A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end; the end opposite to the head is called the tail. On installation, the rivet is placed in a punched or drilled hole, the tail is upset, or bucked, so that it expands to about 1.5 times the original shaft diameter, holding the rivet in place. In other words, pounding creates a new "head" on the other end by smashing the "tail" material flatter, resulting in a rivet, a dumbbell shape. To distinguish between the two ends of the rivet, the original head is called the factory head and the deformed end is called the shop head or buck-tail; because there is a head on each end of an installed rivet, it can support tension loads. However, it is much more capable of supporting shear loads. Fastenings used in traditional wooden boat building, such as copper nails and clinch bolts, work on the same principle as the rivet but were in use long before the term rivet was introduced and, where they are remembered, are classified among nails and bolts respectively.
There are a number of types of rivets, designed to meet different cost and strength requirements: Solid rivets are one of the oldest and most reliable types of fasteners, having been found in archaeological findings dating back to the Bronze Age. Solid rivets consist of a shaft and head that are deformed with a hammer or rivet gun. A rivet compression or crimping tool can deform this type of rivet; this tool is used on rivets close to the edge of the fastened material, since the tool is limited by the depth of its frame. A rivet compression tool does not require two people, is the most foolproof way to install solid rivets. Solid rivets are used in applications where safety count. A typical application for solid rivets can be found within the structural parts of aircraft. Hundreds of thousands of solid rivets are used to assemble the frame of a modern aircraft; such rivets come with rounded or 100° countersunk heads. Typical materials for aircraft rivets are aluminium alloys and nickel-based alloys.
Some aluminum alloy rivets are too hard to buck and must be softened by solution treating prior to being bucked. "Ice box" aluminum alloy rivets harden with age, must be annealed and kept at sub-freezing temperatures to slow the age-hardening process. Steel rivets can be found in static structures such as bridges and building frames; the setting of these fasteners requires access to both sides of a structure. Solid rivets are driven using a hydraulically, pneumatically, or electromagnetically actuated squeezing tool or a handheld hammer. Applications where only one side is accessible require "blind" rivets. Solid rivets are used by some artisans in the construction of modern reproduction of medieval armour and metal couture; until recently, structural steel connections were either welded or riveted. High-strength bolts have replaced structural steel rivets. Indeed, the latest steel construction specifications published by AISC no longer covers their installation; the reason for the change is due to the expense of skilled workers required to install high strength structural steel rivets.
Whereas two unskilled workers can install and tighten high strength bolts, it takes a minimum of four skilled riveters to install rivets. At a central location near the areas being riveted, a furnace was set up. Rivets were placed in the furnace and heated to glowing hot so that they were more plastic and deformed; the rivet warmer or "cook" used tongs to remove individual rivets and throw them to a catcher stationed near the joints to be riveted. The catcher caught the rivet in wooden bucket with an ash-lined bottom, he placed the rivet into the hole to be riveted quickly turned to catch the next rivet. The "holder up or holder on" would hold a heavy rivet set or dolly or another pneumatic jack against the round head of the rivet, while the riveter applied a hammer or pneumatic rivet hammer to the unformed head, making it mushroom against the joint in its final domed shape. Alternatively the buck is hammered less flush with the structure in a counter sunk hole. Before the use of pneumatic hammers, e.g. in the construction of RMS Titanic, the man who hammered the rivet was known as the "basher".
