It is a special material that has been widely used in various fields such as modern industrial construction, chemical equipment, medical care, national defense, even spacecraft and cutting-edge technology. So, how did stainless steel, a powerful metal material, come into being? One of the greatest discoveries of the 19th century was how to make steel. This metal is a mixture of iron and controlled amounts of carbon. It is easy to produce and very strong. Engineers made extensive use of steel in many of the new machines produced in the 19th century. But steel has a big problem, it rusts easily. Tools that are constantly hammered and exposed to moisture will corrode quickly. Over time, scientists have tried to find ways to solve this problem by fusing other metals with steel to form various rust-resistant alloys. On the eve of World War I, the choking smell of war gunpowder had permeated the continent of Europe. For actual combat needs, the British government decided to develop a wear-resistant and high-temperature resistant gun barrel steel to improve weapons. So they handed over the task of smelting steel to metallurgist Henry Brearley. We know that certain chemical elements need to be added to smelt steel, and according to the proportion of their content, we can obtain the various mechanical, physical and chemical properties that people need such as hardness, strength, toughness, plasticity, wear resistance, heat resistance, acid resistance, etc. Performance metal materials. Brel led his assistants to conduct smelting tests of various formulas, but the steel produced failed to meet the requirements for making gun bore materials after testing. Undeterred, Brel re-researched and revised the ratio of added chemical elements, and continued to smelt the steel used to make the gun barrel. The progress of Brill's smelting test work was not smooth, and it failed again and again. They discarded these steel blocks that did not meet the requirements to the open corner of the test site. As time goes by, the scrap steel piles up higher and higher, forming a hill-like pile of scrap steel that has become rusty after being exposed to the sun and rain. One day, the test personnel decided to clean up this batch of discarded test pieces. During the transportation, people discovered that there were several shiny pieces of scrap steel among the pile of corroded steel parts. Why did these pieces of steel show no rust? After picking them up, Brill observed and inspected them repeatedly, and he was also surprised and puzzled. In order to unravel the mystery of this strange thing, he decided to study these strange pieces of steel. Brill recalled carefully and repeatedly checked the steelmaking test records, but there were too many tests to trace back the exact smelting time and formula of these pieces of steel. In order to find out its chemical element content, Brill decided to test it. After testing and analysis, it was found that this is a piece of iron-chromium alloy, which contains 0.24% carbon and 12.8% chromium. Breer was overjoyed. He continued his research and conducted corrosive tests such as water, acid, and alkali. It turned out that the iron-chromium alloy he produced in his smelting experiments was not easy to rust at any time. Stainless steel was discovered in 1912. Scientific exploration is hard and boring work, but it is also full of fun and chance. People say that stainless steel is an invention made accidentally by metallurgist Brel, and is a by-product of the development of gun barrel steel metal materials. In 1915, Brill's discovery of stainless steel was patented in the United States; in 1916, the discovery was patented in the United Kingdom. At this time, Brill and Mosler jointly founded a factory to produce stainless steel tableware, turning scientific and technological achievements into productivity. Due to the popularity of the novel stainless steel tableware, it became popular in Europe and later spread throughout the world. As a result, Brill also won a high reputation and he was revered as the father of stainless steel. However, Brill was not the first discoverer of stainless steel. At the beginning of the 20th century, two French engineers, Guyer and Porous, had discovered that the metal mixed with chromium in iron was bright and corrosion-resistant. Because they did not know what the use of this alloy was at the time, they threw it away rashly. . In 1912, Hermos in the United States also produced stainless steel. At the same time, German metallurgical experts Schutrauss and Maurer also discovered that adding chromium and nickel to smelting could make steel that would not rust. Their discoveries were almost on the same starting line as those of Breer in the UK. However, they did not ask why for the strange phenomena they observed. Instead, they stopped before entering the scientific door to continue research, and therefore they were not the same as the first time. The honorary crown of discovering stainless steel and developing and utilizing it to obtain huge economic benefits passed by. In metal materials science, stainless steel is a special performance steel, which is mainly used as product components or working parts in special environments.
