{"id":419,"date":"2026-01-17T21:42:41","date_gmt":"2026-01-18T03:42:41","guid":{"rendered":"https:\/\/theoldanvil.net\/?page_id=419"},"modified":"2026-01-17T21:42:41","modified_gmt":"2026-01-18T03:42:41","slug":"heat-treating","status":"publish","type":"page","link":"https:\/\/theoldanvil.net\/index.php\/heat-treating\/","title":{"rendered":"Heat Treating"},"content":{"rendered":"\n<p class=\"has-normal-font-size\">Here are my favorite steels to use in the shop that aren&#8217;t mild steel. This list and the uses I have listed are just how I use them. This by no means limits what these steels are good for. <\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>S7 Tool Steel<\/strong><\/h2>\n\n\n\n<p><strong>Type:<\/strong> Shock-resisting tool steel (air hardening)<br><strong>Typical Process Steps:<\/strong> Annealing \u2192 Preheat \u2192 Austenitizing (hardening) \u2192 Quench \u2192 Tempering (usually multiple cycles)<\/p>\n\n\n\n<p><strong>Heat Treatment Guidelines:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Annealing (soften for machining):<\/strong> Heat to ~1500\u20131550\u00b0F (815\u2013845\u00b0C), hold, then furnace-cool slowly.<\/li>\n\n\n\n<li><strong>Preheating:<\/strong> ~1200\u00b0F (650\u00b0C) before hardening; hold to equalize temperature.<\/li>\n\n\n\n<li><strong>Austenitizing (Hardening):<\/strong> \u22481725\u00b0F (940\u00b0C), hold ~1 hr\/inch of thickness.<\/li>\n\n\n\n<li><strong>Quenching:<\/strong> Air quench (still air) for most sections; larger sections may use interrupted oil to increase cooling rate.<\/li>\n\n\n\n<li><strong>Tempering:<\/strong> Two cycles commonly at ~400\u2013450\u00b0F (204\u2013232\u00b0C) to reach desired balance of hardness and toughness; hold ~2 hrs\/in.<\/li>\n<\/ul>\n\n\n\n<p><strong>Notes:<\/strong> S7 air hardens with reduced distortion compared with oil-quenched steels. S7 is my go to for punches and top tools.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>4140 Steel<\/strong><\/h2>\n\n\n\n<p><strong>Type:<\/strong> Medium-alloy Cr-Mo steel, widely used as heat-treatable structural steel rather than a high-end tool steel<br><strong>Typical Process Steps:<\/strong> Normalize (optional) \u2192 Austenitize \u2192 Quench \u2192 Temper<\/p>\n\n\n\n<p><strong>Heat Treatment Guidelines:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Austenitizing (Hardening):<\/strong> ~1550\u20131600\u00b0F (845\u2013870\u00b0C).<\/li>\n\n\n\n<li><strong>Quench:<\/strong> Oil is common to achieve martensitic transformation.<\/li>\n\n\n\n<li><strong>Tempering:<\/strong> Varies widely (\u2248200\u2013650\u00b0C; ~400\u20131200\u00b0F) depending on the required toughness\/hardness.<\/li>\n<\/ul>\n\n\n\n<p><strong>Notes:<\/strong> 4140 is often normalized first to refine grain, then hardened and tempered. It is not typically \u201ctool steel\u201d by classification but is heat-treatable. 4140 is my go too for hammers and top tools. it&#8217;s also a good choice for making hooks and other load bearing items. <\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>440C Stainless Steel<\/strong><\/h2>\n\n\n\n<p><strong>Type:<\/strong> Martensitic stainless tool steel (high-carbon, high-chromium)<br><strong>Typical Process Steps:<\/strong> Anneal \u2192 Preheat \u2192 Austenitize \u2192 Quench \u2192 Temper<\/p>\n\n\n\n<p><strong>Heat Treatment Guidelines:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Annealing (soften for machining):<\/strong> \u22481560\u20131650\u00b0F (850\u2013900\u00b0C), furnace cool.<\/li>\n\n\n\n<li><strong>Preheating:<\/strong> ~1425\u00b0F (775\u00b0C) before austenitize recommended for larger parts.<\/li>\n\n\n\n<li><strong>Austenitizing (Hardening):<\/strong> \u22481850\u20131950\u00b0F (1010\u20131066\u00b0C).<\/li>\n\n\n\n<li><strong>Quench:<\/strong> Oil quench or air cool to ~125\u2013150\u00b0F (50\u201365\u00b0C).