Explosive Welding – Overview, Parts, Working, Types, Uses, Advantages, Disadvantages, and Applications
Overview
| Introduction |
| Parts of Explosive Welding |
| How is Explosive Welding Set Up? |
| Working Of Explosive Welding |
| Types of Explosive Welding |
| What are the Uses of Explosive Welding? |
| What are the Advantages of Explosive Welding? |
| Disadvantages of Explosive Welding |
| Applications of Explosive Welding |
| Conclusion |
Introduction
Explosive welding is a solid-state welding process in which two components are joined by accelerating one of the components at high velocity using the force generated by the explosion of chemical explosives.
| Note:- Solid state welding process means the welding process in which the metal does not melt and the welding happens in a solid state without melting the metal. |
Explosive Welding is typically used to join two or more metal sheets together. Many metals are difficult to weld together, and high bonding strength is easily obtained with the help of explosive welding.
As explosion is used in the process of explosive welding that’s why very few geometries can be produced using this process. Some of the geometries that can be produced using explosive welding are:- plates, tubes and tube sheets.
For welding two metal sheets together explosive welding is necessary because with other welding processes, we can only weld the edges of the metal sheets but with explosive welding, we can weld the edges as well as the inner planes of the metal sheets to be welded.
Properties Of Explosive Welding:-
i) It is a solid-state welding process.
ii) It can be dangerous so should be performed very professionally and with proper safety.
iii) The explosion used in explosive weldings should be a controlled explosion.
Parts Of Explosive Welding:
Here is the list of the parts of the Explosive Welding Process:-
Base plate Or Target plate:
The base plate is the welding plate where the metal or material is placed. It involves the backer, which supports the plate, and minimizes the distortion of the explosion.
Flyer plate:
The flyer Plate is another plate with a lower Density and tensile yield strength than the base plate. The flyer plate is placed parallel to the base plate or at an angle with the base plate.
Buffer plate:
The buffer Plate is positioned above the flyer plate and is used to reduce the effect of the explosion on the upper die of the flyer plate’s surface. This protects the flyer plates from the explosion.
Explosive Material:
The explosive material is placed on the flyer plate, where the explosive processes the metals or other materials. Generally, RDX, TNT, PETNA, and lead azide are commonly used for explosions.
Anvil:-
The anvil is a heavy metal piece over which the explosive welding process is done. The target plate is placed over the anvil. The anvil is large in size because the larger and heavier the anvil, the more efficient it is.
How is Explosive Welding Set Up?
1) At first, the target plate or base plate is fixed over the anvil. The anvil supports the base plate during the explosion.
2) The surface of the flyer plate and the base plate are cleaned properly and all impurities are removed so that there will be no formation of oxides during the welding process.
3) Then the flyer plate is placed over the base plate and the stand-off distance and a stand-off angle are kept between the two plates.
The stand-off distance is about 0.5 to 1 times the thickness of the flyer plate.
4) After that the buffer plate is placed over the flyer plate to protect it from erosion while the welding process.
5) At last, a layer of explosive material is placed over the buffer plate in such a way that the detonator is at the end.
Working Of Explosive Welding:
At first, The detonator is used to ignite the explosive material. Explosion starts from the one end of the explosive material, the end at which the detonator is present.
Because of the explosion, the flyer plate moves at high velocity towards the base plat
A high impact is created between the base plate and the flyer plate due to the collision of these two plates at very high velocity.
Due to high impact, the plates undergo plastic deformation and molecular diffusion as a result of which the two plates are welded together.
Also as the plates are kept at a stand-off angle, so when the explosion starts and one end of the flyer plate collides with the base plate at a very high velocity, the air between the base plate and the flyer plate gets compressed very rapidly due to which a plasma jet is created.
This plasma jet moves from the end at which the explosion starts to the other end.
| Plasma Jet is a jet of very hot air or gas. |
When the two plates collide at an angle, the welding starts from the end at which the explosion starts and proceeds continuously towards the other end following the plasma jet and the ignition of explosive material.
