The Fundamental Steps to Brazing Metals

Lynch Metals has been a provider of aluminum brazing sheets for almost 30 years and is currently North America’s preeminent distributor of the sheet metal. Lynch is unique in the industry because of our relationships with aluminum mills, specialized processing machinery, vast inventory, and our skilled sales staff.

This page will examine the brazing process to familiarize readers with the steps involved and how it compares to welding.

Six Fundamental Steps to Brazing Metals

Brazing, like welding, joins two metal pieces together. Unlike welding, brazing uses a filler metal to form a robust joint, and a flux material to protect the filler. Brazing involves a simple six-step process:

1. Create a good fit with the right clearances. The filler metal gets into the joint through capillary action, so it is critical that the gap between the two base pieces at the joint is correctly spaced. The typical range for this gap is 0.001–0.005” and the optimal value is 0.0015” for most filler metals.

2. Pre-clean the joint. The metal surfaces forming the joint must be free of impurities for the capillary action to work properly. Common impurities on metal surfaces include dirt, grease, oil, and rust. These contaminants can be removed with acidic pickling agents, degreasing solvents, and polishing.

3. Coat the joint with flux. Flux protects the joint from oxidizing at the high temperatures required for brazing. It will dissolve any metallic oxides that form during brazing, so it is important to fully coat the joint with flux using a brush or an applicator gun.

4. Hold the base pieces steady during brazing. The joint gap created in the first step above must be held steady during brazing and until the parts have cooled to form a strong joint. Often times it is possible to do this with gravity if the base pieces are of the right shape and size, but sometimes a jig will be necessary.

5. Braze at the right temperature. Brazing requires melting the filler metal without also melting the base metal, so the temperature must be carefully controlled to achieve this. Additionally, the heat application must be uniform along the joint. This can be judged by watching how the flux’s appearance changes under heat. Once the right temperature is reached, the filler rod or wire is pressed against the joint so that it melts and is sucked into the joint by capillary action, which is improved by the aforementioned flux coating. Be sure that the molten filler flows into the joint and doesn’t stay at the surface of the base pieces.

6. Post-clean the joint. Since flux is corrosive, post-cleaning is just as important as pre-cleaning. Flux is easily washed away by hot water at 120° F or higher. Once the filler has cooled enough, the whole assembly can be quenched in hot water while it is still hot. If the residual flux is green or black—indicating that it is saturated with oxides—a mildly acidic agent will likely be necessary to remove it. If there is any metal oxide residue, it must be removed using a pickling solution.

Brazing vs. Welding

Even though brazing and welding are similar in several ways, there are significant differences between the two techniques:

• The operating temperature for brazing is lower than welding.
• In brazing, the melting point of the filler metal is lower than that of the base metals. Welding is the other way around.
• Brazing works through capillary action, whereas fusion is the working principle of welding.
• Brazing can join different metal types, where welding cannot.

Brazing is the preferred method of joining metals when the base pieces are made from different metal materials. It is also a superior technique when cleaner joints, less thermal distortion, and automation are called for.

Brazing Services From Lynch Metals

Lynch Metals is a one-stop source for aluminum brazing materials and services for a wide variety of industries ranging from aerospace to telecommunications. We are able to provide quick turnaround times thanks to our large and diverse stock of materials and the advanced equipment we use in our processing centers.

Contact us for all your brazing requirements or with questions about our other products and services.

Reduce Your In-House Costs with Lynch Metals

With our large inventory, specialized equipment, and experienced staff, Lynch Metals has become a premier stocking distributor of aluminum brazing sheet in North America. We also offer custom aluminum extrusions, stainless steel alloys, and more. We work with an expansive North American network of aluminum and steel mills to ensure we can procure any material our customers require.

Our expansive service portfolio at Lynch Metals ranges from sheet metal fabrication to finishing services, so we can reduce your in-house costs by providing you with end-to-end service on most projects. There’s no reason to haul a project between service providers or invest in additional equipment and the skilled staff you’d need to operate it. We will save you space, time, money by partnering with you on your next project.

Additional Fabrication Services at Lynch Metals

We offer a wide range of sheet metal fabrication services. We understand that our customers have evolving needs, and we strive continuously to adapt our capabilities to match what our customers require. Our services include:

• Miter cutting: This cutting method cuts along the length or width of sheet metal at an angle of anything other than 90 degrees. Two pieces of miter cut aluminum can be joined together to form a miter joint. 

• Hole punching: Many designs require holes to be drilled or punched to facilitate mounting parts or equipment or routing wiring. We offer a variety of hole punching and drilling services to suit the needs of any design.

• Deburring: Many cutting processes leave edges rough and burred. Unfinished edges may be more subject to corrosion and pose an injury risk to anyone handling the product. Our deburring process smooths out these rough edges for safe handling and improved service life.

In addition to these processes, other value-added services offered by Lynch metals include secondary machining and assembly.

Finishing Services Available

We offer multiple finishing services to protect metal substrates. These include:

• Powder coating: Both protective and decorative, powder coating is a very popular finishing choice. It’s more durable than liquid paint and comes in a variety of colors and textures.

