{"id":308,"date":"2026-04-18T01:53:45","date_gmt":"2026-04-18T01:53:45","guid":{"rendered":"https:\/\/kurtfoundry.com\/?p=308"},"modified":"2026-04-18T01:53:45","modified_gmt":"2026-04-18T01:53:45","slug":"cast-stainless-steel-grades-processes-design","status":"publish","type":"post","link":"https:\/\/kurtfoundry.com\/fr\/blog\/cast-stainless-steel-grades-processes-design\/","title":{"rendered":"Peut-on couler de l'acier inoxydable ? Nuances, proc\u00e9d\u00e9s et r\u00e8gles de conception"},"content":{"rendered":"<p>Chaque famille d'acier inoxydable \u2014 aust\u00e9nitique, ferritique, martensitique, duplex et durci par pr\u00e9cipitation \u2014 poss\u00e8de des \u00e9quivalents moul\u00e9s \u00e9tablis avec des d\u00e9signations ASTM. J'ai coul\u00e9 toutes ces nuances. Mais la question qui devrait suivre \u201c peut-il \u00eatre moul\u00e9 ? \u201d est celle que la plupart des ing\u00e9nieurs ne posent jamais : que se passe-t-il lorsque l'acier inoxydable se solidifie dans un moule au lieu d'\u00eatre lamin\u00e9 en t\u00f4le ?<\/p>\n\n\n\n<p>That answer involves deliberate microstructural differences, a ferrite paradox that surprises engineers trained on wrought alloys, and design rules that go beyond the basic answer. Get the metallurgy right, and cast stainless delivers complex geometries with corrosion resistance matching wrought counterparts. Get it wrong, and you\u2019ll see intergranular corrosion on parts that passed every chemistry check.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Oui, l'acier inoxydable peut \u00eatre moul\u00e9<\/h2>\n\n\n\n<p>Le moulage au sable, le moulage \u00e0 la cire perdue et le moulage centrifuge traitent couramment les alliages d'acier inoxydable. Les fonderies commerciales proposent plus de 30 nuances d'acier inoxydable moul\u00e9 couvrant toutes les grandes familles, avec des pi\u00e8ces moul\u00e9es individuelles allant de moins d'une livre \u00e0 plus de 6 000 livres.<\/p>\n\n\n\n<p>La distinction critique par rapport \u00e0 l'acier au carbone : les alliages inoxydables ont une plage de temp\u00e9rature de solidification plus large \u2014 de 1375 \u00e0 1530 \u00b0C selon la nuance \u2014 et un retrait volumique de 2 \u00e0 3 % lors du refroidissement. Cette plage de solidification plus large rend l'acier inoxydable beaucoup plus sensible \u00e0 la fissuration \u00e0 chaud que l'acier au carbone. Chaque d\u00e9cision concernant le syst\u00e8me de coul\u00e9e, d'alimentation et de refroidissement doit en tenir compte.<\/p>\n\n\n\n<p>I\u2019ve pulled CF8M <a href=\"https:\/\/kurtfoundry.com\/fr\/capabilities\/custom-stainless-steel-castings\/\">pump bodies<\/a> that failed intergranular corrosion testing despite chemistry reports showing 18.48% Cr, 9.55% Ni, and 2.10% Mo \u2014 all within ASTM A351 spec. The root cause was carbide precipitation from improper cooling rate during heat treatment. Chromium carbides formed at grain boundaries, creating chromium-depleted zones that corroded under chloride exposure. Material selection alone is never enough \u2014 process control is the other half of the equation.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Wrought-to-Cast Grade Mapping<\/h2>\n\n\n\n<p>Engineers working with wrought stainless specify 304, 316, 304L, 316L. Their cast counterparts carry SFSA designations that encode composition and service environment in a single string.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">The SFSA Designation System<\/h3>\n\n\n\n<p>The Steel Founders Society of America (SFSA) system works like this: the first letter indicates intended service \u2014 C for corrosion-resistant, H for heat-resistant. The second letter progresses A through Z with increasing nickel content. Trailing numerals express maximum carbon content as a percentage times 100. Suffix letters denote additional alloying elements (M for molybdenum, N for nitrogen).<\/p>\n\n\n\n<p>CF8M decoded: <strong>C<\/strong> (corrosion service) + <strong>F<\/strong> (mid-range nickel) + <strong>8<\/strong> (0.08% max carbon) + <strong>M<\/strong> (molybdenum added). The code tells you composition, service intent, and carbon limit before you open the spec sheet.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Wrought Grade<\/th><th>Cast Equivalent<\/th><th>ASTM Spec<\/th><th>Key Difference<\/th><\/tr><\/thead><tbody><tr><td>304<\/td><td>CF8<\/td><td>A351 \/ A743<\/td><td>5-20% delta-ferrite retained<\/td><\/tr><tr><td>316<\/td><td>CF8M<\/td><td>A351 \/ A743 \/ A744<\/td><td>Mo addition + ferrite<\/td><\/tr><tr><td>304L<\/td><td>CF3<\/td><td>A351 \/ A743<\/td><td>Low carbon (0.03% max)<\/td><\/tr><tr><td>316L<\/td><td>CF3M<\/td><td>A351 \/ A743<\/td><td>Low carbon + Mo<\/td><\/tr><tr><td>410<\/td><td>CA15<\/td><td>A743<\/td><td>Martensitic, air-hardenable<\/td><\/tr><tr><td>2205<\/td><td>CD4MCuN<\/td><td>A890<\/td><td>Duplex, 50\/50 austenite-ferrite<\/td><\/tr><tr><td>17-4 PH<\/td><td>CB7Cu-1<\/td><td>A747<\/td><td>Precipitation-hardened<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Why CF8 Is Not Just \u201c304 in Cast Form\u201d<\/h3>\n\n\n\n<p>This is the most common misconception I correct. CF8 retains 5-20% delta-ferrite deliberately \u2014 making it slightly magnetic. Wrought 304 is processed to be fully austenitic and nonmagnetic. When your QC team pulls a magnet test on a CF8 casting and gets a response, that\u2019s not contamination. That\u2019s the microstructure working as designed.