Macrich Industry Co., Ltd. Blog

In recent years, hot-dip galvanized steel sheets are very popular with customers because of their good corrosion resistance, beautiful appearance, favorable for subsequent processing, low cost and environmental pollution. This article will take you to a comprehensive understanding of hot-dip galvanized steel from the aspects of varieties, uses, development history of production technology and defects. Since the standard electrode potential of zinc is less than that of iron, the galvanized layer has the function of sacrificial anode to protect the steel base in water and humid air, thus greatly prolonging the service life of the steel. Hot dip galvanizing, electro-galvanizing, mechanical galvanizing and thermal spraying (plating) zinc are commonly used in industry, among which hot galvanizing accounts for about 95% of the total amount of galvanizing, the amount of zinc used for hot galvanizing accounts for 40% of zinc production worldwide, and accounts for about 30% of zinc production in China. Hot dip galvanizing is a technological process in which steel, stainless steel, cast iron and other metals are immersed in molten liquid metal or alloy to obtain coatings. Hot galvanizing is the most widely used surface treatment method for steel in the world with the best performance-price ratio. Hot-dip galvanizing products play an inestimable and irreplaceable role in reducing corrosion and prolonging life of steel, saving energy and materials. At the same time, coated steel is also a short-term product with high added value supported and prioritized by the state. At present, China’s hot galvanizing industry has entered a new stage of rapid and sustainable development. The varieties and uses of hot-dip galvanized steel include galvanized steel plate and steel strip, galvanized steel wire and steel wire mesh, galvanized steel pipe, galvanized steel and structural parts, galvanized pipe fittings (malleable cast iron pipe fittings), galvanized parts, fasteners, galvanized device products, etc. Common coatings include pure zinc coating, zinc-aluminum alloy coating (zinc-aluminum rare earth, zinc-aluminum-magnesium, zinc-aluminum-lead), zinc-nickel alloy coating, aluminum-zinc alloy coating (aluminum-zinc-silicon), etc. Galvanized products are widely used in construction, communication, electric power, transportation, energy, automobiles, light industry (household appliances), agriculture, animal husbandry, fishery, petrochemical and other industries. Their main uses are as follows: (1) Light industry and household appliance industry: housings and baseboards of household appliances such as air conditioners, televisions, washing machines, refrigerators, microwave ovens, water heaters, computer baseboards and housings, civil chimneys, kitchenware, buckets, containers, etc. (2) Electric Power and Communication Industry: Electric Power Transmission and Transformation Tower, Communication Tower, armored cable Belt, Galvanized Low Carbon Steel Wire for Communication, Galvanized Steel Wire for Steel Core Aluminum Hinge Wire, Hanger, Galvanized Steel Strand for Suspension and Fastening. Pole cross arm, stay wire and fastener, various cable bridges. (3) Construction industry: various light steel joists for industrial and civil buildings, building floor panels, corrugated boards, roof grilles, Galvanized pipe for ventilation and water supply and drainage. (4) Automobile industry: car body, door, bottom plate, inner plate, etc. (5) Transportation: Highway fence, highway isolation network, light poles for roads and highways, various indicating signs, galvanized structural parts for bridges. (6) Metallurgical and chemical industries: galvanized pipes, structural frames and containers for various low-pressure fluid transportation. (7) Agriculture: Sprinkler irrigation pipes, light steel joists for plastic greenhouses, granaries, storage and transportation containers, farm tools, and galvanized wire for binding. (8) Fishing and animal husbandry: wire ropes for fishing and net fences for animal husbandry. The development of continuous hot dip galvanized steel sheet in China began in the 1970s. In 1979, WISCO introduced the first modern continuous hot galvanizing production line and color-painted steel strip production line from abroad, marking the beginning of the modern galvanizing technology for steel strip in China. The production flow chart of galvanized steel sheet is mainly aimed at automobiles and high-grade household appliances due to the strong economic strength and technical strength of state-owned enterprises, the equipment mostly imported from abroad, high unit output and high product positioning. By 2015, the sales market has grown to more than 70. After 2000, the rise of private enterprises, mainly with steel dealers as the backbone, they are familiar with the market, well-run, the use of hot dip galvanizing unit equipment fully domestic, low unit yield, low investment, low production cost, high efficiency, mainly for low-grade building materials market. By 2008, China’s hot galvanizing production capacity of steel plates has reached the level of developed countries in Europe and America. According to the investigation of relevant departments, the galvanized steel production lines in China are mainly concentrated in the developed areas such as the Yangtze River Delta, Pearl River Delta and Bohai Rim Economic Zone. However, under the influence of relevant national policies and market