How can you Identify Good Weld vs Bad Weld

The welding process is one of the most efficient construction processes in the modern world, and not surprisingly, it is applied in most industries, from cars to aircraft. With careful choice of materials and a skilled weld operator, welds can be very safe.

But there are also risks involved with working with metal at high temperatures, so even small mistakes can become very dangerous.

Tips to Identify Bad Weld vs Good Weld

A good weld is one that has enough heat, the right amount of filler material and creates a sound bond between the base metal.

On the other hand, a bad weld does not have the proper amount of heat, has the wrong amount of filler material, and/or does not form a sound connection between the piece being repaired and the base metal. This article will focus on some of the factors that determine whether or not a weld is good /bad.

There are many types of defects a weld could have. Poor penetration, lack of fusion, mixed or dirty deposits, slag inclusions, porosity, and undercutting are just some examples. A weld that has any of these problems is a bad weld and needs to be corrected immediately.

Poor Penetration

Poor penetration can be a frustrating occurrence that any welder has experienced. The root cause is almost always poor technique by the welder, resulting in weld metal that does not completely fill the joint with fusion on both sides of the seam.

Incomplete penetration is caused by not holding the torch at a constant distance from the work or movement of the weld in either direction.

Another cause can be too much filler metal, which may prevent molten metal from flowing properly into both edges of the joint and leading to incomplete fusion on one side.

Lack of Fusion 

Incomplete fusion can occur for a number of reasons but is typically due to one of the following: 

  • Slow welding speed 
  • Too much heat 
  • Inability to control the heat throughout the weld due to improper electrode positioning 
  • Under-cutting 
  • Inadequate filler material 
  • Improper torch angle 
  • Lack of penetration

Mixed or Dirty deposits 

The cleaning process for shielded metal arc welding is a function of the deposit to be removed and its type. The optimum cleaning method is dictated by the need to remove heavy, hard deposits and retain delicate, thin interpass deposits.

An E-beam cleaner or an abrasive wheel can be used to remove heavy welding scale, while an aggressive grit on a flexible backing pad or interpass brush will do an effective job on deposits not requiring removal to bare metal.

Slag Inclusions 

Incorrect welding can occur when you over-fill the joint with filler metal. This will cause excess slag to remain inside of the weld, and this is known as slag inclusion. Slag inclusion is a serious problem, as it compromises both the strength and aesthetics of the weld.

How to avoid slag inclusion presuming you have already had enough energy Input and proper filler metal, slag inclusion is most often caused by not moving the arc around in your weld.

Moving the arc around is the key here. It will keep the slag in solution and allow it to run out of the weld. It is also important that we use a consistent travel speed while welding.

The important thing to keep in mind when welding is to keep a balance between killing the arc and using too much filler metal. An arc that is stuck on too long will cause slag inclusion if you are welding above a certain voltage or if you are using a filler metal that is too difficult to melt.

If your arc is sticking on too long, back off of the voltage or make sure you have the right type of electrode for your job.

However, pushing an arc on for an excessive amount of time before striking can also cause problems by causing things like excessive to spatter, which will eat into your weld puddle.

Poor Porosity

Porosity is a problem occurring in the welding process due to trapped shield gas. This can cause defects such as incomplete penetration, undercuts, cracking, and lack of fusion, not to mention discoloration and porosity known as bubbles.

These can ruin a weld and make it brittle. If not addressed immediately, this will lead to several more issues which are quite expensive to fix in the long run.

By definition, porosity is the presence of holes inside a weld created from gas trapped in the base material and released on solidification. NO2, O2, and H2 are absorbed in the molten weld pool and become trapped as gases in the solidified weld.

It occurs because of incomplete shielding (from molten slag) protecting the base material being welded. The heat causes gases to be released into the air while they are still liquid. 

Visible Undercutting

In the welding industry, an undercut is a defect in the weld commonly caused by inexperienced or unskilled welders. An undercut can result in a weakened bond between two pieces of metal and their failure to adhere together if too much pressure is applied.

An undercut can also create holes in the base metal through which contaminants can enter with the possibility of causing further degradation to the weld. Itis a defect that appears in a welded joint beneath the surface of the workpiece being welded.

Undercutting occurs when shielded metal arc welding (SMAW), flux-cored arc welding (FCAW), and gas tungsten arc welding (GTAW) use electrodes that have also been used on other pieces of steel, or when the welder does not ground the electrode to keep the excess voltage from reaching the weld pool. This can leave an un-melted area of steel beneath the surface.