Upon cooling, the rivet exerted further force, tightening the joint. The last used high strength structural steel rivets were designated ASTM A502 Grade 1 rivets; such riveted structures may be insufficient to resist seismic loading from earthquakes if the structure was not engineered for such forces, a common problem of older steel bridges. This is. In the seismic retrofit of such structures it is common practice to remove critical rivets with an oxygen torch, precision ream the hole insert a machined and heat treated bolt. Semi-tubular rivets are similar to solid rivets; the purpose of this hole is to reduce the amount of force needed for application by rolling the tubular portion outward. The force needed to apply a semitubular rivet is about 1/4 of the amount needed to apply a solid rivet. Tubular rivets are sometimes preferred for pivot points since the swelling of the rivet is only
Tube bending is the umbrella term for metal forming processes used to permanently form pipes or tubing. One must differentiate between form-bound and freeform-bending procedures, as well as between heat supported and cold forming procedures. Form bound bending procedures like “press bending” or “rotary draw bending” are used to form the work piece into the shape of a die. Straight tube stock can be formed using a bending machine to create a variety of single or multiple bends and to shape the piece into the desired form; these processes can be used to form complex shapes out of different types of ductile metal tubing. Freeform-bending processes, like three-roll-pushbending, shape the workpiece kinematically, thus the bending contour is not dependent on the tool geometry. Round stock is used in tube bending; however and rectangular tubes and pipes may be bent to meet job specifications. Other factors involved in the bending process are the wall thickness and lubricants needed by the pipe and tube bender to best shape the material, the different ways the tube may be used.
A tube can be bent in multiple angles. Common simple bends consist of forming elbows, which are bends that range from 2 to 90°, U-bends, which are 180° bends. More complex geometries include three-dimensional bends. A 2D tube has the openings on the same plane. A two plane bend or compound bend is defined as a compound bend that has a bend in the plan view and a bend in the elevation; when calculating a two plane bend, one must know the bend rotation. One side effect of bending the workpiece is the wall thickness changes. To reduce this the tube may be supported externally to preserve the cross section. Depending on the bend angle, wall thickness, bending process the inside of the wall may wrinkle. Tube bending as a process starts with loading a tube into a tube or pipe bender and clamping it into place between two dies, the clamping block and the forming die; the tube is loosely held by two other dies, the wiper die and the pressure die. The process of tube bending involves using mechanical force to push stock material pipe or tubing against a die, forcing the pipe or tube to conform to the shape of the die.
Stock tubing is held in place while the end is rotated and rolled around the die. Other forms of processing including pushing stock through rollers that bend it into a simple curve. For some tube bending processing, a mandrel is placed inside the tube to prevent collapsing; the tube is held in tension by a wiper. A wiper die is made of a softer alloy such as aluminum or brass to avoid scratching or damaging the material being bent. Much of the tooling is made of hardened tool steel to maintain and prolong the tool's life. However, when there is a concern of scratching or gouging the work piece, a softer material such as aluminum or bronze is utilized. For example, the clamping block, rotating form block and pressure die are formed from hardened steel because the tubing is not moving past these parts of the machine; the pressure die and the wiping die are formed from aluminum or bronze to maintain the shape and surface of the work piece as it slides by. Pipe bending machines are human powered, pneumatic powered, hydraulic assisted, hydraulic driven, or electric servomotor.
Press bending is the first bending process used on cold pipes and tubing. In this process a die in the shape of the bend is pressed against the pipe forcing the pipe to fit the shape of the bend; because the pipe is not supported internally there is some deformation of the shape of the pipe, resulting in an oval cross section. This process is used. Although a single die can produce various shapes, it radius. Rotary draw bending is a precise technology, since it bends using tooling or "die sets" which have a constant center line radius, alternatively indicated as mean bending radius. Rotary draw benders can be programmable to store multiple bend jobs with varying degrees of bending. A positioning index table is attached to the bender allowing the operator to reproduce complex bends which can have multiple bends and differing planes. Rotary draw benders are the most popular machines for use in bending tube and solids for applications like: handrails, motor vehicle roll cages, handles and much more.