The strength of the weld joint created using an explosive welding process is very high.
The Quality of Explosive Welding relies on the following parameters:
1) Detonation’s velocity:
The detonation’s velocity refers to the rate at which the explosion detonates. The velocity of the explosion is kept less than 120 percent of the sonic velocity because it is directly proportional to the explosive type and density. Sonic velocity is the maximum velocity the gas can reach In the pipe or the system.
2) Collision Velocity:
Collision velocity is the velocity at which the flyer plate collides with the base plate or target plate after the explosion.
3) Angle Of Collision:
The angle of collision is the angle at which the flyer plate collides with the base plate.
4) Standoff Distance:
It is used to double the flyer plate’s thickness for thin plates and equal the flyer plate’s thickness for thick plates in the space between the flyer plate and the base plate.
5) Stand-off angle:
Some metals cannot be welded using constant stand-off distance, so for such metals, the flyer plate is kept at an angle to the base plate along with the stand-off distance and this angle between the base plate and flyer plate is known as the stand-off angle.
Types Of Explosive Welding:
Oblique Explosive Welding
In the welding process, the base plate is fixed on the anvil, and the filler plate is used to make an angle. The angle is made between the base plate and the filler plate. This welding is used to join the thin and small plates.
Parallel Explosive Welding
A filler plate is paralleled to the base plate and maintains some standoff distance. The welding is used for welding thick and large plates.
Whether oblique explosive welding or parallel explosive welding should be used should be decided on the basis of thickness and the size of the metal to be welded.
Uses Of Explosive Welding:
1) It is used to make layers over metal to save from corrosion.
2) It is used to weld dissimilar metals which cannot be welded by using other methods. ( Over 260 metal combinations can be joined using explosive welding).
Advantages Of Explosive Welding:
The advantages of explosive welding are as follows:
1) Unlike conventional welding, which generates a heat-affected area (HAZ) capable of metallurgical changes and distortion, explosive welding occurs at room temperature.
2) The properties of explosive welding like varied steel bonding, absence of heat-affected zones, robust metallurgical bonds, and decreased energy consumption make it a valuable method in diverse industries.
3) Explosive welding’s versatility and capability to create strong joints without compromising material properties make explosive welding unique and progressive.
4) Explosive welding has become a member of the method with a good ability for development in substance science and engineering.
5) It requires minimum fixtures.
6) For explosive welding highly skilled labour is not required.
Disadvantages Of Explosive Welding:
Here are some of the disadvantages of explosive welding:
1) It is suitable for welding ductile metal only and not suitable for brittle materials.
2) It limits the designs of the joints.
3) It is dependent on the process of the parameters.
4) Safety precautions are needed to take as it involves higher explosive.
5) It can only be used for simple geometric shapes.
6) Licesnse is necessary for using explosives.
Applications Of Explosive Welding
Explosive welding is widely used in many industries for many different purposes. Some of the uses are as follows:
1) These are used in the automobile industry, where they can be used to weld large structures, such as sheets of aluminium to sheets of stainless steel.
2) It can weld cylindrical components such as pipes, tubes, etc.
3) Cooling fans can be joined together with the help of explosive welding.
4) Explosive welding can weld the glass sheet with steel in a heat exchanger.
5) The chemical industry can use explosive welding to withstand corrosive chemicals and high-pressure conditions.
Wrapping It Up
As we have discussed everything about explosive welding, I hope you find the article informative.
To summarize, The explosive welding process generally involves using a high energy rate to deform the detonation of an explosive, forming a metallurgical bond between the two plates. The process is set up by placing both the flyer plate and the base plate on the interface surface, with the standoff distance and buffer plate set up.
The advantages of explosive welding include its versatility, its ability to create strong joints without compromising material properties and have the potential for substance science and engineering development.
