What is construction steel? What are the application areas of construction steel?

Building steel materials can be composed of various stress-bearing components according to different needs of the structure, and of course, they can also be used as connectors between components. It is widely used in various building structures and engineering structures, such as power transmission towers, lifting and transporting machinery, ships, industrial furnaces, reaction towers, beams, bridges, container racks and warehouse shelves. There are many ways to classify steel, and the main methods are as follows:

1. Steels are classified by quality (1) Ordinary steel (P≤0.045%, S≤0.050%) (2) High-quality steel material steel (P and S both ≤0.035%) (3) High-grade high-quality steel (P≤0.035%, S≤0.030%)

2. Classified by chemical composition (1) Carbon steel: 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 alloying elements ≤5%); b. Medium alloy steel (total content of alloying elements>5~10%); c. High-alloy steel (total content of alloying elements>10 %).

3. Steel is classified according to the forming method

: (1) Forged steel;

(2) Cast steel;

(3) Hot rolled steel;

(4) Cold drawn steel.

4. Steel is classified according to metallographic organization

(1) In annealed state:

a. Hypoeutectoid steel (ferrite + pearlite);

b. Eutectoid steel (pearlite);

c. Over-eutectic steel precipitation (pearlite + cementite);

d.Leeburite steel (pearlite + cementite).

 

(2) Normalizing:

a. Pearlitic steel;

b. Bainite steel;

c. Martensitic steel;

d. Austenitic steel.

 

(3) The steel has no phase change or partial phase change

 

5. Classification by purpose

(1) Steel for construction and engineering:

a. Ordinary carbon structural steel;

b. Low alloy structural steel;

c. Reinforced steel.

(2) Steel structural steel

a. Steel for machinery manufacturing:

(a) Quenched and tempered structural steel;

(b) Surface hardened structural steel:

Including carburized steel, ammonia infiltrated steel, surface hardening 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-strength steel, and valve steel;

c. Electric heating alloy steel;

d. Wear-resistant steel;

e. Low temperature steel;

f. Steel for electrical engineering.

 

(5) Professional steel-such as steel for bridges, steel for ships, steel for boilers, steel for pressure vessels, steel for agricultural machinery, etc.

6. Comprehensive classification (1) Ordinary steel a. Carbon structural steel: (a) Q195; (b) Q215 (A, B); (c) Q235 (A, B, C); (d) Q255 (A, B); (e) Q275. b. Low-alloy structural steel c. General structural steel for specific purposes (2) High-quality steel (including high-quality steel) a. Steel structural steel: (a) High-quality carbon structural steel; (b) Alloy structural steel; (c) Spring steel; (d) free-cutting steel; (e) bearing steel; (f) high-quality structural steel for specific purposes. b. Tool steel: (a) Carbon tool steel; (b) Alloy tool steel; (c) High speed tool steel. c. Special performance steel: (a) stainless acid-resistant steel; (b) heat-resistant steel; (c) electric heating alloy steel; (d) electrical steel; (e) high manganese wear-resistant steel.

7. Classified by smelting method (1) Classified by furnace type

a. Open-hearth steel: (a) Acidic open-hearth steel; (b) Basic open-hearth steel. b. Converter steel: (a) Acid converter steel; (b) Basic converter steel. Or (a) bottom-blown converter steel; (b) side-blown converter steel; (c) top-blown converter steel. c. Electric furnace steel: (a) electric arc furnace steel; (b) electroslag furnace steel; (c) induction furnace steel; (d) vacuum consumable furnace steel; (e) electron beam furnace steel.

(2) According to the degree of deoxidation and pouring system, the steel is divided into a. boiling steel; b. semi-killed steel; c. killed steel; d. special killed steel.

(1) The output reached the highest level in history. From January to June of 2013, the country’s cumulative production of crude steel was 390 million tons, a year-on-year increase of 7.4%, and the growth rate was 5.6 percentage points higher than the same period last year.

