activities

For the assembly and welding of this welded structure, workers with high qualifications and extensive experience are allowed. As Production

hazards in assembling this welded structure in that during assembling this welded structure can move from the place so it is necessary to install strong supports and check the quality of their installation. After assembling this welded structure, a highly qualified welder shall check before welding

stability of this welded structure this check will avoid

accidents. Also, the welder must check the serviceability of the equipment and have a fire extinguisher at the welding site according to fire standards. When the welder works, if the work is in the shop, the illumination of this shop should be good, this will improve the assembly and welding process. There should also be good ventilation at the welder's workplace, this ventilation will ventilate, the room will help not inhale a large amount of harmful gases to the welder. Also ventilation shall have a treatment facility these treatment facilities will prevent pollution of the environment. At the time of welding, in order to avoid electric shock, the welder must have good workwear, all wires must be removed to a safe place. On the site, a large number of welding works are carried out by the master of this site should carry out fire safety measures and introduce

employees in the course of affairs, also the master must have a TB log where all employees of the site must sign it will say that the master

this site held an event.

3.5 Standardization and Certification in Welding

Welding, as a dangerous and harmful process, should first of all be subject to technical regulation. Technical regulation - legal regulation of relations in the field of establishing the application and fulfillment of mandatory requirements and products, the production process,

operation and storage, sales of products. Technical regulation involves two levels: safety and quality. Safety requirements

are mandatory for all organizations and will be reflected in technical regulations .

Technical regulations of two types: general and special. Technical regulations - this document establishes the requirements for technical control objects mandatory for application and testing. Standardization - activities to establish rules and characteristics for their voluntary and repeated use, aimed at achieving decency in the fields of production. Certification - forms carried out by the certification body confirming the compliance of objects with the requirements of technical regulations with the provision of standards and the terms of contracts. Currently, welding has taken a leading place among technological processes in the manufacture and construction of a large number of steel structures of hazardous industries controlled by technical supervision bodies. Oil and gas pipelines, steam and hot water pipelines, high pressure boilers, oil storage tanks, cracking and synthesis columns, handling equipment; steel construction and bridge construction structures, spacecraft and water ship units, reactor units, electronic instruments and much more are produced with

application of modern welding methods. A significant improvement in product quality can be achieved through the introduction of a quality management system and independent certification of production. Welding should be considered as a special process, when the final result cannot be fully verified by subsequent control, testing of the product, and sometimes defects can be detected only during the operation of technical devices. Following the world trends in the development of certification systems in the field of welding production, in Russia in 1992 at the initiative of MSTU named after N.E. Bauman, a joint decision of the Presidium of the Russian Academy of Sciences. Ministry of Science, Higher Education and Technical Policy of the Russian Federation ,

Gosgortekhnadzor of Russia, Gosatomnadzor of Russia and Gosstandart of Russia established the National Certification Committee for Welding Production

(National Monitoring and Welding Agency - NACS). He was tasked with developing rules and procedures for certification (certification) of welding production, as well as creating a system of independent certification centers in all regions of Russia.

certification of welding production (ACS), developed by the NAKS, is based on the principles of independence and priority of requirements of technical supervision bodies. Initially, SASv envisaged coordination of its activities by state executive bodies represented by Rostekhnadzor (See: Aleshin A.P., Pulikovsky A.P. System of certification of welding production. - M.: NAKS, 2007. C. 2-5.). The human factor plays a crucial role in ensuring the quality of products. Therefore, the efforts of the NAKS were primarily aimed at creating requirements for assessing the conformity of welders and welding specialists. Resolution of Gosgortekhnadzor of Russia dated October 30, 1998 No. 63 approved the Rules for certification of welders and welding specialists (PB 0327399). In connection with the need to expand the system of certification of welding personnel for other types of facilities,

as well as welding methods not specified in PB 0327399 were developed and approved by the Decree of the State Gortekhnadzor of Russia dated June 25, 2002 No. 36 (registered by the Ministry of Justice of Russia on July 17, 2002, registration No. 3587) "Technological regulations for certification of welders and welding specialists (RD 0349502)." RD 0349502 describes in more detail the procedures for personnel certification, which is especially important for the legally regulated field of welding processes. Welding materials, equipment and technologies are among the important elements of welding production that ensure the stability of the quality of production of structures. NAKS together with leading specialists in

Welding industry developed procedures for certification of welding materials (RD 0361303), welding equipment (RD 0361403) and welding

technologies (RD 0361503). These regulatory documents regulating the procedures for certification of welding production were put into effect by resolutions of the State Gortekhnadzor of Russia dated June 19, 2003 No. 101,102 and 103, respectively, registered by the Ministry of Justice of Russia.

Conclusion

During the course design process, I was given the task of developing the process of assembling and welding the case.

This project has developed a fundamental technology for manufacturing a given welded structure taking into account the modern level of metallurgical and welding equipment.

Taking into account the requirements of regulatory and technological documents, the optimal seam structural elements, welding materials providing high quality of welded joints, the minimum level of residual welding stresses and deformations, the possibility of using equipment testing and availability for non-destructive testing were selected.

Reasonable selection of assembly and welding equipment was made.

The technology of manufacturing a given design using automatic welding under flux has been developed. The use of such a welding method is more expedient and techno/logical.