{"id":2999,"date":"2024-12-17T21:55:03","date_gmt":"2024-12-17T13:55:03","guid":{"rendered":"https:\/\/taichungbro.com\/?p=2999"},"modified":"2026-10-22T00:33:12","modified_gmt":"2026-10-21T16:33:12","slug":"galling","status":"publish","type":"post","link":"https:\/\/www.taichungbro.com\/en\/2024\/12\/17\/galling\/","title":{"rendered":"Why do stainless steel screws seize up? A table comparing the causes of &quot;galling&quot; and 5 anti-galling measures."},"content":{"rendered":"<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Content<\/h2><nav><ul><li class=\"\"><a href=\"#\u51b7\u92b2\u5f62\u6210\u7684\u539f\u7406\">The principle of cold welding<\/a><\/li><li class=\"\"><a href=\"#\u87ba\u7d72\u4e2d\u7684\u51b7\u92b2\u73fe\u8c61\">Cold welding phenomenon in screws<\/a><\/li><li class=\"\"><a href=\"#\u92c1\u5408\u91d1\u7684\u51b7\u92b2\">Cold welding of aluminum alloys<\/a><\/li><li class=\"\"><a href=\"#\u51b7\u92b2\u7684\u5f71\u97ff\u8207\u9810\u9632\">The effects and prevention of cold welding<\/a><\/li><\/ul><\/nav><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<p class=\"wp-block-paragraph\">Have you ever encountered this situation: when disassembling equipment, you find that the screws are completely stuck, no matter how you turn them, you can&#039;t turn them, and you even break the screwdriver? This is very likely due to a &quot;cold weld&quot; phenomenon. Cold weld sounds like a technical term, but it is actually a physical phenomenon that often occurs in everyday life. Simply put, when two metal surfaces are in close contact, atomic-level bonding may occur at room temperature. This metal-metal joint that can occur without heating is called a cold weld.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This phenomenon is both a friend and a foe in industry. In situations requiring tight joints, cold welding can be beneficial; however, on equipment requiring regular disassembly and maintenance, it becomes a nightmare for engineers. Let&#039;s delve deeper into this fascinating metallic phenomenon!<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u51b7\u92b2\u5f62\u6210\u7684\u539f\u7406\">The principle of cold welding<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Cold welding (or simply &quot;cold weld&quot;; in screw-related applications, it&#039;s often referred to as &quot;thread galling&quot; or &quot;screw galling&quot;) occurs when, at a microscopic scale, a metal surface is not the smooth surface we see with the naked eye, but rather riddled with tiny bumps and depressions. When two metal surfaces come into contact, the actual contact occurs only at the apexes of these tiny bumps. Under high pressure, these contact points undergo localized plastic deformation, causing the distance between metal atoms to shorten sufficiently to form atomic bonds.<\/p>\n\n\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Metal pairing combination<\/th><th>Cold welding risk level<\/th><th>Microscopic failure mechanisms<\/th><th>Recommended anti-jamming and engineering prevention solutions<\/th><\/tr><\/thead><tbody><tr><td><strong>Homogeneous stainless steel (e.g., 304 bolts with 304 nuts)<\/strong><\/td><td><strong style=\"color: #e06c75;\">Extremely high (most common disaster area)<\/strong><\/td><td>The chromium oxide passivation film on the surface fractures under high contact compressive stress, resulting in micro-melting of pure metal atoms at contact.<\/td><td>Replace with 304 stainless steel bolts with 316\/302 stainless steel nuts (due to differences in hardness), apply a molybdenum disulfide anti-seize agent, and use manual slow-speed locking.<\/td><\/tr><tr><td><strong>Aluminum alloy bolts with aluminum alloy bases<\/strong><\/td><td><strong style=\"color: #d19a66;\">\u9ad8<\/strong><\/td><td>Aluminum is soft and chemically reactive, with a large area for plastic deformation, making the alumina film prone to cracking and peeling.<\/td><td>The base is pre-embedded with stainless steel wire thread inserts (Helicoil), anodized, and lubricated with anti-seize grease.<\/td><\/tr><tr><td><strong>Titanium alloy bolts with titanium alloy female parts<\/strong><\/td><td><strong style=\"color: #e06c75;\">Extremely high<\/strong><\/td><td>Titanium has an extremely high coefficient of friction and extremely low thermal conductivity, so the frictional heat from locking cannot dissipate, causing it to seize up instantly.<\/td><td>Surface application of physical vapor deposition (PVD\/DLC) coating, silver plating, or strict application of dry film lubricant.<\/td><\/tr><tr><td><strong>Stainless steel bolts with brass\/bronze nuts<\/strong><\/td><td><strong style=\"color: #98c379;\">Extremely low (engineering recommended)<\/strong><\/td><td>Due to the lattice mismatch between dissimilar metals, brass, with its self-lubricating properties, is less prone to forming shared metallic bonds.<\/td><td>Recommended for aerospace and precision instruments: passive anti-gnawing design, resisting gnawing without additional oiling.<\/td><\/tr><tr><td><strong>Galvanized carbon steel bolts with carbon steel nuts<\/strong><\/td><td><strong style=\"color: #61afef;\">medium to low<\/strong><\/td><td>The galvanized layer on the surface acts as a sacrificial shear protection layer, making it less prone to micro-melting during low-speed locking.