In the first six months, the average daily crude steel output was 2.154 million tons, equivalent to an annual crude steel output of 786 million tons. Among them, it reached a record high of 2.208 million tons in February. Although it dropped from March to June, it still remained at a relatively high level of more than 2.1 million tons. In terms of provinces and regions, from January to June, the crude steel output of Hebei and Jiangsu increased by 6.8% and 13.2% respectively year-on-year. The combined output of the two provinces accounted for 42.4% of the national increase of 26.94 million tons. In addition, Shanxi, Liaoning, Provinces such as Henan and Yunnan have also increased production by more than 1 million tons. In terms of enterprise types, from January to June, the crude steel output of key large and medium-sized iron and steel enterprises increased by 5.5% year-on-year, 2 percentage points lower than the national average increase, but 60% of the increase in production still came from key large and medium-sized iron and steel enterprises.

(2) Low steel prices run. From January to June 2013, the overall performance of the domestic steel market was sluggish. With the large release of crude steel production capacity, market supply and demand have fallen into a state of imbalance, and steel prices have entered a downward channel and have been weakly down for more than four months. As of July 26, 2013, the steel price index fell to 100.48 points, which was lower than 6.6 points at the beginning of the year. The prices of the eight steel products under the key statistics of the Iron and Steel Association have all declined to varying degrees from the beginning of the year, with an average drop of 5.7%. In terms of varieties, the prices of construction wire rod and rebar, which account for a large proportion of China’s steel output, fell by 4.9% and 6.7%, respectively, and the prices of plate and hot-rolled coil fell by 5.7% and 9.7%, respectively.

(3) Steel exports have grown rapidly. The imbalance between supply and demand in the domestic steel market stimulates corporate exports. From January to June, China exported 30.69 million tons of steel, an increase of 12.6% year-on-year; imported steel was 6.83 million tons, a decrease of 1.8%, and imported steel billets and ingots were 320,000 tons, an increase of 50%. Converting billets to crude steel, the cumulative net export was 25.06 million tons, an increase of 17.3% year-on-year, accounting for 6.4% of China’s crude steel output. In terms of export prices, the average export price of bars and wires from January to June was US$624.3/ton, a year-on-year decrease of 18%; and the average price of plates was US$835.2/ton, a year-on-year decrease of 2.8%.

(4) Steel mills and social inventories are running at a high level. The contradiction between market supply and demand spread to the circulation field, and domestic steel stocks continued to grow at the end of the previous year. On March 15, it reached a record high of 22.52 million tons, an increase of 3.51 million tons from the highest point of the previous year, of which 14.32 million tons of construction steel inventory, accounting for 63.6% of the total inventory. After that, with the increase in seasonal consumption, the inventory gradually fell, falling to 15.4 million tons on July 26. The oversupply in the market also pushed up steel mill inventories. In mid-March, the steel inventory of key enterprises reached a historical record, reaching 14.51 million tons, an increase of 29.7% year-on-year. In late June, it fell to 12.68 million tons, still an increase of 29.9% compared with the beginning of 2012. Year-on-year growth of 11.4%.

(5) The profitability of steel mills is declining month by month. In the first half of 2013, the metallurgical industry achieved a profit of 73.69 billion yuan, a year-on-year increase of 13.7%, of which the ferrous metal smelting and rolling processing industry achieved a profit of 45.44 billion yuan, a year-on-year increase of 22.7%. From January to May, the profitability of key large and medium-sized iron and steel enterprises was far below the overall level of the industry, and showed a monthly decline. Although the profit increased by 34%, it was only 2.8 billion yuan, and the sales profit rate was 0.19%. In the month of May, 86 key large and medium-sized iron and steel enterprises only realized profits of 150 million yuan, which was a decline for five consecutive months. Among them, 34 made losses, with losses as high as 40%.

