Exposed structural steel refers to the structural form that keeps the details of steel structure and its joints visible under the premise of meeting the quality requirements of steel structure in the building.

What are the requirements of the AESS standard for the processing of steel profiles?

1. No steel mill rolling trademarks, steel marks or raised marks are allowed;

2. It is forbidden to lift steel and components with bite printing;

3. During assembly, it is forbidden to weld temporary support on the exposed surface of components, and it is forbidden to hammer;

4. Minimum weld exposure;

5. the butt weld width is consistent, straight, and polished to flush with the base material, weld residual height is zero;

6. grinding along the weld length direction, the vertical direction of grinding is easy to lower than the base metal surface;

7. After shot blasting or sandblasting, the visible defects shall be welded and filled or polished to remove the defects.

The chemical composition and mechanical properties of 12Cr1MoV alloy structural steel are excellent, the tensile strength and yield point are above the standard, but also has high plasticity and oxidation resistance. It is widely used in high pressure, ultra high pressure, subcritical superheater, collecting box and main steam conduit. Not only that, the process and weldability of this steel is also excellent.

The two digits at the beginning of the steel number represent the carbon content of the steel, which is expressed by a few millionths of the average carbon content. For example, 40Cr and 25Cr2MoVA alloy tubes, the main alloy elements in the steel are generally expressed by a few percent, except for some microalloy elements. When average alloy content < 1.5%, generally only the element symbol is marked in the steel number, but not the content, but in special circumstances easy to confuse, the element symbol can be marked with the number "1"; The alloy elements in steel, such as vanadium V, titanium Ti, aluminum AL, boron B and rare earth RE, all belong to microalloying elements. Although the content is very low, they should still be marked on the steel number. For example, in 20MnVB steel. Vanadium is 0.07-0.12% and boron is 0.001-0.005%. High quality steel should be added "A" at the end of the steel number to distinguish it from ordinary high quality steel. Special purpose alloy structural steel with a prefix (or suffix) denoting the purpose of the steel. For example, the 30CrMnSi steel specially used for riveting screws is expressed as ML30CrMnSi.

1. Steel used as parts of various machines. It includes carburizing steel, tempering steel, spring steel and rolling bearing steel.

2. Steel used for engineering structures. It includes carbon steel A, B, special steel and ordinary low alloy steel.

What is the material of steel S400

S400 is JIS standard of Japanese steel, equivalent to the domestic Q235A structural steel, can be used for casting, used in casting steel. S400 is a Japanese brand, and the common structural steel in JIS series is mainly composed of three parts: the first part is the material, such as: S for steel, F for iron; The second part represents different shapes, types and uses, such as P for plate, T for tube, K for tool; The third part shows the characteristic number, which is generally the minimum tensile strength. For example: SS400 - the first S represents steel, the second S represents "structure", 400 is the lower limit tensile strength of 400MPa, the overall tensile strength of 400 mpa ordinary structural steel.

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Structural steel is a type of steel used to make building materials of various shapes. Many structural steel shapes take the form of long thin beams with a specific cross-section profile. In most industrialized countries, the shape, size, chemical composition, mechanical properties (such as strength), storage methods, etc. of structural steel are regulated by standards.

Most structural steel shapes, such as i-beams, feature a high area of secondary moments; they are very rigid in the installation relative to their cross-sectional area, so they can support high loads without excessive sagging.

Q195, Q215, Q235, Q345

Q235 represents: carbon structural steel - general plate is a kind of steel material. Q is the yield of this material, and 235 is the yield of this material, which is around 235. The yield value will decrease with the increase of material thickness.

Q235A, Q235B, Q235C, Q235D. This is the grade of distinction, represents, mainly the impact of the temperature is different!

A, B, C, D, the difference is the impact temperature in their performance. They are: Q235A, no impact; Grade Q235B, is 20 degrees room temperature shock;

Grade Q235C, 0 degree impact; Grade Q235D, it's a -20 impact. At different impact temperatures, the impact values are also different.

Element content: Sulfur content of A, B, C and D decreased successively; A and B have the same phosphorus content, followed by C, and D has less phosphorus content.

① Hot dip galvanized steel plate. The sheet steel is dipped into the melted zinc tank so that the surface is adhered to a zinc sheet steel.

② alloyed galvanized steel plate. This steel plate is also made with hot dip method, but after the trough, immediately heat it to about 500℃, fingerprint resistance galvanized sheet wholesale, so that the generation of zinc and iron alloy coating.

③ Electric galvanized steel plate. The galvanized steel plate made by electroplating has good workability. But the coating is thinner, corrosion resistance is not as good as hot dip galvanized sheet:

④ Single-side plating and double-side difference galvanized steel plate. Single-sided galvanized steel plate, that is, galvanized products only on one side. It has better adaptability than double-sided galvanized sheet in welding, coating, rust prevention and processing.

