One of the most important things to think about when welding is whether the metal you’re using will become weaker as you join it with another metal.
So does welding weaken steel? Welding can weaken steel, particularly in the heat-affected zone (or HAZ) when welding at high temperatures. Weakening with welding is most common with cold-rolled steel.
There are three main methods used when joining different metals:
Each technique is used to join metal objects. They can also be a way to fill in gaps in the metal parts. When welding is used, the two metals have to be similar. You can’t weld copper to steel, as an example. Here we’ll look at some facts on whether welding weakens steel.
How Is Welding Applied When Joining Two Metal Parts?
This process requires using high temperatures, which will melt the metal parts to allow them to join. Usually, a filler metal will be used along with it. When the process is done as it should be, the end product will be every bit as strong as the other metal. An inexperienced welder might use too little heat, and this can alter the properties of the metal and cause it to weaken.
Some different kinds of welding can be applied, such as electron beam, MIG, which is an inert metal gas, stir friction, and laser. Another way welding can be used to separate two large structures of metal by using high heat to slice through them. One of the most critical factors in this process and whether it weakens steel is the correct or incorrect use of heat.
Welding Effects And Techniques For Hardening
The only area of steel that can be positively or negatively affected by welding is known as the heat-affected zone or HAZ. This is the only part of the metal that will have any impact, assuming the right metal is used as a filler. The filler metal will not experience any recrystallization and will, therefore, continue to be as strong as the primary metal. It is because of these factors that the only likely area of failure will be in that heat-affected zone.
This happens commonly with cold-rolled steel. If someone is working with that material, then the design of the joints is critical, and it will be necessary to factor in the level of stress the piece will experience when in service. When welding, it’s always essential to remember that the higher the heat used, the quicker the metal might weaken. It’s possible in some cases that post welding with proper heat treatment can correct a mistake.
What Are The Benefits Of Heat Treatment In Preventing Weakened Steel?
Using post-weld techniques and heat treatment is an effective way to strengthen the weld joint. This is accomplished because it tempers the bainite that can form in the heat-affected zone. This will relieve areas that would otherwise potentially crack overtime as stress is applied to it.
Using heat treatment, when done correctly, can actually change the size of the grain, toughness, hardness, and tensile strength. It can improve elasticity, relieve stress, and improve electrical and magnetic qualities.
It is necessary to understand how to do heat treatment properly to get the most benefit. It’s more than just a matter of using a torch on steel and then letting the material cool. The factors that need to be understood and implemented correctly include the temperature of the heat used, the time that it’s applied, and the cooling rate. It will also be necessary to understand any surrounding materials used and how they will influence the overall effectiveness.
It’s important to understand that there’s more than one way this can be done. Some examples include induction heating, molten metal bath, or electrically heated salt, fuel-air or oxy-fuel torches, and natural gas. Some of the controlled cooling methods can consist of a fan or water cooling, cooling the metal in sand, using still air, and even furnace cooling. Controlling the heating and cooling process is most critical for getting the result wanted.
These factors will play the most significant role in determining whether the welding will weaken steel or strengthen it. If it is heated or cooled too slowly or too quickly or at too high a heat, then the result wanted is not achieved. When the steel is saturated with heat throughout and then cooled slowly, it allows for the metal to be easily machined.
What Is Normalizing?
This is what the process it’s called when what the person wants to accomplish is to prepare the steel to receive future heat treatments. It actually helps restructure the internal aspects of the metal, so it helps reduce the impact of internal stresses. This process can slightly soften the metal, but it ultimately prevents it from softening as much as it might without the process.
When thermal methods are used, it will heat the area likely to experience stress. It’ll then cool it slowly, so it changes the metal to alleviate the stressors put on it. When doing this process for steel, a temperature of around 1,100 degrees Fahrenheit is commonly used. Sometimes, the temperature may be as high as 1,150 Fahrenheit. Experts have found that temperatures can reduce the damage done by stress by as much as 80%.
Low Carbon Steels And The Use Of Gas Metal Arc Welding
This method is something that’s been used in several industries but most notably the automobile industry. The industry uses the technique with vehicle bodies and chassis. It’s something that’s been used for decades and more currently, is something used in robotic welding of steel joints. Several studies have been performed to understand the effect of welding on metal such as steel.
Some of these studies have been done when joining the robotic joints. The main thing these studies focus on is the effect of heat, voltage, and current and the results it yields. Some studies have looked at the influence the atmosphere has when using metal arc welding on carbon steel.
Within this industry steel plates that were 25 mm in thickness were of high importance and therefore what was researched. The studies wanted to see what could be done to reduce defects in the welded areas. It was found that when the voltage of the arc was increased, the hardness of the metal decreased. This is similar to other welding methods where higher heat resulted in softer metal.
Some studies suggested that increasing the speed of welding with this method could bring improvements to the welded metal. When the arc voltage is increased, or the welding speed is decreased, then the overall heat input goes up. This then sometimes leads to weakened steel. These factors can reduce the hardness and strength of the welded metal. It can also increase the chance of defects within the metal. This simply means that when the welding speed is increased, the heat input will be decreased, and this lessens the likelihood that errors will form.
Welding Effects Of High Strength Low Alloy Steel
HSLA is a type of steel well adapted for being welded. The most common way of working with this steel is fusion welding. Using this welding method sometimes weakens this steel. Using a technique known as friction stir welding is a way of avoiding the problems of distortion and residual stress that otherwise can take place with this steel.
High strength low alloy steel was made to replace low carbon steel primarily in the automotive industry. This was done to reduce weight and increase the overall strength of the metal. This steel can form a more hardened welded area in the heat-affected zone than its predecessor. This newly-developed steel has higher strength and weldability. And being used in the auto industry, it is also considered indispensable in making large ships and offshore oil platforms.
This type of steel and the welding techniques used are considered imperative primarily when used in automobiles, cruise ships, and even the military’s warships. It’s used for these industries because of its extreme toughness and high strength. Fusion welding has been found to work the best for eliminating any possibility of structural weakness.
Why do welds break?
Welds break because of the built-up stress that accumulates when a heated metal is rapidly cooled. Fracturing is a typical flaw that arises within weld joints and is a kind of tension alleviation that happens through heating up the weld again, to a lesser temperature, and afterward letting it cool off naturally.
What is the effect of welding on yield strength?
When welding, surges in the arc voltage and welding current can cause an increased level of solidity and lower yield durability. It can also impact ductile durability and impact toughness. By raising the welding velocity, you may see an increase in the hardness of welds.