Every fabricator knows the moment. A large enclosure, chassis, or frame comes off the welding table—and something is wrong. A door no longer sits flush. A mounting flange has pulled out of square. A flat panel now carries a visible wave that no amount of body filler will hide. The part is dimensionally out of tolerance, and the root cause traces back to a fundamental reality of fusion welding: intense, localized heat that expands metal, followed by rapid cooling that shrinks it unevenly.
Welding deformation is not a sign of poor workmanship. It is a predictable physical response to the thermal cycle of the welding arc. The difference between a shop that struggles with distortion and one that controls it reliably is not better welders. It is a systematic approach to fixturing, welding sequence, pre-deformation compensation, and post-weld stress management.
At Baosheng Industry, we weld large sheet metal assemblies every day—electrical enclosures, industrial control cabinets, machinery frames, and complex fabrications where multiple panels, brackets, and reinforcements must come together within specified flatness and squareness tolerances. This guide distills the techniques we use to control welding deformation into a practical reference for manufacturing engineers, fabricators, and designers.
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1. Why Welds Deform: The Physics That Drives Distortion
Before discussing solutions, it is essential to understand the root cause. Welding deformation occurs because metal expands when heated and contracts when cooled. The welding arc introduces intense, localized heat—temperatures at the weld pool can exceed 1,500°C—while the surrounding material remains at ambient temperature.
The Thermal Cycle of a Weld
When a weld bead is deposited, the filler metal and the base metal at the joint are heated to their melting point. As this material cools and solidifies, it attempts to shrink. However, the surrounding cold metal resists this shrinkage. This conflict between the shrinking weld metal and the restraining cold metal produces two outcomes:
- Residual stress: The weld zone remains in tension, while the surrounding material is placed in compression. These stresses can approach the yield strength of the material.
- Distortion: When the compressive stresses in the surrounding material exceed its buckling resistance—which is lower for thin-gauge sheet metal than for thick plate—the structure deforms to relieve the stress.
The Three Primary Types of Welding Distortion
| Distortion Type | Description | Typical Appearance | Most Common In |
|---|---|---|---|
| Longitudinal shrinkage | Weld bead contracts along its length, pulling the joined plates toward the weld line | Bowing of panels along the weld axis; overall length reduction | Long seam welds on enclosures and frames |
| Angular (transverse) distortion | Uneven heating through the material thickness causes the plates to rotate around the weld axis | Flanges and panels pull out of plane; corner joints open or close | Fillet welds on T-joints and corner joints |
| Buckling distortion | Compressive stresses in thin sections exceed the panel’s buckling resistance, producing out-of-plane waves | Visible waves or ripples in flat panels adjacent to welds | Thin-gauge sheet metal (< 3mm) with long, unrestrained spans |
Research confirms that “the proper welding sequence is important to reduce the deformation of the workpiece, improve the process quality of the product, reduce the electrode wear, increase the service life of welding machine”. Sequencing is one of the most accessible and cost-effective distortion control tools available to any fabricator—yet it is frequently overlooked in favor of post-weld correction, which is always more expensive than getting the sequence right the first time.
Heat Input: The Root Variable
The fundamental driver of all welding distortion is heat input—the amount of thermal energy introduced per unit length of weld. Heat input is calculated as:
Heat Input (kJ/mm) = (Voltage × Current × 60) / (Travel Speed × 1000)
Reducing heat input reduces the volume of metal that undergoes thermal expansion and contraction, which in turn reduces both residual stress and distortion. Lincoln Electric’s guidance is direct on this point: “Do not overweld”—specifying larger fillet welds than structurally necessary increases heat input and distortion with no strength benefit.
The choice of welding process itself affects heat input:
| Welding Process | Heat Input Characteristics | Distortion Tendency |
|---|---|---|
| GMAW (MIG) — Short Circuit | Moderate heat input; good for thin sheet | Moderate |
| GMAW (MIG) — Spray Transfer | Higher heat input; deeper penetration | Higher |
| GTAW (TIG) | Low heat input; precise control | Lower—preferred for thin gauge and cosmetic welds |
| Laser Welding | Very low heat input; narrow HAZ | Lowest—but requires precise fit-up |
| FCAW (Flux-Cored) | Higher heat input; high deposition rate | Higher—best for thicker sections where distortion is less sensitive |
For large sheet metal assemblies, the process choice must balance productivity with distortion control. A high-deposition process that completes the weld faster may introduce less total heat than a slower, lower-amperage process—even though the instantaneous heat input is higher.
