Materials / Aluminum Fabrication

Fabricating Aluminum Parts: What Makes It Different from Steel

How Is Aluminum Different to Fabricate?

Aluminum’s lower density is the main reason engineers specify it. A 6061-T6 aluminum part weighs roughly 35% of what the same part would weigh in A36 mild steel. That weight reduction matters in aerospace, transportation, material handling equipment, and any application where reducing dead weight improves performance or handling. It also matters when shipped parts are heavy enough that freight cost is a real variable in total landed cost.

The trade-off is that aluminum is softer and less stiff per unit cross-section than steel. Mild steel has a modulus of elasticity around 29 million psi; aluminum is roughly 10 million psi. Parts that are stiffness-critical need to be designed with that difference in mind. A steel bracket that works at 0.125″ thickness may need 0.190″ or more in aluminum to achieve the same stiffness. Experienced engineers account for this in the design. Less experienced ones sometimes get surprised by deflection in aluminum parts that worked fine in steel.

Aluminum also doesn’t respond to processes the same way. It doesn’t spark when cut, which changes the look and feel on the shop floor. It gums up saw blades and cutting tools faster than steel if the wrong tooling or feed rates are used. It dissipates heat quickly during welding, which changes how the weld pool behaves. These are not problems for a shop that works aluminum regularly. They are problems for a shop that treats every metal the same way.

At Paragon, aluminum is a regular part of the production mix alongside steel and stainless. The team knows the material behavior, uses the right assist gases, tooling, and process settings, and understands the alloy differences that affect each operation. If your next project is aluminum, describe the alloy and temper on your drawing. If you’re not sure which alloy fits, describe the application and we can help you sort it out.

Laser Cutting Aluminum: What Changes

The reason nitrogen assist gas is required is straightforward. Oxygen assist gas accelerates cutting in steel by promoting an exothermic oxidation reaction at the cut front. On aluminum, that same oxidation produces aluminum oxide, which has a melting point far higher than aluminum itself, approximately 3700°F vs. 1220°F for aluminum. The result is a rough, contaminated cut edge that interferes with downstream operations like anodizing or welding. Nitrogen is inert: it blows the molten metal out of the cut zone without oxidizing it, leaving a clean, bright edge.

Aluminum’s reflectivity is a real issue for CO2 laser machines, which operate at a wavelength that aluminum reflects efficiently. Fiber lasers operate at a wavelength (around 1 micron) that aluminum absorbs much better. Modern fiber laser machines handle aluminum well. If a shop is quoting aluminum laser cutting on older CO2 equipment, ask about their results and request a sample cut. Fiber laser is the right tool for aluminum.

For more on laser cutting capabilities and material options, see laser cutting services and what metals can be laser cut. Aluminum sheet in common fabrication gauges and plate up to about 0.5″ are routine. Thicker sections may be better suited to waterjet cutting, which has no heat-affected zone and handles thick aluminum without the edge quality tradeoffs of laser on thicker sections.

Gauge selection also matters for aluminum. The sheet metal gauge guide covers how gauge numbers relate to actual thickness and how common aluminum sheet thicknesses map to gauge. Note that aluminum gauges and steel gauges are not the same: a 16-gauge aluminum sheet is not the same thickness as 16-gauge steel. Always specify actual thickness in decimal inches on drawings, not gauge alone, to avoid ambiguity.

Forming and Bending Aluminum Sheet

Springback is the dominant variable in aluminum bending. A press brake set to hit 90 degrees will produce an angle closer to 92-95 degrees in aluminum when the tooling lifts, depending on alloy, temper, and thickness. The brake operator accounts for this by overbending, targeting perhaps 88 degrees in the tool to get 90 degrees in the part. On a well-dialed press brake with an experienced operator, aluminum parts come out accurate. On a poorly set-up process, they come out inconsistent.

For design guidance on parts with multiple bends, see press brake forming explained and design for press brake bending. The principles for aluminum are the same as for steel with the extra note that springback is greater and minimum bend radius requirements are more stringent. Design with at least 1x material thickness as inside bend radius on 5052-H32 sheet. 6061-T6 needs more, often 2x or 3x, depending on thickness.

Grain direction matters more in aluminum than in steel for bent parts. Rolling direction is marked on mill certifications and sometimes on the coil or sheet. Bending with the grain (parallel to the rolling direction) is more prone to cracking on the outside of the bend than bending across the grain. For parts with tight-radius bends in a thicker temper, orient the bend line perpendicular to the rolling direction where possible. This is a detail that belongs on the drawing or in an engineering note to the fabricator.

Work hardening during bending changes the temper locally at the bend. In most fabricated parts this is acceptable. In parts that require subsequent forming or where material properties at the bend are critical, it’s worth discussing with the fabricator. 5052-H32 and 3003-H14 are more tolerant of multiple bending operations than 6061-T6, which can crack at the bend zone in thicker sections if the design doesn’t allow adequate bend radius.

Welding Aluminum: Process and Considerations

The oxide problem in aluminum welding is the central challenge. Every aluminum surface exposed to air is immediately covered with a thin, tenacious aluminum oxide layer. That layer doesn’t melt when you put a TIG arc on it. It needs to be broken down and removed by the AC arc’s cleaning action. Switching the TIG machine to AC provides a positive half-cycle that breaks up and removes the oxide, while the negative half-cycle provides the heat to melt the base metal. DC TIG does not provide this cleaning action and cannot be used for aluminum.

