Buyers Guide: Selecting Fabricators for TIG Welding Services

Why TIG Selection Differs From General Welding

TIG welding is a controlled process. The arc is stable, and the operator has direct control over the heat input. This makes the process effective for stainless steel, aluminum, titanium, and other materials where appearance and integrity matter. General welding quotes often focus on cost per hour. TIG sourcing requires a different focus. You need to verify that the shop can hold tolerances, manage heat, and produce repeatable results.

A fabricator may list TIG on its capability sheet and still lack the experience for your specific part. The gap between a capability statement and actual performance is where projects fail. Before you send RFQs, you need a framework to evaluate the shop. This guide breaks down the specific criteria that matter for TIG-welded sheet metal.

Most sheet metal projects involve thin gauges where the margin for error is small. A welder who can handle thick carbon steel plate may struggle with a 1 mm stainless steel bracket. The heat input required for thick material distorts thin sheet. The shielding gas requirements differ significantly between carbon steel and aluminum. The electrode composition changes based on the alloy being joined. If you approach TIG sourcing with the same questions you would ask for MIG welding, you miss the technical nuances that determine part quality. You are not just buying welds. You are buying process control.

Material and Thickness Capabilities

The first question to ask is about material compatibility. TIG is often used for stainless steel, but it is also common for aluminum and copper alloys. Each material requires different shielding gas mixtures and electrode types. A shop that welds carbon steel with TIG may not be proficient with aluminum.

Ask for the specific alloys the shop has welded recently. For example, a shop experienced with 304 stainless may not have the same workflow for 904L or duplex grades. Thickness also matters. Thin sheet metal, such as 0.5 mm to 1.5 mm, requires low heat input to prevent burn-through and distortion. Thick plate requires different travel speeds and filler wire handling.

When reviewing a quote, specify your material grade and minimum thickness. If the shop cannot confirm experience with that grade, ask if they have performed weld tests. Do not assume that a general TIG capability covers all materials.

Consider the chemical composition of the alloy. 304 stainless is common, but 904L has higher chromium and molybdenum content. It requires different shielding gas mixtures to prevent oxidation. Duplex stainless steel, such as 2205, has a higher yield strength and requires more heat control to maintain the balance between ferrite and austenite phases. Aluminum alloys, like 6061 or 5052, are reactive. They form a surface oxide that must be broken during welding. A shop that specializes in aluminum will use pure argon with a tungsten electrode that is ground differently than a stainless steel electrode.

Thickness dictates the welding technique. For sheet under 1 mm, the operator may use a pulsed TIG technique to modulate the heat input. This reduces the base metal melting pool. For thicker plate, continuous heat input is often necessary. The filler wire diameter changes with thickness. A 1 mm joint might use 1.5 mm filler wire, while a 6 mm joint might use 3 mm wire. If your drawing specifies a particular filler wire, such as ER308L for 304 stainless or ER4043 for 6061 aluminum, the shop must confirm they have that stock and know how to use it.

Ask for recent weld logs. Do not accept a generic statement of capability. Ask for the last three projects where they welded your specific alloy at your specific thickness. If they do not keep records, that is a sign of poor quality control.

Certification and Qualification Standards

Certifications provide a baseline for trust. They are not a guarantee of quality, but they show that the shop has undergone structured evaluation. Look for third-party welder qualification records. These records define the process, the material, the position, and the operator.

For sheet metal, you often care about the welder’s qualification for specific thickness ranges. A welder qualified for 10 mm plate is not automatically qualified for 1 mm sheet. The technique differs. The heat input differs. The risk of distortion differs.

Ask the fabricator for copies of their welder qualification certificates. Check the validity dates. Check the material types. Check the joint configurations. If the shop cannot provide these documents, treat it as a red flag. You may also ask about quality management certifications. These vary by region and industry, but they signal that the shop has documented procedures for non-conforming work and corrective actions.

Welder qualification standards, such as those from AWS or ISO, define the exact parameters under which a welder is tested. The qualification record will list the material type, thickness range, joint preparation, and welding position. A welder qualified for groove joints in thick plate is not automatically qualified for fillet joints in thin sheet. The travel speed, amperage, and filler wire handling differ.

Check the validity period. Qualifications often expire after a certain period of inactivity. If a welder has not been welding a specific alloy in three years, their qualification may be void. Ask for the date of the most recent qualification test. If the test was more than a year ago for your specific material, the shop should requalify the operator before starting your project.

Quality management systems, such as ISO 9001 or industry-specific standards, provide a framework for document control. These systems ensure that the shop has documented procedures for weld preparation, inspection, and non-conforming material handling. They do not guarantee weld quality, but they show that the shop has a structured approach to quality.

Inspection and Testing Protocols

TIG welds are often visually inspected, but visual checks are not enough. You need to define how the shop verifies weld integrity. For thin sheet, penetration is a common failure point. A weld may look good on the surface but fail to fuse the joint fully.

Ask what inspection methods the shop uses. Common methods include visual inspection, dimensional checks, and in some cases, dye penetrant testing or radiographic testing. For most sheet metal, visual and dimensional checks are standard. However, for structural or pressure-containing applications, you may need more rigorous testing.

Define your acceptance criteria before the first weld. Specify the maximum weld height, the minimum groove preparation, and the acceptable range for distortion. If the shop does not have a written procedure for these checks, ask how they ensure consistency. Consistency is the difference between a one-off prototype and a reliable production run.

Visual inspection is the first line of defense. The inspector checks for porosity, undercut, spatter, and weld cap uniformity. For sheet metal, the weld cap should be smooth and consistent. Porosity, which is trapped gas in the weld, can weaken the joint. Undercut, which is a groove below the weld surface, creates stress concentration points.

