{"id":1156,"date":"2026-05-08T03:54:29","date_gmt":"2026-05-08T07:54:29","guid":{"rendered":"https:\/\/www.songhaiflange.com\/?p=1156"},"modified":"2026-05-08T04:58:43","modified_gmt":"2026-05-08T08:58:43","slug":"gb-t-226-91-steel-macrostructure-and-defect-acid-etching-inspection-method","status":"publish","type":"post","link":"https:\/\/www.songhaiflange.com\/es\/2026\/05\/08\/gb-t-226-91-steel-macrostructure-and-defect-acid-etching-inspection-method\/","title":{"rendered":"GB\/T 226-91 Steel Macrostructure and Defect Acid Etching Inspection Method"},"content":{"rendered":"<h1>GB\/T 226-91 \u2014 Steel Macrostructure and Defect Acid Etching Inspection Method<\/h1>\n<div style=\"text-align:center; margin:20px 0;\">\n<a href=\"https:\/\/www.songhaiflange.com\/wp-content\/uploads\/2026\/05\/GB_T_226-91_Steel_Macrostructure_Inspection.pdf\" target=\"_blank\" style=\"background:#1a73e8;color:#fff;padding:12px 24px;text-decoration:none;border-radius:4px;font-weight:bold;\">\ud83d\udce5 Download Original PDF (Chinese Version)<\/a>\n<\/div>\n<p><embed src=\"https:\/\/www.songhaiflange.com\/wp-content\/uploads\/2026\/05\/GB_T_226-91_Steel_Macrostructure_Inspection.pdf\" type=\"application\/pdf\" style=\"width:100%;height:600px;border:1px solid #ddd;\" \/><\/p>\n<p style=\"text-align:center; color:#666;\"><em>Original GB\/T 226-91 Chinese Standard Document (embedded above)<\/em><\/p>\n<h2>1 Scope<\/h2>\n<p>This standard specifies the acid etching method for examining the macrostructure and defects of steel. It is applicable to the inspection of macrostructure and common defects in various steel products including billets, blooms, slabs, bars, and forged pieces.<\/p>\n<h2>2 Terminology<\/h2>\n<ul>\n<li><strong>Macrostructure:<\/strong> The structural features of steel visible to the naked eye or at low magnification (typically up to 10x).<\/li>\n<li><strong>Acid etching:<\/strong> A technique using acid solutions to reveal macrostructural features and defects on a polished steel surface.<\/li>\n<li><strong>Defects:<\/strong> Includes porosity, segregation, shrinkage cavity, cracks, inclusions, white spots, and similar imperfections.<\/li>\n<\/ul>\n<h2>3 Test Specimens<\/h2>\n<h3>3.1 Specimen Dimensions<\/h3>\n<ul>\n<li>Test specimens shall be cut to appropriate sizes from representative locations of the steel product.<\/li>\n<li>Typical specimen size: approximately 150 mm \u00d7 150 mm, with a thickness of 20-30 mm.<\/li>\n<li>For bars and round billets, the full cross-section or half cross-section may be tested.<\/li>\n<\/ul>\n<h3>3.2 Specimen Preparation<\/h3>\n<ol>\n<li>Cut the specimen using mechanical or thermal methods, ensuring no heat-affected zone interferes with the test area.<\/li>\n<li>Machine the test surface to a smooth finish (surface roughness Ra \u2264 3.2 \u03bcm).<\/li>\n<li>Remove all burrs, oil, and contaminants from the surface.<\/li>\n<li>Mark the specimen with identification information before etching.<\/li>\n<\/ol>\n<h2>4 Reagents<\/h2>\n<h3>4.1 Acid Etching Solution<\/h3>\n<p>The following solutions are commonly used:<\/p>\n<ul>\n<li><strong>Hydrochloric acid solution:<\/strong> Commercial concentrated hydrochloric acid (HCl, specific gravity 1.19) mixed with distilled water at a volume ratio of 1:1.<\/li>\n<li><strong>Sulfuric acid solution:<\/strong> For specific steel grades as required.<\/li>\n<\/ul>\n<h3>4.2 Safety Requirements<\/h3>\n<ol>\n<li>All acid solutions shall be prepared in a ventilated etching room or fume hood.<\/li>\n<li>Acid shall always be added to water \u2014 never water to acid \u2014 to prevent splashing.<\/li>\n<li>Operators must wear acid-resistant gloves, aprons, face shields, and boots.<\/li>\n<li>Neutralizing agents (sodium carbonate or lime) shall be available on site for emergency spill treatment.<\/li>\n<\/ol>\n<h2>5 Etching Procedure<\/h2>\n<h3>5.1 Hot Acid Etching Method<\/h3>\n<ol>\n<li>Preheat the acid solution to 60-80\u00b0C in an acid-resistant tank.<\/li>\n<li>Submerge the specimen completely, ensuring the test surface is fully exposed to the solution.<\/li>\n<li>Maintain the temperature at 65-75\u00b0C throughout the etching process.<\/li>\n<li>Etching time: typically 20-40 minutes, depending on the steel type and surface condition.<\/li>\n<li>Remove the specimen and rinse immediately with clean water.