(6) The growth rate of investment in fixed assets in the iron and steel industry has dropped significantly. From January to June 2013, the investment in fixed assets in the iron and steel industry was 303.5 billion yuan, a year-on-year increase of 4.3%, of which the investment in ferrous metal smelting and rolling was 235.6 billion yuan, a year-on-year increase of 3.3%, a decrease of 6.1 percentage points from the same period in 2012; The selected investment was 67.9 billion yuan, an increase of 7.8% year-on-year, and the growth rate dropped sharply by 15 percentage points. Shanghai Construction Steel Prices On May 15th, the prices of Shanghai construction steel products fell partially. Among them, the price of grade 3 rebar fell by 10 yuan/ton, while the remaining varieties remained stable. Looking back at the market yesterday, the downstream terminal demand in the market was sluggish yesterday and Tuesday, and the overall market turnover returned to a low level. In terms of cost, the ex-factory price of Tangshan billet was temporarily stable yesterday. The ex-factory price was 3120 yuan/ton. The price of 63.5% Indian fines fell by US$1/ton to US$131.25/ton. Yesterday the volume and price of construction steel in the Shanghai market were weak. Although the trading volume at the opening on Monday was heavy, but the slump of the spot market yesterday, once again hit the mentality of spot merchants. The market price difference between grade 3 rebar and grade 2 rebar continues to shrink. Traders should pay attention.

On the whole, under the situation of market policy confusion, merchants are not optimistic about the market outlook, especially when the futures steel is adjusted back and the market is sluggish, it will be difficult for prices to rise. It is expected that today’s Shanghai construction steel market prices will weaken and consolidate.

[1] According to data from China Industry Insight Network, the mainstream quotation of the second-class snails in Shanghai is 3470 yuan/ton, which is stable with yesterday’s market quotation. The mainstream price of the third-grade snail market was 3470 yuan/ton, down 10 yuan/ton from yesterday’s market price. The price of three-level seismic steel Daluo Xicheng was 3,510 yuan/ton, which was down 10 yuan/ton from yesterday’s market quotation. The mainstream price of the fourth-grade snail market is 4,200 yuan/ton, which is stable with yesterday’s price. The mainstream price of the high-end line is 3480 yuan/ton, which is stable with yesterday’s market price. The mainstream quotation of the third-grade snail market was RMB 3,610/ton, which was stable with yesterday’s market price. A general term for black and non-ferrous metal materials for construction and composite materials composed of them and other materials. Metallic materials for construction are one of the four major types of materials (steel, cement concrete, wood, and plastic) that constitute the material basis of civil engineering. In the steel distribution industry, unless otherwise specified, construction steel generally refers to the most used wire rod and rebar in construction steel. Aiming at this elite talent, it is also the most scarce in our country. The iron and steel talent network that accepts more steel talents is a professional recruitment and job search website for talents in the steel industry. In the 1770s, humans began to use pig iron as a building material in large quantities. By the beginning of the 19th century, it developed to use wrought iron to build bridges and houses. These materials are limited in their use due to their low strength and poor comprehensive performance, but they are the beginning of the adoption of steel structures. After the mid-nineteenth century, the variety of steel specifications and strength continued to increase. Correspondingly, connection and other technology were also developed. This laid the foundation for the development of large-span and heavy-duty building structures and brought a leap in civil engineering. In the 1850s, a new type of composite building material ─ ─ reinforced concrete appeared. By the 1930s, the emergence of high-strength steel promoted the development of prestressed concrete, and opened a new historical period in which reinforced concrete and prestressed concrete were dominant, and made a new leap in civil engineering. At the same time, countries have successively promoted low-alloy steels with comprehensive properties such as 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 large-span, high-rise, and towering buildings and structures, and the development of energy and offshore platforms, the output of low-alloy steel has increased substantially in the past 30 years, and its output in major steel-producing countries has accounted for 7-10% of the total output of steel, more than 20% in individual countries, 35-50% of which are used for building construction and civil engineering, mainly steel bars, steel structures and plates, and low-alloy steel for civil engineering steel structures The proportion has increased from 10% to more than 30%. Countries are vigorously developing various high-efficiency steels that are different from ordinary steel varieties, including low-alloy steels, heat-strengthened steels, cold-worked steels, economical section steels, and plating, coating, composite, and surface treatment steels, etc., which are used in the construction industry. Obvious economic benefits have been achieved.

