Steel construction?
Time：[2014-8-20] Hits：4324
Steel construction?
1, Foshan Steel system has a light weight, easy installation, short construction period, good seismic performance, contribution to recover faster, less environmental pollution and other comprehensive advantages, good ductility and toughness, impact resistance.
2, types of steel are: different sub-sheet thickness (steel sheet thickness <4mm), the plate (thickness 4-20mm) and thick (thickness 20--60mm) more than 60 kinds of special thick. Steel strip included in the class.
3, ordinary bolts and high-strength bolts difference?
Ordinary bolt general use ordinary carbon steel production, without heat treatment, generally with high-strength bolts quality carbon structural steel or alloy steel production, need to go through quenching and tempering heat treatment to improve the overall mechanical properties. High intensity divided, 8.8, 10.9, 12.9.
From the intensity level: high-strength bolts used 8.8S and 10.9S two intensity levels. Ordinary bolts are generally 4.4, 4.8 5.6 8.8.
From the mechanical characteristics of high-strength bolts and by applying pre-tension power transmission external conflict, ordinary rod bolt by bolt hole wall shear force and shear under pressure to deliver.
4, divided by the force characteristics: type and pressure type of conflict
Conflict-type high-strength bolts are passed external force is based on the conflict between the convergence pieces, when the Commissioner of force equal to the conflict, the conflict is extremely high strength bolts type interface design ultimate load. Thousands of rods at this time slip does not occur, the bolt lever is not cut, bolt hole wall is not under pressure.
Similar pressure-type high-strength bolts and bolts, shear force can be more than a conflict will occur at this time to be convergence between the relative slip components, rod and bolt hole wall touch, convergence rely conflict with bolt rod shear force, pressure joint force transmission.
Pressure type high strength bolts large deformation, not for direct acceptance of convergence dynamic load structure.
5, several types of welding rod
Roughly a dozen: carbon steel electrode, low alloy steel welding rod, molybdenum and chromium-molybdenum steel electrode, low temperature steel electrodes, stainless steel welding, welding electrodes, cast iron welding rod, nickel and nickel alloy rod, copper and copper alloys, aluminum and aluminum alloys and special purpose welding rod.
6, weld defects:
(1) lack of penetration: the parent metal joints in the middle (X groove) or root (V, U groove) of the blunt edge is not completely fused together while leaving local unfused. Incomplete penetration reduces the mechanical strength of welded joints, gaps and ends at the lack of penetration of the formation of stress will set point when weldment accept loads easily lead to cracking.
(2) lack of fusion: between the solid metal and filler metal (between the weld and base metal), or filled (between multi-pass welding weld or solder when layer) is not completely melted metal partial contact, or in spot welding (ERW) when the base material is not complete fusion between the base material together, sometimes often accompanied by the presence of slag.
(3) holes: In the fusion welding process, the gas or the gas within the weld metal is not enough time to overflow outside intrusion prior to cooling and solidifying the metal bath and remains in the internal voids or pores of the weld metal or the outer formed, depending on the pore morphology can be divided into a single, chain porosity, pore density (porosity, including a honeycomb), etc., especially in the electric arc welding due to the metallurgical process time is very short, and soon solidified metal bath, the gas generated in metallurgical processes, gas absorbed by the liquid metal, or welding flux moisture and gas generated by the decomposition at high temperatures, and even a welding environment, too much humidity will decompose at high temperature gas, etc., porosity defects will form precipitates when these gases are too late. Although the pores of stress compared to other defect gathering trend is not so large, but it breaks the weld metal density, reducing the effective cross-sectional area of the weld metal, resulting in reduced strength of the weld.
7, the next NDT is no damage to the workpiece or raw materials in the working status of the premise, to be tested components appearance and internal quality check of a means test.
Common NDT methods:
Ultrasonic testing: use of ultrasound can penetrate deep into the metal material, by entering a cross-sectional another cross-sectional, reflection occurs at the interface between the edge of a method for verifying the characteristics of the defective parts, the part from the exterior when the ultrasonic beam to pass from the probe metals, the reflected wave occurs when the defect is encountered with the part, respectively, to the bottom surface, a phosphor screen formed on the pulse waveform, the pulse waveform is determined according to the position and size of the defect.
Ray detection (X-rays, γ-rays): Use ray penetration testing method to detect objects inside the object defects.
Magnetic particle testing: is used to detect the appearance of ferromagnetic material and a recent appearance defect detection method. When the magnetization of the workpiece, if the workpiece has the appearance of defects, the defects due to the reluctance of the magnetic flux leakage is generated is increased, the formation of the local magnetic field, the magnetic powder will show the shape and position of the defect is shown here, in order to determine the presence of defects.
8, parts processing program: preparation, correction, sheep, cutting, bending, made holes, assembly, welding, testing, rust, paint.
9, the metal surface rust methods: hand-disposal machinery disposal, chemical handling and disposal of four kinds of flame.
(1) manual Disposal:
Hand disposal mainly used blade, wire brush, emery cloth, broken hacksaw and other tools by hand to knock, shovel, scrape, brush, sand approach to reach remove rust, which is a traditional painter rust method is the most concise way without any environmental and construction conditions, but because of poor efficiency and effectiveness, only applies to a small range of rust disposal.
(2) the mechanical descaling method
Mechanical descaling method primarily use some electric, pneumatic tools to reach the clear intention of rust. Common power tools such as electric brush, electric wheel; Fengdonggongju wind moving brush. Electric and pneumatic brush round brush is to use a special wire brush roll, by the impact and conflict rust or mill scale clean, especially the appearance of rust, better, but deep rust difficult to remove. Electric wheel is actually a portable grinder, can move freely in their hands, the use of high-speed rotating grinding wheel to remove the rust, the better, especially for deep rust, and its high efficiency, construction quality is also good, easy to use, is a ideal rust tools. However, the operation should be careful not to punch through the metal skin.
(3) sand blasting, shot blasting disposal method
Sandblasting, shot blasting disposal method with the former old film festival Clear method to use. (4) Disposal Act flame flame disposal method is to use a gas torch is difficult to remove by hand on a small number of deep rust spots, were red-hot, so high temperature so that changes the chemical composition of the oxide rust to reach the rust intentions. The same method, the metal surface to be careful not to let burn, and to prevent the appearance of a large area to produce heat deformation.
(5) Chemical Disposal Act
Chemical treatment method is actually pickling rust method, using an acid solution and a metal oxide (rust) chemical reaction of the salts, and from the metal surface. Acidic solutions are commonly used: sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid. Operation in the acidic solution is applied to the metal parts of rust and rust is removed and slowly allowed to react. Rinse with water after application of rust removal and neutralization reaction with weak alkaline solution, then rinse wipe dry after drying, to prevent rust quickly.
For pickled metal exterior needs through rough disposal or phosphate disposal, mainly to increase the metal surface with paint adhesion.
When diluting concentrated sulfuric acid, sulfuric acid should be slowly poured into the water container, and continue mixing, not vice versa, in order to avoid sulfuric acid splashes wounding.
10, the common lifting equipment: tower crane gantry crane crawler crane truck crane wheel crane mast crane hoisting machine jack turn hoist bridge crane.
