Where did steel, abbreviated as EQL, originate?

Steel is an iron-carbon alloy, and its carbon content is between 0.04% and 2.3%. In order to ensure its toughness and plasticity, the carbon content generally does not exceed 1.7%. Besides iron and carbon, the main elements of steel are silicon, manganese, sulfur and phosphorus. There are various classification methods for steel products, and the main methods are as follows:

[Edit this paragraph] Classification

By quality

1. Steel is classified by quality (1). Ordinary steel (P≤0.045%, S≤ 0.050%). (2) High quality steel (both P and S ≤ 0.035%). (3) High quality steel (P≤0.035%, S ≤

According to the chemical composition

2.( 1) Carbon steel according to chemical composition: steel A. Low carbon steel (C ≤ 0.25%); B medium carbon steel (c ≤ 0.25 ~ 0.60%); C. high carbon steel (C≤0.60%). (2) Alloy steel: a. Low alloy steel (total content of alloy elements ≤ 5%); B medium alloy steel (total content of alloying elements > 5 ~10%); C. high alloy steel (total content of alloying elements > 10%).

According to the molding method of the present invention

3. Steel products are classified according to forming methods: (1) forged steel; (2) cast steel; (3) hot rolled steel; (4) cold-drawn steel bars.

metallurgical structure

4. Steel is classified as (1) annealing according to metallographic structure: a. Submerged arc welding steel (ferrite+pearlite); B.*** steel precipitation (pearlite); C. steel precipitates through steel (pearlite+cementite); D ledeburite steel (pearlite+cementite). (2) normalizing: a. pearlite steel; B. bainite steel; C. martensitic steel; Austenite steel. (3) Steel 5 without phase transformation or partial phase transformation. Classification by use (1) steel for building and engineering: a. ordinary carbon structural steel; B. low alloy structural steel; C. steel bars. (2) Steel structure A. Steel for machinery manufacturing: (a) quenched and tempered structural steel; (b) Case-hardened structural steel: including carburized steel, ammoniated steel and case-hardened steel; (c) free-cutting structural steel; (d) Steel for cold plastic forming: including steel for cold stamping and steel for cold heading. B. Spring steel C. Bearing steel (3) Tool steel: A. Carbon tool steel; B. alloy tool steel; C. high-speed tool steel. (4) Special performance steel: a. Stainless and acid-resistant steel; B. Heat-resistant steel: including oxidation-resistant steel, heat-resistant steel and valve steel; C. electrothermal alloy steel; D. wear-resistant steel; E. low temperature steel; Electrical steel. (5) Professional steel-such as steel for bridges, ships, boilers, pressure vessels and agricultural machinery.

Comprehensive classification

6. Comprehensive classification (1) Ordinary steel A. Carbon structural steel: (a) Q195; (b) Q2 15(A、B)； (c) Q235(A、B、C)； Q255(A、B)； Question 275 .b B. Low-alloy structural steel C. General structural steel for specific purposes (2) High-quality steel (including high-quality steel) A. Structural steel: (a) High-quality carbon structural steel; (b) alloy structural steel; Spring steel; Free cutting steel; Bearing steel; (f) Special-purpose high-quality structural steel. B. Tool steel: (a) carbon tool steel; (b) alloy tool steel; (c) high-speed tool steel. C. Special performance steel: (a) stainless steel and acid-resistant steel; Heat-resistant steel; Electrothermal alloy steel; (d) electrical steel; (e) High manganese wear-resistant steel.

According to the smelting method

7. Classification by smelting method (1) and classification by furnace type A. Open hearth steel: (a) acid open hearth steel; Alkaline open hearth steel. B converter steel: (a) acidic converter steel; Alkaline converter steel. Or (a) bottom-blown converter steel; (b) Side-blown converter steel; (c) Top blown converter steel. C. electric furnace steel: (a) electric furnace steel; Electroslag furnace steel; Induction furnace steel; (d) Vacuum consumable furnace steel; (e) electron beam furnace steel. (2) Steel is divided into a. Boiling steel according to deoxidation degree and gating system; B. semi-killed steel; C. killed steel; D. special killed steel

[Edit this paragraph] Construction steel

abstract

Black and nonferrous metal materials for building and their composites with other materials are collectively referred to. Metal materials for building are one of the four major materials (steel, cement concrete, wood and plastic) that constitute the material foundation of civil engineering. In the iron and steel circulation industry, unless otherwise specified, construction steel generally refers to the largest amount of wire and rebar in construction steel. In view of this elite talent, which is also the most scarce in China at present, there is a steel talent network with more iron people, which is a professional steel industry talent recruitment and job search website.

