Last Updated on August 15, 2021 by weldinghubs
Are you new to welding or have some previous experience? The welding process is crucial for joining metal pieces. First of all, welders need to clear their minds regarding the purpose of the welding process. The primary purpose of welding is to fix the damaged metal pieces and join two essential metal alloys. So it is an integral part of many life repairs and damages.
You may think that whether steel is a suitable metal alloy or not, it can’t withstand the harsh welding temperature as many new welders are curious to know new techniques and their results at different metals.
So here I came up to answer the question, “Does Welding Weaken Steel?”
Yes, Welding can cause steel to weaken at high temperatures, most notably in the heat-affected zone. which is most common with cold-rolled steel.
Welders use three primary methods for joining steel, including soldering, welding, and brazing. Every process has the same purpose of joining steel or metal, but you can’t join two different metals together.
The question of whether welding weakens steel is a common one. In this blog post, we’ll explore whether or not there are any negative impacts to the metal welded, and if so, how much it can be weakened.
We’ll also cover some tips on what you should do to prevent weakening the metal too much when welding. One thing that’s important to note right off the bat is that all metals can weaken with heat exposure-not just steel!
But don’t worry: even without welding, your steel will still have some degree of weakness in it due to heat exposure alone. So let’s take a look at what exactly happens when you weld different types of steels together and how this affects their strength levels.
Here I will share the complete guideline regarding welding and its impact on steel.
So let’s dig into it.
How does welding weaken steel?
Welding is the process of joining two pieces of metal by using heat. The heat input in welding has a great impact on the quality of welded metal. When arc voltage is increased or speed decreased, the overall amount of heat goes up and leads to weakened steel that can result in defects within the metal. This weakened area is usually located in the HAZ right next to the weld joint rather than directly within it.
The intense localized heat of welding can cause metals to recrystallize and soften. The precipitate that gives the metal its strength grows with age, which makes it less effective in hardening the steel after being exposed to high temperatures.
This is especially true for cold-rolled steel, wrought iron, and drawn or rolled aluminum. When working with these materials, joint design is critical, and you must take into account the amount of stress the finished piece will experience in service.
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What can be done to stop the weakening of steel from happening?
After discussing the problem of welding weakening steel, it’s time to talk about a solution. Experts say that post-weld heat treatment is effective for strengthening metal and can be used as an alternative to more costly techniques such as stress relieving or nitriding after laser cutting. Here I will discuss the process of post-weld heat treatment and how it can be used to strengthen the metal.
let’s start by taking a look at what post-weld heat treatment is, and how to perform it.
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Post Weld Heat Treatment (PWHT)
Post weld heat treatment mainly consists of two steps, the tempering process, and the normalizing process. The first step involves heating metal to its critical temperature for long periods of time until it reaches maximum hardness. This can be done in open air or with an inert gas such as nitrogen typically under a protective atmosphere. The second step involves heating the metal to a maximum of 850 degrees Fahrenheit and then slowly cooling it until it reaches room temperature.
Moreover, another two things need to be taken into account- the post-heat holding time and temperature, as well as monitoring the process.
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a) Tempering Process
The tempering process, which is the first step in post-weld heat treatment, has two purposes: Harden the steel by pushing its hardness past what can be achieved through regular annealing; Strengthen the metal by making its hardness more uniform. The second step in post-weld heat treatment, which is the normalizing process, has a single purpose: Strengthening steel by relieving stresses that exist within and between different grains of steel due to heating and cooling at high rates during welding
The tempering process for strengthening metal can be done through two methods. In open-air or with an inert gas such as nitrogen typically under a protective atmosphere, this method requires long periods of time until it reaches maximum hardness. This can be achieved in open-air or with an inert gas such as nitrogen typically under a protective atmosphere. An alternative way to do this first step would be using heated water tanks where workpieces are dipped into hot water after each pass to maintain a high heat during the tempering process.
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b) Post heat holding time and temperature
There are a few factors that affect post-heat holding time and temperature. The thickness of the material and what it is made out of will determine this duration, with thicker items taking longer than thinner ones due to increased levels or stresses on their physical composition.
