{"id":5336,"date":"2026-08-12T01:12:03","date_gmt":"2026-08-12T01:12:03","guid":{"rendered":"https:\/\/ceshi.baoxuanmetal.com\/?p=5336"},"modified":"2026-08-15T09:16:11","modified_gmt":"2026-08-15T09:16:11","slug":"heat-treatment-callouts-sheet-metal-drawings","status":"publish","type":"post","link":"https:\/\/ceshi.baoxuanmetal.com\/de\/heat-treatment-callouts-sheet-metal-drawings\/","title":{"rendered":"How to Specify Heat Treatment Callouts on Sheet Metal Drawings: 5 Requirements, Examples & Common Mistakes"},"content":{"rendered":"

You have designed a formed sheet metal bracket. The prototype passes inspection, the geometry is finalized, and now the production drawing needs a heat treatment callout<\/strong>.<\/p>\n

You open the standards and realize there is no single symbol that says \u201cmake this part harder.\u201d The callout has to be written out \u2014 and it has to be written out correctly, because vague or incomplete heat treatment notes are one of the most common reasons drawings get sent back before production even starts.<\/strong><\/p>\n

This guide walks through exactly what goes into a heat treatment callout on a sheet metal drawing<\/strong>, where to place it, which processes apply to sheet metal parts, and how to avoid the mistakes that cause rework.<\/p>\n

Where Heat Treatment Callouts Belong on a Drawing<\/h2>\n

Heat treatment information does not belong in a single fixed location. Where you place it depends on how the information needs to be read \u2014 by the fabricator, the heat treater, and the quality inspector.<\/p>\n

There are three standard placement options:<\/p>\n

\"Diagram

A clean technical illustration showing an engineering drawing layout with three labeled zones \u2014 general notes block, feature-specific leader line callout, and reference to a separate specification sheet \u2014 indicating where heat treatment information is placed.<\/span><\/p><\/div>\n

General Notes block.<\/strong> This is the most common location for process-level heat treatment requirements that apply to the entire part. On a technical drawing<\/strong><\/a>, a note such as \u201cSTRESS RELIEVE PER AMS 2759\u201d in the title block or notes area tells every downstream reader that the part requires a specific thermal process.<\/p>\n

Feature-specific callout.<\/strong> When heat treatment applies to a specific area \u2014 for example, case hardening only on the teeth of a gear or the wear surface of a bracket \u2014 a leader line or flag note attached to that feature provides clearer instruction than a general note.<\/p>\n

Separate specification sheet.<\/strong> For parts with complex or multi-step heat treatment sequences (anneal, then harden, then temper), a dedicated process specification sheet referenced in the drawing notes keeps the drawing clean and the requirements unambiguous.<\/p>\n

If you are unsure which approach to use, the general rule is: one simple process goes in the notes; area-specific treatment gets a feature callout; multi-step sequences go on a separate sheet.<\/strong><\/p>\n

The Five Elements Every Heat Treatment Callout Must Include<\/h2>\n

A heat treatment callout is not a single line. It is a set of linked information, and leaving out any one element creates room for misinterpretation.<\/strong><\/p>\n

Here are the five items that must appear \u2014 either directly in the callout or by reference to a standard.<\/p>\n

\"Infographic

A horizontal infographic with five labeled sections \u2014 Process Type, Material Designation, Hardness Range, Case Depth, and Inspection Location \u2014 each shown as an icon with a brief example text, arranged in a clean left-to-right layout.<\/span><\/p><\/div>\n

Element 1: Process Type<\/h3>\n

State the specific heat treatment process.<\/strong><\/p>\n

Do not write \u201cheat treat\u201d or \u201charden\u201d \u2014 those terms are too broad and force the heat treater to guess your intent.<\/p>\n

Common process designations include stress relief annealing, full annealing, through hardening, case hardening (carburizing or carbonitriding), and precipitation hardening.<\/p>\n

Each process produces a different microstructure and mechanical result, so the drawing must specify which one is required.<\/strong><\/p>\n

Element 2: Material Designation Using Standard Codes<\/h3>\n

The sheet metal material specification<\/strong><\/a> on the drawing must use the correct standard designation \u2014 not a trade name or a generic material description.<\/p>\n

Write \u201cAISI 1045\u201d instead of \u201cmedium carbon steel.\u201d<\/strong><\/p>\n

Write \u201cSAE 4140\u201d instead of \u201cchrome-moly alloy.\u201d<\/strong><\/p>\n