situation, on the one hand, the original production lines will be concentrated and integrated to a certain extent; on the other hand, the focus of the newly-built production lines will gradually shift to the central and western regions. With the development of China’s economy, construction, automobile, household appliances and other industries have developed rapidly and become the pillar industries of the national economy. The large demand for galvanized steel plates in construction, automobile, household appliances and other industries has greatly promoted the market development and technological progress of China’s continuous zinc coating steel plates. Examples of Application of Hot Dip Galvanized Steel Sheets Hot Dip Galvanized Steel Sheets are used in construction, household appliances, automobiles, light industry and other industries, with construction, automobiles and household appliances as the main industries. At present, China not only has the largest construction market in the world, but also is the largest automobile and household appliance manufacturing country in the world. In recent years, although China’s galvanized sheet production, product quality, process technology and equipment level have been greatly improved, there are still the following four problems: 1. There are large differences in equipment level and many low-yield units; 2. Excess production capacity, weakened downstream demand, insufficient overall operation rate of galvanized sheet strip enterprises, and serious waste of high-configuration units; 3. Private enterprises do not produce according to the standard and the coating thickness is low, resulting in waste of resources. At the same time, there are weak environmental awareness and nonstandard environmental management in enterprises. 4. High-quality automobile panels, functional household electrical appliances panels and high corrosion-resistant building coated steel plates are also imported, and domestic high-end brands are rare. The application field of galvanized products and requirements for galvanization Zinc consumption in the steel industry is mainly used as galvanized products for steel products, including galvanized sheet strips, galvanized steel wire ropes and strands, galvanized welded pipes, galvanized steel structures, etc. The thickness of galvanized products and the thickness of zinc layer will have a great impact on the zinc consumption per ton of steel, and the zinc consumption level per ton of steel for different types and uses of galvanized products varies greatly. With the development of industry standards, the vicious competition phenomenon of reducing costs with thin galvanized coating on hot-dip galvanized sheet will be gradually reduced. For zinc demand for galvanized products, relevant agencies believe that the total demand for zinc in steel industry will still increase slightly in the future with the standardization of the galvanizing industry. For example, as the popularization of steel structure buildings accelerates, the amount of galvanized plates for thick zinc layer buildings will increase. Galvanized steel is gradually replacing uncoated steel in some medium and high-end fields, and zinc consumption in the galvanizing industry will still rise slightly. The development process of hot-dip galvanizing sheet production technology in the main downstream consumer industries of galvanized products is as follows: the development process of hot-dip galvanizing sheet production technology is as follows: the units have developed to high-yield capacity; the hot-dip galvanizing units built since the 1990s have developed to high-yield capacity; there are about 60 sets of hot-dip galvanizing units with a global production capacity of over 300,000 t/ a, with a total production capacity of over 28 million t/a. Specializing in the production of car galvanized sheets and building materials galvanized sheets, different types of units are used for production. The unit process, single equipment configuration and furnace selection are more reasonable, resulting in obvious investment effect and low product cost. Emphasis is placed on substrate surface cleaning. The automobile plate galvanizing unit built in recent years basically adopts alkaline solution electrolytic cleaning and US-steel combined process of total radiation tube heating furnace, and even sets up cleaning sections before and after looper. In order to reduce the investment, the building materials type galvanizing unit mostly adopts the improved Sengimir process, but the unit is equipped with more cleaning sections to make the substrate surface cleaner and the product quality better. The investment of adopting tower furnace is about 25% ~ 30% higher than that of horizontal furnace. In the past, when the unit production capacity was above 300,000 t/ a, tower furnace was often adopted due to the limitation of furnace length, otherwise horizontal furnace was usually adopted. Since the 1990s, manufacturers have paid more attention to the advantages of tower furnace: the furnace has good air tightness; The number of furnace rollers is small and the service life is long. Low maintenance cost; Is conducive to improving the shape of the plate; Shorten the furnace length, etc. Many galvanizing units with a production capacity of 250,000 t/ a or less also use tower furnaces. For example, the 250,000 t/ a hot-dip galvanizing unit built by Solak Iron and Steel Company in December 1990; The 250,000 t/ a hot-dip