Rotary draw benders create aesthetically pleasing bends when the right tooling is matched to the application. CNC rotary draw bending machines can be complex and use sophisticated tooling to produce severe bends with high quality requirements; the complete tooling is required only for high-precision bending of difficult-to-bend tubes with large OD/t ratio and small ratio between the mean bending radius Rm and OD. The use of axial boosting either on the tube free end or on the pressure die is useful to prevent excessive thinning and collapse of the extrados of the tube; the mandrel, with or without ball with spherical links, is used to prevent wrinkles and ovalization. For easy bending processes, the tooling can be progressively simplified, eliminating the need for the axial assist, the mandrel, the wiper die. Furthermore, in some particular cases, the standard tooling must be modified in order to meet specific requirements of the products. During the roll bending pr
A stamping press is a metalworking machine tool used to shape or cut metal by deforming it with a die. In simple terms, a stamping press is the modern day equivalent of a anvil; the difference is that a stamping press uses precision-made male and female dies to dictate the shape of the final product. A press has a bolster plate, a ram. Presses come in various types of frame configurations, C-Frame where the front & left and right sides are open. Straight Side or H-Frame for stronger higher tonnage applications, it is important to size the press and tonnage based on the type of applications, forming, progressive or transfer. Strong consideration should be given to avoiding off-center load conditions to prevent premature wear to the press; the bolster plate is mounted on top of the press bed and is a large block of metal upon which the bottom portion of a die is clamped. Large presses may be equipped with die cushions integrated in the bolster plate to apply blank holder or counter draw forces; this is necessary.
The ram / slide is the moving or reciprocating member that the upper die is mounted to. Ram or Slide guidance is a critical element to assure long die life between die maintenance. Different types of slide guides are available, 4 point V-Gibs or 6 point square gibs on smaller presses and 8 point full length slide guides on larger straight side frame presses. With the dies and material be fed into the die between the bolster and slide, good press designs must account for plastic deformation, other wise known as deflection when frame design and loads are considered; the vertical motion of the slide acts like a hammer to an anvil. When presses are used manually, where an operator is loading and unloading parts, extreme caution should be used and proper methods of safe guarding should be in place. With the addition of safety light curtains and an I-PRESS control, the light curtains can be muted or turned off on the slide upstroke to increase productivity when press is being used in single stroke mode.
Standard modes of operation with up to date safe press controls are OFF-INCH-SINGLE STROKE & CONTINUOUS modes which can be selected via a keyed mode selector switch. Special modes of operation include, MICRO INCH-SSD/SINGLE ON DEMAND & CSD/CONTINUOUS ON DEMAND. Micro Inch is used for die set up near the BDC / Bottom Dead Center, SSD Single Stroke on Demand can be used when long coil feed lengths or automation loading and unloading will trigger SSD. CSD Continuous on Demand is used when press are used in roll form lines or irregular stroking is required when punching holes in large panel with gag feed dies; the most common Mechanical Presses use an eccentric drive to move the press's ram slide, length of stroke or slide travel depends on the crankshaft or eccentric, whereas hydraulic cylinders are used in hydraulic presses. The nature of drive system determines the force progression during the ram's stroke. Mechanical presses have a full tonnage rating point above BDC / Bottom Dead Center, normal full tonnage rating points are.187".25" &.5".
Hence a mechanical press has a tonnage curve and should be operated within the press capacity limits. Link Motion mechanical is yet another option, this provides a slide slow down near BDC / bottom dead center for soft touch tooling; this link feature can improve reduce reverse-snap thru tonnage for blanking operations. On the contrary, Hydraulic Presses do not have a tonnage curve and can produce full tonnage at any point in the stroke; the trade off is speed, a mechanical press is much faster. On the other hand, Hydraulic Presses are much more practical for deep forming or drawing or parts or when dwell time at the bottom is desired. Another key feature with the I-PRESS AB PLUS HYDRO control, is that you can vary the speed and position up to 7 times on the downward stroke. Another classification is single-acting presses versus double- acting presses. Single-acting presses have one single ram. Double-acting presses have a subdivided ram, to manage, for example, blank holding with one ram segment and the forming operation with the second ram segment.
