Building steel structure

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 the steel talent network, which is a professional steel industry talent recruitment and job search website. /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, 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. Various countries vigorously develop various high-efficiency steel products different from ordinary steel products, including low-alloy steel products, heat-strengthened steel products, cold-worked steel products, economical steel products, electroplated steel products, coated steel products, composite steel products and surface-treated steel products. After the application in the construction industry, remarkable economic benefits have been achieved. Metal materials for construction, including ferrous and non-ferrous metal materials, and composite materials of iron and steel materials with various non-ferrous metals and their alloys or with other materials developed in 2 1 century.

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.

Classification: Construction steel products are generally divided into rebar, wire rod, wire rod, round steel,

1, rebar: the specification range of thread is generally 6-50mm, and we usually involve 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm and 20 mm. National allowable deviation: 6- 12mm deviation is 7%, 14-20mm deviation is 5%, and 22-50mm deviation is 4%.

The general fixed length of rebar is 9m and 12m, in which 9m long thread is mainly used for normal road construction and 12m long thread is mainly used for bridge construction.

Rebar can be divided into three categories according to strength: HRB335, HRB400 and HRB500.

2. Wire:

Usually involved specifications are 6.5mm, 8.0mm, 10mm (diameter); There are also 5.5mm, 6.0mm, 7.0mm and so on. At present, the maximum diameter of wire produced in China can reach 30 mm, and the allowable tolerance of wire production is generally 0.4 mm

Common wire rod brands are generally divided into Q 195, Q2 15 and Q235, of which only Q2 15 and Q235 are used for steel wire rods for construction; For example: Q235 (Q refers to the yield strength of steel, and 235 refers to the yield strength of not less than 235Mpa).

According to the rolling speed, wire can be divided into ordinary wire, high wire and quasi-high wire.

3. Snails:

Building steel, as the name implies, is rebar coiled together like a wire rod, and most of them are 6.5-8.0-10-12-14 in the market.

Advantages of rebar: rebar is only 9- 12, and rebar can be intercepted as required.

4, round steel:

Round steel refers to solid strip steel with circular cross section. Its specifications are expressed in millimeters in diameter. For example, "50" is a round steel with a diameter of 50 mm.

Round steel materials: 10#, 20#, 35#, 45#, 304, 3 16, 20Cr, 40Cr, 20CrMo, 35CrMo, 42CrMo, 40CrNiMo, GCr 15, and so on.

Round steel is divided into hot rolling, forging and cold drawing. The specification of hot rolled round steel is 5.5-250 mm. Among them, small round steel of 5.5-25 mm is mostly supplied by bundled straight steel bars, which are often used as steel bars, bolts and various mechanical parts; Round steel larger than 25mm is mainly used to manufacture mechanical parts or seamless steel tube blanks.

The function of building steel:

Steel bars are widely used in various building structures.

Wire rod is not only widely used as reinforcing material for building reinforced concrete, but also suitable for wire rod (special steel) for wire drawing and netting.