How to Weld Chromoly Step-By-Step Guide: Weldlover

Welding is the process that we can use to join two metals by melting them at higher temperatures and then setting them to cool down to create welds. The production of household items to heavy machinery like ships and aircraft involves welding, which indicates how significant it is.

Various welding techniques have been developed to join several metals because it isn’t possible to weld all metals with the same method. The reason behind this is all the metals have different properties and strengths. So that’s why we use other welding procedures for them.

Do you know alloys are more popular for fabrication than metals? It is so because alloys are usually anti-corrosive, ductile, and more durable than metals because they have the unique properties of the metals that are in them. One of these important alloys is Chromoly; if you want to know how to weld Chromoly, then proceed reading.


What Is Chromoly?

Chromoly is the alloy of steel that contains chromium, molybdenum, and other metals as well. American Iron and Steel Institute (AISI) named Chromoly as 4130 steel. 4130 is the code of this alloy that indicates its chemical composition 41 shows it’s a steel of low alloy, including chromium and molybdenum. And 30 reveals 0.3 percent carbon content in the steel. Moreover, the percent of chromium in this alloy ranges from 0.8 to 1.1 percent, and molybdenum ranges from 0.15 to 0.25 percent.

The strength of Chromoly is more than steel when it comes to the weight-to-weight ratio. Due to this fact, it is employed in manufacturing race cars, cycle frames, and the structure of small aircraft. However, it also has an incredible tensile strength when we look at steel, making it difficult for a welder to weld it. Besides, welding of Chromoly needs a higher level of expertise and practice than other alloys.

How to weld Chromoly?

Welding Chromoly is complicated and complex, but you can easily do it if you follow the steps and tips we are going to tell you. You’ll weld like a professional no matter if you haven’t any experience in welding Chromoly by implementing everything given below. The best part is you can weld Chromoly by manipulating both TIG and MIG welding techniques.

Preparing the Tube

No matter which welding technique you are applying on whatever base metals, the first thing you have to do is clean the tube. For this, you’ve to prepare and clean Chromoly alloy first. As we know, Chromoly is very thin; therefore, any little dust on it can cause many problems while welding.

There we suggest you run the tube by lathe at a slow to normal speed. By doing so, you’ll get smoother, shinier, and more durable. Other than that, you can also use acetone to clean Chromoly, which is known for its remarkable cleansing ability. You can also go for Chromoly welding without preparing the tube, but there will be a risk for contamination of welds.

Proper fit and tacking

The next step to weld Chromoly is the procedure of tacking and fitment. Whenever you’re welding Chromoly, just keep this fact in mind that it’s a heat-sensitive material. So you need to be extremely careful when you have to io introduce it to the heat. Always try to heat it gradually.

Also, keep the arc length tighter than ever to produce quality welds. To maintain the arc length, I suggest you use a lot of tacks over one or two broad tacks. The reason is small tacks are convenient to weld and provide great efficiency.

Moreover, there shouldn’t be any gap in the fitment close if there would be, then a broad heat-influenced zone will come into being, and Chromoly will become brittle. As Chromoly is already a hard alloy, if you ever try to make it even harder, you’ll break it.

Setting up the torch

Picking up the right torch that fits the welding application is very important when you have to weld Chromoly. If your welding endeavor is going to take a lot of time, then the weight of the torch will have a significant impact on your performance and efficiency.

We suggest you use a good quality TIG welder if you aim to weld Chromoly with ultimate productivity. You should also use a glass lens when TIG welding Chromoly as that way it will form larger shielding gas which will easily reach tight corners conveniently.

Choose the Filler Metals

When you’ve to weld Chromoly, you’ll have three filler material choices: ER70S-2, ER80S-D2, and 4130 edition of Chromoly. Among all, ER70S-2 and ER80S-D2 are the typical choices of welders when they have to weld Chromoly.

ER80S-D2 is an excellent of the three as it possesses a tensile strength of 80000, which is very close to the base metal, making it an incredible choice as a filler metal. As compared to it, ER70S-2 has a comparatively lower tensile strength which is 70000.

Moreover, 4130 is similar to Chromoly, but it is not widely used to weld Chromoly, but it still is an option for this job.

Do you need to preheat Chromoly before welding?

You don’t need to do more heating of Chromoly before welding it because, in most cases, the thickness of it is no more than 0.12 inches. So it wouldn’t be bad if you start welding Chromoly without preheating it. But if you’ve to weld Chromoly, then you should preheat it to 300 to 400° Celsius.

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