Presses are electronically linked to an automatic feeder which feeds metal raw material through the die. The raw material is fed into the automatic feeder after it has been unrolled from a coil and put through a straightener. A tonnage monitor may be provided to observe the amount of force used for each stroke. Press and automation controls have take a huge leap forward in 2016 with safety, features & functions. A good example is Connected Enterprise with I-PRESS that allows users to log in from any remote device to and individual press; this allows for new job set ups to be downloaded from engineering or trouble shooting and operator assistance to be done from mobile devices or PC's. See a stamping press in action HD Stamping Press 1080p / See the I-PRESS AB PLUS control video
In metalworking and jewellery making, casting is a process in which a liquid metal is somehow delivered into a mold that contains a hollow shape of the intended shape. The metal is poured into the mold through a hollow channel called a sprue; the metal and mold are cooled, the metal part is extracted. Casting is most used for making complex shapes that would be difficult or uneconomical to make by other methods. Casting processes have been known for thousands of years, have been used for sculpture, jewellery in precious metals, weapons and tools. Traditional techniques include plaster mold casting and sand casting; the modern casting process is subdivided into two main categories: expendable and non-expendable casting. It is further broken down by the mold material, such as sand or metal, pouring method, such as gravity, vacuum, or low pressure. Expendable mold casting is a generic classification that includes sand, shell and investment moldings; this method of mold casting involves the use of non-reusable molds.
Sand casting is one of the most popular and simplest types of casting, has been used for centuries. Sand casting allows for smaller batches than permanent mold casting and at a reasonable cost. Not only does this method allow manufacturers to create products at a low cost, but there are other benefits to sand casting, such as small-size operations; the process allows for castings small enough fit in the palm of one's hand to those large enough only for train beds. Sand casting allows most metals to be cast depending on the type of sand used for the molds. Sand casting requires a lead time of days, or weeks sometimes, for production at high output rates and is unsurpassed for large-part production. Green sand, black in color, has no part weight limit, whereas dry sand has a practical part mass limit of 2,300–2,700 kg. Minimum part weight ranges from 0.075–0.1 kg. The sand is bonded together using chemical binders, or polymerized oils. Sand requires little maintenance. Plaster casting is similar to sand casting except that plaster of paris is used instead of sand as a mold material.
The form takes less than a week to prepare, after which a production rate of 1–10 units/hr-mold is achieved, with items as massive as 45 kg and as small as 30 g with good surface finish and close tolerances. Plaster casting is an inexpensive alternative to other molding processes for complex parts due to the low cost of the plaster and its ability to produce near net shape castings; the biggest disadvantage is that it can only be used with low melting point non-ferrous materials, such as aluminium, copper and zinc. Shell molding is similar to sand casting, but the molding cavity is formed by a hardened "shell" of sand instead of a flask filled with sand; the sand used is finer than sand casting sand and is mixed with a resin so that it can be heated by the pattern and hardened into a shell around the pattern. Because of the resin and finer sand, it gives a much finer surface finish; the process is automated and more precise than sand casting. Common metals that are cast include cast iron, aluminium and copper alloys.
This process is ideal for complex items. Investment casting is a process, practiced for thousands of years, with the lost-wax process being one of the oldest known metal forming techniques. From 5000 years ago, when beeswax formed the pattern, to today’s high technology waxes, refractory materials and specialist alloys, the castings ensure high-quality components are produced with the key benefits of accuracy, repeatability and integrity. Investment casting derives its name from the fact that the pattern is invested, or surrounded, with a refractory material; the wax patterns require extreme care for they are not strong enough to withstand forces encountered during the mold making. One advantage of investment casting is; the process is suitable for repeatable production of net shape components from a variety of different metals and high performance alloys. Although used for small castings, this process has been used to produce complete aircraft door frames, with steel castings of up to 300 kg and aluminium castings of up to 30 kg.
Compared to other casting processes such as die casting or sand casting, it can be an expensive process. However, the components that can be produced using investment casting can incorporate intricate contours, in most cases the components are cast near net shape, so require little or no rework once cast. A durable plaster intermediate is used as a stage toward the production of a bronze sculpture or as a pointing guide for the creation of a carved stone. With the completion of a plaster, the work is more durable than a clay original which must be kept moist to avoid cracking. With the low cost plaster at hand, the expensive work of bronze casting or stone carving may be deferred until a patron is found, as such work is considered to be a technical, rather than artistic process, it may be deferred beyond the lifetime of the artist. In waste molding a simple and thin plaster mold, reinforced by sisal or burlap, is cast over the original clay mixture; when cured, it is removed from the damp clay
Metal fabrication is the creation of metal structures by cutting and assembling processes. It is a value-added process involving the creation of machines and structures from various raw materials. A fabrication shop bids on a job based on engineering drawings, if awarded the contract, builds the product. Large fab shops employ a multitude of value-added processes, including welding, cutting and machining. Metal fabrication starts with drawings with precise dimensions and specifications. Fabrication shops are employed by OEMs and VARs. Typical projects include loose parts, structural frames for buildings and heavy equipment, stairs and hand railings; as with other manufacturing processes, both human labor and automation are used. A fabricated product may be called a fabrication, shops specializing in this type of work are called fab shops; the end products of other common types of metalworking, such as machining, metal stamping and casting, may be similar in shape and function, but those processes are not classified as fabrication.