Moreover, the specified holding temperature is one that relieves high residual stress levels and makes microstructural transformations possible. The transformation of the material at a lower heat allows for more ductile properties, making it easier to work with.
It is essential that you take care not to heat the component above its lower transformation temperature. If this happens, detrimental metallurgical effects can result in a weaker metal and impaired mechanical properties will lead to improper functioning of your product.
On the other hand, Leaving metal at a higher temperature than the original tempering limit or for longer than necessary can lead to weakened steel that is below minimum ASME requirements.
c) Monitoring the process
Thermocouples are widely used to measure the cooling rates of components after they have been heated. The thermometer is attached with computer software that monitors and measures how quickly it cools off, in addition to the temperature level before being subjected to long-term heat exposure.
The second step in post-weld heat treatment, normalizing, also has two methods. The first method for this step is to reheat metal at 850 degrees Fahrenheit and then slowly cool it until reaches room temperature. The second way of doing this would be by heating water tanks that are heated up to 900-1000 degrees Fahrenheit where workpieces are dipped into hot water after each pass to reach maximum hardness without completely cooling off.
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What Are The Factors That Affect Welding Performance?
Welding performance depends on various factors that affect its strength and results. In other words, you can say that the weldability of a metal depends on multiple factors, including metallurgy, welding technique, joint design, melting point, and many more. Of course, these factors also influence by the welding torches and the workpiece.
So here, I will discuss every factor to get to know these in detail and follow them effectively.
You may know that metallurgy is one of the basic terms in the welding field. Metallurgy refers to the process of manipulating metals for producing specific shapes. So ensure that you will perfectly heat the metal to get it into a particular condition. If you use an overheating process, then it will damage the metal instead of shaping it.
02. Welding process:
The welding industry includes more than 67 techniques that depend on various factors. Keep in mind that every welding process requires extra heat and pressure according to the welding torch and metal to be weld. So you need to ensure that you will have the accurate welding apparatus for steel not to lose its strength.
03. Joint design:
Welding torches have an electrode that is particular for joint styles. For example, if you want to weld the metal horizontally, you must have the E6011 welding electrode. Similarly, every design requires a particular welding electrode. The combination of welding dimensions and joint significantly affect the welding geometry.
04. Melting point:
Every metal requires a particular temperature for melting and provides the filler material. Welding techniques have torches that provide sufficient heat to metal and melt it at requires melting temperature. Moreover, metals with medium melting points provide superior weldability.
05. Weld preparation:
Welding preparation steps are essential for better weldability. Every welding technique demands special pre-welding preparation. Cleaning the metal base is one of the crucial steps in weld preparation time.
Ensure that you follow the weld preparation direction according to every welding technique. It will help you to get an effective weld.
06. Electrical resistance:
Metal creates and resistance against the electrical current—however, the metal with high or increased electrical resistance demand heat energy for effective welding. Moreover, the unsuitable combination of electrical current and metal resistance provides bad weldability.
Effect on Heat Transformation Zones in Metal
The welding process includes a high level of heat or also known as the heat-affected zone. Every welding effect during heat affected area depends on the parent metal temperature capacity, travel velocity, and the cooling time after welding the two metal joins that turn into solid.
Heat gradient in the metal workpiece can damage the welding joints or cause mechanical damage, leading to tearing micro-fissures. So it is essential to take precautionary measures that help to reduce mechanical injuries. Precautionary steps from heat-affected include eth preheating of the workpiece, post welding heat treatments, and restriction of heat output.
The heat transformation zone is somehow similar to the heat-affected site. Moreover, if you see the damages at the heat transformation zone, it is essential to use the chill blocks, post-heat blankets, quenching, and many more. But keep in mind that all these precautionary instruments depend on the welding procedure and the welding material.
If you have a unique welding exotic alloy, you need to have a special welding process that can weld the alloy by providing a suitable heat zone.