For thin-gauge sheet metal welding, a water-cooled jig is useful to carry heat away from the welded components. This heat-sink approach is particularly effective when combined with proper sequencing, as it prevents heat accumulation from building up across multiple weld passes.
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2. Fixturing and Rigid Restraint: The First Line of Defense
The most direct method of controlling welding distortion is to physically restrain the workpiece from moving during welding. When properly designed, a welding fixture prevents the components from shifting as thermal stresses develop, forcing the shrinkage to be accommodated by plastic deformation rather than gross distortion.
The Rigid Fixation Principle
The rigid fixation method is very effective at reducing deformation, and allows welding to proceed without excessive consideration of the welding sequence. In production environments where multiple identical assemblies are fabricated, rigid fixturing provides the most repeatable distortion control.
The fixture constrains the part during the entire thermal cycle—heating, welding, cooling—and the part is released only after it has cooled sufficiently that residual stresses will not produce distortion beyond the tolerance band. The fixture absorbs the shrinkage forces that would otherwise pull the assembly out of shape.
Fixture Design for Distortion Control
For sheet metal assemblies, fixture layout—specifically the positioning of clamping elements—directly determines how effectively the fixture resists deformation. Research demonstrates that optimum fixture layout can be achieved by selecting the optimal number of fixture elements with optimum locations to reduce the maximum deformation of the sheet metal workpiece caused by clamping and welding forces.
Key principles for welding fixture design:
| Fixture Principle | What It Achieves | Practical Application |
|---|---|---|
| Clamp close to the weld line | Minimizes the unsupported span where buckling can occur | Position clamps within 50–75mm of the weld seam on thin-gauge material |
| Use sufficient clamp points | Distributes restraining force across the assembly | Rule of thumb: one clamp per 300mm of weld length for sheet metal < 3mm |
| Heat-sink backing bars | Conducts heat away from the weld zone, reducing the HAZ width | Copper or aluminum backing bars behind the weld joint; can be water-cooled for production |
| Tack weld before full welding | Establishes geometry before significant heat input | Tack at 50–75mm intervals on thin sheet; every 100–150mm on thicker sections |
| Pre-set the joint gap | Compensates for weld shrinkage closing the gap | Use shims, wedges, or adjustable clamps to set gaps slightly wider than nominal |
For large thin-wall assemblies such as storage boxes and enclosures, specialized welding deformation control fixtures incorporate front and rear covers, connectors, and locators that maintain the entire structure in alignment during welding. This comprehensive fixturing approach is essential when the assembly must maintain flatness tolerances across large surface areas.
For thick plate and large structural fabrications, the heat of welding alone can be enough to cause significant distortion. In these cases, rigid fixturing combined with careful sequencing and intermittent welding is necessary to keep the assembly within tolerance.
The Limitation of Rigid Fixturing Alone
Rigid fixturing prevents visible distortion during welding, but it does not eliminate residual stress. The stresses that would have caused distortion remain locked in the part. When the part is subsequently machined—for example, when a welded frame is stress-relieved and then milled flat—the release of these residual stresses can cause new distortion that was not present when the part came off the welding table.
This is why fixturing must be part of a comprehensive distortion control strategy that includes sequencing, pre-deformation, and stress relief, rather than the sole method relied upon.
3. Welding Sequence: The Most Cost-Effective Distortion Control Tool
If fixturing is the most direct method of distortion control, welding sequence is the most cost-effective. It requires no additional equipment, no special tooling, and no extra processing time. It simply requires that the weld passes be performed in an order that balances shrinkage forces rather than allowing them to accumulate in one direction.
The law of welding deformation is that the deformation caused by the first weld seam is the largest, and the deformation caused by each subsequent weld seam generally cannot offset each other unless the sequence is deliberately planned to do so. This fundamental principle means that the sequence of welding operations can either amplify distortion—if all welds are placed on one side of the assembly—or minimize it—if the sequence balances heat input symmetrically.
Sequence Strategies That Reduce Distortion
Symmetrical Welding: When welds are placed on both sides of the neutral axis of the assembly, alternate between sides. Weld a seam on the left side, then a seam on the right side, then back to the left. This balances the shrinkage forces and prevents the cumulative pull that occurs when all welds on one side are completed first.