• Wet painting for aluminum: When powder coating isn’t a viable option, wet paint can be applied to sheet metal via spray, pump, or pressurized vessel. A myriad of custom color options are available and paint is often the most economical choice for smaller projects. 

• Anodization: This process creates a strong, corrosion-resistant, anodic oxide finish so metals can withstand even the harshest environments. Anodization is used for satellite parts, skyscrapers, computer hardware, appliances, and much more. Anodized parts are attractive, low-maintenance, and environmentally responsible. To anodize aluminum, the metal is put into an acid electrolyte bath and then subjected to an electric current to combine the oxygen combine with the aluminum atoms. Anodization is not a coating, but instead becomes part of the aluminum piece, which can then be painted or sealed as desired for additional protection.

We’ve perfected our metal fabrication services over the years to serve an array of clients in the aerospace, industrial, automotive, signage, and telecommunications industries. By expanding to provide additional fabrication and finishing services, we act as a one-stop shop for all our customers’ fabrication needs. We’re committed to growth and innovation, so you can expect us to stay on top of trends, top-level processing equipment, and industry needs.

Contact us today for more information about our metal fabrication services and how we can support your project.

The Metals Most Commonly Used for Extrusions

The extrusion process pushes metal through a pre-formed die to shape it into a carefully designed cross-sectional profile. This process can achieve intricate cross-sections while simultaneously creating a quality surface finish. Many find this process especially useful for weak or brittle metals, since extruding relies entirely on compression and shearing.

The extrusion process is available in two different types. Continuous extrusions, in theory, can go on forever, creating one endless piece of material. Semi-continuous extrusions, conversely, are created in sections and create multiple extruded pieces.

How Is Metal Extruded?

Extruding metals may also increase the strength of the material and can be done with either hot or cold material.

Hot Extrusion

Heated billets of metal are hydraulically compressed into cylinders that contain dies. The dies allow the pressurized billet to escape via orifices of the desired shape. The metal emerges from these openings as a continuous bar with the same cross-sectional shape as the die opening. With the use of two sets of dies, stepped extrusions are created.

Lubricant reduces friction, protecting the die surfaces. Graphite is often used on non-ferrous alloys, and glass is the lubricant of choice for hot steel extrusion. The extrusion process can produce a wide array of configurations, including complex non-uniform and non-symmetrical shapes that would be difficult or impossible to roll. Metal extrusions can easily replace cumbersome or uneven seams created through other methods such as joining, welding, or riveting.

Cold Extrusion

The extrusion of cold metal has gone by a variety of names, including:

• Impact extrusion
• Cold forging
• Cold extrusion forging
• Cold pressing
• Extrusion pressing

However, cold extrusion is likely the most common term in the steel sector. Impact extrusion is also a widely accepted term for the cold extrusion of non-ferrous metals.

The process usually involves a high-speed punch, which strikes a metal blank within a die cavity. The force of the punch drives the blank through space between the punch and die. The speed and distance of the punch can be controlled via various mechanical settings on the machine itself. The thickness of the final extruded part is will be determined by the distance setting.

Cold extrusion offers high strength, because of severe strain-hardening, good finish, stringent accuracy, and lower production costs due to less operational setup and requirements.

Which Metals Are Used for Custom Extrusions?

Almost any metals can be extruded, though doing so can be cost-prohibitive for high strength alloys. Below is a list of the most common metals used independently, or as alloys, as well as examples of their common end uses.

Aluminum

Manufacturers can extrude aluminum—the most frequently extruded material—using either the hot or cold methods. Extruded aluminum can be fabricated, painted, and anodized, and it produces complex cross-sections with aesthetically pleasing surface finishes. Because of its high corrosion resistance and excellent thermal conductivity, extruded-aluminum products play large roles in the construction, automotive, aerospace, industrial, and domestic product manufacturing sectors. Because of its light weight and affordability, aluminum is the metal of choice for extrusion projects that seek to optimize strength without sacrificing the end product’s weight.

Brass

Brass extrusions create end products that resist corrosion, benefiting applications that require optimal performance for long periods in various weather or atmospheric conditions. Brass-extruded products are known for their durability and aesthetic appeal, providing a golden glaze on handrails, doors, columns, furniture, gates, and other ornamental materials. Brass products also form major parts of automotive components, pipe connectors, and industrial machinery.

Titanium

Like aluminum, titanium provides a similar level of strength compared to heavier metals like steel, but its density is lighter, allowing manufacturers to reduce the amount their end products weigh. Aerospace manufacturers especially value titanium for its heat-resistant properties, keeping its shape at temperatures exceeding 800°C. Extruded titanium also undergoes a number of finishing processes such as heat treatment to refine grain structure and chemical treatment to enhance machinability.

Nickel

Nickel extrusion creates high-strength products that are silver-gray in appearance. Despite nickel’s toughness, extruded-nickel products retain a degree of malleability that allow them to perform well in a variety of applications. Because nickel can withstand direct impacts without weighing too much, it’s ideal for door and window fasteners, locks, mining equipment, musical instruments, animal harnesses, electronic components, and industrial machinery. Nickel also can be alloyed with metals including silver, copper, and zinc, creating a variety of color customization options and allowing it to be used for a range of architectural purposes.