<\/td><td>Keep the threads clean and free of grit, and tighten to the standard torque value to prevent excessive preload from damaging the coating.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">The comparison table clearly shows that the most common problem on-site, &quot;stainless steel screws seizing immediately upon tightening,&quot; is not due to poor thread tolerance, but rather because the micron-sized chromium oxide protective film on the surface of homogeneous Wosfield stainless steel (such as A2-70\/304) ruptures instantly under high-pressure friction, allowing the pure, fresh metal surface to directly contact and generate atomic-level metallic bond micro-fusion (thread galling). As long as one understands...<strong>&#039;Using dissimilar metals, reducing the locking speed of power tools (&lt;30 RPM), and using an anti-jamming agent containing molybdenum disulfide&#039;<\/strong>These three principles can eliminate cold welding accidents of 95% and above at the design and assembly stage. For further information on the selection of high-strength fasteners, please refer to [link\/reference]. <a href=\"https:\/\/www.taichungbro.com\/en\/2024\/09\/24\/titanium-screw\/\" style=\"color: #00c8d7; text-decoration: underline;\">What are titanium screws? Why are they so expensive? An analysis of the advantages and disadvantages of titanium screws.<\/a> \u8207 <a href=\"https:\/\/www.taichungbro.com\/en\/2023\/10\/28\/screw\/\" style=\"color: #00c8d7; text-decoration: underline;\">Do you recognize all the different types of pipe threads? Analysis of the most common pipe thread depths.<\/a>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Metal atoms mainly pass through<a href=\"https:\/\/zh.wikipedia.org\/zh-tw\/%E9%87%91%E5%B1%9E%E9%94%AE\" target=\"_blank\" rel=\"noopener\">Metallic bond<\/a>In essence, this bonding is caused by a shared electron cloud formed between atomic nuclei by free electrons. When two metal surfaces are brought close enough (typically a few atomic spacings), these free electrons can form new bonds between the two metals. This is the nature of cold soldering \u2013 a rearrangement and bonding of metal atoms that occurs at room temperature.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">However, in real-world environments, metal surfaces are typically covered by an oxide film. This oxide film hinders direct contact between metal atoms, thus inhibiting the formation of cold welds. But when sufficient pressure is applied, this oxide film may rupture, exposing the fresh metal surface underneath. Once the fresh metal surfaces come into contact, cold welds can easily occur.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Key factors affecting cold welding formation include:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Contact pressure: Higher pressure helps to break down the surface oxide layer and increase the actual contact area.<\/li>\n\n\n\n<li>Surface cleanliness: Clean metal surfaces are more prone to cold welding.<\/li>\n\n\n\n<li>Hardness of metals: Softer metals are more prone to plastic deformation and therefore easier to cold weld.<\/li>\n\n\n\n<li>Compatibility of crystal lattice structures: Similar crystal lattice structures are more likely to form stable metallic bonds.<\/li>\n<\/ol>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><img fetchpriority=\"high\" decoding=\"async\" width=\"490\" height=\"581\" src=\"https:\/\/taichungbro.com\/wp-content\/uploads\/2024\/12\/galling.webp\" alt=\"\" class=\"wp-image-3009\" style=\"width:333px;height:auto\" srcset=\"https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling.webp 490w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling-253x300.webp 253w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling-10x12.webp 10w\" sizes=\"(max-width: 490px) 100vw, 490px\" \/><figcaption class=\"wp-element-caption\">Screws that have experienced cold welding<\/figcaption><\/figure>\n<\/div>\n\n\n<div style=\"height:var(--wp--preset--spacing--30)\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<h5 class=\"wp-block-heading has-text-align-center\" id=\"\u60f3\u4e86\u89e3\u6709\u95dc\u7ba1\u87ba\u7d0b\u3001\u76f4\u87ba\u7d0b\u3001\u9310\u87ba\u7d0b\u3001\u5c3a\u5bf8\u8868\u793a\u3001\u82f1\u5236\u7ba1\u87ba\u7d0b\u3001\u516c\u5236\u7ba1\u87ba\u7d0b\u7684\u77e5\u8b58\u55ce\uff1f-\u5ef6\u4f38\u95b1\u8b80\uff1a\u300a\u7ba1\u87ba\u7d0b\u767e\u767e\u7a2e-\u4f60\u90fd\u8a8d\u8b58\u55ce-\u300b\">Want to learn about arc welding, TIG welding, MIG welding, and CO2 welding? <br>Further Reading :<a href=\"https:\/\/www.taichungbro.com\/en\/\" data-type=\"link\" data-id=\"https:\/\/taichungbro.com\/2023\/10\/28\/screw\/\" target=\"_blank\" rel=\"noopener\">&quot;The 6000-Degree Process \u2013 An Indispensable Arc Welding Technology&quot;<\/a><\/h5>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<div style=\"height:11px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u87ba\u7d72\u4e2d\u7684\u51b7\u92b2\u73fe\u8c61\">Cold welding phenomenon in screws<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">In engineering practice, cold welding of screws is arguably one of the most common and troublesome problems. The design of screws and nuts inherently creates conditions that make cold welding particularly easy to occur: the threads have a large contact area, high pressure is generated during tightening, and the contact surfaces often experience minor friction and deformation.