<\/li>\n<li>Neutralize the surface with a 5-10% sodium carbonate solution.<\/li>\n<li>Rinse again with clean water and dry with warm air or in an oven at 50-80\u00b0C.<\/li>\n<\/ol>\n<h3>5.2 Cold Acid Etching Method<\/h3>\n<ol>\n<li>Apply the acid solution at room temperature to the prepared surface using a brush or by immersion.<\/li>\n<li>Maintain contact time: 10-30 minutes depending on steel type.<\/li>\n<li>Keep the surface uniformly wet by periodically reapplying the acid solution.<\/li>\n<li>Rinse, neutralize, and dry as specified in 5.1.<\/li>\n<\/ol>\n<h3>5.3 Special Considerations<\/h3>\n<ul>\n<li><strong>Stainless steel:<\/strong> May require aqua regia (HCl:HNO\u2083 = 3:1) for adequate surface reveal.<\/li>\n<li><strong>Tool steel:<\/strong> May require extended etching time (30-60 min).<\/li>\n<li><strong>High-alloy steel:<\/strong> Adjust acid concentration and temperature per material specifications.<\/li>\n<\/ul>\n<h2>6 Evaluation of Macrostructure<\/h2>\n<h3>6.1 General Requirements<\/h3>\n<p>Examine the etched surface under uniform, adequate lighting (\u2265300 lux). Use visual inspection supplemented by low-magnification optical tools (up to 10x) when necessary.<\/p>\n<h3>6.2 Common Macrostructural Defects<\/h3>\n<h4>6.2.1 Center Porosity (\u4e2d\u5fc3\u758f\u677e)<\/h4>\n<p>Sponge-like voids in the central region of the cross-section, caused by gas shrinkage during solidification. Evaluate by comparing with standard reference charts.<\/p>\n<h4>6.2.2 General Segregation (\u4e00\u822c\u504f\u6790)<\/h4>\n<p>Non-uniform distribution of alloying elements creating dark or light patches on the etched surface. Rated on a severity scale from 0 (none) to 5 (severe).<\/p>\n<h4>6.2.3 Spot Segregation (\u70b9\u72b6\u504f\u6790)<\/h4>\n<p>Isolated dark or light spots indicating localized segregation of phosphorus, sulfur, or carbon. Evaluate by size, number, and distribution.<\/p>\n<h4>6.2.4 Inverse V-segregation (\u9006V\u5f62\u504f\u6790)<\/h4>\n<p>V-shaped segregation pattern emanating from the center, typically seen in continuously cast billets.<\/p>\n<h4>6.2.5 Shrinkage Cavity (\u7f29\u5b54)<\/h4>\n<p>Cavity or void in the central region caused by metal shrinkage during solidification. Classified as residual (remaining from ingot casting) or secondary.<\/p>\n<h4>6.2.6 Crack (\u88c2\u7eb9)<\/h4>\n<p>Linear discontinuities visible on the etched surface, including:<\/p>\n<ul>\n<li>Internal cracks (internal rupture)<\/li>\n<li>Subsurface cracks (below surface)<\/li>\n<li>Fissures (small-scale cracks)<\/li>\n<\/ul>\n<h4>6.2.7 White Spot (\u767d\u70b9)<\/h4>\n<p>Small, bright circular or elliptical spots on the etched surface (typically 2-15 mm in diameter), indicating hydrogen-induced internal cracks. White spots are considered a critical defect and are generally not acceptable in most applications.<\/p>\n<h4>6.2.8 Inclusion (\u5939\u6742\u7269)<\/h4>\n<p>Visible non-metallic inclusions on the etched surface, including slag inclusions and oxide inclusions.<\/p>\n<h4>6.2.9 Flaw \/ Bubble (\u6c14\u6ce1)<\/h4>\n<p>Surface or near-surface cavities formed by gas evolution during solidification.<\/p>\n<h4>6.2.10 Forging Weld Defect (\u953b\u9020\u710a\u5408)<\/h4>\n<p>Imperfect fusion zone in forged products, visible as a discontinuous line on the etched surface.<\/p>\n<h3>6.3 Grain Flow (\u7ea4\u7ef4\u6d41\u7ebf)<\/h3>\n<p>The directional flow pattern of the metal grain structure revealed by etching. Evaluate for uniformity, direction consistency, and any flow line disruption that may indicate processing defects.<\/p>\n<h2>7 Rating and Classification<\/h2>\n<p>Each defect type shall be rated using the reference charts specified in the applicable standard. Ratings are typically given on a scale of 0 to 5, where:<\/p>\n<ul>\n<li><strong>Level 0:<\/strong> No visible defect<\/li>\n<li><strong>Level 1:<\/strong> Slight \/ negligible<\/li>\n<li><strong>Level 2:<\/strong> Moderado<\/li>\n<li><strong>Level 3:<\/strong> Noticeable<\/li>\n<li><strong>Level 4:<\/strong> Severe<\/li>\n<li><strong>Level 5:<\/strong> Very severe<\/li>\n<\/ul>\n<p>Acceptance criteria shall be per the relevant product standard or as agreed between the manufacturer and purchaser.