In order to prevent an undercut, a welder must master the process of positioning and control. Metal is joined by allowing the filler rod to flow into the joint like water and thus provides a strong weld between two pieces of metal.

In order to do this, you must learn to control the movement of your welding torch and power settings.


The main problem with welders is that most of them tend to leave behind spots. These are small bits of molten metal that fall as droplets onto the surrounding surface during the welding operation.

Spatter is a common problem involving the process of welding. The main goal in preventing spatter is to keep the surface of the weld-free from particles and to protect it from thermal shock.

Welding spatter happens when you acquire maximum surface speed and too much tapering force applied on the base material.

Welding is the process of using resistance to produce heat, which is used to melt parts together. Spatter is a by-product of welding and can cause damage to equipment and also create puddles on the ground.

It’s caused when excessive voltage, improper margin gas flow rates for specific metals being welded, and too much current intensity at high currents.

Good welders know how to avoid welding spatter, but if it does occur, there are some ways to prevent it from contaminating the entire surface of the weld area.

For instance, you can insert an end mill or a countersink into the welded part to vacuum away the spatter and any other contaminants left behind.


No one wants to see a welding defect in their work. But cracks can occur if too much pressure is applied to the material or if it cools down too quickly.

In addition, the heat and electricity from welding can cause the metals to expand and contract in different ways.

Welding crack can be a common problem for welders, especially when the materials being welded have high working tensile strength and low elastic limit.

In order to prevent this problem, experienced welders will ensure that the material is cooled down slowly and evenly by filling the cracks while they are still hot with clean or oiled sand or stone.

Stick Welding

Everybody wants a stick in their life. Stick with Stick welding to work with a range of materials, including alloy steel, carbon steel, stainless steel, iron, nickel, copper, and even aluminum. Stick with Stick welding to enjoy its versatility, safety, and ultimately better welds.

The air-cooled version is called shielded metal arc welding (SMAW) or manual metal arc welding (MMA), although it’s also known as lux shielded arc welding. It’s not hard to win friends with your handiwork.

Above all, stick welders are creators, building some of the strongest, most durable structures found anywhere.

With a range of skills that can make people envious, stick welders can build anything just about anywhere; on the boat in the middle of the lake or under the bridge after hours. They are paid well in most industries and serve as a staple to society.

Figuring out whether or not your stick weld is good or bad is relatively simple. If your weld is straight, uniform, and looks something like the weld above, you’re probably doing ok. Have fun trying some of these points in mind during your next project!

Good Stick Weld

  • Good welds are straight and uniform.
  • They are no variations in thickness
  • There are no drops or holes in the bead.
  • They’re not crooked.
  • Better weld joint performance
  • Weld with less spatter and smooth weld surface
  • without the problems that could arise from traditional welding methods
  • Have a smooth and uniform weld surface for faster finishing.

Bad Stick Weld

  • It needs a good spatter cleaning
  • The bead width is not consistent in some areas
  • Lack of fusion
  • weld beads are visible
  • Breaks/cracks in the weld surface
  • Undercut, bad bead

TIG Welding

You may look like a superhero when you’re dressed in your TIG welding suit (that’s why they make them so cool), but it’s not magic that makes you a blacksmith. It’s strength, stamina, and skill. You’re going to need that skill to get through this blog post!

Check out how the characteristics bad and good of the TIG welding process work with the metal being welded to create the ultimate forge job.

TIG welding is not to be confused with the Tigger character from Winnie the Pooh. In fact, a TIG welder does not wear a brightly colored tail or bounce around and knock things over in a disorganized way.

Rather, TIG welding is a method of joining metal by using a gas torch to melt another piece of metal called filler material and then using it to seal the joint. The term “tungsten inert gas” refers to the combination of shielding gas used (typically argon) with tungsten as the filler material.

A TIG welder directs an electric current through the base metal and filler material, known as an electrode. This creates an arc (similar to electricity powering a light bulb), which melts both pieces of metal into one joined piece during welding.

When you’re looking at a TIG weld, if you see a flat bead that looks like it was painted with paint or solid metal, not a distinct pattern of overlaid welds, then that’s not good. Inferior TIG welders will get that wide, painted look.

The patterns should be visible. It’s not an exact science. If the welds are visible and the edges are sharp, then that’s probably a TIG welder worth considering.