Metallic materials for construction, including ferrous and non-ferrous metal materials, as well as composite materials of iron and steel materials developed in the 21st century, various non-ferrous metals and their alloys, or in combination with other materials. The construction industry mainly uses steel in ferrous metal materials, and cast iron is mainly used for cast iron products (such as pressure pipes, etc.). China’s construction steel is mostly low-carbon steel (carbon content less than 0.25%), medium-carbon steel (carbon content 0.25 to 0.60%) and low alloy steel smelted by open hearth and oxygen top-blown converters, with boiling steel or killed steel process In production, boiling steel has worse performance than killed steel due to impact, aging, and cold brittleness. It is limited in certain structures during use, such as railway bridges and heavy-duty working crane beams. The mechanical properties of semi-killed steel are better than rimmed steel but close to killed steel, but its finished product yield is close to rimmed steel, and it has been promoted and used in China. Classification: The types of construction steel products are generally divided into rebar, wire rod, coiled screw, round steel 1, rebar: ·The specification range of thread is generally 6-50mm, and we usually involve 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm, 25mm, 28mm, 32mm, 36mm, 40mm, etc. The deviation allowed by the country: 6-12mm deviation is within ±7%, 14-20mm deviation is within ±5%, 22-50mm deviation is within ±4%. ·Rebars are generally fixed in lengths of 9m and 12m, of which 9m long threads are mainly used for normal road construction, and 12m long threads are mainly used for bridge construction. Rebar can be divided into three categories according to its strength: HRB335, HRB400, and HRB500. 2. Wire: ·The usual specifications are 6.5mm, 8.0mm, 10mm (diameter); in addition, there are 5.5mm, 6.0mm, 7.0mm and so on. At present, the maximum diameter of wire rod produced in our country can reach 30mm. In addition, wire production generally allows tolerances within ±0.4mm. ·Common grades of wire rods are generally divided into three types: Q195, Q215, and Q235. Among them, there are only two grades of Q215 and Q235 for construction steel wire rod; for example: Q235 (Q-refers to the yield strength of steel, 235 refers to the yield strength of not less than 235Mpa). According to the rolling speed, the wire rod can be divided into: normal wire, high wire and quasi-high wire 3. Coil: steel for construction, as the name implies, it is rebar coiled together like wire, generally 6.5-8.0-10- on the market Mostly 12-14. Advantages of coiled snails: there are only 9-12 rebars, and coiled snails can be intercepted at will. 4. Round steel: Round steel refers to a solid long steel with a circular cross section. The specifications are expressed in millimeters of diameter. For example, “50” means round steel with a diameter of 50 mm. Round steel material: 10#, 20#, 35#, 45#, 304, 316, 20Cr, 40Cr, 20CrMo, 35CrMo, 42CrMo, 40CrNiMo, GCr15, 65Mn, 50Mn, 50Cr, 3Cr2W8V, 20CrMnTi, 5CrMnMo, etc. Round steel is divided into three types: hot rolled, forged and cold drawn. The specification of hot-rolled round steel is 5.5-250 mm. Among them: 5.5-25mm small round steel is mostly supplied in straight strips, 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 billets. The role of building steel: Rebar is widely used in various building structures. In addition to a large number of wires used as reinforcement for building reinforced concrete, they are also suitable for wire drawing and wire (special steel). The commonly used steel materials in construction mainly include steel bars for reinforced concrete, steel wires, steel strands and various types of materials.

The steel bars used in the structure are often divided into hot-rolled steel bars and cold-worked steel bars according to different processing methods.

(1) Hot rolled steel bars. The finished steel bars that are formed by hot rolling and naturally cooled are called hot-rolled steel bars. Hot-rolled steel bars are divided into round steel bars and ribbed steel bars according to their shape. Ribbed steel bars include crescent ribs, spiral ribs, and herringbone ribs according to different cross-sectional forms of ribs. According to different steel types, hot-rolled steel bars are carbon steel bars and ordinary low-alloy steel bars. According to the strength of steel bars, it is divided into four grades: I, II, III, and IV. Grade I steel bars are smooth round steel bars made of carbon steel, with the steel grade HPB235; grades II, III, and IV are ribbed steel bars made of low-alloy steel, with the grades HRB335, HRB400 and HRB500. Class I-III hot-rolled steel bars have good welding performance, good plasticity and toughness, and are suitable for non-prestressed concrete structures with lower strength requirements. Prestressed concrete structures require the use of higher-strength steel as stress reinforcement.