galvanizing unit built in September 1991 in Luxembourg’s dideland steel works; BHP Aluminum and Zinc Plating Unit in California, USA, etc. Tower furnaces are also used in several newly put into operation hot galvanizing units in China. Continuously improve the efficiency of the heating furnace, preheat the strip steel with heating waste gas to save energy and avoid deformation of the strip steel; The continuous furnace is provided with cooling sections with different forms according to product performance requirements. Setting a thermal tension adjusting roller to optimize the in-furnace tension of the strip steel; The heating section is provided with a high-precision anti-heat warping Fermentation starter roller, and the heating section is additionally provided with an induction heater; Heating technologies such as a drum-pumping pulse control burner and a multi-stage combustion radiant tube are adopted, so that the adjustment range of the burner and the service life of the radiant tube are improved, heating uniformity is facilitated, NOx content can be reduced, and environmental protection is facilitated; Improve furnace roller cambering and furnace roller surface spraying technology. Continuous improvement of galvanizing equipment Galvanizing equipment includes air knives, sinking rolls, stabilizing rolls and ancillary equipment, zinc pots and zinc adding equipment, etc. Over the years, air knife manufacturers have been continuously improving their air knives. The air knives produced by several famous professional manufacturers such as Fangdeng, AOC, Duma and Kohler have their own characteristics. The general direction is to enable the air knives to automatically track the strip steel and keep a stable distance from the strip steel. So that the air knife can be integrally assembled and adjusted and has an accurate positioning mechanism; Dynamic control of stable pressure in nozzle area can be realized. Double-lip rotary air knife and better knife The Lips clearance curve are adopted, and a fast knife The Lips cleaning device is arranged; The installation of fast and slow opening and accurate resetting systems in the horizontal direction of the air knife has greatly improved the air knife. The shape, spacing and bearing of the sink roll flour zinc trough have also been improved to improve stability and service life. Most zinc pots use fluxing ceramic zinc pots. The volume of zinc pots tends to increase to facilitate the stability of zinc liquid. The lower edge of sink roller is at least 800mm away from the bottom of the pot for modern large-scale units, while the volume of zinc pots for hot galvanizing units that produce automobile panels should be larger. The development of coreless zinc pot is also relatively mature. SMS has also developed a sink-roller-free zinc pot. A vertical zinc pot is designed according to the magnetohydrodynamic sealing principle formed by electromagnetic moving field. The strip steel vertically passes through the zinc liquid in the zinc pot, and there is no easy corrosion in the zinc pot. This technology has completed the industrial test stage and has won the order for steel production in eastern South Korea, attracting the attention of the industry. The leveling effect with better performance adopts four-roller rolling machine, with dry and wet leveling processes and large and small diameter working rollers. And the work roll flour is shot peened or electron beam roughened to meet different requirements for extension and surface finish. For different kinds of products, good results can be obtained by adopting different matching methods of rolling machine and tension leveler. The perfect post-treatment process can adopt passivation treatment, phosphating treatment, alloying treatment or organic coating according to different requirements of users. At present, we are continuously developing and developing better passivator formula. At present, chromate is mainly used for passivation treatment, but activators such as fluoride and phosphoric acid are added to obtain thicker chromate films. When fluoride is present in the passivation solution, the formation of the passivation film can be accelerated and the passivation film can be fine and bright. In the research of non-toxic or low-toxic inorganic corrosion inhibitor as passivator, non-toxic water-soluble acrylic acid resin is added with a small amount of molybdate and phosphate to obtain a passivating solution (namely ACM), which is used to replace toxic chromate for passivation treatment. It can delay the time when white rust is generated in the galvanized layer, and its corrosion resistance is close to the chromate passivation level. Although the technology is not very mature at present, it is the general trend to replace chromate passivation with chromium-free passivation due to environmental protection considerations. The phosphatized hot-dip galvanized steel sheet can replace the traditional galvanized steel sheet and be used on the outer panel of household appliances, which can not only prolong the service life of products, but also reduce the material cost. On-line phosphating treatment of hot galvanizing line has great development potential. Fingerprint resistance and application of inorganic lubricating film and organic lubricating film are hot research topics. The zinc alloy coated steel plate developed with zinc alloy coating has better performance than galvanized steel plate, so its production ratio increases year