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Stainless steel screws are particularly prone to cold welding, which is closely related to their material properties. A dense chromium oxide protective film (passivation film) forms on the surface of stainless steel, which effectively prevents metal corrosion under normal conditions. However, during the tightening process, the friction between the threads can damage this protective film. Once the protective film is damaged, the exposed fresh metal surface is particularly susceptible to cold welding because:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Although stainless steel has strong self-healing capabilities, the formation of a new oxide layer is relatively slow, allowing more time for direct contact between the metal surface and the surrounding metal.<\/li>\n\n\n\n<li>Stainless steel has strong plastic deformation ability, which makes it easy to generate a larger actual contact area under pressure.<\/li>\n\n\n\n<li>Crystal structure of stainless steel<a href=\"https:\/\/zh.wikipedia.org\/zh-tw\/%E5%A5%A5%E6%B0%8F%E4%BD%93\" target=\"_blank\" rel=\"noopener\">Worth Field Iron<\/a>(Series) is conducive to the formation of interatomic bonds<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">Furthermore, temperature variations in the operating environment can exacerbate cold welding. When equipment undergoes thermal cycling, screws and nuts experience additional stress due to thermal expansion and contraction, further increasing the contact area and pressure. Especially at high temperatures, the increased activity of the metal makes cold welding more likely to occur.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It&#039;s worth noting that the surface roughness of the screw also plays a crucial role. Appropriate surface roughness reduces the actual contact area, helping to minimize the occurrence of cold welds. This is why some screws undergo special surface treatments, such as electroplating and nitriding, to alter their surface properties. However, paradoxically, if the surface is too smooth, it can actually increase the intermolecular contact area, leading to a higher risk of cold welds.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u92c1\u5408\u91d1\u7684\u51b7\u92b2\">Cold welding of aluminum alloys<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Aluminum alloy threads are also prone to cold welding, which is closely related to the material properties of aluminum. Although an aluminum oxide protective film forms on the surface of aluminum, this film is relatively soft and easily damaged. During the tightening process, friction between the threads can easily break this protective film, exposing the fresh aluminum surface underneath. Another characteristic of aluminum is its relatively soft metallic properties and high plasticity. This means that aluminum alloy threads are prone to deformation during tightening, increasing the actual contact area. The increased contact area, combined with the high chemical reactivity of aluminum, significantly increases the probability of cold welding. Cold welding of aluminum alloy threads is particularly important to consider in engineering applications, especially in aerospace or lightweight industrial applications, where aluminum alloys are frequently used to reduce weight. To prevent cold welding of aluminum alloy threads, special surface treatments, such as anodizing, or the use of specialized anti-seize lubricants are typically employed. Sometimes, nuts of different materials (such as steel nuts) are even specially selected to match the aluminum alloy screws, using the pairing of dissimilar metals to reduce the risk of cold welding.<\/p>\n\n\n\n<div style=\"height:var(--wp--preset--spacing--30)\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<h5 class=\"wp-block-heading has-text-align-center\" id=\"\u60f3\u4e86\u89e3\u6709\u95dc\u7ba1\u87ba\u7d0b\u3001\u76f4\u87ba\u7d0b\u3001\u9310\u87ba\u7d0b\u3001\u5c3a\u5bf8\u8868\u793a\u3001\u82f1\u5236\u7ba1\u87ba\u7d0b\u3001\u516c\u5236\u7ba1\u87ba\u7d0b\u7684\u77e5\u8b58\u55ce\uff1f-\u5ef6\u4f38\u95b1\u8b80\uff1a\u300a\u7ba1\u87ba\u7d0b\u767e\u767e\u7a2e-\u4f60\u90fd\u8a8d\u8b58\u55ce-\u300b\">Would you like to learn about IC encapsulation, plastic packaging, transfer molding, compression molding, and injection molding molds? <br>Further Reading :<a href=\"https:\/\/www.taichungbro.com\/en\/2024\/06\/03\/ic_package\/\" data-type=\"link\" data-id=\"https:\/\/taichungbro.com\/2023\/10\/28\/screw\/\" target=\"_blank\" rel=\"noopener\">\u300aUnderstanding Common IC Plastic Packaging Molds\u300b<\/a><\/h5>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity is-style-wide\"\/>\n\n\n\n<div style=\"height:11px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u51b7\u92b2\u7684\u5f71\u97ff\u8207\u9810\u9632\">The effects and prevention of cold welding<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Cold welding can cause serious maintenance problems and equipment damage in industrial applications. When bolt assemblies are cold welded, it not only makes disassembly difficult but can also lead to bolt breakage or thread damage, thus affecting the normal operation and maintenance efficiency of the equipment. In the worst case, it may be necessary to remove the cold-welded bolts by destructive methods such as cutting, drilling, or electrical discharge, which not only increases maintenance costs but may also damage adjacent parts.