Dimensional checks are critical for sheet metal. The shop should measure the part after welding to ensure it meets your drawing tolerances. For example, if a flange must be within 0.5 mm of its nominal dimension, the shop should verify this with calipers or a CMM. If the part distorts during welding, the shop must be able to identify the cause and correct it.

For critical applications, non-destructive testing may be required. Dye penetrant testing can detect surface and near-surface cracks. Radiographic testing can detect internal voids or lack of fusion. These tests are more expensive and time-consuming. They are typically reserved for structural or safety-critical parts. Discuss with the shop which tests are necessary for your application. Do not assume that visual inspection is sufficient for all projects.

Distortion Control and Fixturing

Heat is the enemy of thin sheet metal. TIG welding introduces heat that expands the metal. As it cools, the metal contracts. If uncontrolled, this causes warp, bow, or out-of-square joints. A competent fabricator will have a strategy for managing this.

Look for evidence of fixturing capability. Do they use dedicated fixtures for your part? Do they clamp the workpiece to a rigid table? Do they use jigs to hold components in position during welding? Do they weld in a specific sequence to balance heat?

Ask the shop to describe their fixturing process. A vague answer is a warning sign. A specific answer should mention clamps, fixtures, or welding sequence. If the shop cannot explain how they control distortion, the risk of rework increases. Rework on TIG welds is costly. It may require grinding, re-preparing, and rewelding.

Fixturing is the primary method for controlling distortion. The workpiece must be held rigidly during welding. If the part is not clamped, the heat causes movement. For thin sheet, even small movements can result in significant distortion. A good shop will use dedicated jigs that hold the part in its final position. These jigs may include pins, clamps, or magnets.

Welding sequence is the second method for controlling distortion. The operator must weld in a specific order to balance heat input. For example, instead of welding a long seam in one direction, the operator may weld short segments in a staggered pattern. This allows the metal to cool and contract before the next segment is welded. Ask the shop to describe their welding sequence for your part. If they do not have a documented sequence, they may not be able to control distortion.

Consider the part geometry. A flat plate is easier to control than a box-shaped enclosure. A box-shaped enclosure has multiple welds that interact with each other. The heat from one weld affects the adjacent welds. The shop must have experience with your specific geometry. Ask for examples of similar parts they have welded. Review their distortion control strategy for those parts.

The Criteria Table

Use this table to structure your evaluation. It summarizes the key points discussed above.

Criterion	What to look for	Why it matters
Material Experience	Recent weld logs for your specific alloy and thickness	Ensures the operator has practiced your exact material conditions
Welder Qualification	Certificates matching your joint type and thickness range	Validates that the operator has been tested for that specific task
Inspection Method	Defined procedures for visual, dimensional, and penetration checks	Provides objective evidence that the weld meets your standards
Fixturing Strategy	Dedicated jigs or clamps and a documented welding sequence	Minimizes distortion and maintains part geometry during heat input
Quality Records	Traceability of materials and weld parameters	Supports corrective action if a defect is found later

Requesting Sample Welds

The most practical step is to request a sample. Do not wait for the final production run to see if the shop can weld your part. Ask for a test piece or a small batch. This allows you to evaluate the weld in the context of your actual design.

Provide the shop with a drawing that includes weld symbols and notes. Specify the filler wire if you have a preference. For example, if you use ER308L for 304 stainless, state it clearly. If you have a standard for weld appearance, provide a reference.

Review the sample against your acceptance criteria. Check the weld cap. Look for porosity, undercuts, or lack of fusion. Measure the distortion. If the sample is not acceptable, ask the shop to identify the root cause. A good shop will analyze the issue and propose a fix. A poor shop will blame the drawing or the material.

When requesting a sample, specify the quantity. A single test piece is useful, but a small batch of three to five pieces provides better data. It allows you to assess consistency. If the first piece is good but the third piece is poor, the shop lacks process control.

Provide the shop with your drawing and acceptance criteria. Include weld symbols, filler wire specifications, and dimensional tolerances. If you have a reference for weld appearance, provide a photo or a standard. For example, you might reference a specific AWS standard for weld appearance. This removes ambiguity. The shop should understand exactly what you expect.

Review the sample carefully. Check the weld cap for uniformity. Look for porosity, which appears as small holes in the weld. Check for undercut, which is a groove below the weld surface. Measure the distortion with a straightedge or calipers. If the sample does not meet your criteria, ask the shop to identify the root cause. A good shop will analyze the issue and propose a fix. They may suggest a different welding sequence, a different fixture, or a different filler wire. A poor shop will blame the drawing or the material.

A Decision Checklist

Use this checklist to finalize your selection. It forces you to verify the details before you sign the contract.

1. Confirm the shop has welded your specific material grade recently.
2. Verify the welder qualification matches your thickness and joint type.
3. Review the inspection protocol and confirm it covers your critical dimensions.
4. Ask for a description of the fixturing and welding sequence.
5. Request a sample weld and evaluate it against your acceptance criteria.
6. Check the shop’s responsiveness to quality issues in past projects.
7. Confirm the lead time and the process for handling rework.
8. Review the quality management documentation for traceability.
9. Evaluate the communication style during the quote process.
10. Make a decision based on evidence, not just price.

Final Thoughts

Selecting a fabricator for TIG welding services is a technical decision. It requires you to look beyond the price list and evaluate the shop’s process. The best fabricators are transparent about their capabilities. They provide documentation, sample work, and clear communication.

Focus on the details. Material, thickness, fixturing, and inspection are the pillars of a good TIG weld. If the shop can demonstrate control over these areas, you are likely to get a part that meets your requirements. If the answers are vague, keep looking. The right partner will make the process straightforward.