Backstep Welding: Rather than welding continuously from one end of a seam to the other, backstep welding divides the seam into short segments and welds each segment in the opposite direction to the general progression. Instead of creating a continuous weld from start to end, backstep welding works backward, gradually reducing localized heating and cooling. The technique functions by dividing the weld into short increments, depositing the weld metal in a direction opposite to the direction of progression.
Skip Welding: Similar to backstep welding, skip welding lays short weld segments in a predetermined, evenly spaced sequence along the seam rather than in continuous order. A common pattern is to weld segments in the order 1, 3, 5, 2, 4, 6, which distributes heat more evenly than welding 1-2-3-4-5 sequentially.
Intermittent (Stitch) Welding: Rather than welding a continuous seam, intermittent welding places short weld segments separated by unwelded gaps. This reduces the total heat input, since only a fraction of the joint length is welded. The unwelded gaps allow each weld segment to cool independently, preventing the heat accumulation that drives distortion.
For large structural fabrications, the proper welding sequence is an effective method to prevent welding deformation, and research has demonstrated that changing the welding sequence significantly alters the residual stress distribution generated by the arc welding process due to the effect of temperature gradients.
Practical Sequencing Rules for Large Sheet Metal Assemblies
| Assembly Type | Recommended Sequence | Rationale |
|---|---|---|
| Rectangular enclosure (4 corners) | Weld corners in cross-pattern: 1-3-2-4 or 1-4-2-3 | Balances diagonal shrinkage |
| Long seam on a panel | Backstep weld: divide seam into 4–6 segments, weld each segment in reverse direction | Distributes heat; prevents progressive bowing |
| Frame with multiple cross-members | Weld from center outward, alternating sides | Allows free expansion during welding |
| T-joint fillet welds | Tack both sides, then alternate weld sides every 150–200mm | Prevents angular pull toward the first-welded side |
| Stiffened panel (plate + ribs) | Weld all ribs to panel from center outward, alternating rib positions | Minimizes panel buckling by distributing heat symmetrically |
For chassis customization and sheet metal enclosures, strip welding, backstep welding, and symmetrical welding methods should be adopted in the construction sequence to avoid welding deformation.
The Limits of Sequencing
While sequencing is powerful, it has limits. For very long welds on thin material, even a perfectly sequenced weld will introduce enough total heat to cause some distortion. In these cases, sequencing must be combined with fixturing, pre-deformation, or intermittent welding to achieve acceptable results. Research has shown that while backstep welding generally decreases distortion, using too many steps can actually increase distortion—indicating that for a given structure, an optimal number of segments exists.
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4. Pre-Deformation and Pre-Cambering: Anticipating the Inevitable
When the magnitude of welding distortion can be predicted—through experience, testing, or simulation—the most efficient approach is often to set the components in the opposite direction before welding, so that the welding distortion brings them back to the correct position rather than pushing them out of tolerance.
Pre-Cambering and Pre-Bending
Pre-cambering involves deliberately setting the parts to be joined slightly out of position, in the direction opposite to the expected welding deformation. The amount of pre-set is determined by the anticipated shrinkage. When the weld cools and shrinks, it pulls the pre-cambered assembly into the correct position.
This technique is particularly effective for:
- Long beams and frames where longitudinal shrinkage causes predictable bowing
- T-joints where angular distortion pulls the vertical member toward the weld side
- Butt welds in thin plate where the weld line pulls the plate edges toward each other and upward
The Industrial Practice
In heavy industrial fabrication, pre-cambering is a standard production technique. For large structural fabrications, plates are pre-set with a calculated curvature before welding, and the welding shrinkage brings them to the required flatness. This approach has been successfully demonstrated in the production of structural components, where pre-deformation combined with optimized welding parameters achieved effective distortion control suitable for mass production.
For large-scale structural components, fabricators may use different methods to control welding distortion, including separate or combined application of process parameter optimization, fixturing, and pre-deformation techniques, all of which have been demonstrated to effectively control distortion, improve product quality, and increase yield.
Practical Implementation
The key to successful pre-deformation is knowing how much to pre-set. This is typically determined through one of three methods:
- Empirical measurement: Weld a test assembly without pre-set, measure the resulting distortion, and apply the inverse as pre-set on production parts.
