Contact Welding Coursework

Contents

INTRODUCTION

1. CONSTRUCTABILITY

1.1 Characteristic of the article

1.2 Welding mode parameters. Welding cyclogram

1.3 Welding Process

2. CALCULATION OF TRANSFORMER PARAMETERS

2.1 Initial data for transformer calculation

2.2 Calculation of secondary circuit resistance of the machine

2.3 Transformer primary winding diagram

2.4 Core section

2.5 Geometric dimensions of transformer

2.6 External characteristics of the machine

3. DESCRIPTION OF PLANT OPERATION

3.1 Description of operation of the accessory

3.2 Schematic Pneumatic Diagram

4. OCCUPATIONAL SAFETY

5. TECHNICAL AND ECONOMIC INDICATORS

REFERENCE REGULATORY DOCUMENTS

Appendix A (reference) Bibliographic list

Summary

The purpose of the work is to get acquainted with the physical essence and technological features of electrical contact butt welding, with the device and operation of the butt welding machine, to select technological modes for welding of given samples and to build a device for increasing the productivity and quality of welding. As a result of the work, the parameters of the welding mode and the transformer were calculated, the welding cyclogram, the processability of the welding process were described, and the external characteristics of the transformer and the design of the appliance were built.

Introduction

Butt welding is a welding process in which parts are connected along the entire plane of their touch, as a result of heating. It is a type of contact welding, therefore, its technology is based on the thermal impact of electric current according to the Joule-Lenz law and the compression force of welded parts. Depending on the metal grade, the section area of the parts to be connected, and the quality requirements of the joint, butt welding can be performed in several ways: resistance, continuous melting, and heated melting. As product material SCh25 cast iron and cross-sectional areas of the connected details up to 100000 mm², we choose butt welding as continuous melting.

Fusion welding is used to connect parts with a section area of ​ ​ up to 100,000 mm ², such as pipelines, reinforcement of reinforced concrete products, butt joints of shaped steel. This method produces various long-length articles, closed-form parts, as well as complex parts from simple blanks.

During butt welding with continuous melting, the parts are gradually brought closer when the current source is turned on. The end faces touch along separate protrusions. Since the area of the resulting bridge contacts is very small, due to the high density of current flowing through them, they are quickly heated and melted. Part of the metal explodes and in the form of sparks flies out of the joint. Contaminants from the surfaces of the blanks are also present in the emitted melt. Further convergence of parts leads to the formation and melting of new jumper contacts. As a result of this continuous process, a layer of liquid metal is formed at the ends. After the ends are melted over the entire surface, precipitation is carried out. The ends quickly get closer with great effort. At the same time, the liquid metal with oxide films is extruded from the joint outward and, when solidified, forms a grat, which is usually removed in hot form.

Description of plant operation

Description of operation of accessory

The butt welding process includes a welding operation and a number of auxiliary operations for maintaining and moving the weld assembly. The assembly and welding device ensures quality and efficiency of welding. The function of the assembly and welding fixture is to remove the grate after welding.

Pipes are supplied to the butt machine using drive trolleys with lifting prismatic bases. Mechanism for lifting prismatic base is made in form of screw-nut transmission. Pipes are installed in current-carrying jaws and clamped, thus our blanks are fixed. Clamps are designed taking into account shape of parts, required accuracy and speed of their installation with provision of reliable fixation of parts and supply of current to them. Knives are installed on movable clamps for removal of grat from solid alloy VK8. For maintenance and repair, the knives are removable and it is possible to adjust their vertical position. The welder then presses the start button to start the welding cycle. When welding is finished, grat is removed. Internal clamp is removed by means of TKUS1 installation, external clamp is removed by means of uncompressed movable clamp, at that the article is fixed by fixed clamps. After removing the grat, the sponges are expanded and the products are removed from the machine using a stacker.

Schematic pneumatic diagram

Compressed air from the network is supplied through the HV valve to the HP moisture separator and is distributed through two channels, in each of which the CG reducers and MR oil sprinklers are installed. Through the first channel, air with the help of pneumatic distributors P enters pneumatic cylinders C of butt machine clamps. Throttle valves are installed in channels that lead to lower chamber of pneumatic cylinders, which ensures smooth process. The second channel is again divided into two channels, where air is supplied to the two installations. The first installation is a stacker, which is installed under the pipe. With the help of a pneumatic cylinder, the stacker shelves rise up until the pipe support point is on them. Since the shelves are installed at an angle (the angle of inclination is not more than 300), the pipe rolls down it and leaves the clamps of the welding machine. The second unit is an internal grating device. Using pneumatic cylinders, the grating rod changes its length. Air inlet to pneumatic cylinders in the second channel is similar to the first one.

Technical and economic indicators

The main technical and economic indicators characterizing the efficiency of butt welding use: labor intensity (productivity), the cost of manufacturing welded assemblies, metal capacity of welded products, electricity costs and other auxiliary materials.

Labor intensity is determined by the time spent on the welding operation - piece time. It is also necessary to take into account the cost of time for surface preparation (10% tps), control (10 15% tps) and operations for processing nodes (10 15% tps).

Knowing the unit time (1 min), the discharge of work, the number of simultaneously employed workers and the current tariff grid, you can find a monetary expression of the labor intensity of the welding operation.

The manufacturing cost of the entire welding unit also includes energy costs [5].