Other metals

Metal extrusion also works well with copper, zirconium, and beryllium. Electronics manufacturers in particular rely on extruded copper to create wire, and it also forms essential parts of electrodes for welding, pipes, bars, and tubes. Zirconium benefits a wide range of forming and mechanical applications, and beryllium appears in many military and commercial guidance systems as well as the structural components of satellites and spacecraft, alloying well with copper.

Lynch Metals Offers Custom Aluminum Extrusions

Strong, durable, and light, extruded aluminum offers design flexibility as a corrosion-resistance choice for a wide variety of needs. Aluminum’s physical characteristics of malleability and ductility allow it to be easily extruded. At one third the density and stiffness of steel, extruded aluminum provides for both strength and stability at an efficient production cost. Coming with a low recyclability cost, aluminum has a very high rate of scrap recovery, making it a highly economical and environmentally sustainable material.

At Lynch Metals, we specialize in working with our customers to develop cost-effective engineered material solutions, such as extruded aluminum. Feel free to contact us with your questions regarding aluminum extrusion sourcing and distribution to see how Lynch Metals can positively impact your bottom line.

Lynch Metals Is a Premier Distributor of Aluminum Alloys to Various Industries

About Lynch Metals

Since opening in 1991, Lynch Metals has a premier North American supplier of aluminum fin stock and brazing sheet. While our initial focus was on aerospace, today we have expanded into other sectors, including automotive, signage, and telecommunications. We offer a range of in-house metal processing services for our customers, including:

• Slitting and Rewinding

We are the only distributor to operate a Kampf high-speed slitter, which runs at 1600 feet per minute. In addition we also have Chicago Slitter, Goebel, and Rusch slitters in house, and we have three Rowe cut-to-length processing lines. We can custom cut widths between 10 ft. and 60 ft. Rewinding inner core widths vary in size, according to each machine’s capability.

• Precision Saw Cutting

Our MetlSaw precision saw cutting machines produce burr-free edges, eliminating the need for smoothing and other secondary processes after cutting. These high-speed saws cut through both ferrous and non-ferrous materials, and are adept at achieving high production volumes. Our MetlSaw can cut a maximum of length of 192”, a maximum width of 24”, and a maximum thickness of 8”.

• Blanking

Many industries find customized blanks to be an economical alternative to stock sheet sizes. The signage sector also relies on blanks to manufacture products. Our advanced technology enables precise length tolerances of 0.01”. Cut-to-order blanks reduce waste, granting economies of scale and reduced costs.

Aluminum Alloys for the Aerospace Sector

The aerospace industry often chooses aluminum due to its strength-to-weight ratio and its inherent resistance to corrosion. Demand for aluminum in this sector is expected to double by 2028. As a distributor for several mills, Lynch Metals is poised to keep up with the increasing demand for aluminum parts and components. We can supply the fin stock and brazing sheets you need, when you need them.

Our proprietary Multiclad brazing sheet is well-suited for use by the aerospace sector. This unique brazing sheet consists of three layers instead of two, containing a 3003 interlayer between the 4000 Series cladding and the 6000 core. The result is a thinner, stronger sheet suitable for the stresses and harsh environments posed by aerospace applications.

Brazing Sheet for the Automotive Industry

Aluminum offers ideal properties for the automotive industry, including its crashworthiness—it absorbs shock twice as well as steel. Due to an increased focus on fuel efficiency and reducing emissions, lightweight aluminum is being used more in vehicle production.

Shortages of materials affect the entire supply chain, and this can be crippling in automotive. We source our brazing sheets from large, global producers, ensuring. stock is always available when you need it.

For easy identification, we can also mark the clad side of the brazing sheet with either a stencil or vinyl coating. These markings help to eliminate errors during production, ultimately reducing waste and reducing costs.

Channel Letter Coil and Aluminum Blanks for Storefront Signage

For storefront signage, we provide both channel letter coil and flat sheet stock. Our channel letter coil is used to manufacture three-dimensional lettering. We have more than 30 colors of aluminum for signage in stock to match your storefront or business aesthetic. Aluminum’s lighter weight and flexibility allow for creativity in your sign design.

Our customized blanking line enables us to produce signage with a variety of corner radii and holes. Aluminum signage withstands the day-to-day effects of outdoor conditions – up to and including severe weather – ensuring your sign will look professional for a long time to come.

4000 Series Aluminum Alloys for Telecommunications

The 4000 series aluminum alloy is created via a combination of aluminum and silicon. Due to its fluidity, this alloy is suitable for welding applications in the telecommunications industry. We can also use the 4000 series as brazing filler materials.

Lynch Metals: Your Premier Metal Supplier

Our extensive inventory expands beyond aluminum, and also includes stainless steel and nickel alloys. With our custom stocking program and Just-in-Time deliveries, you can free up valuable floor space while eliminating the hassle of excessive inventory. To speak with a salesperson, receive a quote, or have a catalog sent to you, please contact us.