Good TIG Weld

  • Tightly patterned welds
  • No weld spatter or burnout
  • It’s neat and tidy, patterned
  • Patterned welding is all about smooth beads with a distinct arrangement
  • Signs of burnout (color change)
  • Consistent weld appearance throughout the weld
  • A distinct pattern with no pores on the surface of the welding area

Bad TIG Weld

  • Burn out is visible
  • Undercutting is visible 
  • Use tungsten to fill in the weld
  • This bead is wide but lacks a distinct pattern
  • Tungsten visible in the weld bead

MIG Welding

MIG welding is the most common type of welding used at home, and it’s recommended for beginners. MIG stands for inert metal gas, and this type of welding is ideal for aluminum, stainless steel, and mild steel.

The process is fast when you have an experienced operator, and since less filler material is used with this style of welding, there’s no spatter or slag to remove.

MIG welding, also called GMAW, or metal inert gas welding is a type of arc welding used to join metal pieces. The process uses a base metal and an electrode wire that acts as the filler material.

The MIG process uses an inert shielding gas to protect the weld area from atmospheric contamination by keeping most of the common air oxidizers away from.

Learning how to weld can be difficult, but once you’ve mastered it, the opportunities are endless. A MIG welder gun is used when welding pieces together. It is a versatile tool thanks to its multi-voltage capability and its ability to be mobile.

One of the perks of being able to use a welder instead of having to solder or braze is that it is faster, and your final product comes out smoother than using another type of welding machine.

There are several factors that determine the quality of your weld. First, there needs to be a proper fit between the filler metal rod and the wire feeder. The filler material needs to be in contact with the welding wire. An incomplete arc is another sign of a poor weld.

A large puddle of melted filler material around a small bead is also bad. Finally, if you see cracking along the weld, it’s a sign of a poor MIG weld.

Good MIG Weld

  • a weld that has a smooth and consistent bead
  • experience no cracking on the bead
  • weld bead is flat with no bulges or gaps (convex or concave)
  • The weld has no holes and the slug

Bad MIG Weld

  • The weld is cracked along the length of the bead.
  • lack of penetration
  • Weaker joint
  • create a thinner bead

Oxy welding methods include gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and gas shielded metal arc welding (GSMAW).

Oxy welding is a great method for joining different types of metals, including those that are sensitive to heat or difficult to weld, like aluminum.

This type of welding is usually done in a confined space, which is called a pressure vessel. This makes it advantageous for joining thin pieces of metal, like aluminum or bronze.

It also excels at welding different metals together, like steel and copper. In fact, this type of welding was used to create the Statue of Liberty.

Understanding the elements of good or bad welds can make all the difference between saving time, money, and materials and being forced to redo your work.

In addition, understanding when a weld is good or bad will make all of your welding jobs more efficient and accurate.

Good Oxy Weld

  • Consistent flow when working with beads
  • No holes
  • ample amount of penetration
  • metals should be completely fused together

Bad Oxy Weld

  • undercutting and insufficient penetration
  • Inadequate penetration
  • The fusion of metals is inconsistent
  • overlapping area

Common Qualities Of A Good Weld

Here are some common qualities for a good welding you can easily identify.

Have Good Penetration

Penetration is a weld’s ability to fuse together the pieces of metal and is essential in creating a good weld. Penetration increases with time and heat; thus, the rate of penetration must be controlled for best results.

Deep penetration welds are produced when the welding current causes the arc to be drawn or “drawn into” the work so that it melts its way through. Deep penetration is a natural outcome of correct electrode selection and correct voltage control.

A good common practice is to run an initial shockwave to tack the weld and then finish the weld after using a filler rod.

This, however, is based on 50% penetration and 25% in materials with high conductivity. Proper welding procedures should always be followed correctly.

No Holes and Cracks

Porosity, often seen on the surface of welds as small pore-like pores, are tiny voids. Porosity is caused by the oxygen and nitrogen gases in the atmosphere.

These gases may form when the electrode tip becomes contaminated or when there is enough moisture in the air or insufficient shielding gas mixing with the torch.

A good weld should be free of porosity and show a smooth, solid appearance. Pores in steel are caused by the solidification of oxygen and nitrogen when the weld pool is cooling. Porosity 0.1–0.2% will cause defects such as porous welds, cracks, or cored structures.

In welding, there are different types of porosity that can occur in a weld. Distributed porosity is distributed pores on the surface of the weld.

It occurs when gas particles become trapped in the molten weld pool. The gases are released when the pool cools, leaving pores in the weld.

Porosity is one of the biggest problems that you encounter when practicing welding. This is a phenomenon that occurs in bad welds and characterizes itself on the surface of welds in the form of holes or pores.