<\/li>\n\n\n\n<li><strong>Tempering:<\/strong> Often twice at ~300\u2013500\u00b0F (149\u2013260\u00b0C) to achieve a range of hardness (e.g., ~56\u201360 HRC).<\/li>\n<\/ul>\n\n\n\n<p><strong>Notes:<\/strong> Tempering above ~425\u00b0C (~800\u00b0F) can reduce impact strength and corrosion resistance; cryogenic treatment can reduce retained austenite before tempering. This is my main choice for kitchen knives as it&#8217;s dishwasher safe.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>5160 Steel<\/strong> (Spring Steel)<\/h2>\n\n\n\n<p><strong>Type:<\/strong> High-carbon chromium spring steel<br><strong>Typical Process Steps:<\/strong> (Optional Normalize) \u2192 Austenitize \u2192 Oil Quench \u2192 Temper<\/p>\n\n\n\n<p><strong>Heat Treatment Guidelines:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Austenitizing (Hardening):<\/strong> ~1500\u20131525\u00b0F (815\u2013830\u00b0C).<\/li>\n\n\n\n<li><strong>Quench:<\/strong> Oil quench (medium oil).<\/li>\n\n\n\n<li><strong>Tempering:<\/strong> Typically two cycles at ~350\u2013400\u00b0F (175\u2013205\u00b0C) to reduce brittleness and achieve ~58\u201361 HRC in many applications.<\/li>\n<\/ul>\n\n\n\n<p><strong>Notes:<\/strong> Normalizing before hardening is a common optional step to refine grain and relieve stress. This is the most common type of steel in coil spring found in scrap yards, it&#8217;s also a common steel in leaf springs. This is my go too steel for things like pry bars and other tools that need some flex in them. <\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>D2 Tool Steel<\/strong><\/h2>\n\n\n\n<p><strong>Type:<\/strong> High-carbon, high-chromium air-hardening tool steel<br><strong>Typical Process Steps:<\/strong> Annealing \u2192 Preheat \u2192 Austenitize \u2192 Air Quench \u2192 Temper (often multiple cycles)<\/p>\n\n\n\n<p><strong>Heat Treatment Guidelines:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Annealing:<\/strong> ~1200\u20131250\u00b0F (650\u2013677\u00b0C) slow cool (or slower anneal at ~850\u00b0C).<\/li>\n\n\n\n<li><strong>Preheating:<\/strong> ~1200\u20131250\u00b0F (650\u2013677\u00b0C) before austenitizing.<\/li>\n\n\n\n<li><strong>Austenitizing (Hardening):<\/strong> \u22481796\u20131877\u00b0F (980\u20131025\u00b0C).<\/li>\n\n\n\n<li><strong>Quench:<\/strong> Air quench is typical, though larger sections may be oil or salt bath quenched to complete transformation.<\/li>\n\n\n\n<li><strong>Tempering:<\/strong> Often double or triple tempers Hold for 2 hours per temper (e.g., ~200\u2013500\u00b0F \/ ~150\u2013260\u00b0C),  60-62 HRC<\/li>\n<\/ul>\n\n\n\n<p><strong>Notes:<\/strong> D2 is known for high wear resistance and minimal distortion due to air-hardening. Great for punches to work cold or hot. <\/p>\n","protected":false},"excerpt":{"rendered":"<p>Here are my favorite steels to use in the shop that aren&#8217;t mild steel. This list and the uses I<\/p>\n<p><a href=\"https:\/\/theoldanvil.net\/index.php\/heat-treating\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\">Heat Treating<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-419","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/theoldanvil.net\/index.php\/wp-json\/wp\/v2\/pages\/419","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/theoldanvil.net\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/theoldanvil.net\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/theoldanvil.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/theoldanvil.net\/index.php\/wp-json\/wp\/v2\/comments?post=419"}],"version-history":[{"count":1,"href":"https:\/\/theoldanvil.net\/index.php\/wp-json\/wp\/v2\/pages\/419\/revisions"}],"predecessor-version":[{"id":420,"href":"https:\/\/theoldanvil.net\/index.php\/wp-json\/wp\/v2\/pages\/419\/revisions\/420"}],"wp:attachment":[{"href":"https:\/\/theoldanvil.net\/index.php\/wp-json\/wp\/v2\/media?parent=419"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}