Pre-weld cleaning matters as much as process selection. Aluminum joint faces should be mechanically cleaned (stainless wire brush, dedicated to aluminum only) and then wiped with acetone immediately before welding. Any contamination, oil, moisture, or oxide that remains in the joint ends up in the weld as porosity. Porosity in aluminum welds compromises strength and can cause leaks in pressure-containing parts. For structural or pressure-containing aluminum weldments, include weld quality requirements on the drawing.

Distortion is more pronounced in aluminum welding than in steel welding because aluminum conducts heat away from the weld zone much faster. This creates steep thermal gradients that produce more distortion per weld pass. Managing distortion requires sequencing the weld passes to balance heat input, using fixturing to hold the assembly during welding, and allowing proper cool-down between passes on multi-pass welds. Large aluminum weldments require planning: welding sequence matters as much as weld parameters.

For an overview of the welding processes Paragon uses across materials, see welding types in metal fabrication and welding services. TIG welding is the standard process for aluminum structural work. MIG (GMAW) with aluminum wire and spool gun is used for higher-volume production welds where TIG would be too slow. Both produce good results in the right application. Specify the weld quality standard (AWS D1.2 for structural aluminum) if your application requires it.

Common Aluminum Alloys for Fabrication

The alloy designation system tells you a lot about what you’re working with. The four-digit number is the alloy series: 3xxx is aluminum-manganese, 5xxx is aluminum-magnesium, 6xxx is aluminum-magnesium-silicon. The temper designation after the dash (H32, T6, H14) describes the work-hardening or heat-treatment state. H tempers are strain-hardened. T tempers are thermally treated. The number that follows indicates the specific process. Higher numbers within a temper family generally mean higher strength.

5052-H32 is the default choice for most sheet metal fabricated parts: enclosures, brackets, panels, covers, and structural components that need to be bent, welded, and possibly anodized. It’s readily available in standard gauges from 0.040″ through 0.250″, corrosion-resistant without surface treatment in most environments, and bends well down to 1x material thickness inside radius. If you don’t have a specific reason to use something else, 5052-H32 is usually the right answer for sheet metal work.

6061-T6 is the right choice when you need higher strength, better machinability, or structural performance. It machines cleanly, holds tighter tolerances in machined features, and has significantly higher tensile strength than 5052. The trade-off is formability. 6061-T6 is much stiffer and harder than 5052, and it’s prone to cracking at tight bend radii, especially in thicknesses above 0.125″. Parts with multiple bends in 6061-T6 need to be designed with adequate radii. Parts that need to be machined after forming are often better off in 6061 for the machinability improvement. For comparison of aluminum and steel material properties, see galvanized vs stainless vs mild steel.

3003-H14 is a softer, highly formable alloy used where strength isn’t a priority. Ductwork, tanks, light-duty enclosures, and decorative trim are common applications. It bends tightly without cracking, forms well into complex shapes, and welds easily. It’s not the choice for structural parts or anything that needs to hold load. But for light sheet metal work where you need to make complex bends or deep draws, 3003-H14 is worth specifying.

Finishing Aluminum Parts

Mill-finish aluminum (2B or as-rolled) is acceptable for many indoor applications where the part won’t see moisture, chemicals, or abrasion. Aluminum naturally forms a thin, self-healing oxide layer that provides moderate atmospheric corrosion resistance without any applied coating. For parts going into dry, indoor environments with no aggressive chemistry, bare aluminum is often the right choice. It saves cost, saves lead time, and avoids finish compatibility issues.

Anodizing is the most common finish specified for aluminum parts that need better corrosion resistance, hardness, or color. Type II anodize (standard, 0.0002-0.001″ thick) provides good corrosion resistance and a consistent, colorable surface. Type III hard anodize (hardcoat, 0.001-0.003″ thick) provides significantly higher surface hardness and wear resistance for parts with sliding or abrasion contact. Anodizing is an outside process that Paragon coordinates as needed. Build the lead time into your schedule and specify the anodize type, color, and thickness on the drawing.

Powder coating on aluminum is done in-house at Paragon with pretreatment chemistry designed for aluminum. The pretreatment process differs from the chemistry used on steel: aluminum gets a chromate or chrome-free conversion coating prior to powder application to promote adhesion and provide a corrosion-inhibiting base layer. Without the conversion coating, powder adhesion to aluminum is poor and will peel under field conditions. Verify that any powder coat shop you use applies the right pretreatment for aluminum, not just the steel pretreatment line.

For anodized aluminum that will also be powder coated (for color matching to other components, for example), the sequence matters. Anodize first, then powder coat. Powder coating on top of a sealed anodize layer requires surface prep. Discuss the finish system with your fabricator at the quoting stage, not after the parts are fabricated. See powder coating services for more on what Paragon’s finishing operation covers.

Parts with threads, tight-tolerance bores, or mating surfaces that require masking during finish operations should have masking requirements noted on the drawing. Anodize adds a controlled layer thickness to every surface, which affects the fit of mating interfaces. If hole diameters are critical before and after anodize, note the pre-anodize dimension on the drawing. The anodize processor will mask or size accordingly. Getting this right on the drawing prevents rework at assembly.