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H-beam of Maanshan Iron and Steel Co., Ltd. has become the first choice for large-scale buildings and steel structures because of its excellent mechanical and service properties, high strength and toughness, economic cross section, pollution-free and renewable during manufacturing and use, energy saving, high efficiency, earthquake resistance, safety and environmental protection, and is widely used in municipal engineering, electric power, petrochemical, metallurgical, transportation, industrial workshops and other fields. According to statistics, Masteel's hot-rolled H-beam production line produced 4.8 million tons of high-quality hot-rolled H-beam from 1998 to last year, of which 850,000 tons were exported. From 2002 to 2005, the accumulated profit of hot-rolled H-beam in Masteel was 2.3 billion yuan, and the foreign exchange earned was 65.438+0.6554 million dollars. The domestic market share of high-quality special H-beam reaches 654.38+000%.
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H-beam is an economical steel with better mechanical properties developed from I-beam, and it is named because its cross section is the same as the English letter "H". The characteristics of hot-rolled H-beam are as follows:
1, wide flange, large lateral stiffness and strong bending resistance.
2. The two surfaces of the flange are parallel to each other, which makes the connection, processing and installation simple and convenient.
3. Compared with welded I-beams, it has the advantages of low cost, high precision, small residual stress, no need for expensive welding materials and weld detection, and saves the manufacturing cost of steel structures.
4. Under the same section load, the weight of hot-rolled H steel structure is reduced by 15%-20% compared with traditional steel structure.
5. Compared with the concrete structure, the hot-rolled H-beam structure can increase the usable area and reduce the structural weight.
6.h-beam can be processed into T-beam and honeycomb beam, and can be combined into various cross-sectional forms, which greatly meets the requirements of engineering design and production.
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stainless steel
Stainless steel is a modern material with a history of 60 years.
Since the invention of stainless steel at the beginning of this century, stainless steel has combined the image of modern materials with excellent reputation in architectural application, which has made its competitors envious.
As long as the steel grade is selected correctly, processed properly and maintained properly, stainless steel will not be corroded, pitted, rusted and worn. Stainless steel is also one of the strongest building metal materials. Because stainless steel has good corrosion resistance, it can permanently maintain the integrity of engineering design. Chromium-containing stainless steel also has both mechanical strength and high ductility, which is easy to manufacture and meets the needs of architects and structural designers.
In architecture, building and structural industries, the key to the success of stainless steel lies in its good corrosion resistance.
Why is stainless steel resistant to corrosion?
All metals will react with oxygen in the atmosphere and form an oxide film on the surface. Unfortunately, the iron oxide formed on ordinary carbon steel continues to be oxidized, which makes the corrosion expand and eventually forms holes. The surface of carbon steel can be ensured by electroplating with paint or oxidation-resistant metals (such as zinc, nickel and chromium), but as we all know, this protection is only a film. If the protective layer is destroyed, the steel below will begin to rust.
The corrosion resistance of stainless steel depends on chromium, but because chromium is one of the components of steel, the protection methods are different.
When the chromium content reaches 10.5%, the atmospheric corrosion resistance of steel is significantly improved, but when the chromium content is higher, the corrosion resistance is still improved, but it is not obvious. The reason is that when steel is alloyed with chromium, the types of surface oxides change, similar to those formed on pure chromium metal. This tightly attached chromium-rich oxide protects the surface from further oxidation. This kind of oxide layer is extremely thin, and the natural luster of steel surface can be seen through it, which makes stainless steel have a unique surface. Moreover, if the surface layer is damaged, the exposed steel surface will react with the atmosphere to repair itself, re-form this "passive film" and continue to play a protective role.
So all stainless steels have the same feature, that is, the chromium content is above 10.5%.
Types of stainless steel
The word "stainless steel" refers not only to one kind of stainless steel, but to 100 kinds of industrial stainless steel, and each developed stainless steel has good performance in its specific application field. The key to success is to find out the purpose first, and then determine the correct steel grade. For more details about stainless steel, please refer to the "Stainless Steel Guide" floppy disk compiled by NiDI.
Fortunately, there are usually only six kinds of steel related to the application field of building structures. They all contain 17 ~ 22% chromium, and the better steel also contains nickel. Adding molybdenum can further improve the atmospheric corrosivity, especially the corrosion resistance to chlorine-containing atmosphere.
