English IV – Technical English for Engineering (TEfE)
U28 – NON–MECHANICAL JOINTS 1
A – WELDING
➢ Process of permanently joining two pieces of material by heating the joint between them.
▪ The heat melts the edges of the components being welded together, and...
▪ Once the material has become molten (liquid), then fusion occurs.
✓ When the joint fuses, material from each component is mixed together, joining to form a solid
weld.
✓ Metal is often welded. It is also possible to weld plastic.
➢ Welding is usually used to join components of the same base metal – that is, the metal the
components are made of.
▪ It is possible, though more difficult, to weld certain dissimilar materials.
✓ For example, copper can be welded to steel.
✓ Often, a filler is added during welding.
▫ This is new material, of the same type as the base metal, which is melted into the weld pool
- the molten metal at the joint during welding.
▪ Problems with welding:
✓ Discontinuity ➔ occurs where joints are not completely solid.
✓ Residual stress ➔ this is force- for example, tension- which is 'trapped' around the joint.
▫ It can occur after welding, as a result of contraction in the weld zone (or fusion zone), the
area that was the weld pool.
▫ It can also occur in the heat-affected zone (HAZ) –the material close to the weld pool, which
was subjected to high temperature, and was modified by the heat.
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English IV – Technical English for Engineering (TEfE)
➢ WELDING DISSIMILAR METALS
▪ Definition ➔ dissimilar metals are “materials or material combinations that are difficult to join”,
why? Because…
✓ of their individual chemical compositions or
✓ of large differences in physical properties between the two materials being joined.
▪ Process ➔ for the most part is extremely similar to the welding of two similar metals.
✓ Copper and steel are two metals which are often welded together, but both possess very
different properties and are not mutually soluble.
✓ So, since nickel is soluble with both of them and so can be used as the buttering layer, either
as a whole piece of nickel or as smaller nickel deposits on the steel surface.
▪ Some material combinations cannot be fusion welded successfully, and nothing can be done
to alter their metallurgical properties, so that only leaves changing the process itself. Some
examples are:
✓ aluminum and steel (carbon or stainless steel),
✓ aluminum and copper,
✓ and titanium and steel.
▪ Metals farther apart should not be used together. For example:
✓ aluminum [13] and copper [29] should not be used together, but…
▫ “Copper and aluminum have drastically different melting temperatures. Copper has a melting
temperature of 1984°F; Aluminum has a melting temperature of 1221°F. This means that if you
were to join the two materials using fusion processes, you would run the risk of overheating
and weakening the aluminum. In fact, with fusion processes, you will always change the
material properties of one or both materials due to melting.”
✓ copper [29] and bronze, an alloy consisting primarily of copper [29], commonly with tin [50]
(12%) and often with the addition of other metals (such as aluminum [13], manganese [25] ,
nickel [28] or zinc [30]) can be.
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English IV – Technical English for Engineering (TEfE)
ULTRASONIC WELDING OF PLASTICS
PLASTIC PARTS JOINED USING LASER
WELDING
WELD POOL DIAGRAM
WELD (FUSION) ZONE
WELD (FUSION) ZONE
HEAT-AFFECTED ZONE
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English IV – Technical English for Engineering (TEfE)
VOCABULARY , PRONUNCIATION , CONCEPTS AND DEFINITIONS
T ERM
P RONUNCIATION
M EANING
➢ Buttering layer (n)
▪
✓ capa de base/agarre
➢ Dissimilar (a)
▪
✓ disímil, distinto
➢ Filler metal (n)
▪
✓ metal de relleno
➢ Fusion (n)
▪
✓ fusión, unión, aleación, mezcla
➢ Heat-affected zone (HAZ) (n)
▪
✓ zona afectada por el calor
➢ Join (n)
▪
✓ unión, junta
➢ Join (v)
▪
✓ unir
➢ Joint (n)
▪
✓ junta, bisagra, unión, articulación
➢ Molten
▪
✓ fundido, derretido, líquido
➢ Weld (n)
▪
✓ soldadura
➢ Weld (v)
▪
✓ soldar
➢ Weld pool (n)
▪
✓ baño de soldadura
➢ Welded together, (to be)
▪
✓ Ser/estar soldados entre sí
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English IV – Technical English for Engineering (TEfE)
B – COMMON GAS AND ARC WELDING TECHNIQUES
➢ SHIELDED METAL ARC WELDING (SMAW), generally called arc welding or stick welding...