Cutting is done by shearing, or chiseling. Bending is done via press brakes, tube benders and similar tools. Modern metal fabricators use press brakes to coin or air-bend metal sheet into form. CNC-controlled backgauges use hard stops to position cut parts to place bend lines in specific positions. Assembling is done by welding, binding with adhesives, threaded fasteners, or further bending in the form of crimped seams. Structural steel and sheet metal are the usual materials for fabrication. Fabrication comprises or overlaps with various metalworking specialties: Fabrication shops and machine shops have overlapping capabilities, but fabrication shops concentrate on metal preparation and assembly. Machine shops cut metal, but focus on the machining of parts on machine tools; some firms do machining. Blacksmithing has always involved fabrication, although that term has not always been used. Welder-produced products referred to as weldments, are examples of fabrication. Boilermakers specialized in fabricating boilers, but the term is now used more broadly.
Millwrights specialized in setting up grain mills and saw mills, but now perform a wide range of fabrication. Ironworkers known as steel erectors engage in fabrication, they work with prefabricated segments, produced in fab shops, that are delivered to the site. Standard metal fabrication materials are: Plate metal Formed and expanded metal Tube stock Welding wire/welding rod Casting A variety of tools are used to cut raw material; the most common cutting method is shearing. Special band saws for cutting metal have hardened blades and feed mechanisms for cutting. Abrasive cut-off saws known as chop saws, are similar to miter saws but have a steel-cutting abrasive disks. Cutting torches can cut large sections of steel with little effort. Burn tables are CNC cutting torches powered by natural gas. Plasma and laser cutting tables, water jet cutters, are common. Plate steel is loaded on the table and the parts are cut out as programmed; the support table consists of a grid of bars. Higher-end burn tables may include CNC punch capability using a carousel of taps.
In fabrication of structural steel by plasma and laser cutting, robots move the cutting head in three dimensions around the cut material. Forming converts flat sheet metal into 3-D parts by applying force without adding or removing material; the force must be great enough to change the metal's initial shape. Forming dies. Machinery can regulate force direction. Machine-based forming can combine welding to produce lengths of fabricated sheeting. Proper design and use of tools with machinery creates a repeatable form that can be used to create products for many industries, including jewelry, automotive, construction and architectural. Machining is a specialized trade of removing material from a block of metal to make it a desired shape. Fab shops have some machining capability, using metal lathes, mills and other portable machining tools. Most solid components, such as gears, bolts and nuts, are machined. Welding is the main focus of steel fabrication. Formed and machined parts are assembled and tack-welded in place rechecked for accuracy.
If multiple weldments have been ordered, a fixture may be used to locate parts for welding. A welder finishes the work according to engineering drawings or by their own experience and judgement. Special measures may be needed to correct warping of weldments due to heat; these may include redesigning the piece to require less welding, employing staggered welding, using a stout fixture, covering the weldment in sand as it cools, post-weld straightening. Straightening of warped steel weldments is done with an oxyacetylene torch. In this specialized work, heat is selectively applied to the steel in a slow, linear sweep, causing the steel to contract in the direction of the sweep as it cools. A skilled welder can remove significant warpage this way. Steel weldments are annealed in a low-temperature oven to relieve residual stresses. S
Metalworking is the process of working with metals to create individual parts, assemblies, or large-scale structures. The term covers a wide range of work from large ships and bridges to precise engine parts and delicate jewelry, it therefore includes a correspondingly wide range of skills and tools. Metalworking is a science, hobby and trade, its historical roots span cultures and millennia. Metalworking has evolved from the discovery of smelting various ores, producing malleable and ductile metal useful tools and adornments. Modern metalworking processes, though diverse and specialized, can be categorized as forming, cutting, or joining processes. Today's machine shop includes a number of machine tools capable of creating a precise, useful workpiece; the oldest archaeological evidence of copper mining and working was the discovery of a copper pendant in northern Iraq from 8,700 BCE. The earliest substantiated and dated evidence of metalworking in the Americas was the processing of copper in Wisconsin, near Lake Michigan.