Atmospheric corrosion resistance
Experience shows that the degree of atmospheric corrosion is different in different regions. For the sake of explanation, it is suggested that the regions should be divided into four categories, namely rural areas, cities, industrial areas and coastal areas.
Rural areas are basically pollution-free areas. The population density in this area is low and there are only pollution-free industries.
This city is a typical residential, commercial and light industrial area, where there is light pollution, such as traffic pollution.
Industrial areas are areas where heavy industry causes air pollution. Pollution may be caused by gases formed by fuel oil, such as oxides of sulfur and nitrogen, or other gases released by chemical plants or processing plants. Suspended particles in the air, such as dust or iron oxide precipitation produced during steel production, will also aggravate corrosion.
Coastal areas usually refer to areas within a mile from the sea. However, the ocean atmosphere can spread inland, especially on the island. The prevailing wind comes from the ocean and the climate is bad. For example, the weather in Britain is like this, so the whole country belongs to the coastal areas. If the wind is mixed with sea fog, especially because of salt deposition and accumulation caused by evaporation, coupled with less rain, it is not often washed away by rain, and the conditions in coastal areas are even more unfavorable. If there is industrial pollution, it is more corrosive.
Studies in the United States, Britain, France, Italy, Sweden and Australia have determined the influence of these areas on the atmospheric corrosion resistance of various stainless steels. The related contents are briefly introduced in the Brief Introduction of Architects published by NiIDI. The tables in this book can help designers choose the most cost-effective stainless steel for different fields.
When making a choice, it is important to determine whether there are still local factors that affect the use of the site environment. For example, when stainless steel is used under the factory chimney, near the exhaust baffle of air conditioner or near the waste yard, abnormal conditions will occur.
Maintenance and cleaning
Like other materials exposed to the atmosphere, stainless steel will get dirty. Future lectures will analyze the design factors that affect maintenance and cleaning costs. But rain washing, hand washing and dirty surface are still related.
The effect of rain erosion is determined by placing the same slats directly in the atmosphere and in the shed. The effect of manual cleaning is determined by manually scrubbing the right side of each lath with a sponge dipped in soapy water every six months. The results show that, compared with being placed in a shed or an unwashed place, washing with rainwater and manual scrubbing to remove dust and deposits on the surface have a good effect on the surface condition. In addition, it is also found that the surface processing conditions also have an influence, and the lath with smooth surface is better than the lath with rough surface.
Therefore, the interval of washing is influenced by many factors, and the main influencing factor is the required aesthetic standard. Although many stainless steel curtain walls are only cleaned when cleaning the glass, generally speaking, the stainless steel used for external walls is cleaned twice a year.
Typical use
Most of the use requirements are to keep the original appearance of the building for a long time. When determining the type of stainless steel to be selected, the main considerations are the required aesthetic standards, the corrosiveness of the local atmosphere and the cleaning system to be adopted.
However, more and more other applications only seek structural integrity or impermeability. Such as roofs and side walls of industrial buildings. In these applications, the owner's construction cost may be more important than beauty, and the surface is not very clean.
The effect of using 430 stainless steel in dry indoor environment is quite good. However, in rural and urban areas, if you want to keep its appearance outdoors, you need to clean it frequently. In heavily polluted industrial areas and coastal areas, the surface will be very dirty and even rusty. However, in order to obtain the beautiful effect in outdoor environment, nickel-containing stainless steel must be used. Therefore, 304 stainless steel is widely used in curtain walls, side walls, roofs and other building applications, but in the industrial or marine atmosphere with severe corrosiveness, it is best to use 3 16 stainless steel.
Now, people have fully realized the advantages of using stainless steel in structural applications. Some design standards include 304 and 3 16 stainless steel. Because "duplex" stainless steel 2205 combines good atmospheric corrosion resistance with high tensile strength and elastic ultimate strength, it is also included in European standards.
Product shape
In fact, stainless steel is made according to all standard metal shapes and sizes, and there are many special shapes. The most commonly used products are thin plate and strip steel, and special products are also medium plate, such as hot rolled structural steel and extruded structural steel. There are also round, oval, square, rectangular and hexagonal welded or seamless steel pipes and other forms of products, including profiles, bars, wires and castings.
character of surface
As will be mentioned later, many different commercial surface treatments have been developed to meet the aesthetic requirements of architects. For example, the surface can be highly reflective or dull; Can be smooth, polished or embossed; It can be colored, colored, electroplated or etched on the surface of stainless steel to meet various requirements of designers for appearance.