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1376\" height=\"768\" src=\"https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-2.png\" alt=\"Diagramme de comparaison microstructurale montrant les \u00eelots de ferrite delta dans l&#039;acier inoxydable moul\u00e9 CF8 par rapport \u00e0 l&#039;acier inoxydable corroy\u00e9 enti\u00e8rement aust\u00e9nitique 304\" class=\"wp-image-306\" title=\"\" srcset=\"https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-2.png 1376w, https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-2-300x167.png 300w, https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-2-1024x572.png 1024w, https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-2-768x429.png 768w\" sizes=\"auto, (max-width: 1376px) 100vw, 1376px\" \/><\/figure>\n\n\n\n<p>Cast grades also allow wider Cr and Ni composition windows to accommodate solidification variables that don\u2019t exist in wrought processing. The resulting grain structure is coarser, tensile strength is generally lower, and fatigue resistance follows different curves. CF8M minimum tensile strength per ASTM A351 is 70 ksi with 30% elongation \u2014 adequate for most applications, but not interchangeable with wrought 316 in fatigue-critical service.<\/p>\n\n\n\n<p>Before you specify the grade, understand the service conditions. A CF8 casting in a chloride environment above 60 C will likely develop stress corrosion cracking. For that service, you need CF8M or CF3M at minimum.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Why Ferrite Changes Everything<\/h2>\n\n\n\n<p>Delta-ferrite \u2014 the magnetic, body-centered cubic phase retained in cast austenitic stainless \u2014 is simultaneously the most important and most misunderstood feature of cast stainless steel.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">The Ferrite Paradox<\/h3>\n\n\n\n<p>Ferrite does three things that make casting possible. It prevents hot tearing during solidification by disrupting crack propagation paths. It blocks stress-corrosion crack growth because ferrite pools within the austenitic matrix impede crack propagation. And it forces carbide precipitation into the ferrite phase rather than at austenite grain boundaries, reducing intergranular attack susceptibility.<\/p>\n\n\n\n<p>The nuclear power industry requires a minimum of 5-7% ferrite for weldability. Foundry practice for corrosion-resistant castings typically targets 4-6%.<\/p>\n\n\n\n<p>Three variables control ferrite content, and only one belongs to the metallurgist: chemical composition (the ASTM A800 formulae balancing Cr, Mo, and Si against Ni, C, Mn, and N), section thickness, and heat treatment. Section thickness is the variable most engineers overlook \u2014 thicker sections solidify slower and produce higher ferrite. The foundry has very little control over section thickness; the part designer determines it. Your geometry decisions directly influence the metallurgical outcome.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Temperature Limitations<\/h3>\n\n\n\n<p>The tradeoff appears above 315 C (600 F). Ferrite begins degrading metallurgically, and in the 425-650 C range, carbide precipitation shifts to ferrite pool edges. ASTM A351 explicitly states that grades CF3A, CF3MA, and CF8A are not recommended for service above 425 C (800 F). The very feature that makes these alloys castable limits their high-temperature service \u2014 a constraint wrought austenitic grades with minimal ferrite do not face.<\/p>\n\n\n\n<p>For high-temperature stainless applications, specify H-series (heat-resistant) cast grades, which incorporate higher carbon for elevated-temperature strength at the expense of ambient corrosion resistance.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Which Casting Process Fits Stainless Steel<\/h2>\n\n\n\n<p>Sand, investment, and centrifugal casting all work for stainless \u2014 but stainless steel\u2019s wider freezing range means every process needs adjusted gating and thermal management compared to carbon steel.<\/p>\n\n\n\n<p>Sand casting handles the broadest weight range and works for most stainless grades. Expect tolerances of +\/-0.010 inches on the first linear dimension and +\/-0.005 per additional inch. Minimum section thickness for CF8M starts at 3\/16 inch. Sand casting is the default for valve bodies, pump housings, and structural components where investment casting\u2019s cost premium isn\u2019t justified.<\/p>\n\n\n\n<p>Investment casting achieves tolerances within +\/-0.003 inches on holes and delivers superior surface finish. It earns its premium on thin-walled, geometrically complex parts \u2014 impeller vanes, surgical housings, aerospace brackets \u2014 where machining from wrought bar would waste most of the raw material.