Welding Procedure

There is no denying the fact that welding is one of the most important processes or techniques used in the fabrication and manufacturing of different products.

You need to use welding, be it tank fabrication, window frames, vehicle parts, or pipelines.There are limitless applications of welding. So, it’s important to make sure that the weld is done right because if not, it affects the whole manufacturing process, and your final product will not be good.

But how to check welding quality? Well, there is a welding quality control checklist you need to tick mark while inquiring about each welding step during fabrication.

We will tell you everything about how you can check the quality of welding and what are the steps to follow.

However, before starting the actual welding inspection information, some prior knowledge about different terms is very important.

What is Welding Inspection?

It is a series of quality assurance checks done by a welder or a related professional in between and after the welding process is done. It ensures that the fabrication is high quality and safely done besides making sure that there is no fault in the finished piece.

We all know that welding is a part of multiple industries, so it is important to check the welding quality and do a thorough inspection for the safety of welders and civilians alike.

Welding inspection experts are needed in a number of industries like:

• Military
• Manufacturing
• Automobiles
• Aerospace
• Construction
• Ship and boat building
• Oil and gas sector
• Amusement parks
• Railroads

What is the Importance of Welding Inspection?

We have already mentioned that you need to check welding quality before, during, and after the whole welding process to ensure safety at every step.

If the welding inspection is performed well, it means the final piece will have no discontinuities, and you can send it to the next stage of fabrication.

There is a difference between the purpose of checking the welding quality before and during and after welding. The former welding inspection is done mainly for the safety of welders and workers.

The inspection done after the welding is for the safety of the civilians and to check overall the deformities of the subject piece.

Another aspect of welding check quality control is the annual inspection. It is basically for the high stress welding assignments and is often considered as a separate safety protocol in different industries.

Welding is a tricky and dangerous job and the ones doing it are at constant risk of burns and other dangers. The light and heat emitted during the welding process is very dangerous for the eyes and skin and can cause severe eye damage and burns if there are no precautions taken.

That is why it’s a protocol for the welders to wear goggles, masks, fireproof jackets, and gloves to reduce heat and light exposure.

Besides, there are other risks associated with welding like inhaling hazardous gasses/fumes and working in harsh environments as some of the welding work is underwater or factories in confined spaces.

Weld inspectors make sure that the welders or workers working nearby are following all the necessary safety protocols. They also make sure that the rules and regulations are up to date and are authorized by a legal body.

American Welding Society, besides some other certified boards, educates the welding inspectors and gives certifications to only those inspectors who are well versed with welding symbols, safety codes, testing, and welding designs.

What are the Stages of Welding Quality Check?

There are three stages of welding quality inspection. Let’s see what these are and how they benefit the whole process:

There are several techniques to check welding quality that you can use at every step of welding inspection.

We have explained some of them in detail with their use cases further in the guide.

What are Different Types of Welds and What are Their Faults You May Inspect?

It is a known fact that welding is done to join two or different metal pieces/sheets together so they have joints. Based on these joints, there are multiple types of welding.

Welding quality checking is never complete if you don’t understand the types of welding. So, it’s important to learn about the basics, especially if you’re a weld inspector or someone planning to become one.

Let’s see what these types are and how to identify their faults!

1. Lap Joint Welding

Lap Joint

It is a type of welding when you weld two metallic pieces in an overlapping position, one being on top of the other. This weld is pretty helpful to cater sheets of variable thickness. However, welders still use it for same size and thickness of metal sheets.

2. Corner Joint Welding

Corner Joint

When two metals are fused perpendicular to each other or at 90 degrees to one another so that the intersecting point makes an L shape. You can use corner joint welding for shipping containers, boxes, frames, and other applications.

3. Butt Joint Welding

Butt Joint

It is the most frequently used welding technique and most easiest one. In it, two pieces are joined side by side along the same plane. You can customize this weld in different ways according to the requirements. Welders opt for this method for pipeline and large structure welding.

