DEVELOPMENT OF TECHNOLOGY AND CREATION OF TEST EQUIPMENT FOR PRESSURE WELDING OF HIGH-LOAD THIN-WALLED HETEROGENEOUS STEEL TUBULAR PARTS

Abstract

Introduction. Magnetically impelled arc butt welding (MIAB) method differs from the existing arc methods by high productivity, stable quality of welded joints, high degree of mechanization and automation of the technological process and so on. Welding is performed automatically, which significantly reduces the influence of the
operator-welder on the quality of welded joints. The optimal values of the magnetic field induction components for thin-walled tubular parts with a diameter of 212 mm are determined. The basic technological parameters on welding of tubular details in stationary conditions are defined, it is: qualitative preparation of end faces of pipes;
optimal distribution of induction of the control magnetic field (CMF); arc voltage; the magnitude and order of programming the welding current; the rate of closure of the arc gap in the process of upset. The influence of liquid metal melt in the arc gap during upset on the formation of welded joints of pipes is determined. Metallographic
studies showed no defects in the weld line and a relatively small area of thermal impact. Mechanical properties of welded joints at the level of mechanical properties of the base metal. Studies have been conducted to determine the
parameters that affect the stable movement of the arc along the thin-walled edges of tubular parts and the influence of liquid metal melt in the arc gap during heating on the formation of welded joints.
Problem Statement. Pipes of small diameters (up to 220 mm) are used in various industrial enterprises and construction of pipelines. The work requires high-performance automatic welding methods that allow obtaining stable and reliable welded joints.
Purpose. The purpose is to raise labor productivity and to save materials by using equipment and technology for press welding of magnetically controlled arc of thin-walled tubular parts.
Materials and Methods. Steel thin-walled tubular parts with a diameter of 42mm and 212 mm, with a wall thickness of 2.5… 3 mm were used for research on press welding. To create a control magnetic field, magnetic systems for tubular parts with a diameter of 212 mm were developed. Experimental welding was performed and
samples of welded joints of pipes with a diameter of 212 mm with a wall thickness of 3 mm were investigated. In the course of the research, the main parameters are recorded and the welding process is controlled by computer.

Results. The main technological parameters: preparation of pipe ends; magnitude and distribution of control magnetic field induction; the arc voltage; the magnitude and order of programming the welding current; the rate
of closure of the arc gap during upset, which affects the formation of welds have been determined. The experimental industrial technology for welding of thin-walled tubular details with a diameter up to 212 mm for the
purpose of its industrial use and the concept of the welding equipment has been developed, patents for the invention have been received.
Conclusions. The mechanical and metallographic tests have shown that the properties of welded joints are at the level of the properties of the base metal. The use of press welding technology for tubular parts increases productivity and automates the welding process. The influence of the bandwidth of the liquid molten metal in the arc gap, while heating, on the formation of welded joints of pipes has been experimentally established. The main technological parameters and their influence on the quality of welded joints in the process of heating, the ends, and the upset of thin-walled tubular parts have been determined. Experimental industrial technology for press welding of thin-walled tubular parts has been developed and industrial tests have been conducted, in accordance with the customer's requirements.