(2) Cold drawn steel bars. The hot-rolled steel bar is fixed at one end at room temperature, and the other end is stretched, so that the stress exceeds the yield point until plastic deformation occurs. This method is called cold-drawn processing. The yield point of the steel bar after cold drawing can be increased by 20%-30%. For example, the yield point and tensile strength of the steel bar after aging treatment (that is, the natural weight of 15-20d after cold drawing or heating to 100-200 ℃, heat preservation for a period of time) are further improved Improved, but the plasticity and toughness are correspondingly reduced. Cold-drawn grade I steel can be used as non-prestressed tensile steel bars, and cold-drawn grades II, III, and IV can be used as prestressed steel bars.

(3) Cold drawn low carbon steel wire. A steel wire made of Q235 (or Q215) hot-rolled round wire rod with a diameter of 6.5-8mm through a wire-drawing machine for multiple strong cold-drawing processes. According to “Code for Acceptance of Construction Quality of Concrete Structure Engineering” (GB 50204-2002), cold drawn low-carbon steel wire is divided into two grades, A and B. Grade A is used for prestressed steel wire, and Grade B is used for non-prestressed steel wire, such as welding. Nets, welded skeletons, structural steel bars, etc. Steel ingots with various cross-sections made by hot rolling are called section steels (or sections). According to different cross-sectional shapes, section steel is divided into round steel, square steel, flat steel, hexagonal steel, angle steel, Gongning steel, channel steel, steel pipe and steel plate, etc. Sectional steel belongs to the steel structure for steel structure. Sectional steels with different cross-sections can be made into various steel components as required. There are two main types of section steels according to their chemical composition: carbon structural sodium and low-alloy structural steel.

(1) Angle steel: Angle steel, commonly known as angle iron, is a long strip of steel with two sides perpendicular to each other in an angle shape. There are equilateral angle steel and unequal angle steel. Angle steel is widely used in various building structures and engineering structures, such as building beams, bridges, power transmission towers, lifting and transporting machinery, ships, industrial furnaces, reaction towers, container racks and warehouse shelves. The two side widths of equilateral angle steel are equal, and its specifications are expressed in millimeters of side width * side width * side thickness, such as “30*30*3”. It can also be expressed by model number, which is the number of centimeters on the side width, such as 3#. The angle steel can be composed of various stress-bearing members according to the different needs of the structure, and can also be used as a connection between the members. Take the centimeters of the side length as the number. Generally, large angles with a side length of 12.5cm or more are medium-sized angles between 5cm and 12.5cm, and small-sized angles with a side length of less than 5cm. The price structure of angle steel is more difficult to find, but it is basically the same as construction steel and plate. It is also relatively cheap for the middle group of products, and the price of large and small angles is slightly more expensive. The representative specification of angle steel is 5#.

(2) Channel steel: Channel steel is a long steel with a groove-shaped section. Channel steel is mainly used in building structures, vehicle manufacturing and other industrial structures. Its specification representation method, such as 120*53*5, means that the waist height is 120 mm, the leg width is 53 mm, and the waist thickness is 5 mm. It is 12# channel steel. For channel steel with the same waist height, if there are several different leg widths and waist thicknesses, a, b, and c should be added to the right of the model to distinguish them, such as 25#a, 25#b, 25#c, etc. Channel steel is divided into ordinary channel steel and light channel steel. The specifications of hot-rolled ordinary channel steel are: 5#-40#, 5#-8# is small channel steel, 10#-18# is medium channel steel, and 20#–40# is large channel steel. Channel steel products are relatively cheap in the middle group price, and large and small channels are slightly more expensive. The representative specification of channel steel is 25#.