- Experience-based estimation: Experienced fabricators develop a sense for how much a given joint configuration will pull, and apply pre-set accordingly. As one practitioner notes, “we generally rely on experience and testing to find the amount of welding deformation, and then set up the corresponding inverse deformation on the fixture”.
- FEA simulation: For high-value or high-volume production, finite element analysis can predict welding distortion and determine the optimal pre-deformation profile.
Pre-deformation fixtures are designed to hold the assembly in the pre-set position during welding. For example, a door frame welding pre-deformation fixture may include positioning mechanisms for the door立柱 (pillars), pre-set reverse deformation mechanisms, and fixture positioning mechanisms. The fixture not only restrains the assembly but also maintains the specific pre-cambered geometry until welding is complete.
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5. Post-Weld Stress Relief: Restoring Dimensional Stability
Even with optimized fixturing, sequencing, and pre-deformation, welded assemblies retain residual stresses. When these assemblies are subsequently machined, subjected to service loads, or exposed to temperature cycles, those residual stresses can redistribute—causing distortion that appears long after the welding is complete.
Post-weld stress relief addresses this by reducing the magnitude of residual stresses, improving dimensional stability for the service life of the part.
Thermal Stress Relief (Post-Weld Heat Treatment)
Thermal stress relief is the most widely used method for reducing residual stresses in welded fabrications. The mechanism is straightforward: at elevated temperatures, the yield strength of the metal decreases. Residual stresses that approach the material’s yield strength at room temperature exceed the reduced yield strength at the stress-relieving temperature. The material undergoes localized plastic deformation—micro-yielding—which relaxes the residual stresses.
The study of thermal and vibration-based stress relief techniques concluded that both methods reduced stress intensity and altered mechanical properties, with thermal treatment being the most significant in stress reduction. The stress relief by heat treatment occurs because the treatment temperature promotes a reduction in the yield and tensile strength stresses, allowing the material to deform under lower stress values.
Typical thermal stress relief parameters for common sheet metal materials:
| Material | Stress Relief Temperature | Hold Time | Cooling Method |
|---|---|---|---|
| Mild Steel (CRS, HRS) | 595–675°C (1100–1250°F) | 1 hour per 25mm of section thickness | Furnace cool to 315°C, then still air |
| 304 Stainless Steel | 400–450°C (750–840°F) | 1–2 hours | Air cool (note: avoid 425–870°C range to prevent sensitization) |
| 316 Stainless Steel | 400–450°C (750–840°F) | 1–2 hours | Air cool |
| 5052 Aluminum | 175–260°C (350–500°F) | 1–2 hours | Air cool |
| 6061 Aluminum | 175–260°C (350–500°F) | 1–2 hours | Air cool (note: may partially reduce T6 temper strength) |
Case studies have shown that post-weld conditioning can reduce distortion by 50% to 95% and, in some instances, double the fatigue life of the joint compared to as-welded conditions.
Vibratory Stress Relief (VSR)
For large assemblies where furnace size or cost makes thermal stress relief impractical, vibratory stress relief offers an alternative. VSR subjects the welded structure to controlled mechanical vibration, typically at sub-resonant or near-resonant frequencies. The cyclic loading causes localized micro-yielding in high-stress regions, allowing stress redistribution through time-dependent plastic flow.
Research on welded frames—specifically components of packaging machines—has demonstrated that vibratory stress relief accelerates the relaxation of welding-induced stresses compared to free relaxing (simply allowing the part to rest at room temperature). The method is particularly useful for large-scale welded frames where furnace-based thermal stress relief is impractical.
VSR compared to thermal stress relief:
| Factor | Thermal Stress Relief | Vibratory Stress Relief (VSR) |
|---|---|---|
| Stress reduction | 50–80% | 30–60% |
| Equipment cost | High (furnace) | Moderate (vibration system) |
| Size limitation | Furnace dimensions | Minimal; large structures can be treated in sections |
| Processing time | Hours (heating + soaking + cooling) | 30–60 minutes |
| Effect on mechanical properties | Can reduce strength (aluminum alloys) | Minimal change |
| Dimensional stability improvement | Significant; well-documented | Moderate to significant; dependent on structure geometry |
The Importance of Stress Relief Before Machining
For any welded assembly that will be subsequently machined—frames that will be milled flat, mounting surfaces that will be CNC-machined to tight tolerances—stress relief before machining is essential. If residual stresses are not relieved, the removal of material during machining releases stresses unevenly, causing the part to warp. A frame that was within flatness tolerance after welding may be 0.5mm or more out of flat after machining if residual stresses were not addressed.