<\/p>\n\n\n\n<p>Centrifugal casting suits pipe fittings, bushings, and cylindrical geometries where centrifugal force produces a denser, more uniform grain structure than static pouring.<\/p>\n\n\n\n<p>Regardless of process, stainless casting demands tighter process control than carbon steel. I\u2019ve seen a well-established CF8M casting \u2014 over 50,000 successful pours \u2014 develop surface shrinkage after nothing more than a riser sleeve change. Solidification modeling identified the fix: gating redesign and riser adjustments that cut scrap by an additional 1.5%. One variable change in a mature process caused defects.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1376\" height=\"768\" src=\"https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-4.png\" alt=\"Sectioned cast stainless steel CF8M part showing internal shrinkage porosity defect near the riser connection area\" class=\"wp-image-307\" title=\"\" srcset=\"https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-4.png 1376w, https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-4-300x167.png 300w, https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-4-1024x572.png 1024w, https:\/\/kurtfoundry.com\/wp-content\/uploads\/2026\/03\/stainless-steel-casting-possible-4-768x429.png 768w\" sizes=\"auto, (max-width: 1376px) 100vw, 1376px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">Is Your Part a Good Casting Candidate?<\/h2>\n\n\n\n<p>Before you send an RFQ, run your component through four filters.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Geometry complexity.<\/strong> Parts with internal passages, undercuts, or organic shapes that would require multi-axis machining from wrought bar are strong casting candidates. Simple prismatic shapes that machine efficiently from plate or bar stock rarely justify casting tooling costs.<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Production volume.<\/strong> Pattern and tooling costs amortize over quantity. Below 25-50 pieces for sand casting (or below 100 for investment casting), machining from wrought stock is often more economical. Above those thresholds, per-unit casting cost drops sharply.<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Tolerance requirements.<\/strong> As-cast sand casting tolerances (+\/-0.010 to 0.015 inches) require secondary machining for tight-tolerance features. If your entire part demands tight tolerances, machining from wrought may cost less than casting plus finish machining. If only mating surfaces need precision, casting the near-net shape and machining critical features wins.<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Service conditions.<\/strong> Cast stainless matches wrought corrosion resistance for most environments. But cast austenitic grades face the ferrite-driven temperature ceiling at 425 C, and property variability is inherently wider \u2014 I\u2019ve seen Brinell hardness swing from 158 to 204 across castings from the same heat. If your application demands tight mechanical property consistency or service above 425 C, wrought material is the safer specification.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">L'essentiel<\/h2>\n\n\n\n<p>Stainless steel is absolutely castable across every major alloy family, and the cast equivalents have decades of proven field performance. The engineering challenge isn\u2019t whether it can be done \u2014 it\u2019s recognizing that cast CF8M behaves differently than wrought 316 in ways that affect your design, your specification, and your quality expectations.<\/p>\n\n\n\n<p>Specify the ASTM cast designation, not the wrought grade. Account for ferrite content in your service temperature evaluation. And design your section thicknesses knowing that geometry controls metallurgy in a casting. Get those three decisions right, and cast stainless becomes one of the most versatile manufacturing options available.<\/p>","protected":false},"excerpt":{"rendered":"<p>Every stainless steel family \u2014 austenitic, ferritic, martensitic, duplex, and precipitation-hardened \u2014 has established cast equivalents with ASTM designations. I&#8217;ve [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":306,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[1],"tags":[],"class_list":["post-308","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/posts\/308","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/comments?post=308"}],"version-history":[{"count":1,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/posts\/308\/revisions"}],"predecessor-version":[{"id":721,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/posts\/308\/revisions\/721"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/media\/306"}],"wp:attachment":[{"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/media?parent=308"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/categories?post=308"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kurtfoundry.com\/fr\/wp-json\/wp\/v2\/tags?post=308"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}