Special lecture on mechanical equipment: “Pumps” – Learn a little every day (10): Pump materials – “Improve yourself””

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This post was last edited by A Dai A Mu on 2013-12-12 at 12:34. In order to encourage more people to come and discuss as well as to study more actively, the top five users each time will receive a “Reward for Active Learning.” Some people might think that it’s terrifying to spend their working days doing nothing, performing tasks that seem like menial chores, not knowing what to do or what to learn; day after day, year after year, with no vision for their future We must start working hard from now on; even if we learn a little knowledge every day, it will add up over time and help us enrich ourselves. We need to set clear goals – only by filling our minds first can we enrich other aspects of our lives as well. . . . . . Just spend a short ten-odd minutes every day, and you will see the future! ! ! (Anyway, I have learned it; whether you learn it or not is up to you. Those who know it include that great expert Hai Chuan, aside from others. . . ) Enough talk – let’s start with the basics today~~! With so many themed posts posted over these days, everyone must have benefited a lot, thank you all for your support~~! Welcome everyone to listen. I have started broadcasting, and I hope those who, like me, want to gain knowledge every day will listen. Let’s learn together every day and discuss~~! These past few days, many people have asked questions, and I’ll do my best to answer them all. There might be some I haven’t encountered before, but there are still plenty of people in our community who can help answer them. @AidaiAmu @hcwang12345 @YiHuXiangMing @tjdxz @YouDianDai @NewbiesInHaiChuan @LoveStory @ManTianYun @ZhaoQingsheng Yesterday, I started using the self-priming pump; at everyone’s request, I’ll explain today the materials used in this pump~~~ The special lecture on pumps is coming to an end. I hope that those of you who are interested in pumps have any questions regarding other aspects of them; for the issues that come up frequently, I will write a separate article to address them~~! Pump materials: Six common materials for pump casings. 1. Cast iron: Gray cast iron is the most commonly used type of cast iron; it is employed for the casing, impeller, pump cover, and suspension components of ordinary water pumps, with three different grades typically being used. Ductile iron is a type of cast iron with good comprehensive properties. Due to its mechanical properties being similar to those of steel, along with superior casting and machining properties compared to steel, it is often used as a substitute for cast steel. Due to constraints such as casting, the company is not currently producing this material. II. Stainless Steel: The most widely used type of stainless steel is austenitic stainless steel. Except for a few media such as hydrochloric acid and dilute sulfuric acid, austenitic stainless steel is an excellent corrosion-resistant material and is the most commonly used corrosion-resistant material in chemical pumps. Additionally, high-alloy stainless steels (Grade 20 alloy) and duplex stainless steels are also ideal corrosion-resistant materials. III. Cast steel: The strength of cast steel increases; generally, when the pressure is greater than 1.6 Mpa, cast steel is used for pressure-bearing components! IV. Carbon structural steel: It is usually divided into ordinary carbon structural steel and high-quality carbon structural steel. V. Alloy steels: The most representative alloy steel is 40Cr, which is commonly used as material for high-strength pump shafts. VI. Non-metallic materials: Non-metallic materials used in pumps are primarily for sealing purposes, such as polytetrafluoroethylene, fluororubber, nitrile rubber, etc. Among them, polytetrafluoroethylene is used for gaskets in chemical pumps and as a static seal in mechanical seals due to its excellent corrosion resistance and high-temperature tolerance; it is suitable for almost all chemical media at temperatures up to 250°C. Its disadvantages are high hardness and difficulty in installation. Fluororubber is also a good material for withstanding high temperatures and corrosion; its maximum temperature tolerance is around 160°C. Unless the customer has specific requirements, the company’s chemical pumps use seals made of this material ； Nitrile rubber is mainly used for static sealing in oil-resistant or clean water environments. Material selection for pumps: 1. Sulfuric acid, as one of the highly corrosive substances, is an important industrial material with a wide range of applications. Sulfuric acid at different concentrations and temperatures causes varying degrees of corrosion to materials. For concentrated sulfuric acid with a concentration of over 80% and a temperature below 80°C, carbon steel and cast iron exhibit good corrosion resistance; however, it is not suitable for sulfuric acid that flows at high speeds, and thus cannot be used as material for pumps and valves ； Common stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) also have limited utility in sulfuric acid media. Therefore, pump valves for transporting sulfuric acid are typically made of high-silicon cast iron (which is difficult to cast and process) or high-alloy stainless steel (grade 20 alloy). Fluoroplastics exhibit good resistance to sulfuric acid, making the use of fluorinated liner pumps (F46) a more economical option. 