Common welding defects

Many different types of weld defects in the internal and external common weld defects can be summarized as follows:

First, the weld size requirements of sub-solder wave thick, rough shape, weld height is too low or too high to enhance, varying the width of weld and fillet weld wave unilateral or excessive settlement, etc. are substandard weld size requirements, because:

Bevel angle weldment assembly space improper or uneven.
Welding current is too large or too small, improper selection of welding specifications.
Win a speed differential, the electrode (or welded to) the angle properly.
Second, the crack

Shape of the crack tip sharp, severe stress concentration, and impact on the bear alternating load, a greater impact of static tension is the most dangerous of the weld defects. According to the causes can be divided from the cold cracking, hot cracking and reheat cracking and so on.

(Cold crack) means a crack generated below 200 ℃, which is closely related with the hydrogen, and its main causes are:

Thick piece of large selection of pre-heating temperature and slow cooling after welding measures inappropriate.
Inappropriate selection of welding consumable  .
Welded joints rigid, process unreasonable.
Produced near the weld and its rigid organization.
Inappropriate choice of welding specifications.
(Thermal cracking) refers to cracks generated more than 300 ℃ (mainly solidification cracking), and its main causes are:

Composition. Welding of pure austenitic steel, high nickel alloy steel and some non-ferrous metals prone.
Weld contains more sulfur and other harmful impurities.
Welding conditions and the inappropriate choice of joint shape.
(Reheat crack) is annealed to eliminate stress cracks. Refers to the welding zone of high intensity, due to post weld heat treatment or high temperature use, resulting in the heat affected zone of intergranular cracks, and its main causes are:

Annealing heat treatment to eliminate undue stress.
Alloy composition. Such as chromium molybdenum vanadium boron and other elements have a tendency to increase the reheat cracking.
Welding consumables, welding specification poor choice.
Structural design of large stress concentration caused by the irrational.
Third, the stomatal

In the welding process, due to the gas too late to escape in time or in the weld metal surface inside the hole formed, the causes are:

Welding electrodes  , flux drying is not enough.
Welding process is not stable enough, the high arc voltage, arc too long, too fast welding speed and current is too small.
Filler metal and base metal surface oil, rust, etc. is not removed.
Back technique is not used arc melting point.
Preheat temperature too low.
Arc and not to stagger the position of extinction.
Protect the poor welding area, pool area is too large.
AC prone to porosity, DC reverse the tendency of the smallest pores.
Fourth, welding tumor

In the welding process, the molten weld metal to flow outside the base metal without melting the metal formed on the tumor, it changes the cross-sectional area of ??the weld on the dynamic load disadvantage. The causes are:

Arc too long, the bottom welding current is too large.
Li welding current is too large, improper operation of Article swing.
Weld assembly gap is too large.
V. Crater

Ending at the seam in the obvious lack of meat and depression. The causes are:

When arc welding operations received improper extinction time is too short.
Aluminium welding wire and cut off the power at the same time, without first stopping and then power wire.
VI undercut

The edge of the weld arc melting the base metal, the weld metal has not been added and left gaps. Undercut the force weakens the joint section, the joint strength decrease, resulting in stress concentration, so that may lead to a breach in the biting edges. The causes are:

Current is too large, the arc is too long, inappropriate speed operation section, the arc heat is too high.
SAW low voltage, welding speed is too high.
Rod, wire tilt angle is not correct.
VII slag

In the weld metal fusion line positions exist within or inclusions. Influence on the mechanical properties of slag, the effect and the number and shape of the inclusions. The causes are:

Multi-layer welding, each welding slag is not removed.
Rust on the left thick weldments.
The physical properties of electrode coating inappropriate.
Bad solder layer shape, bevel angle poorly designed.
Weld pool width and penetration depth ratio is too small, too deep undercut.
Current is too small, too fast welding speed, the slag floats too late.
VIII, no penetration

Between the base metal or base metal and deposited metal between the local lack of fusion phenomenon. It generally exists in one side welding of weld toe, is very sensitive to the stress concentration, fatigue and other properties on the strength of greater impact. The causes are:

Poor design of the groove, the angle is small, blunt edge of a large, small gap.
Welding rod, wire angle is not correct.
Current is too small, low voltage, welding speed too fast, the arc is too long, there are magnetic blow and so on.
Weldments on thick rust is not removed.
When submerged arc welding side.
 

keywords: Mig Welding Wires