It is easy to keep the surface state. Dust can only be removed by occasional cleaning. Because of its good corrosion resistance, graffiti pollution or similar other surface pollution can also be easily removed.
design
For more than 60 years, architects have been choosing stainless steel to build cost-effective permanent buildings. Many existing buildings fully illustrate the correctness of this choice. Some of them are very ornamental, such as the Chrysler Building in new york. But in many other applications, the role of stainless steel is not so noticeable, but it plays an important role in the aesthetics and performance of buildings. For example, because stainless steel is more wear-resistant and compressive than other metal materials with the same thickness, it is the designer's first choice when building sidewalks in places with large traffic.
For more than 70 years, stainless steel has been used as a structural material for building new buildings and restoring historical sites. The early design was calculated according to the basic principles. Today's design specifications, such as ANSI/ASCE-8-90 Code for Design of Cold-formed Stainless Steel Structures and Structural Stainless Steel Design Manual jointly published by NiDI and Euro Inox, simplify the design of structural members, and have long service life and good integrity.
Future prospects
Because stainless steel has many ideal properties required by building materials, it can be said to be unique among metals, and its development continues. In order to improve the performance of stainless steel in traditional applications, the existing types have been improved, and new stainless steel is being developed to meet the strict requirements of advanced building applications. Due to the continuous improvement of production efficiency and quality, stainless steel has become one of the most cost-effective materials chosen by architects.
Stainless steel combines performance, appearance and use characteristics, so it will still be one of the best building materials in the world.
Identification method of stainless steel
Number and representation of steel
(1) Use international chemical element symbols and national symbols to represent chemical components, and use Arabic letters to represent component content;
Such as: China-Russia 12CrNi3A.
(2) The series or number of steel is represented by a fixed number of digits; Such as: USA, Japan, 300 series, 400 series, 200 series;
(3) with Latin letters and sequence number, only for use.
Numbering rules in China.
(1) Use element symbols
② uses: hanyu pinyin, open hearth steel: p, boiling steel: f, killed steel: b, grade a steel: a, T8: Te8,
GCr 15: ball
◆ Composite steel and spring steel, such as 20CrMnTi 60SiMn (C content is expressed in parts per ten thousand).
◆ Stainless steel and alloy tool steel (C content is expressed in thousandths), such as: 1Cr 18Ni9 thousandths (i.e.
0. 1%C), stainless C≤0.08%, such as 0Cr 18Ni9, and ultra-low carbon C≤0.03%, such as 0Cr 17Ni 13Mo.
International stainless steel marking method
The American Iron and Steel Association uses three numbers to represent various standard grades of malleable stainless steel. These include:
① Austenitic stainless steel is marked with 200 and 300 series numbers,
② Ferritic and martensitic stainless steels are represented by 400 series numbers. For example, some common austenitic stainless steels.
It is marked with 20 1, 304, 3 16, 3 10.
③ ferritic stainless steel is marked with 430 and 446, and martensitic stainless steel is marked with 4 10, 420 and 440C.
Remember, biphasic (austenite-ferrite),
④ Stainless steel, precipitation hardening stainless steel and high alloy with iron content less than 50% are usually named by patent names or trademarks.
4). Classification and grading of standards
4- 1 rating:
① National standard GB
② Industry standard YB
③ Local standards
④ enterprise standard Q/CB
4-2 Classification:
① product standard
② Packaging standard
③ Method standard
④ Basic standards
4-3 standard grades (divided into three grades):
Grade Y: international advanced level.
Class I: international average level.
Class H: domestic advanced level.
4-4 National Standards
GB 1220-84 Stainless Steel Rod (Grade I)
GB424 1-84 stainless steel welding plate (class h)
GB4356-84 Stainless Steel Welded Disc Garden (Grade I)
GB 1270-80 Stainless Steel Pipe (Grade I)
Gb12771-91stainless steel welded pipe (grade y)
GB3280-84 Stainless Steel Cold Plate (Grade I)
GB4237-84 Stainless Steel Hot Plate (Grade I)
GB4239-9 1 stainless steel cold-rolled strip (grade 1)