2. Hydrochloric acid: The vast majority of metal materials are not resistant to corrosion by hydrochloric acid (including various stainless steel materials); high-molybdenum high-silicon iron can only be used in hydrochloric acid at temperatures below 50°C and with a concentration of less than 30%. Unlike metal materials, the vast majority of non-metallic materials exhibit good corrosion resistance to hydrochloric acid; therefore, rubber-lined pumps and plastic pumps (such as polypropylene, fluoroplastics, etc.) are the best choices for transporting hydrochloric acid. 3. Most common metals are rapidly corroded and damaged by nitric acid; stainless steel is the most widely used material resistant to nitric acid, exhibiting good corrosion resistance to nitric acid of all concentrations at room temperature. It is worth noting that stainless steels containing molybdenum (such as 316 and 316L) do not have better corrosion resistance to nitric acid than ordinary stainless steels (such as 304 and 321), and in some cases their resistance is even lower. For high-temperature nitric acid, titanium and titanium alloy materials are commonly used. 4. Acetic acid is one of the most corrosive organic acids; ordinary steel suffers severe corrosion in acetic acid at all concentrations and temperatures. Stainless steel is an excellent material resistant to acetic acid, and 316 stainless steel containing molybdenum can also be used in high-temperature environments as well as with dilute acetic acid vapor. For demanding applications such as high-temperature, high-concentration acetic acid or environments containing other corrosive agents, high-alloy stainless steel or fluoroplastic pumps can be used. 5. Alkalis (sodium hydroxide): Steel is widely used in sodium hydroxide solutions at temperatures below 80°C and with concentrations up to 30%. Many factories still use ordinary steel at temperatures of 100°C and concentrations below 75%; although corrosion increases, it remains cost-effective. Ordinary stainless steel does not have a significant advantage over cast iron in terms of corrosion resistance to alkaline solutions; it is not recommended to use stainless steel unless a small amount of iron is allowed to be present in the medium. For high-temperature alkaline solutions, titanium and titanium alloys or highly alloyed stainless steels are commonly used. 6. Ammonia (ammonium hydroxide): Most metals and non-metals suffer only mild corrosion in liquid ammonia and ammonium hydroxide solutions; only copper and its alloys are not suitable for use. 7. Saltwater (seawater): Ordinary steel experiences a low rate of corrosion in sodium chloride solutions as well as in seawater and brackish water; coating protection is generally required ； Various types of stainless steel also have very low uniform corrosion rates, but local corrosion may occur due to chloride ions; therefore, 316 stainless steel is generally the better choice. 8. Alcohols, alkanes, esters, and ethers: Common alcohol-based media include methanol, ethanol, ethylene glycol, propanol, etc.; alkanes include propane, butane, etc.; ester-based media comprise various methyl esters, ethyl esters, etc.; ether-based media include dimethyl ether, diethyl ether, butyl ether, etc. These substances generally have no corrosive properties, and most common materials can be used with them. When making a selection, it is necessary to consider the properties of the medium and relevant requirements in order to make a proper choice. It is also worth noting that alcohols, esters, and ethers are soluble in various rubbers, which helps to avoid mistakes when selecting sealing materials. There are many other media that cannot be listed here one by one. In short, when selecting materials, one must not act casually or blindly; it is advisable to consult relevant information and draw on proven experience. Knowledge of Metal Materials I. Classification, grades, and properties of cast iron. Both cast iron and pig iron are iron-carbon alloys with a carbon content greater than 2.11%; *traditionally, the molten iron produced directly in blast furnaces or the raw iron blocks are referred to as pig iron ； Pig iron that has been remelted with additives and cast into cast iron parts is called cast iron. Based on the form in which carbon exists in cast iron, it can be classified into white cast iron, gray cast iron, malleable cast iron, and ductile iron. 1. White cast iron: In this type of cast iron, all the carbon exists in the form of cementite; it is called white cast iron because its fracture surface appears bright white. 2· Gray cast iron: In this type of cast iron, most or all of the carbon exists in the form of flake graphite; it is called gray cast iron because of its gray fracture surface, and it is also known as ordinary cast iron. During pump repair, gray cast iron is commonly used to manufacture components such as balance rings, shaft sleeves, and sealing rings. Gray cast iron possesses excellent castability, machinability, wear resistance, and shock absorption. Its compressive strength and hardness are similar to those of carbon steel, but its tensile strength and ductility are lower. Gray cast iron is denoted as “HT□—□”; the meaning of each component is shown in the table below. Explanation of cast iron codes: Examples of name codes and their meanings – Gray cast iron HT20—40: “HT” represents the first letters of the Chinese pinyin for “gray iron”. The first set of numbers after “HT”, 20, indicates the minimum tensile strength (kgf/mm2), while the second set of numbers, 40, indicates the minimum bending strength. Ductile iron QT45—5: “QT” represents the first letters of the Chinese pinyin for “ductile iron”. The first set of numbers after “QT”, 45, indicates the minimum tensile strength (kgf/mm2), while the second number, 5, indicates the minimum elongation rate. Malleable iron KT30—6: “KT” represents the first letters of the Chinese pinyin for “malleable iron”. The first set of numbers after “KT”, 30, indicates the minimum tensile strength (kgf/mm2), while the second number, 6, indicates the minimum elongation rate. Carbon steel ZG15: “ZG” represents the first letters of the Chinese pinyin for “cast steel”. The number 15 after “ZG” indicates the average carbon content. 