Copper was hammered until brittle heated so it could be worked some more. This technology is dated to about 4000-5000 BCE; the oldest gold artifacts in the world come from the Bulgarian Varna Necropolis and date from 4450 BCE. Not all metal required fire to work it. Isaac Asimov speculated that gold was the "first metal", his reasoning is. In other words, gold, as rare as it is, is sometimes found in nature as the metal. There are a few other metals that sometimes occur natively, as a result of meteors. All other metals are found in ores, a mineral-bearing rock, that require heat or some other process to liberate the metal. Another feature of gold is that it is workable as it is found, meaning that no technology beyond a stone hammer and anvil to work the metal is needed; this is a result of gold's properties of ductility. The earliest tools were stone, bone and sinew, all of which sufficed to work gold. At some unknown point the connection between heat and the liberation of metals from rock became clear, rocks rich in copper and lead came into demand.
These ores were mined. Remnants of such ancient mines have been found all over Southwestern Asia. Metalworking was being carried out by the South Asian inhabitants of Mehrgarh between 7000–3300 BCE; the end of the beginning of metalworking occurs sometime around 6000 BCE when copper smelting became common in Southwestern Asia. Ancient civilisations knew of seven metals. Here they are arranged in order of their oxidation potential: Iron +0.44 V, Tin +0.14 V Lead +0.13 V Copper −0.34 V Mercury −0.79 V Silver −0.80 V Gold −1.50 V. The oxidation potential is important because it is one indicator of how bound to the ore the metal is to be; as can be seen, iron is higher than the other six metals while gold is lower than the six above it. Gold's low oxidation is one of the main reasons; these nuggets are pure gold and are workable as they are found. Copper ore, being abundant, tin ore became the next important players in the story of metalworking. Using heat to smelt copper from ore, a great deal of copper was produced.
It was used for simple tools. However, copper by itself was too soft for tools requiring stiffness. At some point tin was added into the molten copper and bronze was born. Bronze is an alloy of tin. Bronze was an important advance because it had the edge-durability and stiffness that pure copper lacked; until the advent of iron, bronze was the most advanced metal for weapons in common use. Outside Southwestern Asia, these same advances and materials were being discovered and used around the world. China and Great Britain jumped into the use of bronze with little time being devoted to copper. Japan began the use of bronze and iron simultaneously. In the Americas things were different. Although the peoples of the Americas knew of metals, it was not until the European colonisation that metalworking for tools and weapons became common. Jewelry and art were the principal uses of metals in the Americas prior to European influence. Around 2700 BCE, production of bronze was common in locales where the necessary materials could be assembled for smelting and working the metal.
Iron was beginning to be smelted and began its emergence as an important metal for tools and weapons. The period that followed became known as the Iron Age. By the historical periods of the Pharaohs in Egypt, the Vedic Kings in India, the Tribes of Israel, the Maya civilization in North America, among other ancient populations, precious metals began to have value attached to them. In some cases rules for ownership and trade were created and agreed upon by the respective peoples. By the above periods metalworkers were skilled at creating objects of adornment, religious artifacts, trade instruments of precious metals, as well as weaponry of ferrous metals and/or alloys; these skills were finely honed and well executed. The techniques were practiced by artisans, atharvavedic practitioners and other categories of metalworkers around the globe. For example, the granulation technique was employed by numerous ancient cultures before the historic record shows people traveled to far regions to share this process.