So, what is the secret of stainless steel? It turns out that stainless steel with special physical and chemical properties is added with alloying elements during smelting, such as molybdenum, titanium, copper, diamond, nickel, niobium, manganese and carbon, but chromium chemistry The ingredient content must be within the range of 12.0%-19.0%. According to the added alloying elements, stainless steel is divided into chromium stainless steel and nickel-chromium stainless steel; according to the metallographic structure characteristics of stainless steel, it can be divided into martensite type, ferrite type, austenitic type and precipitation hardening type. With the rapid development of science and technology, there are now more than 100 types of stainless steel. For example, it is not only resistant to corrosion in the air, but also acid-resistant. This type of stainless steel is called acid-resistant steel. Since all stainless steels are determined by their elemental content, not all stainless steels can resist corrosion from various media: commonly referred to stainless steels can only resist atmospheric exposure corrosion (temperature, humidity, sunshine, rainfall and Corrosion from atmospheric pollutants, etc.), and over time, the surface will become discolored and even rusty. However, these flaws cannot erase the brilliance of stainless steel's performance, nor can it shake its position of being widely used. Known as stainless steel, it is a major scientific discovery that changed the course of human civilization in the 20th century. Later, other researchers discovered that in order to enhance the ductility and formability of stainless steel, nickel was added to stainless steel to achieve this effect. In order to reduce costs, researchers later obtained standard stainless steel whose chromium content can be less than the original 14% but not less than 10.5%. Finally, it was found that #304, which has pure quality and good surface brightness (following the Japanese stainless steel product number), is 18-10. 18 means that the stainless steel contains 18% chromium, and 10 means that the stainless steel contains 10% nickel. , and the remaining 72% is the iron content. The invention of stainless steel is a major achievement in the history of world metallurgy. At the beginning of the 20th century, Fe Cr and Fe Cr were discovered by L.B. Guillet in France in 1904 and 1906 and A.M. Portevin in France in 1909 and 1911 respectively; W.Giesen discovered Fe Cr and Fe Cr in the United Kingdom in 1907 and 1909 respectively. -Corrosion resistance of Ni alloy. P.Monnartz proposed many ideas on stainlessness and passivation theory in Germany from 1908 to 1911. The inventors of industrial stainless steel include: H. Brearly, who developed martensitic stainless steel containing Cr12% and 13% in the UK in 1912 and 1913; C. Dantsizen, who developed it in the United States in 1911 and 1914. Ferritic stainless steel containing Cr14% 16%, C 0.07% 0.15%; E. Maurer and B. Strauss 1912 and 1914 developed in Germany containing C < 1%, Cr 15 % 40%, Ni<20% austenitic stainless steel. In 1929, B. Strauss obtained the patent for low-carbon 18-8 (Cr-18%, Ni-8%) stainless steel. In order to solve the sensitized intergranular corrosion of 18-8 steel, E. Houdreuot of Germany invented Ti-containing 18-8 stainless steel (equivalent to the current 1Cr18Ni9Ti or AISI 321) in 1931. At almost the same time, the Unieux Laboratory in France discovered that when austenitic stainless steel contains ferrite, the intergranular corrosion resistance of the steel will be significantly improved, thus developing gamma+alpha duplex stainless steel. In 1946, R. Smith etal of the United States developed martensitic precipitation hardening stainless steel 17-4PH; subsequently, semi-austenitic precipitation hardening stainless steel 17-7PH and PH15 had high strength and could be cold worked. -7Mo and others came out one after another. At this point, the main steel types in the stainless steel family, namely martensite, ferrite, austenite, alpha + gamma duplex and precipitation hardening stainless steel types, are basically complete, and have continued to this day.
Of course, in the 1940s and 1950s, Ni-saving Cr-Mn-N and Cr-Mn-Ni-N stainless steel, ultra-low carbon (C≤0.03%) austenitic stainless steel; in the 1960s, γ:α was close to 1 The emergence of α+γ duplex stainless steel and C+N≤150ppm high-purity ferritic stainless steel and maraging stainless steel are also major developments in the field of stainless steel. However, these new steel types are still essentially the aforementioned The five major categories of stainless steel are just new developments of certain steel types in specific steel categories. In stainless steel, in addition to C, Cr, Ni and other elements, according to the performance requirements of different uses, elements such as Mo, Cu, Si, N, Mn, Nb, Ti and other elements are further used to alloy or further reduce the C, Si in the steel. With Mn, S, P and other elements, many new steel types have been developed. For example, high-purity, high-chromium molybdenum ferritic stainless steel 00Cr25Ni4Mo4, 00Cr29Mo4Ni2, 00Cr30Mo2 and high-Mo N-containing Cr-Ni duplex stainless steel 00Cr25Ni7Mo3N, 00Cr25Ni7Mo3CuN, etc. are used to solve the pitting and crevice corrosion of chloride; in order to improve the low Nitrogen-controlled stainless steel that emerged due to the strength and corrosion resistance of carbon and ultra-low carbon Cr-Ni austenitic stainless steel; developed to improve the local corrosion resistance of Cr-Ni austenitic stainless steel and inhibit the precipitation of intermetallic phases in the steel Super austenitic stainless steel with high Cr, Mo and high nitrogen content, such as 00Cr25Ni20Mo6CuN, 00Cr24Ni22Mo7Mn3CuN; high silicon (Si 6%) stainless steel developed to resist fuming nitric acid and concentrated sulfuric acid (93% 98%). In addition, there are some special stainless steels available, such as nuclear energy grade, nitric acid grade, urea grade, food grade stainless steel, etc. According to statistics, there are more than a hundred brands worldwide that have been included in various standards (including factory standards), and there are even more non-standard brands that have not been included in the standards. Despite this, the stainless steel grades currently mass-produced and widely used in various industrially advanced countries are limited to nearly a dozen grades of martensite, ferrite and austenite. There are more than 100 types of stainless steel in use today, with varying proportions of chromium, nickel and other metals. All of these steels have unique properties, such as being easily formed when cold or being resistant to impact and rust.