The development of steam locomotion was one of the most important developments of the industrial revolution, and railways are still a vital part of our society today. Modern handling equipment requires smooth, continuous rail tracks that must be well-welded to avoid shocks at joints and damage to wheels and other mechanical parts. Welding of rails refers to joining two separate rail ends and repairing damaged rail ends. Most of the rail welding processes are similar to the methods used in general welding. However, there are three types of rail welding commonly practiced by top welding railways companies. Puddle arc welding, Exothermic welding, and Flash butt welding.
This blog will cover the main aspects of rail welding. The primary intent is to give an insight into the different types of rail welding used in modern railways.
Let’s begin the journey by finding the purpose of welding the rails.
Contents
What is the purpose of rail welding?
Railways bring together several different materials and equipment and require high levels of investment. The rail network comprises several parts, including the rails, sleepers, ballast, and the signal box. The rail is the backbone of the railway and is made of steel and other materials. The foremost purpose of welding rails is to expand the length by joining two or more tracks. Rail welding also reduces the cost of repairing old rails. Thus increasing the life of the rail tracks, downsizing the number of fishplates, increasing the strength joint, and making the rail track thrifty.
Keep reading our article if you are looking for helpful advice regarding the type of rail welding most suitable for your project.
Types of rail welding
Welding might not be the most glamorous job. Still, it’s essential, like rail-welders, who often get overlooked even though they play a critical role in a country’s transportation network. Suppose you are going to start a job as a welder in railways or are just curious to know about rail welding types. Let us help you!
Below is the detail about three commonly used methods of rail welding:
- Butt or Flash Butt welding
- Exothermic or Alumino-thermic or Thermite welding
- Puddle or electric arc or enclosed arc welding
Butt Welding
Butt welding is the most reliable and popular method used in rail welding. It does not use any filler material, which reduces the cost and gives a smooth weld. This is the most in-demand method in all the manufacturing industries due to its low cost, reliability, and quality weld with lead time reduction.
In this method, two rail profiles are placed adjacent to each other at a calculated distance that is based on rails thickness and composition—now Connecting the power supply to the rails. Both rail edges are heated by resistance heat, which melts the end faces. When the temperature reaches a certain depth, apply a compressive force to complete the weld.
Characteristics of Butt welding
- This process is highly automated.
- It creates a durable and best-quality bond.
- Safe and modernized techniques are used.
- Appropriate for a large number of fishplates weld.
- Low cost involved for a large number of joints.
- It is reliable for both crane and ground tracks.
- This process will give exceptional mechanical properties regarding elongation, fatigue, and tension.
Exothermic Welding
This process is also knowns as alumino-thermic or thermite welding. Exothermic welding is a conventional welding process that is gradually replaced by butt welding. In this process, molten metal is used to join two rail ends.
The first step should involve cleaning rail ends because any scrap or spoilage can cause a weak bond. Now, line up the endpoints horizontally about 25mm apart. The rail is set between ceramic molds and preheated to very high temperatures. When it has gained the right temperature, the molten metal will pour into the molds as a filler that bond the rail tracks.
Don’t forget to wear proper personal protective gear when working with thermic welding because the high temperature can cause severe damage.
Characteristics of Thermic welding
- Thermic welding is a good fit for rail on sleepers.
- As it does not involve any external power, this makes it a more pocket-friendly process than the others.
- It is precisely used for rail application instead of high crane tracks because of the danger involved in welding with molten metal.
- Apparently, good weld.
- This welding is appropriate for broken rail repair, on-site rail joints, and heavy transportation.
Puddle Arc or Electric Arc Welding
After butt weld, puddle arc is well known for welding rails. In this welding process, an electric current produces heat for welding joints.
Before starting the process, make sure that all the equipment and railroads must be cleaned thoroughly to avoid any weld defects and weak bonds. Puddle arc welding uses copper blocks and electrodes in the welding process.
Welding rod melts steel rail by the heat generated on end fronts, filling the reciprocal gap. The copper blocks retain the weld pool together to create a fully welded joint. After cooling, the rail end will start to combine and make a strong bond.
Characteristics of Puddle arc weld
- This process applies to all situations, whether high crane tracks or ground rail.
- It produces a strong bond.
- It can be done manually.
- More usage of the electrode wire.
- Smooth and uniform finished weld.
- Involve fewer health hazards compared to other welding processes.
FAQ’S
1- Why rails are welded?
The main reason for welding rails is to expand the length by joining two or more tracks. Joints in tracks are a lot like bones in humans. They provide strength and support while allowing movement. Welded rails give you a strong and smooth ride and involve less maintenance.
Trains run at a very high speed and produce less friction. Rail welding might be more costly compared to the jointed tracks. However, welded rails are like artificial joints. They’re more expensive up front but require less maintenance over time.4
2- What are the various methods of welding rails?
Rail welding is much like ordinary welding involving joining two metal pieces by applying heat and pressure. However, there are four primary methods used in rail welding. They are:
- Butt or Flash Butt welding
- Exothermic or Alumino-thermic or Thermite welding
- Puddle or electric arc or enclosed arc welding
- Gas pressure welding
Ending Notes
The welding of rails is an important subject to be familiar with as a rail worker or engineer. Among all three mentioned methods, every method has its pros and cons. For instance, the thermite process is a very suitable form of welding rails when you are doing work at the site. Because no extra electricity is needed, you can generate enough heat during the chemical reaction.
However, the welded joint is weak in strength compared to the flash butt welded joint. On the other hand, the butt weld method is most budget-friendly but can be embraced efficiently only in a workshop, which requires capital investment.
The puddle arc method is suitable when you know your job well and want to work manually with electrodes. So the choice is yours. I hope this blog will give you a better understanding of the welding of the rails and their types.
If you want to learn more about welding, please read our article Career in welding and is welding hard to learn?