4. Tee Joint Welding

Tee Joint

Well, it is evident from the name that it is a type where two pieces are welded perpendicular to each other exactly at the center to form a T in the middle. Tee joint welding is the best for joining tubes or pipes to a stable base.

5. Edge Joint Welding

Edge Joint Welding

Edge joint welding is a type when you fuse two metals through their edges that are nearly parallel or exactly parallel to each other. Unlike other types, this one doesn’t give a strong weld and hence cannot be used for high-stress welding. You can make use of this welding type for supplemental support inside structures.

Common Welding Faults

Proper inspection techniques and following a complete welding quality control checklist is vital to make sure that you don’t neglect any mistake, even if it is a minor one.

Some of the issues are very evident and can be seen clearly by just looking at them. They are beginner’s mistakes.

However, many are not visible clearly to the naked eye, so you have to go through a series of quality assurance steps to confirm them.

1. Corrosion

Corrosion

Corrosion is inevitable and can be seen in metals in one way or the other. The same is the case with welds. Welds are quite exposed to corrosion. Though it’s unavoidable, you can control it to some extent by inspection to determine the extent of it at a certain weld.

Welders need to avoid microstructure discontinuities and excessive stress during welding. Also, it’s important to check metal degradation before welding to delay the exposure of corrosion.

2. Inadequate Fusion

Lack of Fusion

Inadequate fusion or lack of fusion is also called overlap. It happens when you’re joining two metals and the metal starts flowing on the other or base instead of joining with it.

Some common causes of this are:

• Dirty plates
• Low temperature than required
• Improper fluxing

3. Burn-Through

Burn-Through

This weld fault is when the base metal melts and creates a hold spreading to the welded seam. It is also called melt-through and is a rookie mistake.

The weld inspectors and the manufacturer reject this type of weld in the beginning on their own.

Burn-through parts are sometimes accepted if the hole is not deep and is not wide. Still, they should be regularly inspected from time to time.

4. Lamellar Tearing

Lamellar Tearing

Lamellar tearing is when weld lines or cracks appear on the base metal when you apply high stress. You can most often see this in butt and tee joint welding.

There can be the following three causes of this fault:

• Wrong welding orientation
• Accidental excessive stress
• Incorrect use of metals

5. Incomplete Penetration

Incomplete Penetration

When the two metals don’t join together at the root, then this fault is known as incomplete penetration. This one basically happens when the joint style is wrongly selected.

Its causes are:

• High travel rate
• Too big or too small root opening
• Inaccurate angle/joint

6. Slag Inclusion

Slug Inclusion

This welding mistake occurs when you see a nonmetallic hardened layer on the weld. You can mostly see this in SAW, SMAW, and flux-cored welding. It’s essential to remove this layer from the weld. It will spread and make small pours on the weld.

7. Porosity

Porosity

When the weld pocket has more gas instead of solid metal, it creates tiny pores on the metal weld. These gases appear as a result of chemical reactions during metal cooling or welding.

The most frequent cause is overheating.

8. Undercutting

Undercutting

Undercutting means the base metal burns at the toe of the weld. It happens because of a lengthy arc and overheating.

How to Check Welding Quality?

There are two main ways to check welding quality: non-destructive and destructive. We will discuss these two in detail as each has different smaller categories.

Non-Destructive Welding Inspection

This inspection is done without damaging or changing the welded pieces and can be performed by the welder himself instead of a separate inspector.

Non-destructive inspection is accurate but it needs only professional inspectors to perform and expensive devices. You can do this in the following ways:

• Visual Inspection

The most cost-effective, quick, and easiest welding quality check is through visual inspection.

The welder or inspector look thoroughly to point out any physical deformity such as melt-through, cracks, or undercutting.

Visual inspection is a good technique to check for discontinuities regularly on different materials.

However, the drawback is that it cannot detect porosity and slag inclusions as they are internal faults and human eye cannot process deeper mistakes.