3. Malleable iron: Malleable iron possesses higher strength than gray cast iron, as well as a certain degree of plasticity and toughness. 4· Ductile iron: When molten iron is subjected to spheroidization treatment before casting, the carbon in it exists in the form of spherical graphite, which is why it is called ductile iron. Ductile iron possesses high tensile strength and plasticity, making it suitable for use as crankshafts and connecting rods in diesel engines and compressors. The grade of ductile iron is denoted as “QT□—□”, with the meanings of each element shown in the table above. II. Classification, grades, and properties of steel Steel refers to an iron-carbon alloy with a carbon content of less than 2.11%. 1. Classification of steel: There are many types of steel, which can generally be classified based on their chemical composition, quality, manufacturing methods, and applications. Classified by chemical composition ⊙Carbon steel. The steel contains no other alloying elements apart from carbon. The properties of steel are primarily adjusted based on the level of carbon content. Based on their carbon content, they can be roughly divided into: low-carbon steel: with a carbon content generally less than 0.25%. Medium carbon steel: The carbon content is generally between 0.25% and 0.60%. High-carbon steel: Generally has a carbon content of more than 0.6% ⊙ Alloy steel. It refers to steel that contains one or more appropriate amounts of alloying elements, thereby possessing improved or special properties. Based on the total content of their alloying elements, they can also be classified as follows: low-alloy steel: the total content of alloying elements is less than 3%. Medium alloy steel: The total content of alloying elements is 3% to 10%. Alloy steels can also be classified into manganese steel, chromium steel, silicomanganese steel, etc., based on the types of alloying elements they contain. If anyone would like to learn more in depth about a particular material, please reply to me and I will provide a detailed explanation of that material~! ! ! Below are my special series of lectures on mechanical equipment – “Pumps”. Learn something new every day: (16) Pneumatic diaphragm pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1257985-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (15) Pneumatic diaphragm pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1257433-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (14) Mixed-flow pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1257224-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (13) Axial flow pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1256970-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (12) Jet vacuum pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1256707-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (11) Automotive pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1256253-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (10) Pump materials – “Improve your knowledge” http://bbs.hcbbs.com/thread-1255790-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (9) Self-priming pumps and pump materials – “Improve your knowledge” http://bbs.hcbbs.com/thread-1255635-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (8) Oil seals – “Improve your knowledge” http://bbs.hcbbs.com/thread-1255340-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (7) Seals – “Improve your knowledge” http://bbs.hcbbs.com/thread-1255132-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (6) O-rings – “Improve your knowledge” http://bbs.hcbbs.com/thread-1254912-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (5) Pump structure – “Improve your knowledge” http://bbs.hcbbs.com/thread-1254630-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (4) Pump structure – “Improve your knowledge” http://bbs.hcbbs.com/thread-1254625-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (3) – “Improve your knowledge” http://bbs.hcbbs.com/thread-1253809-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (2) Schematic diagram of centrifugal pumps – “Improve your knowledge” http://bbs.hcbbs.com/thread-1253590-1-1.html. Lectures on mechanical equipment – “Pumps”: Learn something new every day (1) Pump selection – “Improve your knowledge”. These are my special posts; I will continue to update them daily. Please give me your support, listen, and discuss! ； If there’s any direction that needs to be explained, feel free to contact me. If many people ask for it, I’ll create a separate post to go over it~~! :) A series of special lectures on mechanical equipment titled “Pumps” – a summary post with new knowledge shared every day, continuously updated at http://bbs.hcbbs.com/thread-1256318-1-1.html. Everyone is welcome to listen; I’ve already started broadcasting these sessions, hoping that those who want to gain knowledge every day will hear them. Let’s learn together every day and discuss~~! Learn a little bit every day, making progress little by little~~!