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6. Design-Level Prevention: Reducing Distortion at the Source
The most effective distortion control occurs not on the shop floor, but at the design stage. Good design eliminates unnecessary welds, reduces heat input, and builds in features that resist distortion.
Design Principles for Distortion-Resistant Weldments
Minimize weld metal. Specify the smallest fillet size that meets structural requirements. “Do not overweld” is the first rule of distortion control—”specifying a larger weld than is needed to handle the design loads will increase the amount of shrinkage and result in greater distortion”.
Use intermittent welds where continuous welds are unnecessary. A 50% intermittent weld (weld segments alternating with gaps) reduces total heat input by approximately 50% compared to a continuous weld of the same size. For non-structural seams, stitch welding is often sufficient and dramatically reduces distortion.
Balance welds around the neutral axis. Where possible, place welds symmetrically so that shrinkage forces on one side are balanced by shrinkage forces on the opposite side. A T-joint with fillet welds on both sides distorts less than the same joint welded on one side only.
Design for accessibility. Ensure that clamps, fixtures, and heat sinks can be positioned close to the weld joint. A weld seam that is inaccessible to clamping will be difficult to restrain effectively.
Consider part consolidation. A single formed sheet metal part—bent rather than welded—eliminates the weld entirely and the distortion that comes with it. Where design allows, replacing a welded corner joint with a bent corner eliminates both the welding operation and the associated distortion.
The Most Effective Design Strategy
As one experienced fabricator notes, “while backstepping and sequence welding are good techniques for minimizing warpage, good design is the best eliminator”. The design decisions made before the first part reaches the shop floor determine the distortion control challenge that fabricators must solve. Investing in design-level prevention returns far greater savings than investing in post-weld correction.
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7. Practical Distortion Control Checklist for Large Sheet Metal Assemblies
Before starting production on a welded sheet metal assembly, run through this checklist:
Design Stage:
- Weld sizes minimized to structural requirements—no overwelding
- Intermittent welds specified where continuous welds are not structurally required
- Welds balanced symmetrically around the assembly’s neutral axis where possible
- Part consolidation evaluated: can any welded joints be replaced with bent features?
Pre-Welding Preparation:
- Material flatness verified; warped stock corrected before welding
- Joint fit-up verified; gaps within tolerance for the selected welding process
- Fixture clamping points positioned close to weld lines
- Tack welds placed at appropriate intervals to establish geometry before full welding
Welding Execution:
- Welding sequence planned and documented (symmetrical, backstep, skip, or center-outward as appropriate)
- Heat input controlled: welding parameters (voltage, current, travel speed) set to minimize total heat while achieving required penetration
- Interpass temperature monitored; assembly allowed to cool between passes when specified
- For thin-gauge material (< 3mm), intermittent or stitch welding used unless continuous weld is structurally required
Post-Welding:
- Assembly left in fixture until cooled to handling temperature
- Post-weld stress relief specified if assembly will be subsequently machined or must maintain tight tolerances in service
- Dimensional inspection performed after cooling; critical dimensions verified against drawing tolerances
- Straightening or correction performed if necessary—preferably through controlled methods rather than uncontrolled hammering
How Baosheng Controls Welding Deformation
At Baosheng Industry, welding deformation control is integrated into our manufacturing process from the design review stage through final inspection:
- Free manual DFM review for every sheet metal project, including evaluation of weld sizes, joint designs, and distortion risk factors
- Custom welding fixtures designed and fabricated in-house for production runs—optimized clamp positioning, heat-sink backing bars, and pre-deformation capability where required
- Documented welding procedures with specified sequences, parameters, and inspection criteria for each assembly
- Post-weld stress relief capability including thermal treatment for dimensionally critical assemblies
- Post-weld machining on our CNC machining centers for assemblies requiring machined surfaces after welding—stress relieved before machining to ensure dimensional stability
- ISO 9001:2015 certified quality system with full dimensional inspection and documentation
We invite customer audits of our facility. Walk the shop floor, review our welding procedures, and see our distortion control methods in practice.
