What are the defects that can be identified by NDT techniques?

This method allows for the detection of corrosion, misalignment, damage, cracks, and more. Visual testing is inherent in most other types of NDT as they will generally require an operator to look for defects.

What is defect in NDT?

Generally a defect can be defined as a region of a material or a structure that has different physical properties and existed from the start (construction defect) or a region who its physical properties has been altered compared to its neighborhood over time.

What is NDT techniques?

NDT (Non-Destructive Testing) refers to an array of inspection techniques that allow inspectors to collect data about a material without damaging it. It refers to an array of inspection methods that allow inspectors to evaluate and collect data about a material, system, or component without permanently altering it.

What are the types of casting defects?

TYPES OF CASTING DEFECTS

Gas Porosity: Blowholes, open holes, pinholes.
Shrinkage defects: shrinkage cavity.
Mold material defects: Cut and washes, swell, drops, metal penetration, rat tail.
Pouring metal defects: Cold shut, misrun, slag inclusion.
Metallurgical defects: Hot tears, hot spot.

What are the common welding defects?

So below we’ll learn about the 7 most common welding defects, their types, causes and remedies.

Weld Crack. 1.1 Causes of cracks: 1.2 Remedies:
Porosity. 2.1 Causes of porosity:
Undercut. 3.1 Causes:
Incomplete Fusion. 4.1 Causes:
Incomplete Penetration. 5.1 Causes:
Slag Inclusion. 6.1 Causes:
Spatter.

What are different types of defects?

Following are the common types of defects that occur during development:

Arithmetic Defects.
Logical Defects.
Syntax Defects.
Multithreading Defects.
Interface Defects.
Performance Defects.

What are the two types of welding defects?

Welding defects are broadly classified into two categories, and those are: External welding defects (Defects occur on the upper surface of the welded work). Internal welding defects (Defects occur under the surface of the welded work).

How many types of welding defects are there?

three types

What are the 5 parameters of welding?

WELDING PROCEDURES

5 essentials for proper welding procedures. Correct electrode size.
1) CORRECT ELECTRODE SIZE.
2) CORRECT CURRENT.
3) CORRECT ARC LENGTH or VOLTAGE.
4) CORRECT TRAVEL SPEED.
5) CORRECT ELECTRODE ANGLE.
8 FACTORS to consider in selecting arc welding electrodes.

What is crack in welding?

Weld cracking refers to a depression left at the termination of a weld where the weld pool is left unfilled. Most forms of weld cracking result from the shrinkage strains that occur as the weld metal cools. If the contraction is restricted, the strains will induce residual stresses that cause cracking.

What causes porosity in welding?

Porosity is caused by the absorption of nitrogen, oxygen and hydrogen in the molten weld pool which is then released on solidification to become trapped in the weld metal. As little as 1% air entrainment in the shielding gas will cause distributed porosity and greater than 1.5% results in gross surface breaking pores.

How do you fix porosity in welding?

The best approach is to remove all of the material that has any trace of porosity. I sometimes do this with an abrasive cut-off disc, making a tiny slice in the weld, which removes the porous area.

How do you reduce porosity in welding?

5 Tips For Preventing Weld Porosity

Keep It Clean. The surface of your materials must be clean and dry.
Check Your Gas Flow. Monitor the flow from your gas shield.
Check Your Equipment. Hose maintenance includes making sure there are no leaks or kinks – that can affect the flow from your gas shield.
Calm Conditions.
Slow and Steady.

Can you weld over porosity?

If the porosity or any other discontinuity exceeds allowable limits it needs to be removed. Porosity does not “burn out”, it travels from weld pass to weld pass and never leaves the original weld pass. It must be removed by air carbon arc gouging and / or grinding.

How much porosity is acceptable in a weld?

How Much Porosity Is Acceptable In A Weld. When it comes to porosity, the American Welding Society dictates that the sum of the diameters of visible porosity should not exceed 3/8 inches, or 9.5 mm, in any linear inch of the weld, or exceed 3.4 inches or 19 mm, in any 12-inch length of a weld.

What are the sources of porosity?

Porosity is caused by the absorption of nitrogen, oxygen and hydrogen in the molten weld pool which is then released on solidification to become trapped in the weld metal. Nitrogen and oxygen absorption in the weld pool usually originates from poor gas shielding.

What is excessive spatter in welding?

MIG setups use electrode wire that bonds with the metal to form the weld, and spatter is the excess molten wire that bonds with everything else. Too much spatter can lead to downtime for cleanup and wasted materials. And, if it bonds with your workpiece it can be especially painful.

How do you reduce spatter?

MIG techniques As mentioned, consistency in wire speed minimizes spatter. Likewise, consistency in travel speed, along with a steady hand, ensures a clean weld. The more consistent you can be with the technique your weld requires, the less spatter will occur. Find the right angle, speed, and line, then stick to it.

Why do welders spatter?

Spatter is caused by several factors. The main factor is a disturbance in the molten weld pool during the transfer of wire into the weld. This is usually seen when the welding voltage is too low or the amperage is too high for a given wire and gas combination.

What are the effects of too high or too low current settings?

Voltage that is too high can cause premature failure of electrical and electronic components (e.g. circuit boards) due to overheating. The damage caused by overheating is cumulative and irreversible.

Why is undervoltage bad?

Undervoltage increases the operating current causing overheating which will shorten the life of the motor. Furthermore, large loads may fail to start if the starting torque is not sufficient due to low voltages. These stresses on the motor will eventually lead to mechanical failure.

How can voltage drop be reduced?

The simplest way to reduce voltage drop is to increase the diameter of the conductor between the source and the load, which lowers the overall resistance. In power distribution systems, a given amount of power can be transmitted with less voltage drop if a higher voltage is used.

How do you perform a voltage drop test?

To check the entire circuit, connect the meter positive lead to a clean spot on the starter motor case and the meter negative lead to the negative battery post. Crank the engine and note the reading. The voltage drop on the negative side should be 0.3 volts or less.