welding defects

Welding Defects

This article will cover some welding defects that are sometimes overlooked or not considered. Each welding project requires careful considerations. They include:

* The process, the type of welding i.e. stick, MIG, TIG.
* The composition of the base metal and thickness.
* The welding position, i. e. flat, vertical, horizontal, overhead.
* The weld joint and type.
* Electrical supply and equipment.
* And finally, the welding techniques to be used.


To minimize the chance of welding defects be sure to consider 1) the travel speed of the pass; 2) the size and type electrode; 3) machine settings; 4) make sure the welding is done in accordance with the plan and the current conditions.

Most of, or a great deal of, welding defects can be identified by the "naked eye." By knowing what is likely to produce welding defects you will learn how to avoid them. Production without defects saves time, materials, repair costs, and a decrease in productivity.

The two following causes for weld rejection should not be but are often overlooked 1) is the weldor proficient with the process being used? 2) is the welding rod supply up to standards? Use only properly stored, dried, and maintained welding rods. (Check out our entire inventory of Welding Rod Ovens.)

Welding defects include poor penetration. It's the failure of the welding rod and base metal to fuse together. It's caused by a root face that is too big; a root opening that is too small; an electrode that's too large; slow travel speed or a machine setting that's too low.

Poor fusion is the failure to blend the layers of weld metal together with the base metal. A lack of fusion is caused by " . . . failure to raise to the melting point of the base metal or the deposited weld metal," (Miller Electric Mfg. Co.) It's caused by improper fluxing; dirty plate surfaces; improper electrode size or type; wrong current settings. Electrodes that do not meet the storing, drying and maintenance specifications also cause it.

Undercutting is another problem that causes welding defects. It burns away the base metal at the toe of the weld. It's caused by a current adjustment that is too high; an arc gap that is too long or failure to fill up the crater completely with weld metal.

Porosity looks "sponge like," or like tiny "bubbles" in the weld. It's caused by gases being released by the cooling weld because a current setting is too high or arc is too long.

Slag inclusion occurs when the slag is not chipped and cleaned properly and then another pass is made over the top. To avoid, 1) prepare the groove and weld properly before each pass; 2) thoroughly clean in between passes; check the machine settings against those suggested by the manufacturer; 3) hold a smaller weld puddle.


What does a welding inspector does?

Welding Quality Control

WELDING SYMBOLS


SS 304-316

BASICS OF WELDING (FOR STUDENTS)

AIR CAR

Pre fabricated house

Alloy steel

What is micro air vehicle?

What are Alloy Steels?

Welding-alloy-steel needs first an answer to the above question. Alloy Steels are materials of special compositions, developed to permit the deployment of elevated mechanical properties that make them the most suitable selection for important applications like bridges, high rise towers and lifting equipment. By utilizing the most out of improved strength, hardness, ductility and impact resistance through innovative design, it is possible to build lighter structures with considerable economical gains.

Welding-alloy-steel, Heat Treatable, Quenched and Tempered Alloy Steels is a challenging proposition that needs understanding and preparation. These steels have 0.25 to 0.5%C, that is medium carbon content, and typically up to 5% total alloy content.

WELDING QUALITY CONTROL

In the fabrication or repair of equipment, tests are used to determine the quality and soundness of the welds. Many different tests have been designed for specific faults. The type of test used depends upon the requirements of the welds and the availability of testing equipment. In this section, nondestructive and destruc- tive testing are briefly discussed.

NON-DESTRUCTIVE TESTING

Non-destructive testing is a method of testing that does not destroy or impair the usefulness of a welded item. These tests disclose all of the common internal and surface defects that can occur when improper welding procedures are used. A large choice of testing devices is available and most of them are easier to use than the destructive methods, especially when working on large and expensive items. Visual Inspection Visual inspection is usually done automatically by the welder as he completes his welds. This is strictly a subjective type of inspection and usually there are no definite or rigid limits of acceptability. The welder may use templates for weld bead contour checks. Visual inspections are basically a comparison of finished welds with an accepted standard. This test is effective only when the visual qualities of a weld are the most important.

welding symbols