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Preventing cold welding can be approached from several angles. Firstly, material selection is crucial; avoid using bolt assemblies made of the same material, especially when using stainless steel. For example, copper or nylon washers can be used to form a protective layer between the screw and nut. In cases where the same material must be used, surface treatments can alter the characteristics of the contact surfaces, such as nitriding, electroplating, or anodizing.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Proper use of lubricant is also key to preventing cold solder joints. Many specialized lubricants are available on the market.<a href=\"https:\/\/www.henkel-adhesives.com\/tw\/zh_tw\/product\/anti-seize-lubricants\/loctite_lb_8008_c5-a0.html\" target=\"_blank\" rel=\"noopener\">Anti-seizing agent<\/a>(Anti-Seize Compound) These lubricants typically contain fine metal particles or mineral powders (such as graphite) that can form a protective film on metal surfaces. When selecting a lubricant, factors such as the temperature and chemical corrosivity of the operating environment must be considered. In some high-temperature applications, special ceramic-based anti-seize compounds may be required.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large is-resized\"><img decoding=\"async\" width=\"1024\" height=\"1024\" src=\"https:\/\/taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-1024x1024.webp\" alt=\"\" class=\"wp-image-3008\" style=\"width:448px;height:auto\" srcset=\"https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-1024x1024.webp 1024w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-300x300.webp 300w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-150x150.webp 150w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-768x768.webp 768w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-12x12.webp 12w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-500x500.webp 500w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-600x600.webp 600w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2-100x100.webp 100w, https:\/\/www.taichungbro.com\/wp-content\/uploads\/2024\/12\/galling2.webp 1280w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">LOCTITE screw lubricant<\/figcaption><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\">Controlling the installation process is equally important. Excessive tightening torque increases the risk of cold welding, so using a torque wrench to control the tightening torque is a good preventative measure. At the same time, dry friction between the threads should be avoided during installation, ensuring proper lubrication of the thread surfaces. In high-vibration environments, special anti-loosening designs, such as spring washers or nylon-embedded nuts, can also be used. These designs not only prevent screws from loosening but also reduce the risk of cold welding.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For bolts that have already undergone cold welding, special care must be taken during disassembly. A penetrant can be used, or appropriate impact force can be applied to break the cold weld interface. If necessary, heating can be used, utilizing the principle of thermal expansion and contraction to assist disassembly. However, these remedies are often of limited effectiveness; therefore, prevention is better than cure, and cold welding issues should be fully considered during the design and installation phases.<\/p>","protected":false},"excerpt":{"rendered":"<p>Why do stainless steel screws easily get stuck instantly? This article analyzes the frictional micro-melting mechanism of thread galling, and includes a risk comparison table for cold welding of stainless steel\/aluminum\/titanium alloys and 5 practical solutions to prevent seizing.<\/p>","protected":false},"author":1,"featured_media":3000,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[45],"tags":[122,65,253],"class_list":["post-2999","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industrial-knowledge","tag-122","tag-mechanical","tag-253"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts\/2999","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/comments?post=2999"}],"version-history":[{"count":1,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts\/2999\/revisions"}],"predecessor-version":[{"id":3852,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts\/2999\/revisions\/3852"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/media\/3000"}],"wp:attachment":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/media?parent=2999"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/categories?post=2999"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/tags?post=2999"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}