Heat treaters rely on the exact alloy code to set furnace temperatures, soak times, and quench media. An incorrect or vague material reference can result in an entire batch being processed to the wrong specification.<\/p>\n

Element 3: Hardness Value and Range<\/h3>\n

Specify hardness as a range, not a single value.<\/strong><\/p>\n

A callout of \u201c40\u201345 HRC\u201d<\/strong> is realistic and achievable; \u201c42 HRC\u201d<\/strong> is not, because hardness varies across a part due to differences in section thickness, edge proximity, and material heat lot.<\/p>\n

Also specify the correct hardness scale.<\/p>\n

Rockwell C (HRC) is standard for hardened steels; Rockwell B (HRB) for annealed or soft materials; Brinell (HB) for larger components.<\/p>\n

Mixing scales without a conversion note is a frequent source of rejection<\/strong> \u2014 hardness conversions are approximate, and compounding approximations introduces error.<\/p>\n

Element 4: Case Depth (When Applicable)<\/h3>\n

For case-hardened parts \u2014 those that are carburized or carbonitrided \u2014 the callout must distinguish between effective case depth<\/strong> (measured from the surface to a specific hardness level, typically 50 HRC) and total case depth<\/strong> (the full distance carbon has diffused into the part).<\/p>\n

Specify which one you mean, and give a range.<\/strong><\/p>\n

For example:<\/p>\n

\u201cEffective case depth 0.007\u20130.012 in. at 50 HRC.\u201d<\/strong><\/p>\n

A single case depth value, like a single hardness value, leaves too much room for interpretation.<\/p>\n

Element 5: Inspection Location<\/h3>\n

The drawing must indicate where hardness testing should be performed.<\/strong><\/p>\n

Heat treatment alters the surface and core of a part differently, and hardness readings taken at the wrong location can falsely indicate that the process failed.<\/p>\n

For a formed bracket, the critical inspection point might be the bend radius; for a wear surface, it might be the functional contact area.<\/p>\n

Mark the inspection point on the drawing with a leader note or reference it in the general notes.<\/strong><\/p>\n

Common Heat Treatment Processes for Sheet Metal and How to Call Them Out<\/h2>\n

Sheet metal parts typically undergo a narrower range of heat treatment processes than heavy machined components. The following four are the most common.<\/p>\n

\"Four-panel

A four-panel grid showing simplified visual representations of stress relief annealing, full annealing, through hardening and tempering, and case hardening, each panel including the process name and a typical drawing callout example.<\/span><\/p><\/div>\n

Stress relief annealing<\/h3>\n

This is the most frequently specified post-forming treatment for sheet metal.<\/p>\n

Stress relief can reduce residual stresses introduced during sheet metal bending<\/strong><\/a>, stamping, or welding without significantly changing the material\u2019s hardness or strength.<\/p>\n

Typical callout:<\/p>\n

\u201cSTRESS RELIEVE PER AMS 2759-1, METHOD X.\u201d<\/strong><\/p>\n

Full annealing<\/h3>\n

Used when the part needs maximum ductility \u2014 for example, a component that will undergo further forming operations after the initial cut.<\/p>\n

Full annealing heats the material above its upper critical temperature and slow-cools it.<\/p>\n

Typical callout:<\/p>\n

\u201cANNEAL PER AMS 2759-1 TO MAX 150 HB.\u201d<\/strong><\/p>\n

Through hardening and tempering<\/h3>\n

For sheet metal parts that require high hardness across the full cross-section \u2014 springs, wear plates, cutting blades.<\/p>\n

The callout must specify both the hardening and tempering steps, because tempering is what controls the final hardness.<\/strong><\/p>\n

Typical callout:<\/p>\n

\u201cHARDEN AND TEMPER TO 42\u201348 HRC PER AMS 2759-2.\u201d<\/strong><\/p>\n

Case hardening (carburizing or carbonitriding)<\/h3>\n

Less common on thin sheet metal because the case-to-core ratio can be unfavorable on thin sections, but used on thicker sheet or plate components that need a hard surface with a tough core.<\/p>\n

Typical callout:<\/p>\n

\u201cCARBURIZE TO EFFECTIVE CASE DEPTH 0.010\u20130.015 IN. AT 58\u201362 HRC PER AMS 2759-3.\u201d<\/strong><\/p>\n

Sheet Metal\u2013Specific Concerns: Distortion, Tolerances, and Post-Form Heat Treatment<\/h2>\n