(3) I-beam: I-beam is also a steel beam, which is a long steel with an I-shaped cross-section. Which I-beam is widely used with various building structures, bridges, vehicles, supports, machinery, etc. Its specifications are expressed in millimeters of waist height (h) * leg width (b) * waist thickness (d), such as “工160*88*6. It can also be expressed by model number, which represents waist height in centimeters, such as work 16#. For I-beams with the same waist height, if there are several different leg widths and waist thicknesses, a, b, and c must be added to the right of the model to distinguish them, such as 25#a, 25#b, 25#c, etc. 8#– 18# is a small I-beam, 20#–63# is a large I-beam. The price structure of the I-beam is also relatively cheap for intermediate pitch products, and the price of large and small I-beams is slightly more expensive. The representative specifications of I-beam are 25#.

(4) H-shaped steel: H-shaped steel is an economical cross-section steel optimized and developed from I-beam with better mechanical properties. It is named after its cross-section is similar to the English letter “H”. Its characteristics are as follows: wide flange, large lateral rigidity, and strong bending resistance; the two surfaces of the flange are parallel to each other, making connection, processing and installation easy. H-beam specifications are expressed by waist height, flange width, and web thickness. For H-beam steel with waist height of 200mm, flange width of 200mm, web thickness of 12mm, and flange thickness of 15mm, the specification method is 200*200* 12*15.

(5) Cold-formed steel: Cold-formed steel is the main material for making light steel structures. It is made of steel plates or steel strips by cold-formed forming. It can produce various types of uniform wall thickness but complex cross-sectional shapes that are difficult to produce by general hot rolling methods. Profiles and cold-formed steels of different materials. In addition to being used in various building structures, cold-formed steel is also widely used in vehicle manufacturing and agricultural machinery manufacturing.

(6) Special-shaped steel: including gear ring, horseshoe steel, magnetic pole steel, presser foot steel, shallow channel steel, small channel steel, T-shaped steel, ball flat steel, feeder steel, hot-rolled hexagonal steel, etc., in addition to rivets Steel, farm tool steel, window frame steel. Cold-rolled ribbed steel bars: cold-rolled ribbed steel bars are made of ordinary low-carbon steel or low-alloy steel hot-rolled round wire rod as the base material, which is cold-rolled on the surface to have three or two sides after being cold-rolled or cold-drawn. Rebar with crescent-shaped transverse ribs. The cold-rolled auxiliary steel bars in reinforced concrete structures and prestressed concrete structures can be selected according to the following regulations: 550-grade steel bars should be used as the main force bars, erecting bars, stirrups and structural steel bars in reinforced concrete structural members. Grade 650 and 800 steel bars should be used as the main force-bearing reinforcement in prestressed concrete structural members. In addition, the concrete strength grade of reinforced concrete structures using cold-rolled ribbed steel bars should not be lower than C20; the concrete strength grade of prestressed concrete structural members should not be lower than C30. Note: For structural members in indoor high humidity or open air environment, the concrete strength grade shall not be lower than c30. The strength standard value, strength design value and elastic modulus of concrete should be adopted in accordance with the relevant provisions of the current national “Specification for Design of Concrete Structures (GB 500l0-2002). The raw materials for the production of angle steel are mainly low-carbon square billets. Angle steel is a carbon structural steel for construction. It is a section steel with a simple section. It is mainly used for metal components and the frame of factory buildings. In use, it requires good weldability, plastic deformation performance and certain mechanical strength. Angle steel is used in many fields, but angle steel sometimes rusts. Although stainless steel angle steel has appeared now, angle steel is still used, so we need the maintenance method of angle steel at this time.

Maintenance method of angle steel:

First, it is not suitable for long-term storage after rust removal for steel with severe corrosion, and should be used as soon as possible. Before the materials are put into storage, they should be protected from rain or mixed with impurities;

Second, the materials that have been dipped in water should be cleaned in time by different methods according to their properties, such as steel wire brush with high hardness, cotton cloth with low hardness;

Third, the materials should be checked frequently after they are put into the warehouse. If there is rust, the rust layer should be removed;

Fourth, after the surface of general steel is cleaned, it is not necessary to apply oil, but for high-quality steel, alloy thin steel plate, alloy steel pipe, etc., the inner and outer surfaces of the steel must be coated with anti-rust oil before storing; the above content is the angle steel Maintenance skills, angle steel is a simple section steel, a carbon structural steel for construction, mainly used for metal components and the frame of the factory building.

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