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The six major defects of welding, their causes, hazards and preventive measures are all hereTime of issue : 2021- 11-05
1、 Appearance defect appearance defect (surface defect) refers to the defect that can be found from the workpiece surface without the help of instruments. The common appearance defects include undercut, weld bead, depression and welding deformation. Sometimes there are surface pores and surface cracks, and the root of single-sided welding is not fully welded.
A. Undercut
It refers to the depression or groove formed in the base metal part along the weld toe. It is the gap left by the lack of sufficient supplement of deposited metal after the arc melts the base metal at the weld edge.
The main causes of undercut are that the arc heat is too high, that is, the current is too large, the strip conveying speed is too small, the angle between electrode and workpiece is incorrect, the swing is unreasonable, the arc is too long, and the welding sequence is unreasonable. The magnetic bias blow of arc in DC welding is also a cause of undercut. Some welding positions (vertical, horizontal and vertical) will aggravate undercut, which reduces the effective cross-sectional area of base metal and the bearing capacity of the structure. At the same time, it will also cause stress concentration and develop into crack source.
Prevention of undercut: correcting the operation posture, selecting reasonable specifications and adopting good strip transportation methods will help to eliminate undercut. When welding fillet weld, AC welding instead of DC welding can also effectively prevent undercut.
B. Weld bead
The liquid metal in the weld flows to the base metal that is not melted due to insufficient heating or overflows from the root of the weld. The metal tumor formed after cooling that is not fused with the base metal is the weld bead. Too strong welding specification, too fast melting of welding rod, poor quality of welding rod (such as eccentric core), unstable characteristics of welding power supply and improper operation posture are easy to cause weld beading, which is easier to form weld beading in horizontal, vertical and overhead positions.
Weld beading is often accompanied by incomplete fusion and slag inclusion defects, which is easy to lead to cracks. At the same time, the weld bead changes the actual size of the weld and will bring stress concentration. The weld bead inside the pipe reduces its inner diameter and may cause blockage of flow animals.
Measures to prevent weld beading: make the weld in the flat welding position, correctly select the specification, select the non eccentric core electrode and operate reasonably. -
Research and Application of New Type Metal Anticorrosive Coating Preparation TechnologyTime of issue : 2016- 06-21
HC Surface Treatment Network News: As the energy crisis becomes more and more prominent, the development and utilization of rich marine resources has been paid more and more attention. The ability to develop marine resources not only reflects the level of a country's marine technological innovation and its promotion and application, but also reflects the country's competitive potential and comprehensive national strength in the marine field. At present, my country's exploration and development in the marine field is continuously heating up, and more and more marine engineering facilities are put into
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Zinc-nickel infiltration layer metal anti-corrosion technology projectTime of issue : 2016- 06-21
Chongqing Dayou Surface Technology Co., Ltd. is a scientific and technological enterprise established to develop and introduce internationally advanced metal and non-metal surface treatment technologies. It has self-developed zinc-nickel infiltration layer and imported chemical autophoretic metal anticorrosion technology, and has annual processing Capacity of tens of thousands of tons.
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Application of zinc-nickel infiltration layer on PC beam of rail transit lineTime of issue : 2016- 06-21
HC Surface Treatment Network: Abstract: For a long time, due to the acid rain atmosphere in the severe high temperature climate in Chongqing, the metal structural parts of the track beam, especially the easily rusty Q235 ordinary steel finger plate components, have been seriously rusted during the operation of the track line. , Has jeopardized the unblocked rail line and the safety of train operation.
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Application of embedded parts construction technology and zinc-nickel infiltration layer anticorrosion technology in subway engineeringTime of issue : 2016- 06-21
At present, China has become the country with the fastest development of urban rail transit in the world. With the rapid development of rail transit construction in my country, many problems and weaknesses have been exposed in the construction of rail transit projects in various places, such as extensive installation and construction of equipment, facilities, and components, which has caused serious damage to the civil structure of subway tunnels and corrosion of parts.
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Anti-rust categories and characteristicsTime of issue : 2016- 06-21
To effectively prevent the corrosion of metal parts and equipment, the current anti-rust methods can be roughly divided into four categories:
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Zinc-nickel infiltration layer metal anti-corrosion technology projectTime of issue : 2016- 06-21
The "Zinc-Nickel Infiltrated Metal Anti-corrosion Technology" independently developed by the company has become Chongqing Light Rail because of its unique high anti-corrosion, high hardness, high wear resistance and its advantages in energy saving, environmental protection,
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Development of anti-corrosion coatingsTime of issue : 2016- 06-21
According to incomplete statistics, there are more than 1,000 varieties of anti-corrosion coatings in my country. The traditional classification of resins includes epoxy, epoxy asphalt, asphalt, chlorinated rubber, chlorosulfonated polyethylene, polyvinyl chloride, perchloroethylene, and urushiol resin. , Ethyl silicate, high chlorinated polyethylene, polyurethane, polyurethane asphalt, phenolic, alkyd paint, etc.
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Anti-rust treatment method of applying anti-rust oilTime of issue : 2016- 06-21
Soaking method: Some small items are immersed in anti-rust grease, so that the surface is adhered with a layer of anti-rust grease. The thickness of the oil film can be achieved by controlling the temperature or viscosity of the anti-rust grease.
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Passivation principle anti-rust treatmentTime of issue : 2016- 06-21
The mechanism of passivation can be explained by thin film theory, that is, it is believed that passivation is due to the action of metal and oxidation properties. When it acts, a very thin, dense, good covering performance, and firmly adsorbed on the metal surface is formed.
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渝ICP备16005686号