However, as a beginner, you may not know the appropriate heat transformation zone for exotic alloy. But if you have trained under the expert, then you will get to see every technique effectively. Moreover, this kind of weld procedure can only be wielded by the approved professionals to carry out this procedure. They will know all about the comprehended material like steel, weld join type, and welding position. These factors ensure that metal has perfect weld and didn’t lose its strength.
A professional welder can effectively regulate the heat required to weld the particular metal and provide an ideal weld suitable for metal.
So in this way, steel strength doesn’t lose its value and gets perfect, robust, and attractive welding beads.
Mechanical Damage From Thermal Gradients In The Workpiece And Weld Joint
Now you know that the welding process can weaken the steel and other metals at the point of welding joints. So it is clear that it may have mechanical damages due to any reason. The thermal gradient is one of the common reasons that cause mechanical injuries in metal joints and workpiece. So to avoid these mechanical damages, you need to take few precautionary measures that ensure a superior quality weld.
Moreover, common mechanical damages occur due to the poor welding surface of meta that cause damage during welding, handling, pre-welding preparation, and dressing. These mechanical damages also occur due to incorrect use of apparatus like grinders, hammers, and chipping materials. So to avoid these damages, you need to take the ideal welding equipment.
So here, I will share some typical mechanical damage that occurs due to thermal gradient.
Hot crack is one of the typical mechanical damage in the welding industry. It occurs after or during the welding process due to overheating of metal. So to prevent the hot crack, you need to cool the metal right after welding quickly. Moreover, if you face a hot crash during the welding procedure, ensure the preheating of the metal piece. Preheating the metal piece refers to the heat application at the metal workpiece, so it doesn’t instantly bear the overheat from the welding torch.
Every welder needs to have less spatter during the welding process. It refers to the tiny particles of metal spread around the extended area due to overheating metal and other reasons. It is hard to control the spatter, and it can also cause many mechanical damages. So it is essential to use the correct heat amount according to the welding torch and metal to be weld.
What is Normalizing?
Normalizing refers to the preparation of steel to get heat treatment. It helps in restructuring the internal aspects of metal, so it has reduced interior weld strain. Normalizing help to soften the metal but didn’t allow the steel to get heat stress. It also will enable the metal to cool down gradually.
It changes the metal stressor state, so if you need to maintain the temperature around 1,100 oF for steel welding after using this procedure. But during the welding process, the temperature may increases to 1,150 oF. Professionals have experience in reducing the temperature to that help to decrease the chances of damage up to 80%.
So by summing up the above discussion, it is clear that welding can weaken the steel. But by using professional experience and advice, you can maintain the strength of steel. Moreover, make sure that you will take adequate preventive measures to keep the power of the welding pool.
I hope this article will help you understand the steel welding strength and get an effective weld pool.
Why do welds break?
Welding pool breaks due to internal stress when it exceeds the mental strength. Welding cracks also occur during the process, so you need to take preventive measures.
Does welding affect the strength of a material?
The welding process has tensile strength that depends on the base metal and welding torch. Suppose you don't have control over metal composition and moisture. So to yield a strong weld, ensure that you will notice the material strength.
Why are welds weak points?
The welding pool is strong, but the metal may have some weak points that cause damage tothe welding pool. The weakness of weld also depends on the base metal. So stronger the metal robust weld you have after the cooling process.
How do you strengthen steel after welding?
There are many ways to strengthen welding. It includes solidifying grain structure, applying solid material, transforming hard alloy, and many more. So you can use any of the effective methods to strengthen metal after welding.
How many times can you Re-weld Steel?
If your steel welding pool break, then it's time to re-weld it. But now, how many times you will re-weld the steel. It depends on the strength of steel alloy to bear the high heat treatment. So check out the steel metal strength and apply welding treatment according to it.
Does steel weaken with heat?
Steel requires a heat treatment for different purposes like softening, remodeling, and many more. Heat weakens the steel due to excessive temperature and slow cooling time. However, it only weakens the steel if used in an incorrect state.
Does mild heating steel weaken it?
Heat in the suitable temperature range can affect the steel strength. Some metals also require heat to increase their strength, like creating ductile products. However, mild heat can also weaken the steel.