Advanced Structural and Technological Method of Reducing Distortion in Thin-Walled Welded Structures.

Piotr Horajski,Stanislaw Legutko,Pawel Kaldunski,Radoslaw Patyk,Leon Kukielka,Lukasz Bohdal

doi:10.3390/ma14030504

Piotr Horajski, Stanislaw Legutko + Show 4 more

Open Access

https://doi.org/10.3390/ma14030504

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Abstract

The article presents an innovative method of reducing welding distortions of thin-walled structures by introducing structural and technological changes. The accuracy of the method was demonstrated on the example of welding the stub pipes to the outer surface of a thin-walled tank with large dimensions, made of steel 1.4301 with a wall thickness of 1.5 × 10−3 (m). During traditional Gas Tungsten Arc Welding (GTAW), distortions of the base are formed, the flatness deviation of which was 11.9 × 10−3 (m) and exceeded the permissible standards. As a result of structural and technological changes, not only does the joint stiffness increase, but also a favorable stress state is introduced in the flange, which reduces the local welding stresses. Numerical models were developed using the finite element method (FEM), which were used to analyze the residual stresses and strains pre-welding, in extruded flanges, in transient, and post-welding. The results of the calculations for various flanges heights show that there is a limit height h = 9.2 × 10−3 (m), above which flange cracks during extrusion. A function for calculating the flange height was developed due to the required stress state. The results of numerical calculations were verified experimentally on a designed and built test stand for extrusion the flange. The results of experimental research confirmed the results of numerical simulations. For further tests, bases with a flange h = 6 × 10−3 (m) were used, to which a stub pipe was welded using the GTAW method. After the welding process, the distortion of the base was measured with the ATOS III scanner (GOM a Zeiss company, Oberkochen, Germany). It has been shown that the developed methodology is correct, and the introduced structural and technological changes result in a favorable reduction of welding stresses and a reduction in the flatness deviation of the base in the welded joint to 0.39 × 10−3 (m), which meets the requirements of the standards.

Highlights

In mechanical engineering, welding is most often used as inseparable connections of components
The paper presents typical problems occurring during TIG welding of stubs-pipes for thin-walled large-size tanks made of t = 1.5 × 10−3 (m) thick steel 1.4301
A new, innovative method of reducing welding deformations has been developed for the construction of thin-walled large-size tanks with stub pipes by using a new base geometry with an opening with a flange and performing an additional technological operation–flange extrusion

Summary

Introduction

In mechanical engineering, welding is most often used as inseparable connections of components. In the case of large-size welded steel structures, mainly of low stiffness, the basic problem is their deformation in the form of permanent displacements and deformations. When designing and producing large-size structures, prototypes are usually used. In such cases, it is not possible to perform tests or introduce changes to production. CAE methods are rarely used to design technologies, especially those with a complex course of physical phenomena. The reason is that the construction of numerical models of technological processes is complicated and goes beyond the scope of typical engineering knowledge. Welding of elements is a difficult process to design, because the connected parts are subjected to complex thermal phenomena and structural changes

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