by year. Among them, the aluminum zinc alloy coating (Galvalume), zinc aluminum alloy coating (Galfan) and zinc iron alloy coating (Galvanneal) are developed rapidly. Recently, a zinc-plated aluminum-magnesium alloy coating (ZAM) has been developed for newly manufactured steel in Japan, and its corrosion resistance is 10 times as high as that of traditional galvanized plates. Aluminum-zinc alloy and zinc-aluminum alloy coated steel plates have better corrosion resistance, coating property and formability than common hot galvanized steel plates, and are suitable for building materials, light industry and other industries. Zinc-iron alloy coated steel plate has better coating property, corrosion resistance and weldability than zinc-aluminum alloy and aluminum-zinc alloy coated steel plate, so it is widely used in automobile manufacturing. In order to adapt to the production of zinc alloy coated steel plates, the galvanizing unit mostly adopts lifting and moving double plating pots so as to quickly change the types of coatings. In 1998, the coreless zinc pot developed by Yingda Company of the United States was put into production. The zinc pot has low energy consumption and low investment and is very suitable for alloy coating production. The zinc-iron alloy diffusion furnace tends to adopt high frequency induction heating in the heating section and resistance heating in the soaking section, thus realizing annealing according to an optimized curve and more accurately controlling the iron content in the galvanized layer. The development of lead-free zinc plating for spangles-free steel plates can produce spangles-free steel plates. This coating can reduce intergranular corrosion, thus it has long service life, is conducive to environmental protection, is suitable for automobile manufacturing and is suitable for color coated substrates. Several years ago, Europe stopped producing ordinary spangles steel plates, so the production of non-spangles steel plates has obvious development trend. The development of ultra-deep drawing and high-strength steel galvanized sheets to produce heavy deep drawing and ultra-deep drawing grade hot galvanized sheets for automobiles adopts IF steel, and the continuous furnace is not provided with an over-aging section, thus simplifying the furnace body structure and production control. Production enterprises focus on the development of hot-dip galvanized sheet of high-strength steel. Usually, the high content of Si and M n in high-strength steel is not conducive to adhesion of zinc layer. The successful production of low-Si dual-phase steel galvanized sheet and dual-phase steel galvanized alloyed sheet has been realized through adjustment of chemical composition, especially addition of Mo element. The TRIP hot dip galvanized steel sheet obtained by replacing Si with Al is equivalent to the traditional CM nSi TRIP steel, but the addition of Al element brings some problems to the steelmaking and hot rolling processes, and the problem is being solved. In recent years, equipment for producing ultra-thin coated plates such as air knives have been continuously improved, and double-flour hot-dip galvanized plates with a coating of 25-30g/m can be produced. The plates are mostly used in the electrical appliance industry and can replace some electrogalvanized or partially electroplated tin steel plates. Single-sided hot-dip galvanized sheet is decreasing day by day. The single-sided hot-dip galvanizing process is cumbersome and the production cost is high. Therefore, it tends to replace single-sided galvanized sheet or double-flour hot-dip galvanized sheet with different thickness. Attention to the Development of Hot-Rolled Hot-Dip Galvanized Sheet With people’s attention to energy-saving and economical materials and the development of thin slab continuous casting and rolling production, more thin gauge hot-rolled coils can be produced. The production of hot-rolled hot-dip galvanized sheet is paid attention to and developed. Its products are mainly used in the construction field as steel structures, cable racks, ventilation pipes, granaries, etc. At present, hot-rolled hot-dip galvanized sheet accounts for about 8% ~ 9% of the total galvanized sheet production in the world. Han Steel, Tang Steel and other enterprises in China have all completed hot-rolled hot-dip galvanized units. The level of automation control is getting higher and higher. The whole line is controlled by computer, which can be realized.

Carbon steel bending elbow produced by Taituo: small-diameter metal bends are obtained by bending, then this small-diameter metal bend is called bending elbow. The simmering bend needs to be explained separately: simmering bend refers to the processing of pipes into bends, generally refers to metal pipes for hydropower specialty and electrical PVC threading pipes; Simmer bend: refers to metal bends of water supply and drainage specialty, and bends of small diameter can be obtained by simmer bending; Simmer elbow: small-diameter metal elbow is obtained by simmering and bending small-diameter metal, then this kind of small-diameter metal elbow is called simmering elbow, which is divided into two types according to whether there are segments: segment mandrel head and segment mandrel head. The manufacture of the segmented mandrel is complicated, the cost is high, and the service time is long. The non-segment mandrel is simple to manufacture and low in cost, but the front end wears quickly.