Bad porosity holes are filled with carbon dioxide (CO2) because it is a gas that easily enters the solidifying weld pool, so at a certain moment when the metal cools down, it chills and causes CO2 to start leaving the metal until there is no longer any, thus leaving only the empty space in its place. The most common types of pores are wormholes, crater pores, and sleeves.

No Tint or Shade

Did you know? Welding is the second oldest metalworking process after forging. It is widely used to join metals. That’s the reason why engineers and architects tend to mix up blow and welding wherever they can. The right weld will have a color-free appearance.

The correct amount of shielding gas is necessary for a successful weld. Oxidation occurs when a welding torch is used without sufficient shielding gas.

Impurities in the metal and gases particular to a welding process (excluding oxygen) will cause oxidation on the surface of the weld. This color hue may appear on some or all of the weld beads.

An oxidation-rich surface interferes with achieving penetration, as well as causing porosity, and other defects called lack of fusion or cold lapping. The lack of fusion results in weak spots in the weld, which can cause it to break.

So that, The color of a good weld will be free from purple, blue, or yellow hues. A lack of proper shielding gas or flux contamination can cause the appearance of these colors on the metal being welded.

Joint Strength Quality

A weld joint is an interface of base materials and heat-affected zone, in which the heat-affected zone is a region of weld metal to the heat source and has properties close to those of the base materials.

Strength is one of the most important properties of a weld joint, which directly determines whether a weld joint can withstand working loads. Strength means the strength of rupture(deformation) under mechanical stress.

Joint efficiency can be defined as the ratio of the maximum strength that a joint can sustain to the strength of base materials. Loads applied on a weld joint mainly work on the base material, and stress concentrations easily occur in joints.

When different stress conditions are applied to joints, their strengths are different. We can estimate how strong joints are by using certain standard test conditions.

Heating up high-tensile steel or aluminum alloy or the welding of work-hardened austenite stainless steel or heat-treated aluminum alloy makes these metals weaker. The efficiency of this joint can be as low as 70%-80% of that of the base material, and it has a tendency to crack.

How to Test Weld

After you have welded something, it is important to get a full inspection of the work that you have done. Such an inspection will not only ensure that the piece of metal you just welded together is structurally sound.

A good weld and a bad weld can look awfully similar at times. To ensure that your weld is up to snuff, you can subject it to a number of tests—such as exposing it to an x-ray—that will give you a good insight into its quality.

X-ray defines the penetration, interface, penetration size, and porosity of a weld. The highest quality welds will have excellent fusion, fusion boundary definition, and little or no.

Below is a list of the most tested welding tests. These are by no means the only ones, but they should give you plenty of information on the quality of your work.

Welding inspection and monitoring services provide accurate weld data to improve weld quality, mitigate risk and save costs. Welding services include NDT inspections, physical property testing, analysis, and failure investigations.

Non-Destructive Weld Testing

Non-destructive testing is any technique that allows the examination of a material, component, or structure without causing damage.

NDT methods include ultrasonic, magnetic particle, radiography, liquid penetrant, and eddy current testing. A list of non-destructive testing methods and applications is available on the SSPC website.

Destructive Weld Testing 

In destructive weld testing, a sample is removed from the joint and then tested to determine the quality of the weld.

Destructive weld tests are used in industry to check the quality of welds on materials such as metals and alloys, ceramics, and composites, among others. Many materials, such as stainless steel, can be brittle if exposed to certain welding methods.

Other materials, such as most aluminum alloys and magnesium, are vulnerable to hydrogen attacks during high-temperature heat-treating processes. This guide explains destructive weld-testing methods commonly used in industry today.

Final Thoughts

Welding is a welding process in which two pieces of metal are joined with the help of heat and pressure, which results in the formation of an alloy called steel.

There are four basic techniques involved in this process – MIG (inert metal gas), Stick (shielded metal arc), TIG, and OXY-ACETYLENE.

If you want to try welding and don’t see yourself as having the patience for a more delicate MIG or TIG welding process, the Stick technique will probably be what you prefer.

A smaller space can often be more easily dealt with using Stick welding because the shorter welding rods mean less heat and a quicker weld time.

Welding may seem hard to learn by just reading manuals, but it can actually be learned fairly quickly. It’s one of the most important construction processes today and is used in just about any building project or professional trade.

This guide will help teach you exactly how welding works, how to spot a good weld vs. a bad weld, and how to properly weld different types of metals together.

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