How To Weld Chromoly

How To Weld Chromoly? Best & Easy Way

Welding is the process of joining metals by creating a high-pressure, high-temperature bond. The metal is heated until the atoms soften and flow into one another, and the resulting chemical reaction creates enough force to hold the filler metal, such as flux, in place.

The arc is struck and the filler metal melts, forcing it to flow into the joint. The process can be repeated several times to weld the metal together. The process has many applications and can be used for everything from architectural and structural work to automobile and aerospace manufacturing.

Welding is used in many manufacturing fields, but the different types of welding material have different ways of processing materials for welding. Depending on applications, every metal with a combination of other metals has different strengths so there are also different ways of welding process. Since different metals have different compositions, properties, and strengths they can’t be welded by using the same techniques. One such alloy metal is Chromoly.

Welding Chromoly

Chromoly steel is an alloy of steel that contains iron and carbon and may include manganese and nickel. It’s typically stronger than its counterparts, which makes it a popular material for building. Chromoly alloy is the name given to 4130 steel. The code 41 defines that Chromoly contains chromium with 0.8 to 1.1% ratio and molybdenum with 0.15 to 0.25%, while 30 indicates 0.30% of carbon content.

Chromium is an important component of steel, as it increases the strength of the steel and improves its resistance to corrosion. Chromoly steel is also considered to be a lightweight steel alloy.

Welding Chromoly – Steps You Should Follow

The process of welding Chromoly is a little bit different from other alloys. It requires more preparation and some technical know-how to work with it. If you are a beginner then the following steps and tricks will help you to weld chromoly. 

1. Preparing the Tube

Preparing the Tube

Clean the tube thoroughly before starting because any alloy residue that may be left on it after coming from other welding works will affect your Chromoly welding process in terms of appearance and durability. If you have access to a lathe, we recommend you to run the tube through the lathe at slow to medium speed to ensure flawless finishing of chromoly. It will give you a smoother, cleaner, and crystal appearance.

2. Fit and Tacking

Now moving on to the next step which is fitment and tacking, always keep in mind that chromoly is a temperature sensitive metal. While introducing heat to it, make sure you’re exposing heat a bit more gradually, keeping your arc length tighter than the usual arc length. For keeping weld in a place, we recommend you numerous tacks over 1 or 2 big tacks as it offers more consistency.

3. Torch Setup

Choosing the best torch for your application is extremely important. If you are working for multiple hours, the weight and mobility of the torch will end up mattering a lot. For this alloy, a high quality Tig welder will be a perfect choice. We also recommend you a gas lens over regular nozzles because the diameter of the gas lens will form a larger gas shield so you can hang out your tungsten a bit farther and reach tighter corners with ease.

Welding Chromoly

4. Choosing Filler Material For Chromoly

The fundamentals of welding processes remain the same, but minor alterations can make a big difference. Your welding filler metals are important in developing high-quality welds. There are three options available for you as a filler material when you are welding chromoly. These include the ER80S-D2, ER70S-2, and 4130 versions of this alloy. 

When welding chromoly steel, it is essential that you use special metal filler materials and welding rods to ensure that the finished welds do not fail. ER80S-D2 alloy ribbed electrode is an excellent choice for welding chromoly.

The ER80S-D2 has more tensile strength which is relatively close to choromly that is 80,000 which makes it a great option for welding. The ER70S-2 has comparatively less strength that is., 70,000 but it offers good weldability and flexibility. 4130 is an alloy that is most commonly used for various types of welded construction.

Its combination of high tensile and yield strength, low fatigue, and toughness make it ideal for a variety of applications. 4130 alloy steel is heat treatable and has good weldability which makes it a good option for welding chormoly. But it’s not an ideal option with Thin Wall Tube. 

When the Chromoly steel has to be hardened after welding, it is necessary to have a filler metal that has the same strength and properties as chromoly, such as 4130 steel.  However, one drawback is the high carbon levels of 4130 steel which make them sensitive to cracking. 

Tips For Chromoly Welding

  • Welding is all about creating strong connections between two metals, and Chromly steel is a high-grade steel that is commonly used for strength and durability. Welding Chromoly steel can be tricky and prone to errors since it tends to have smaller grains and more impurities that can affect the strength of the weld. Here are a few tips for welding Chromoly steel that should help you produce a stronger, cleaner weld.
  • While welding chromoly there is no need to preheat the metal if it is under 0.120” thickness. If the tube is thicker than 0.12 inches then you need to preheat it at 300 to 400 degrees Fahrenheit.
  • For welding chromoly, if you are using tig welder it should be slower than normal.
  • We recommend you to use a lift arc start instead of a scratch start because lift arc is comparatively more stable. All you need is to torch the tungsten to the base metal, start the pedal, lift the welder and go.
  • Slope in and out gradually as chromoly is quite temperamental. Since sloping in and out fastly will make it brittle.
  • Keep the tungsten close to the material as much as possible to make sure the arc cone is narrow.
  • The weld should not be cooled quickly because the fast cooling leads to cracking. Therefore, make sure there is no source of cooling or breeze in the welding room.

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