This and many other ancient techniques are still used by metalsmiths today. As time progressed metal objects became more common, more complex; the need to further acquire and work metals grew in importance
Soldering is a process in which two or more items are joined together by melting and putting a filler metal into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involve melting the work pieces. In brazing, the filler metal melts at a higher temperature. In the past, nearly all solders contained lead, but environmental and health concerns have dictated use of lead-free alloys for electronics and plumbing purposes. There is evidence. Soldering and brazing are thought to have originated early in the history of metal-working before 4000 BC. Sumerian swords from c. 3000 BC were assembled using hard soldering. Soldering was used to make jewelry items, cooking ware and tools, as well as other uses such as in assembling stained glass. Soldering is used in plumbing and metalwork from flashing to jewelry and musical instruments. Soldering provides reasonably permanent but reversible connections between copper pipes in plumbing systems as well as joints in sheet metal objects such as food cans, roof flashing, rain gutters and automobile radiators.
Jewelry components, machine tools and some refrigeration and plumbing components are assembled and repaired by the higher temperature silver soldering process. Small mechanical parts are soldered or brazed as well. Soldering is used to join lead came and copper foil in stained glass work. Electronic soldering connects electrical wiring and electronic components to printed circuit boards by utilizing a metallic alloy substance called solder; this special alloy is melted by using a soldering iron, a wave bath, or a specialized oven, as it joins conductors to PCBs, wires. Musical instruments brass and woodwind instruments, use a combination of soldering and brazing in their assembly. Brass bodies are a soldered together, while keywork and braces are most brazed. Soldering filler materials are available in many different alloys for differing applications. In electronics assembly, the eutectic alloy of 63% tin and 37% lead has been the alloy of choice. Other alloys are used for plumbing, mechanical assembly, other applications.
Some examples of soft-solder are tin-lead for general purposes, tin-zinc for joining aluminium, lead-silver for strength at higher than room temperature, cadmium-silver for strength at high temperatures, zinc-aluminium for aluminium and corrosion resistance, tin-silver and tin-bismuth for electronics. A eutectic formulation has advantages when applied to soldering: the liquidus and solidus temperatures are the same, so there is no plastic phase, it has the lowest possible melting point. Having the lowest possible melting point minimizes heat stress on electronic components during soldering. And, having no plastic phase allows for quicker wetting as the solder heats up, quicker setup as the solder cools. A non-eutectic formulation must remain still as the temperature drops through the liquidus and solidus temperatures. Any movement during the plastic phase may result in cracks. Common solder formulations based on tin and lead are listed below; the fraction represent percentage of tin first lead, totaling 100%: 63/37: melts at 183 °C 60/40: melts between 183–190 °C 50/50: melts between 183–215 °C For environmental reasons, lead-free solders are becoming more used.
They are suggested anywhere young children may come into contact with, or for outdoor use where rain and other precipitation may wash the lead into the groundwater. Most lead-free solders are not eutectic formulations, melting at around 250 °C, making it more difficult to create reliable joints with them. Other common solders include low-temperature formulations, which are used to join previously-soldered assemblies without unsoldering earlier connections, high-temperature formulations which are used for high-temperature operation or for first assembly of items which must not become unsoldered during subsequent operations. Alloying silver with other metals changes the melting point and wetting characteristics, tensile strength. Of all the brazing alloys, silver solders have the broadest applications. Specialty alloys are available with properties such as higher strength, the ability to solder aluminum, better electrical conductivity, higher corrosion resistance; the purpose of flux is to facilitate the soldering process.
One of the obstacles to a successful solder joint is an impurity at the site of the joint, for example, oil or oxidation. The impurities can be removed by mechanical cleaning or by chemical means, but the elevated temperatures required to melt the filler metal encourages the work piece to re-oxidize; this effect is accelerated as the soldering temperatures increase and can prevent the solder from joining to the workpiece. One of the earliest forms of flux was charcoal, which acts as a reducing agent and helps prevent oxidation during the soldering process; some fluxes go beyond the simple prevention of oxidation and provide some form of chemical cleaning. Many fluxes act as a wetting agent in the soldering process, reducing the surface tension of