The difference between these types is dependent upon the amount of other elements included in the material. For example, the amount of carbon in the metal determines the difference between cast iron and steel. The three most common types of ferrous metals are iron, steel, and tungsten carbide.
For those looking for an indicator that iron is included in a material, one of the easiest ways to check is through the use of a magnet. If the magnet is attracted to the material, then it is likely that some amount of iron is included making it a ferrous metal.
The Processes to Weld Ferrous Metals
Now that we have established some basics regarding ferrous metals, let us examine the different kinds of processes that can be used to Weld these metals. They include:
- arc welding
- oxyacetylene gas welding
- spot welding
- induction welding
- resistance welding
Each of these processes has its own pros and cons, but it is also important to understand that the composition of the ferrous metal plays a role in the process that can be used.
Welding Sheet Metals
To make sure we are all on the same page here, let us start with a description of what “sheet-metal” exactly means. For our purposes, these types of metals are restricted to a thickness of up to and including 1/8 of an inch (3.2 mm).
When welding sheet metals up to 1/16 of an inch, you can easily accomplish this through fledging the edges at the joint. The phalange is must be welded so that they are equal to the overall thickness of the metal, maybe even a little thicker than that. These edges should be aligned with the flanges and tack should be welded at least every 5 inches to 6 inches.
When working with heavy angles or bars, it is important that you clamp each side of the joint so that you prevent any type of distortion or buckling. The raised edges must be melted equally which creates a weld that is nearly flush with the surface of the sheet-metal. When you control the welding speed and the flame motion, you are able to create a quality fusion on the underside of the sheet without actually burning through the metal at all.
In addition, a square butt joint of up to 1/16 of an inch in thickness can be made on the sheet-metal by using a rust-resisting, copper-coated low carbon filler rod. You would align the joint and tack the edges in the same way that you did for the flanged to edge joints.
There may be instances where you need to make an inside edge or corner weld. If you find that this is necessary, ensure that you don’t burn through the sheet. This requires taking control of the amount of heat the welding tool is providing. You can accomplish this by following this procedure:
- Using a 1/8 inch low-carbon welding rod, heated until about ½ inch of the rod is molten.
- Hold the molten end of the rod so that is directly above the joint you are intending to weld.
- Sweep the flame across the molten end of the rod. This will deposit the molten material in the seam. You are going to find that the molten weld is large in comparison to that of a light gauge sheet. You also find that the heat is enough to preheat the sheet-metal. If you pass the flame across the material quickly, the filler material will be distributed evenly across the joint. This additional heat helps to produce a complete fusion of the joint. This type of method is commonly used in repairs of automobile bodies, metal containers, and other similar types of applications.
If you are working with a sheet-metal that ranges from 1/16 inch to 1/8 inch, a butt joint is commonly used. A 1/8 inch copper-coated low-carbon filler rod is normally used. You should use the forehand method of welding on butt joints.
Welding Ferrous Steel
Steel is a term that can be applied to many different ferrous metals. However, each of these steels could very differently in terms of their chemical and physical properties. To make this a little clear, steels that contain iron are generally divided into two types: carbon and alloy. When you know which one you are dealing with, then using the proper welding technique is easy.
Carbon Based Steel
When carbon is the primary group, then you want to use a welding process that employs higher amounts of temperature. Using an oxyacetylene flame, you want heats that are between 2450°F and 2750°F, temperatures high enough to be able to combine the steels properly.
As the flame passes through the material, it turns it from a solid to a liquid state. This is referred to as the “soft range”. Controlling that soft range is what a skilled welder is able to do.
To ensure that a good weld is created, the welding rod is placed in the molten puddle. The base and rod are then melted together to solidify the joint. As an important note, it is important to ensure that you avoid heating a large portion of the joint. If you do this, as the heat dissipates it will cause the metal to adhere but it will not fuse. This can be avoided by directing the flame towards the sides and bottom of the welded joint.
The welded metal should be added in sufficient quantities so that it fills the joint without leaving any undercut or overlap.
One of the primary concerns you face is with impurities. When oxygen, nitrogen, or carbon get into the weld, it increases the likelihood of such things as flag, oxides, porosity, or blowholes being included.
When oxygen becomes the impurity, it creates iron oxide. If this occurs, you want to remove those iron oxides. An oxidizing flame will cause the steel to foam, which gives off sparks. The oxides are then distributed throughout the metal, which can lead to it becoming porous or brittle. You can remove these oxides by using a wire brush after the battle has cooled.
A carburizing flame will add carbon into the weld. This causes the battle to start boiling. If this happens, then the metal will become hard and brittle.
When nitrogen enters it creates nitrites. This greatly reduces the strength of the metal and the weld, weakening it.
A lot of factors have to be considered to avoid adding these impurities. This includes monitoring the speed of the weld, adjusting the flame properly, and creating the right size puddle. After extensive amount of experience in welding ferrous metals, welders are able to control these types of impurities, ensuring they did not become a factor.
Welding Steel Plates
In metal plates that are up to be 16 inch in thickness, joints must be prepared between the edges so that they are equal to the plate thickness. This ensures that the flame and welding rod will be able to penetrate to the root of the joint. To do so, you want to ensure that you have accommodated for expansion and contraction to occur. This will eliminate the possibility of warping of the plates or cracking in the weld.
When dealing with plates that are bigger than 316 inch, the edges should be beveled to ensure that you are getting full penetration. Failure to do so will not create a good weld and will deny proper fusion.
Those plates that are between ½ inch and ¾ inch should be prepared using a U-type joint. In doing this, the root face is able to cushion the first bead or layer of the weld metal. Welders should use the backend method to weld these plates. As an important note, it is not recommended to use oxyacetylene welding for plates of this thickness.
In welding plates that are ¾ inch or thicker, you want to use the double V or double U type of joint. This allows for welding to her mom on both sides of late.
To close out this article, we want to give you some additional information to keep in mind. The first of these is that you can use a well-balanced neutral flame to weld just about any type of steel. You just want to ensure the flame does not allow for oxidizing. If you are unsure about this, do some more research. We have articles available that describes oxidizing.
If you are welding alloys that are high in carbon, nickel or chromium, then you want to use a flame that has a slight excess of settling. However, know that you can increase your welding speed by using a slightly reduced flame. You also want to avoid excessive gas pressure, as this can create cold shuts or laps.
As you are welding, you want to ensure that the pool of molten metal progresses evenly throughout the seam. The inner cone tip of the flame should not come in direct contact with the welding rod, base metal, or molten puddle. You also want to protect the flame from atmospheric conditions so that impurities do not enter the molten metal.
As one last tip, the end of the welding rod should be melted and placed in the molten puddle under the protection of the flame and its envelope. Do not allow the rod to melt above the puddle. Some believe this is a good to me, allowing it to drip into the metal, but that opens the door for impurities to get inside your weld.