brief history

/kloc-In the 1970s, human beings began to use pig iron as a building material in large quantities, and by the beginning of 19, they had developed to use wrought iron to build bridges and houses. These materials are limited in use because of their low strength and poor comprehensive performance, but they are the beginning of people's adoption of steel structures. /kloc-Since the middle of the 9th century, the specifications and varieties of steel products have been increasing, the strength has been continuously improved, and the corresponding connection technology has also been developed, which has laid the foundation for the development of building structures in the direction of large span and heavy load, and brought about a leap in civil engineering. In 1950s, from 65438 to 2009, a new composite building material-reinforced concrete appeared. In the 1930s, the appearance of high-strength steel promoted the development of prestressed concrete, and created a new historical period in which reinforced concrete and prestressed concrete dominated, and civil engineering made a new leap. At the same time, the state vigorously promotes low-alloy steel with low carbon, low alloy (adding less than 5% alloying elements), high strength, good toughness, weldability and corrosion resistance. With the enlargement of bridges, the development of buildings and structures to large span, high-rise and towering, and the development of energy and offshore platforms, the output of low-alloy steel has increased greatly in the past 30 years, accounting for 7 ~ 10% of the total steel output in major steel-producing countries, and in some countries it exceeds 20%, of which 35 ~ 50% is used in housing construction and civil engineering, mainly for steel bars, profiles and plates for steel structures. In recent years, various countries have vigorously developed various high-efficiency steels different from ordinary steels, including low-alloy steel, heat-strengthened steel, cold-worked steel, economic steel, electroplated steel, coated steel, composite steel and surface-treated steel. After the application in the construction industry, obvious economic benefits have been achieved.

Classification and application

Metal materials for construction, including ferrous and non-ferrous metal materials, and composite materials developed in recent years with various non-ferrous metals and their alloys or with other materials. Among ferrous materials, steel is mainly used in construction industry, and cast iron is mainly used as cast iron products (such as pressure pipes). ). Most of the construction steels in China are low carbon steel (carbon content is less than 0.25%), medium carbon steel (carbon content is 0.25 ~ 0.60%) and low alloy steel, which are smelted by open hearth furnace and oxygen top-blown converter and produced by boiling steel or killed steel process. Among them, boiling steel is worse than killed steel in impact, aging and cold brittleness, and its use in some structures is limited, such as railway bridges and crane beams made by heavy industry. The mechanical properties of semi-killed steel are better than that of boiling steel and close to that of killed steel, but the yield of finished products is close to that of boiling steel, which has been widely used in China. Building steel products are generally divided into four categories: profiles, plates (including steel belts), pipes and metal products: ① profiles. Steel for steel structure mainly includes angle steel, I-beam, channel steel, square steel, crane track, metal doors and windows, steel sheet pile steel and so on. (See hot rolled steel, cold-formed steel, metal for doors and windows). Steel bars for reinforced concrete structures can be divided into wire rods (5 ~ 9 mm in diameter) or small profiles (more than 9 mm in diameter). The former is hot-rolled wire rod (including heat-treated steel bar), and the latter is straight round or threaded steel bar (see Hot-rolled Steel Bar and Heat-treated Steel Bar for Prestressed Concrete). Two plates. Mainly steel for steel structure, and medium plate and thin plate for building structure. Plates are widely used to build buildings, structures, containers and equipment, such as houses, towers, bridges, pressure vessels, offshore oil platforms and construction machinery. Thin plates are widely used in roofs, walls and floors of building structures after being pressed (see steel plates and profiled steel plates). ③ Tubing. Mainly used for trusses, towers and masts and other steel structures (see steel pipes). (4) Metal products. The main products used in civil engineering are steel wire (including steel wire used in covered electrode), steel wire rope, prestressed steel wire and steel strand. The low-carbon steel wire in steel wire is mainly used for Tara wire, binding steel bars and scaffolding, making round nails and screws, and cold-drawn low-carbon steel wire for steel wire mesh or small prestressed members. Prestressed steel wire and its stranded wire are the main materials of prestressed structure. Construction steel is generally expressed by steel grade and corresponding strength grade, and strength grade is generally expressed by molecular formula: molecule represents minimum yield point (conditional yield point σ 0.2 without obvious yield step); Denominator represents the minimum tensile strength in MPa. For example, 20MnSi steel bar is grade 34/52, that is, the minimum yield point is about 340 MPa and the minimum tensile strength is about 520 MPa. Non-ferrous metal materials for construction mainly include aluminum, copper, zinc, lead, magnesium and rare metals. Copper, lead and zinc are mainly used as coating materials for hardware or steel plates. Aluminum mainly adopts deformed aluminum alloy plate in building structure, which is widely used in roof, wall and other enclosure structures. Rare metals are generally used as additive elements in steel, which can improve the properties of steel. Development Direction As various buildings and structures have higher and higher requirements for their functions under various complex conditions, the development trend of building metal materials will be as follows: ① Low alloy steel with high efficiency steel as the main body will be further developed and applied. The structural material is low alloy steel, which saves 20 ~ 60% steel compared with ordinary carbon steel. All kinds of cold and hot processed steel (such as heat-treated steel bars, quenched and tempered steel plates, etc.). ), economic steel (such as rolled H-beam, profiled steel plate or aluminum plate, thin-walled cold-formed steel plate, etc. ), plated (coated) steel plates and various composite steel plates will be further popularized and applied in the construction industry. (2) With the development of production technology in metallurgical industry, construction steel will develop in the direction of high strength, corrosion resistance, fatigue resistance, easy welding, high toughness or wear resistance. For example, when used in building structures and bridges, profiles and plates made of atmospheric corrosion-resistant steel have comprehensive properties such as high strength, corrosion resistance and fatigue resistance, which can reduce the self-weight of the structure, improve the service life and reduce the project cost. (3) With the development of low-alloy steel, various welding materials and processes will be improved and matched continuously. For example, the development of low-alloy high-toughness CF steel, offshore platform steel, Z-direction steel and oil and gas pipeline steel will inevitably promote the development of welding materials in the direction of high crack resistance, high toughness and low impurity.