<\/p>\n<h2>8 Test Report<\/h2>\n<p>The test report shall include the following information:<\/p>\n<ol>\n<li>Heat number and grade of steel<\/li>\n<li>Product type and dimensions<\/li>\n<li>Specimen identification and sampling location<\/li>\n<li>Etching method used (hot\/cold, acid type, temperature, duration)<\/li>\n<li>Inspection conditions (lighting, magnification)<\/li>\n<li>Defect types identified with severity ratings<\/li>\n<li>Reference standard used for evaluation<\/li>\n<li>Conclusion (pass\/fail)<\/li>\n<li>Name of inspector and date of test<\/li>\n<\/ol>\n<h2>9 Safety and Environmental Protection<\/h2>\n<ol>\n<li>All etching operations must be conducted in designated areas with proper ventilation.<\/li>\n<li>Waste acid solutions shall be collected and treated before discharge in accordance with environmental regulations.<\/li>\n<li>Used neutralization sludge shall be disposed of as hazardous waste.<\/li>\n<li>Operators must receive safety training and use appropriate personal protective equipment (PPE) at all times.<\/li>\n<\/ol>\n<h2>10 Summary Table of Defect Types<\/h2>\n<table border=\"1\" cellpadding=\"5\" style=\"border-collapse:collapse;width:100%;\">\n<tr style=\"background:#f5f5f5;\">\n<th>Defect Type<\/th>\n<th>Chinese Term<\/th>\n<th>Descripci\u00f3n<\/th>\n<\/tr>\n<tr>\n<td>Center Porosity<\/td>\n<td>\u4e2d\u5fc3\u758f\u677e<\/td>\n<td>Sponge-like voids in the center region<\/td>\n<\/tr>\n<tr>\n<td>General Segregation<\/td>\n<td>\u4e00\u822c\u504f\u6790<\/td>\n<td>Non-uniform element distribution<\/td>\n<\/tr>\n<tr>\n<td>Spot Segregation<\/td>\n<td>\u70b9\u72b6\u504f\u6790<\/td>\n<td>Localized dark or light spots<\/td>\n<\/tr>\n<tr>\n<td>Shrinkage Cavity<\/td>\n<td>\u7f29\u5b54<\/td>\n<td>Central cavity from solidification shrinkage<\/td>\n<\/tr>\n<tr>\n<td>Crack<\/td>\n<td>\u88c2\u7eb9<\/td>\n<td>Linear discontinuity<\/td>\n<\/tr>\n<tr>\n<td>White Spot<\/td>\n<td>\u767d\u70b9<\/td>\n<td>Hydrogen-induced internal cracks<\/td>\n<\/tr>\n<tr>\n<td>Inclusion<\/td>\n<td>\u5939\u6742\u7269<\/td>\n<td>Visible non-metallic particles<\/td>\n<\/tr>\n<tr>\n<td>Bubble<\/td>\n<td>\u6c14\u6ce1<\/td>\n<td>Gas-formed surface cavity<\/td>\n<\/tr>\n<tr>\n<td>Grain Flow<\/td>\n<td>\u7ea4\u7ef4\u6d41\u7ebf<\/td>\n<td>Directional grain structure pattern<\/td>\n<\/tr>\n<\/table>\n<hr>\n<p><em>This is a translated version of GB\/T 226-91 for reference purposes only. The original Chinese standard shall prevail in case of discrepancies.<\/em><\/p>\n<p><em>Published by SongHai Flange \u2014 Your trusted source for flange and piping standards reference.<\/em><\/p>\n<p><strong>WhatsApp:<\/strong>\u00a0+86-18658777855<br \/>\n<strong>Correo electr\u00f3nico:<\/strong>\u00a01007788887@qq.com<br \/>\n<a href=\"https:\/\/www.720yun.com\/vr\/a6ajt7ynrw0\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-1480\" src=\"http:\/\/www.songhaiflanges.com\/wp-content\/uploads\/2026\/04\/4-1.webp\" alt=\"\" width=\"1290\" height=\"2317\" title=\"\"><\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>GB\/T 226-91 \u2014 Steel Macrostructure and Defect Acid Etching Inspection Method \ud83d\udce5 Download Original PDF (Chinese Version) Original GB\/T 226-91 Chinese Standard Document (embedded above) 1 Scope This standard specifies the acid etching method for examining the macrostructure and defects of steel. It is applicable to the inspection of macrostructure and common defects in various [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[81,77,71,66,70],"class_list":["post-1156","post","type-post","status-publish","format-standard","hentry","category-blog","tag-ansi","tag-carbon","tag-facing","tag-flange","tag-standard"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/posts\/1156","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/comments?post=1156"}],"version-history":[{"count":3,"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/posts\/1156\/revisions"}],"predecessor-version":[{"id":1166,"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/posts\/1156\/revisions\/1166"}],"wp:attachment":[{"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/media?parent=1156"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/categories?post=1156"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.songhaiflange.com\/es\/wp-json\/wp\/v2\/tags?post=1156"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}