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Customer (Date post:18/03/2014)
What is non-submergence? Causes and remedies?
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Answer by:

Non-submerged welding is a serious defect in welded connection that may cause cracks.

Non-submerged welding occurs in an angle of a weld, a welding edge or in middle of weld layers.

Welding structure is mostly destroyed by non-submerged welding.


Causes and remedies:



- Welding edge provided is inappropriate. Its beveling angle is too small

- Welding current is small or welding speed is so fast

- The angle of welding rod is improper and the way of placing electrode is incorrect.

- Length of arc pole is excessive

- Make welded connection clean before welding. Increase beveling angle and weld clearance.

- Increase welding current and lower welding speed…




Customer (Date post:17/03/2014)
What is slag mixture? Cause and remedies?
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Answer by:

Slag mixture is a defect, which is easy to occur in welds, weld slag and non-metallic impurities. It may appear on surface of welds or at root of welds…

Any weld with slag will influence significantly on impact strength and flexibility of weld metal and decrease working capacity of welded connection under dynamic load.


Cause and Remedies:



- Welding current is small, insufficient heat quantity to make metal melted and make slag unable to escape from welding area.

- Welding edges are not clean or slag is not removed completely during tack weld or multi-layer weld.

- Welding angle is not reasonable and welding speed is high.

- Cold speed is so fast, making slag unable to escape.

- Increase welding current appropriately. Execute welding by short arc and increase arc stopping time

- Clean workpiece before welding. Remove slag on tack welds and weld layers.

- Change properly the angle and method of moving welding rod. Lower welding speed to prevent slag from mixing into welding area or from melting ahead of welding area.


Customer (Date post:17/03/2014)
What is blowhole? Cause and remedies?
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Answer by:

Blowhole is a phenomenon in which the air in weld metal cannot release when such weld metal becomes solid.

Blowhole may appear inside or on surface of a weld, or focus or disperse inside a weld.

The existence of blow hole in a weld diminishes working section, load bearing strength and tightness of welded connection.


Cause and remedies:



- Carbon content in basic metal or workpiece is so high.

- Welding materials get humidity and surface of welding components is dirty, oily, rusty, vaporous,… during welding.

- Arc length is excessive and welding speed is high




- Use welding materials with low carbon content

- Before welding, keep welding materials dry and their surface clean.

- Keep length of arc pole short and lower welding speed.

- Not remove weld slag immediately after welding. Extend heating period of welds.

- For MIG/MAG welding, use shielding gas properly with high purity. Gas supplied for welds must be sufficient during welding.

Customer (Date post:17/03/2014)
What is a crack? How temperature at which the crack occurs? How such crack is discovered?
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Answer by:

A crack is one of most serious defects of welded connection. It may occur on surface or inside a weld as well as in thermal influence area.

The crack may arise at different temperatures:

- Hot crack: arising from crystallization of welded connection when temperature is relatively high (over 1,000oC).

- Cold crack: arising after completion of welding process and at below 1,000oC. Cold crack may appear after several hours or days.

Cracks have different sizes, including microcrack or rough crack. Rough cracks destroy structure after working. Microcracks gradually extend to form rough cracks during working of structure.


Cracks can be discovered visually or by a magnifier for rough cracks on surface of welded connection. For microcracks inside welds, they can be discovered only when such testing methods as ultrasound, magnetic test, radiography,…

Customer (Date post:17/03/2014)
How are deffects of weld?
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Answer by:

Errors of form, size and metal distribution of welding structure in comparison with design standards and technical requirements that reduce strength and working capacity of such structure are called welding defects.

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