Free DFM Review • In-House Welding & Fixturing • ISO 9001:2015 Certified • Post-Weld Stress Relief • Direct Engineer Communication
Frequently Asked Questions (FAQ)
Q1: What causes the most welding distortion in sheet metal assemblies?
Answer: Welding distortion is driven by the thermal cycle of the arc: localized heating to temperatures exceeding 1,500°C expands the metal, and rapid cooling causes it to shrink. This shrinkage creates residual tensile stress in the weld zone and compressive stress in the surrounding material. When compressive stress exceeds the buckling resistance of the sheet metal, the assembly deforms. The three primary distortion types are longitudinal shrinkage (bowing along the weld axis), angular distortion (rotation around the weld), and buckling (out-of-plane waves in thin panels).
Q2: How effective is backstep welding at reducing distortion?
Answer: Backstep welding is one of the most effective no-cost distortion control techniques available. By dividing a long weld seam into short segments and welding each segment in the opposite direction to the general progression, backstep welding distributes heat more evenly and prevents the progressive heat accumulation that drives distortion. Research shows that backstep welding generally decreases distortion, though the optimal number of segments depends on the specific structure—too many segments can increase distortion in some cases.
Q3: What is pre-cambering, and when should it be used?
Answer: Pre-cambering (also called pre-setting or reverse deformation) involves deliberately positioning the components slightly out of alignment in the direction opposite to the expected welding distortion before welding begins. When the weld shrinks during cooling, it pulls the pre-cambered assembly into the correct position rather than out of tolerance. This technique is particularly effective for long beams, T-joints, and butt welds where the magnitude and direction of distortion are predictable. The amount of pre-set is typically determined through empirical testing, experience, or FEA simulation.
Q4: How does vibratory stress relief (VSR) compare to thermal stress relief?
Answer: Thermal stress relief (furnace heating) typically reduces residual stresses by 50–80% and is the most established method, but requires a furnace large enough to accommodate the assembly and involves several hours of processing time. Vibratory stress relief (VSR) reduces stresses by 30–60% using controlled mechanical vibration at sub-resonant frequencies over 30–60 minutes, and can be applied to very large structures that exceed furnace dimensions. For large welded frames that will be subsequently machined, thermal stress relief is generally preferred when furnace capacity allows; VSR is a practical alternative for oversized structures.
Q5: How can I design sheet metal assemblies to minimize welding distortion?
Answer: Key design principles include: specify the smallest fillet weld size that meets structural requirements (do not overweld); use intermittent welds where continuous welds are unnecessary; balance welds symmetrically around the neutral axis of the assembly; design joint locations so that clamps and fixtures can be positioned close to the weld line; evaluate whether part consolidation (replacing a welded joint with a bent feature) can eliminate welds entirely. Good design is the most effective distortion control tool—it prevents distortion before any welding begins.
Q6: Does rigid fixturing eliminate welding distortion completely?
Answer: No. Rigid fixturing prevents visible distortion during welding, but the residual stresses that would have caused distortion remain locked in the part. When the part is subsequently machined or subjected to service loads or temperature cycles, these residual stresses can redistribute and cause new distortion. Fixturing is most effective when combined with proper sequencing, controlled heat input, and post-weld stress relief to address the residual stress that fixturing alone cannot eliminate.
Q7: What is the best welding process for minimizing distortion in thin sheet metal?
Answer: For thin sheet metal (< 3mm), processes with lower heat input and faster travel speeds minimize distortion. GTAW (TIG) provides the lowest heat input and greatest control, making it ideal for cosmetic and precision welds. Short-circuit GMAW (MIG) offers a good balance of productivity and heat control. Laser welding has the lowest heat input and narrowest heat-affected zone but requires precise joint fit-up. Regardless of process, using a water-cooled jig or copper backing bar to carry heat away from the weld zone further reduces distortion.
Q8: When is post-weld heat treatment necessary for sheet metal assemblies?
Answer: Post-weld heat treatment is necessary when: the assembly will be subsequently machined (residual stress release during machining causes warping); the assembly must maintain tight dimensional tolerances throughout its service life; the material is susceptible to stress corrosion cracking in the service environment; or the assembly will experience cyclic loading where residual tensile stress reduces fatigue life. For mild steel fabrications that will be CNC-machined after welding, stress relief at 595–675°C is standard practice.