▪ It involves striking an electric arc between the workpiece and an electrode – an electrical
conductor.
✓ The heat from the arc melts the base metal.
✓ The electrode consists of a welding rod, a stick of metal of the same type as the workpiece.
▫ It provides the filler, thus making the rod consumable, meaning that, eventually it is used
up (consumed in its entirety).
▫ The rod is also coated with a material called flux, that when heated, it produces a shielding
gas, which protects the molten metal from oxygen.
▫ Without this gas, the hot metal would combine with the oxygen in the air, and this would
weaken the weld.
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English IV – Technical English for Engineering (TEfE)
➢ GAS WELDING
▪ It happens when heat comes from a torch which burns oxyfuel – a mixture of oxygen (O2) and
a gas fuel.
✓ The gas fuel burns much hotter in oxygen than it would in the air.
✓ The most common fuel is acetylene (C2H2)- called oxyacetylene when mixed with oxygen.
✓ Welding rods provide filler, but flux is not required, as the burning oxyfuel produces carbon
dioxide (CO2) which acts as a shielding gas.
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English IV – Technical English for Engineering (TEfE)
➢ GAS METAL ARC WELDING (GMAW), oftentimes called MIG welding (Metal Inert Gas)
▪ an arc is struck between the workpiece and a wire which is made of the same metal as the base
metal.
✓ The wire acts as a consumable electrode, supplying filler.
✓ A shielding gas, often argon (Ar), is blown onto the weld pool.
Shielding gas blends for carbon steel GMAW
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English IV – Technical English for Engineering (TEfE)
➢ GAS TUNGSTEN ARC WELDING (GTAW) – often called TIG welding (Tungsten Inert Gas)
▪ An arc comes from an electrode made of tungsten (W).
✓ However, the tungsten is non-consumable, that is, it does not melt, and is not consumed as
filler during the welding process.
✓ Whenever necessary, a separate welding rod is used to supply filler.
✓ As with MIG welding, a shielding gas such as argon is blown onto the weld.
GTAW / TIG WELDING
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English IV – Technical English for Engineering (TEfE)
VOCABULARY , PRONUNCIATION , CONCEPTS AND DEFINITIONS
T ERM
P RONUNCIATION
M EANING
➢ Arc welding (n)
▪
✓ soldadura por arco/electrógena
➢ Consumable (n)
▪
✓ consumible
✓ arco eléctrico
➢ Electric arc (n)
▪
➢ Electrode
▪
Descarga eléctrica luminosa entre
dos electrodos en el seno de un gas
que se ioniza.
✓ electrodo, (material de) aporte
✓ Fundente, revestimiento
Producto químico usado en proceso
de soldar y en la fabricación de
circuitos impresos y otros
componentes electrónicos. Sirve,
entre otras funciones, para aislar del
contacto del aire, disolver y eliminar
los óxidos que pueden formarse y
favorecer la permeabilidad del
material base por el metal de
aportación fundido, consiguiendo
que el metal de aportación pueda
fluir y se distribuya en la unión.
➢ Flux (n)
▪
➢ Gas welding (n)
▪
✓ soldadura con gas
➢ GMAW welding (n)
▪
✓ soldadura en cualquier posición
➢ MIG welding (n)
▪
✓ soldadura de metal de gas inerte
➢ Oxyfuel (n)
▪
✓ combustible oxigenado
➢ Shielding gas (n)
▪
✓ gas protector
➢ Stick welding (n)
▪
✓ soldadura con electrodo
revestido
➢ Strike (v)
▪
✓ encender, golpear
▪
✓ soldadura de gas inerte de
tungsteno, soldadura en arco
pulsado
➢ TIG welding (n)
➢ Torch (n)
cutting torch
propane torch
oxyacetylene torch
welding torch
➢ Welding rod (n)
✓ Soplete
soplete cortador
soplete de propano
soplete de oxiacetileno
soplete de soldadura
▪
✓ Varilla/barra para soldar/de
soldadura
▪
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Professional English in Use – Engineering
Mark Ibbotson – Cambridge University Press
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