Weldability Checker

Check if an alloy is weldable and get carbon equivalent (CE) analysis for steel grades.

Finder

How to Use

  1. 1
    Enter the Base Metal Composition

    Input the alloy grade or chemical composition (wt%) of the base metal. For steels, the carbon equivalent (CE) is automatically calculated using the IIW formula.

  2. 2
    Specify Welding Process and Thickness

    Select the welding process (SMAW, GMAW, GTAW, SAW) and enter material thickness; these parameters determine heat input range and cooling rate, which critically influence weld microstructure.

  3. 3
    Review Preheat and Post-Weld Recommendations

    Read the tool's preheat temperature, interpass temperature limits, and any mandatory post-weld heat treatment (PWHT) requirements based on the alloy and joint configuration.

About

Weldability is not a single property but a collection of characteristics governing how an alloy responds to the fusion welding process — including susceptibility to cracking, distortion, and property degradation in the heat-affected zone. Carbon and alloy steels are assessed primarily through carbon equivalent calculations, while austenitic stainless steels require attention to ferrite content and sensitization, and aluminum alloys are evaluated for hot-cracking tendency based on their solidification range and grain structure.

The AlloyFYI Weldability Checker translates composition data and welding parameters into actionable guidance consistent with AWS D1.1 (structural steel), ASME Section IX (pressure vessels), and ISO 15614 (welding procedure qualification) requirements. Engineers and welding engineers can verify preheat requirements, select appropriate filler metals, and identify post-weld heat treatment obligations before committing to a welding procedure specification (WPS). Early identification of weldability constraints prevents costly rework and non-conformance reports during fabrication.

FAQ

How is carbon equivalent used to predict weldability?
The International Institute of Welding (IIW) carbon equivalent formula is CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15. Steels with CE below 0.35 are generally weldable without preheat; CE between 0.35 and 0.60 requires preheat to prevent hydrogen-induced cold cracking; CE above 0.60 demands careful procedure qualification, significant preheat, and often low-hydrogen electrodes. Note that CE is a guide for low-alloy steels; high-alloy grades such as stainless steels and tool steels require different assessment approaches.
What is hydrogen-induced cold cracking and how is it prevented?
Hydrogen-induced cracking (HIC), also called delayed cracking or underbead cracking, occurs when atomic hydrogen diffuses into the heat-affected zone (HAZ) and concentrates at regions of high residual stress and susceptible microstructure (typically martensite). It can appear hours or days after welding. Prevention involves using low-hydrogen consumables (E7018, LH electrodes with moisture-resistant coatings), applying preheat to slow cooling and allow hydrogen to diffuse out, performing post-weld hydrogen-release soaking (typically 200–300°C for 2 hours), and minimizing joint restraint to reduce residual stress.
Can austenitic stainless steels be welded without special precautions?
Austenitic grades like 304 and 316 are generally considered readily weldable due to their low CE and lack of martensite formation. However, two concerns arise: hot cracking (solidification cracking) in the weld metal, mitigated by maintaining a ferrite number (FN) of 3–10 in the deposit using balanced consumables; and sensitization of the HAZ in non-low-carbon grades (304 vs. 304L), where carbide precipitation at grain boundaries depletes chromium and creates susceptibility to intergranular corrosion. Using L-grade base metal and filler, or stabilized grades (321, 347), prevents sensitization.
What post-weld heat treatment is required for pressure vessel steels?
Most pressure vessel codes (ASME Section VIII, PD 5500, EN 13445) mandate PWHT for carbon and low-alloy steels above a certain thickness — typically 32 mm (1.25 in) for carbon steel — or whenever the material's carbon equivalent or specified Charpy impact requirements make stress relief necessary. Typical PWHT for carbon steel involves heating to 595–650°C, soaking at one hour per 25 mm of thickness, then slow cooling to prevent re-introduction of harmful thermal gradients. PWHT reduces residual welding stresses and tempers any hard martensite in the HAZ.
How do I select filler metal for dissimilar metal welding?
Dissimilar metal welding — for example, joining carbon steel to stainless steel — requires a filler that is compatible with both base metals, manages dilution effects, and accommodates the differential thermal expansion of the joint. A 309L filler is commonly used for carbon-to-304/316 joints because its higher chromium and nickel content buffers against carbon dilution from the steel side. For joints involving nickel alloys or elevated-temperature service, nickel-base fillers such as ERNiCrFe-7 (Alloy 52) are preferred. Always verify that the selected filler's thermal expansion coefficient is compatible with service conditions to avoid fatigue cracking at the fusion line.
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