• Magnetic Particle Weld Inspection

Certain magnetic probes are placed at the surface of the metal and a magnetic field is established around the weld.

If the magnetic particles start accumulating at these magnetic ends, it means there is a crack or some fault. If nothing happens, it means the weld is crack-free.

There are some limitations to this technique because you can use them for certain materials only and for some situations only. Otherwise, it is one of the best non-destructive inspection method.

• Liquid Penetrant Testing

This non-destructive technique helps detect very fine microscopic cracks on the welded surface that the naked eye cannot. It is also known as dye penetrant testing.

For this, a fluorescent dye/liquid is poured on the metal surface where it’s welded and allow it to dry.

After drying, the dye will appear where there are cracks or imperfections against the material color.

It is a beginner-level welding quality checking technique and cannot detect internal faults just like visual inspection.

• Radiographic Weld Inspection

Unlike the techniques mentioned above, this one identifies not only surface deformities but also internal ones.

Similar to the medical X-ray of human beings, a photographic film displays the internal faults when X-rays are passed through the welded area.

Based on discontinuities, you get variable shapes and sizes of graphs indicating porosity and cracks.

Welders cannot perform this test since it requires safety protocols, and only professional inspectors can perform it.

• Ultrasonic Weld Inspection

During this technique, a high powered frequency is passed through the weld.

If it finds any discontinuity along its path, it reflects back to the sender, known as a transducer. This reflected signal is then read and interpreted to identify the type and size of the weld fault.

• Destructive Welding Inspection

It is the opposite of a non-destructive technique. Here, the weld is destroyed to check the internal and mechanical mistakes.

There are several reasons why this technique is used, including analysis of weld failure, inspection of sampling, research inspection, and to obtain training certificate.

• Macro Etch Weld Inspection

For macro etch testing, a small chunk of welded surface is scraped as a sample and polished carefully. Then, it is etched from the center and reacted with a mild acid.

This etched sample piece provides a full internal biopsy and helps identify various cracks or fusion failures. This technique is also referred as cut and etch technique.

• Guided Band Test

This test determines the structural integrity and ductility of the different welded joints. There are dozens of bend tests and most of them are used as a part of training programs.

• Transverse Tension Weld Inspection

It basically determines the tension per unit in any cross-sectional area of the metal where welding is done. In other words, it determines the breaking point of different welds.

Let’s move to the welding quality control checklist that you need to follow no matter what testing technique you use.

• Welding Quality Control Checklist

Though there are custom steps in every welding quality control checklist based on the specific task and the material, there are some general things included in every checklist.

Checklist for Pre-Weld Inspection

• Check the blueprints and all necessary documents prior to welding.
• Inspect that all the materials and tools are available.
• Look for the physical appearance of the materials.
• Make sure that the welding space and tools are clean.
• Ensure the welder knows how to weld safely or qualified.
• Preheat the welding energy source.

Checklist for During-Weld Inspection

• Keep in check that the safety protocols are followed during welding.
• Monitor temperature, heat input, voltage, and energy source during welding.
• Check every welding pass carefully.
• Visually inspect any discontinuities.

Checklist for Post-Weld Inspection

• After welding, inspect for cracks or other deformities.
• Perform non-destructive and destructive tests if necessary.
• Look for the length and thickness of the weld.

Conclusion

Welding is undoubtedly one of the most important processes in the fabrication of different things, like storage tanks, windows, frames, pipelines, and so many others. There are dozens of applications, including the oil & gas sector, aerospace, automobile, construction, military, and so many other industries.

It’s important to check the welding quality to make sure the finished pieces are perfect before going to the buyer. So, how to check welding quality? There are three stages to check welding quality which are before, during, and after weld inspection stages. A professional weld inspector performs various non-destructive and destructive tests to check cracks, porosity, slag inclusions, incomplete penetration, undercutting, and other faults.

By carrying out inspections throughout the welding process, manufacturers can detect problems early, maintain consistent weld quality, and ensure the finished product meets the required standards before delivery.