⑤ Alloy, composite galvanized steel plate. It is made of zinc and other metals such as lead, zinc alloy or composite plating of steel plate.

With the continuous expansion of the use of hot galvanized sheet, the following purposes can be achieved by polishing the strip steel in the modern continuous hot dip galvanizing unit:

(1) Improve the flatness and flatness of the sheet, but also the surface of the zinc particle flattening, so that the surface of the strip smooth, which is especially advantageous for later deep drawing and other occasions with higher precision;

② The polishing roll used has been pre-shot peening, so the surface of the plating plate has a certain roughness after polishing. It can improve the adhesion of the coating, but also can store a certain amount of grease, in the deep drawing process, the lubrication of the die is beneficial;

③ For the plating plate after painting treatment, although the surface is controlled into small zinc flowers, small zinc flowers can still be exposed through the paint layer. Therefore, for some high requirements of galvanized sheet, small zinc flower surface needs to go through polishing treatment. This can make the galvanized sheet obtain a more uniform silver appearance;

(4) By finishing, the lower yield point can be reduced to make the yield platform disappear or less obvious, which can prevent the slip line in the future drawing or deep drawing, and improve the possibility of deep drawing.

The coating thickness formula is: Dz = Gz (Sz*dz), where: Dz -- coating thickness mm, Gz -- per square meter coating weight g, Sz -- coating area mm2, dz -- zinc specific gravity, the above formula can be simplified as: Dz = 0.000139Gz

The causes of white rust are: hot dip galvanizing and other acid, alkali, salt and other corrosive media together; Passivation film or anti-film is destroyed; Passivation or oiling effect is not good; The storage warehouse is not well ventilated and damp; Galvanized sheet in the transport of water; Transported at low temperature and stored at high temperature, condensate is formed.

When the hot galvanized sheet is in the humid air, especially when the air contains SiO2, CO2, NO2 and NO and other acidic substances, the surface of the galvanized layer will soon produce loose white rust. The main components of white rust are ZnO and Zn (OH) 2. This kind of white rust not only affects the appearance, but also brings great difficulties to the future use.

There are three ways to test the corrosion resistance of hot-galvanized sheet: salt spray test; Wet test; Erosion test.

Chromate passivation treatment of galvanized sheet can form passivation film, its chemical reaction formula is as follows: Zn+H2GrO4-ZnGrO2=H2

The trivalent chromium in solution passivation group is insoluble in water, and its chemical properties are not active, which plays the skeleton role, while the hexavalent chromium is easily soluble in water, which can play the role of re-passivation when the passivation film scratches, and has the healing effect of passivation film. Therefore, within a certain limit, passivation film can prevent steam or moist air directly erosion galvanized sheet, zinc layer plays a protective role.

large zinc flower is normal zinc flower, according to the normal production process can produce large zinc flower, its crystal core diameter is not less than 0.2mm; The diameter of the crystalline nucleus less than 0.2mm is called small zinc flower, which is generally not identifiable by the naked eye.

Dark spots are formed by further oxidation of white rust. The main causes of white rust are:

Poor passivation, passivation film thickness is not enough or uneven; No oil on the surface or residual water on the strip surface; The surface of the strip contains water when it is rolled up. Passivation not completely dried; Getting wet or rain-soaked during transportation or storage; The storage time of finished products is too long; Galvanized sheet and other acid and alkali and other corrosive media contact or stored together.

The main reasons for zinc layer shedding are: Surface oxidation, silicon compounds, cold bound emulsion is too dirty, NOF section oxidation atmosphere and protective gas dew point is too high, air fuel ratio is unreasonable, hydrogen flow rate is low, furnace aerobic infiltration, strip into the pot temperature is low, RWP section furnace pressure is low and door suction, NOF section furnace temperature is low, Grease evaporation is not enough, zinc pot aluminum content is low, unit speed is too fast, insufficient reduction, zinc liquid residence time is too short, coating thickness.

Known: the production specification is 0.75×1050mm, and the coil weight is 5 tons. What is the length of the coil? (The specific gravity of galvanized sheet is 7.85g/cm3)

Solution: L = G/ (h×b×p) = (5×1000)/(0.785×1.050×7.5) = 808.816m

Answer: The coil is 808.816m long.

Mainly: peeling, scratches, passivation spots, zinc particles, thick edge, air knife stripes, air knife scratches, exposed steel, inclusion, mechanical damage, poor steel base performance, wave edge, ladling bend, inappropriate size, embossing, zinc layer thickness, roll printing, etc.

There are two kinds: air-cooled and water-cooled.