Heat treatment on sheet metal is not the same as heat treatment on a 50 mm steel block.<\/p>\n

Thin sections heat and cool quickly, warp more easily, and respond differently to quenching.<\/strong><\/p>\n

These factors directly affect what you write on the drawing.<\/p>\n

Distortion is the primary risk.<\/h3>\n

A flat sheet metal part that is through-hardened will almost certainly distort. The thinner the part, the greater the distortion.<\/strong><\/p>\n

\"Diagram

A technical illustration showing a flat sheet metal bracket on the left in its pre-heat-treatment state with flatness tolerance noted, and on the right the same bracket after through hardening with visible warpage and a callout indicating the distortion measurement.<\/span><\/p><\/div>\n

If the application requires tight flatness tolerances after heat treatment, the drawing must call out the flatness requirement as a post-heat-treatment measurement \u2014 not just as a forming tolerance.<\/strong><\/p>\n

Otherwise, the part may pass forming inspection but fail after hardening.<\/p>\n

Stress relief after forming reduces downstream problems.<\/h3>\n

Specifying stress relief annealing before any final machining or critical dimension verification is a standard practice for formed sheet metal parts.<\/p>\n

On the drawing, place the stress relief note before the final tolerance callout in the process sequence<\/strong> so the fabricator knows the order of operations.<\/p>\n

Dimensional compensation may be needed.<\/h3>\n

Heat treatment can cause predictable dimensional changes, including small amounts of growth or shrinkage, depending on the process and the specific sheet metal materials<\/strong><\/a> being treated.<\/p>\n

For precision assemblies, the sheet metal design<\/strong><\/a> should define critical final dimensions as post-heat-treatment requirements and account for any predictable thermal movement during forming and processing.<\/p>\n

This is uncommon on simple sheet metal brackets but critical on parts that interface with mating components.<\/p>\n

Common Mistakes That Cause Rework \u2014 and How to Avoid Them<\/h2>\n

The most expensive heat treatment problems are not caused by the heat treater. They are caused by unclear drawings.<\/strong><\/p>\n

Here are the five mistakes fabricators see most often.<\/p>\n

Writing \u201cheat treat to spec\u201d without specifying which spec.<\/h3>\n

There are dozens of heat treatment standards, and each one covers different processes, materials, and acceptance criteria.<\/p>\n

\u201cHeat treat per spec\u201d means nothing unless the spec number is named.<\/strong><\/p>\n

Specifying a single hardness value instead of a range.<\/h3>\n

Hardness is not uniform across a part.<\/p>\n

A single value like \u201c45 HRC\u201d is either unachievable in some areas or too loose in others.<\/p>\n

Always specify a range that accounts for the part\u2019s geometry and material.<\/strong><\/p>\n

\"Side-by-side

A split comparison showing two engineering drawing callouts side by side \u2014 the left side labeled “Incorrect” shows a single hardness value “45 HRC,” and the right side labeled “Correct” shows a hardness range “42\u201348 HRC,” with a brief annotation explaining why a range is required.<\/span><\/p><\/div>\n

Using trade names instead of standard designations.<\/h3>\n

\u201cStainless 304\u201d is acceptable in conversation but not on a production drawing.<\/p>\n

The correct callout is \u201cASTM A240 Type 304\u201d<\/strong> or the equivalent standard for your region and application.<\/p>\n

Trade names can refer to different compositions across suppliers.<\/p>\n

Omitting inspection locations.<\/h3>\n

If the drawing does not say where to test hardness, the heat treater will test wherever is convenient \u2014 which may not be the critical functional area.<\/p>\n

This leads to parts that pass hardness testing but fail in service.<\/strong><\/p>\n

Mixing hardness scales without explanation.<\/h3>\n

If the drawing specifies \u201c40 HRC\u201d in one note and \u201c380 HB\u201d in another, the reader has to convert \u2014 and hardness conversions are approximate.<\/p>\n

Specify one scale throughout<\/strong>, or if multiple scales are unavoidable, note the conversion basis (e.g., \u201cper ASTM E140\u201d<\/strong>).<\/p>\n

Quick Checklist Before You Send That Drawing<\/h2>\n

Before releasing a production drawing with a heat treatment callout, verify these items:<\/p>\n

\"Pre-release

A clean checklist-style infographic showing seven review items that should be verified before releasing a drawing with a heat treatment callout, each item accompanied by a simple checkmark or checkbox graphic.<\/span><\/p><\/div>\n