Characteristics of selected processes of inseparable joining of materials: welding and soldering
Most products, ranging from simple toys to advanced electronic systems and ending with large-size equipment, contain material combinations. Thanks to joints, often of different materials, objects can fulfill their functional function. This article will allow us to familiarize ourselves with the selected methods of bonding, i.e. welding and soldering.
Technologies of materials joining processes
Bonding is based on joining various material elements into a structural whole. As part of this activity, detachable and non-detachable connections can be created. Detachable joints can be dismantled (disassembly does not damage materials or fasteners). Among the separable connections, the following types can be distinguished:
On the other hand, a feature of inseparable connections is the fact that it is impossible to separate the individual components of the connection without damaging the construction itself. This applies to both the connected elements and the connecting element. However, within the processes related to the creation of inseparable joints, there are such groups as: welding, fusing, soldering, gluing and riveting.
Briefly and succinctly about welding, gluing and riveting
Briefly speaking, welding consists in joining elements by heating them and obtaining a melt at the point of connection. This is done with or without the addition of binder. As for gluing, it involves placing a layer of glue, a non-metallic substance with adhesive properties (ensuring adhesion and adhesion), between the surfaces to be joined. The type of adhesive often determines the strength, reliability and durability of the joint, i.e. the resistance of the joint to high temperatures and its elasticity. Riveting is the creation of riveted joints using the so-called rivets, cold or hot. This type of technology is based on mechanical action and uses the frictional force and the properties of the geometry of the individual elements to form the joint. However, in this article, we will focus on welding and soldering.
In the case of welding, the materials are bonded by applying thermal energy and applying a clamping force. This process does not use a binder. In welding, at the point of contact between the surfaces of the materials, the zones become plasticized, sometimes even to a liquid state. The clamping force is a decisive factor in obtaining the right connection. Welding methods differ from each other and these differences boil down, among others, to the type of energy used, how it is applied to the joint and how pressure is exerted.
Among the welding methods, the following are particularly distinguished:
- electric resistance welding involves the connected elements in an electric circuit; on the basis of the Joule-Lenz law, the heat generated by the flow of electricity accumulates in places with the highest electrical resistance; the best results can be obtained with a high current intensity and a short time of its flow,
- electric butt welding, in this welding technique, the connection is created by exerting pressure on the materials placed face to face and heating the contact area with electricity,
- diffusion welding is characterized by a constant state of aggregation of materials during the process - the material is warmed to a temperature lower than its solidus value; this welding uses adhesion and diffusion (dispersion and mixing of different molecules); they are carried out in vacuum chambers or under protective atmosphere conditions,
- explosive welding - here the connection of elements is caused both by the clamping force, dynamically applied to the joined elements, and the local explosion of an explosive material,
- friction welding and pressure welding - mutual rubbing materials generate heat at their contact; the process is conditioned by two factors: temperature lower than the solidus of materials and diffusion of particles,
- ultrasonic welding - the elements are joined by obtaining mechanical vibrations of a given amplitude and frequency as well as as a result of pressure and thus obtained thermal energy; in this method, an electric to mechanical converter and the so-called vibrating pin (allows to direct vibrations to connected elements),
Soldering is characterized by the fact that the materials are joined under the influence of thermal energy, while maintaining the solid state of these materials and using a metal binder, the so-called February. Solder melting must occur at a temperature lower than the temperature of the parts to be soldered, most often metal or ceramic. Solder wets the surfaces of materials, spreads over them and penetrates into their pores. After cooling down, it turns out that intermolecular bonds were formed at the junction site (through adsorption, diffusion in different directions, as well as the formation of intermetallic phases).
Types and methods of soldering
The types of the soldering process are:
- soft - the binder has a melting point of up to 450 degrees Celsius,
- hard - the binder has a melting point of over 450 degrees Celsius,
- high-temperature - the binder has a temperature of over 1000 degrees Celsius.
Known soldering methods are:
- using a soldering iron, a dedicated tool soldering,
- furnace, carried out under vacuum conditions, in an atmosphere of inert gases or deoxidizing gases, or with the use of fluxes (compounds reducing the proportion of non-metallic substances from the surface of elements),
- bathing, fluxing, salted, liquefied solder baths,
- induction, uses a kind of induction heating,
- flame - the method of heating the joint here is a gas flame,
- microwave - uses microwave technology as a heat source,
- a stream of hot gases, carried out with the use of gas burners, lamps and soldering nozzles
- electrical resistance and induction.
Summary of bonding methods
Joining materials is an area of interest for both science, technology and business (industry). Different environments develop it and cooperate with each other to maximize profitability, process efficiency and quality of connections. The aforementioned profitability, efficiency and quality in the discussed scope translate into products and their value for recipients and consumers.