The detection technology is advanced. Faced with the trend of economic globalization, we will, in the spirit of dedication, credibility and innovation, mold corporate culture with elite teams, improve product quality with corporate culture, promote the development of enterprise groups with hard work and hard work team spirit, and follow the business philosophy that quality leads to market and innovation leads to development. In the future development, we will persevere and earnestly perform our duties.

Manufacturer of high-quality central round bend pipe
No matter what kind of machinery and equipment and pipelines, most of them are bent pipes, which are mainly used for oil transportation, gas transportation, infusion, etc. In pure bending, the outer arm wall of the middle layer is thinned by tensile stress 1 under the action of external force distance m, and the inner compressive stress. The cross section of the tube is changed by the resultant force N1 and N2. Based on this factor, RX and SX are the main reasons for the quality decline of bent pipes. Therefore, in GBJ235-82, RX values under various pressure levels and the thinning amount on the outside are clearly specified, so as to control the values of RX and SX and ensure the quality. As mentioned in the previous article, when bending, the outer side of the material is pulled, while the position of the neutral axis under internal pressure is different from the bending method. When working in top bending (compression bending), the neutral axis is about 1/3 away from the outer wall, and when working in rotary bending (back bending), the neutral axis is 2/3 away from the outer wall. Therefore, it is beneficial to use rotary bending method for bending thin-walled pipelines.

Pipe benders can be roughly divided into numerical control pipe benders, hydraulic pipe benders, etc. Purpose of pipe bender: Hydraulic pipe bender is mainly used for laying and repairing pipelines in electric power construction, public railway construction, boilers, bridges, ships, furniture, decoration, etc. It has the advantages of multiple functions, reasonable structure, simple operation, convenient movement, installation, etc. This machine not only has the function of bending pipe, but also can use the oil cylinder as a hydraulic jack. Compared with numerical control bending pipe equipment, it has the characteristics of low price and convenient use, occupying the leading product position in the domestic pipe bender market. The numerical control pipe bender can bend pipes with one bending radius (single mode) or two bending radii (double mode) in a cold state, and is widely used for bending various pipe fittings and wires in industries such as automobiles, air conditioners and the like. Pipe benders are mainly used for plastic forming of pipes. The bending pipe is made of materials such as cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metal and plastic, etc. and the process flow of hot bending pipe. after the straight pipe is fed, an induction ring is sleeved on the part of the steel pipe to be bent by a bending pipe pushing machine, the pipe head is clamped by a mechanical rotating arm, and a medium-frequency current is introduced into the induction ring to heat the steel pipe. when the temperature of the steel pipe rises to a plastic state, the steel pipe is pushed by mechanical thrust at the rear end of the steel pipe to be bent, and the bent steel pipe part is rapidly cooled by coolant, so that the bent pipe is continuously bent out while heating, pushing, bending and cooling.
The pipe is bent by using a complete set of bending dies, and is divided into two processes of cold heating and hot pushing.

Manufacturer of high-quality central round bend pipe
Carbon steel bending elbow produced by Taituo: small-diameter metal bends are obtained by bending, then this small-diameter metal bend is called bending elbow. The simmering bend needs to be explained separately: simmering bend refers to the processing of pipes into bends, generally refers to metal pipes for hydropower specialty and electrical PVC threading pipes; Simmer bend: refers to metal bends of water supply and drainage specialty, and bends of small diameter can be obtained by simmer bending; Simmer elbow: small-diameter metal elbow is obtained by simmering and bending small-diameter metal, then this kind of small-diameter metal elbow is called simmering elbow, which is divided into two types according to whether there are segments: segment mandrel head and segment mandrel head. The manufacture of the segmented mandrel is complicated, the cost is high, and the service time is long. The non-segment mandrel is simple to manufacture and low in cost, but the front end wears quickly.

In order to create the Taituo brand, improve the popularity of the enterprise, and establish the image of the enterprise, we solemnly promise to you with the principle of ” * favorable price, * considerate service, * and reliable product quality” in the spirit of ” all pursuit of high quality and customer satisfaction”. We are responsible for explaining the common sense of pipe fittings to users of our products. Regarding the quality problems raised by users, we guarantee that users in the city will be in place within 24 hours, users in the province will be 72 hours, and users outside the province will be required to send professionals to solve them within 5 days. Three Guarantees are implemented for products. For quality problems that occur during the service life cycle, three guarantees are implemented for products that are proved to be quality problems in our factory. We are willing to provide customers with 100% satisfactory after-sales service with good faith management concept, excellent products, reasonable product prices.