The CWI examination contains three parts, each two (2) hours long. Increasing the carbon content of steel decreases the likelihood of cracking problems. Porosity is considered to be the most critical discontinuity. Undercut can be caused be a slow travel speed.

What weld discontinuity is considered to be the most severe?

Cracks – Cracks are the most detrimental discontinuity for the integrity of a welded connection. Cracks, in any amount, will constitute a defect with very few exceptions.

Which is strongest fillet joint?

TIG welding produces the strongest type of weld.

What causes arc strikes?

Arc strike

This is a defect caused by instantaneously striking an arc on the base material. In other words, an arc strike is a spot of failed arc ignition which was not fused by subsequent welding and remained on the base material. Arc strike may be the cause of cracking in the base material.

What part of fillet weld that is melted during welding?

Fusion Zone

The zone of base metal melted during the weld (as determined with a cross-section). Sometimes referred to as filler penetration.

4 Types of Welding Explained: MIG vs TIG vs Stick vs Flux Core

What is throat of a weld?

The throat is the shortest distance from the root to the face of the weld. To measure this dimension in a regular mitre or flat faced fillet weld is relatively simple. The shape is that of an isosceles triangle, the throat being 0.7 of the leg length.

What is the leg of the weld?

Leg– The distance from the joint root to the toe of the weld. Face– The exposed surface of a weld on the side from which welding was done.

What causes a weld to crack?

The major cause of a crack is when internal stresses exceed the strength of the weld metal, the base metal, or both. And once a focal point for these stresses—that is, a stress riser—develops and accumulates, a crack can propagate.

What causes welds to fail?

A weld that is too small or too short for the application can fail from tension, compression, bending or torsional loads. If a weld is made to be in an application where a cyclical load is going to be applied, it will be beneficial to consider a filler metal option with increased impact toughness and ductility.

What causes bad welding?

Weld defects are often caused by improper technique or parameters, such as poor shielding gas coverage or incorrect travel speeds.

Which weld is the strongest?

TIG welding is often considered the strongest weld since it produces extreme heat, and the slow cooling rate results in high tensile strength and ductility. MIG is also an excellent candidate for the strongest type of weld because it can create a strong joint.

Which welding joint is the weakest?

The minimum cross-section of the fillet is at the throat. Therefore the failure due to tensile stress occurs at the throat section. Thus the weakest area of the weld is the throat.

Which type of corner joint is the strongest welding?

Open Corner Joint

Among corner joint welds, this type is the strongest weld joint. For welding corner joints on heavy plates, open corner joints are the best choice, because joints of high strength are possible.

What are the 3 most common defects in welding?

Among the commonly known welding defects, incomplete penetration and fusion, porosity and slag inclusions are the most common to affect welding strength.

What are the major discontinuities that affect weld quality?

Weld discontinuities can be defined as "an interruption of the typical structure of a weld, such as a lack of homogeneity in the mechanical, metallurgical or physical characteristics of the weld." Weld discontinuities include porosity, slag inclusions, incomplete fusion, incomplete joint penetration, excessive melt- ...

What is porosity in a weld?

Porosity is the presence of cavities in the weld metal caused by the freezing in of gas released from the weld pool as it solidifies. The porosity can take several forms: distributed. surface breaking pores.

Where do weld failures occur?

Failure of welded construction steel components can occur due to inappropriate design, wrong steel choice or quality, substandard welding processes and through defective maintenance. Welded constructional steel joints in particular are highly sensitive to issues of fatigue, weld corrosion and/or weld quality.

Is it possible to break a weld?

Usually, you can undo welding using torch cutting, plasma cutting, drills, grinding or circular saws, or oxy-acetylene torches. There are a couple of ways to perform this other than just applying a strong force to the weld. The procedure of removing welds relies on the weld type you would like to undo.

What are 5 welding defects?

Following are the types of welding defects:

• Porosity and Blowholes.
• Undercut.
• Weld crack.
• Incomplete fusion.
• Slag inclusion.
• Incomplete penetration.
• Spatter.
• Distortion.

Can you weld on top of weld?

It should be remembered that welding over weld metal is actually a very common occurrence. Multi-pass welds after all are manufactured by welding over weld metal! There are also many accepted procedures in which welds overlap.

Where do stress cracks usually start in a weld?

Heat Affected Zone Crack

A HAZ crack can originate at the toes of the weld or a few millimeters from the weld altogether. The most common causes for this type of crack are: excess hydrogen, high residual stress levels on the weld, and high carbon content on the base material.

How do you prevent cracks in welding?

Hot Crack: How it occurs and how it can be prevented

Use lower heat input. The use of lower heat input increases the cooling speed of the weld metal, which minimizes the time spent in the brittle temperature range. ...

Use larger groove radius. ...

Use ferrite-controlled filler metals.

What is a root of a weld?

The points at which the weld metal intersects the base metal and extends furthest into the weld joint.

What are the components of a weld?

There are three main components needed to create a weld. These are: A heat source such as an electric arc, a flame, pressure, or friction. The most common heat source is an electric arc.

What is a root face in a weld?

The measurements of the portion of the groove face within the joint root.

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