Welding & Metal Fabrication: Testing, Fatigue & Failure

Hydrogen cracking may also be called cold cracking or delayed cracking. The principal distinguishing feature of this type of crack is that it occurs in ferritic steels, most often immediately on welding or a short time after welding. In this issue, the characteristic features and principal causes of hydrogen cracks are described.

Techniques and practical guidance on the avoidance of hydrogen cracks are described.

Lamellar tearing can occur beneath the weld especially in rolled steel plate which has poor through-thickness ductility. The characteristic features, principal causes and best practice in minimising the risk of lamellar tearing are described.

The characteristic features and principal causes of porosity imperfections are described. Best practice guidelines are given so welders can minimise porosity risk during fabrication.

The characteristic features and principal causes of slag imperfections are described.

The article in the September/October issue of Connect established some basic facts about fatigue and the statement was made that a welded joint exhibited no clearly established fatigue limit as in an unwelded component. In this article we will be looking at some of thereasons for this behaviour.

This second article on shape imperfections refers mostly to fillet welds but there are two additional butt weld imperfections that require some comment.

The hardness of a material can have a number of meanings depending upon the context, which in the case of metals generally means the resistance to indentation. There are a number of test methods of which only the Brinell, Vickersand portable hardness testing will be covered in this article.

The previous article dealt with the conventional Vickers and Brinell hardness tests. This second article reviews micro-hardness and portable hardness testing.

A video clip from Corus showing what non-destructive testing (NDT) is and the methods commonly used in non-destructive testing of welded steel components to ensure there is no unacceptable defects which can affect the mechanical properties of metallic component. Processes include magnetic particle testing and ultrasonic testing.

See feature article beginning on page 26.

This article describes the characteristic features and principal causes of lack of sidewall and inter-run fusion. General guidelines on best practice are given so that welders can minimise the risk of imperfections duringfabrication.

The characteristic features and principal causes of incomplete root fusion are described. General guidelines on 'best practice' are given so welders can minimise the risk of introducing imperfections during fabrication.