In order to improve the surface hardness and wear resistance of a500 square and rectangular tube, it can be heat treated.
Heat treatment of square and rectangular pipes is one of the important processes in steel pipe manufacturing. Compared with other processing processes, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but changes the internal microstructure of the workpiece, or changes the workpiece The chemical composition of the surface gives or improves the performance of the workpiece.
The characteristic is to improve the inherent quality of metal square tubes. In order to make these pipes have the required mechanical properties, physical properties and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment processes are often indispensable. Steel is the most widely used material in the mechanical industry. The microstructure of steel is complex and can be controlled through heat treatment. Therefore, the heat treatment of steel is the main content of metal heat treatment. In addition, aluminum, copper, magnesium, titanium, etc. and their alloys can also change their mechanical, physical and chemical properties through heat treatment to obtain different performance properties.
When the rectangular tube is heated, the workpiece is exposed to the air, and oxidation and decarburization often occur (that is, the carbon content on the surface of the steel part is reduced), which has a very negative impact on the surface properties of the parts after heat treatment. Therefore, metals should usually be heated in a controlled atmosphere or protective atmosphere, in molten salt, and in a vacuum. Protective heating can also be performed by coating or packaging methods.
The method of effectively and closely combining pressure processing deformation and heat treatment to obtain good strength and toughness of the workpiece is called deformation heat treatment; heat treatment performed in a negative pressure atmosphere or vacuum is called vacuum heat treatment, which not only enables The workpiece will not be oxidized or decarburized, and the surface of the treated workpiece will be kept smooth and clean, improving the performance of the workpiece. It can also be chemically heat treated by penetrating agent.
Surface heat treatment is a metal heat treatment process that only heats the surface layer of the workpiece to change the mechanical properties of its surface layer. In order to only heat the surface of the workpiece without transferring too much heat into the interior of the workpiece, the heat source used must have a high energy density, that is, a large amount of heat energy is given to the workpiece per unit area, so that the surface or part of the workpiece can be heated for a short or instant. reach high temperatures. The main methods of surface heat treatment include flame quenching and induction heating heat treatment. Commonly used heat sources include oxygen acetylene or oxygen propane and other flames, induced current, laser and electron beam.
Chemical heat treatment is a metal heat treatment process that changes the chemical composition, structure and properties of the surface of the workpiece. The difference between chemical heat treatment and surface heat treatment is that the former changes the chemical composition of the surface layer of the workpiece. Chemical heat treatment is to heat the workpiece in a medium (gas, liquid, solid) containing carbon, salt medium or other alloying elements, and keep it warm for a long time, so that the surface of the workpiece can penetrate elements such as carbon, nitrogen, boron and chromium. After the elements are infiltrated, other heat treatment processes such as quenching and tempering are sometimes performed. The main methods of chemical heat treatment include carburizing, nitriding, and metalizing.
Heat treatment is one of the important processes in the manufacturing process of mechanical parts and tools and molds. Generally speaking, it can ensure and improve various properties of the workpiece, such as wear resistance, corrosion resistance, etc. It can also improve the structure and stress state of the blank to facilitate various cold and hot processing.
1.What is heat treatment of square tube?
Heat treatment refers to a metal thermal processing process in which a500 metal square tube is heated, kept and cooled in a solid state to obtain the expected structure and properties.Heat treatment of square and rectangular pipes is one of the important processes in steel pipe manufacturing. Compared with other processing processes, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but changes the internal microstructure of the workpiece, or changes the workpiece The chemical composition of the surface gives or improves the performance of the workpiece.
The characteristic is to improve the inherent quality of metal square tubes. In order to make these pipes have the required mechanical properties, physical properties and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment processes are often indispensable. Steel is the most widely used material in the mechanical industry. The microstructure of steel is complex and can be controlled through heat treatment. Therefore, the heat treatment of steel is the main content of metal heat treatment. In addition, aluminum, copper, magnesium, titanium, etc. and their alloys can also change their mechanical, physical and chemical properties through heat treatment to obtain different performance properties.
2.A500 rectangular tube heat treatment process
The heat treatment process of the hollow section generally includes three processes: heating, insulation, and cooling. Sometimes there are only two processes: heating and cooling. These processes are interconnected and cannot be interrupted.(1)Heating
Heating is one of the important processes of heat treatment. There are many heating methods for steel pipe heat treatment. The earliest ones used charcoal and coal as heat sources, and more recently liquid and gaseous fuels were used. The application of electricity makes heating easy to control and has no environmental pollution. These heat sources can be used for direct heating, or indirect heating through molten salt or metal, or even floating particles.When the rectangular tube is heated, the workpiece is exposed to the air, and oxidation and decarburization often occur (that is, the carbon content on the surface of the steel part is reduced), which has a very negative impact on the surface properties of the parts after heat treatment. Therefore, metals should usually be heated in a controlled atmosphere or protective atmosphere, in molten salt, and in a vacuum. Protective heating can also be performed by coating or packaging methods.
(2)Insulation
Heating temperature is one of the important process parameters of the heat treatment process. Selection and control of the heating temperature are the main issues to ensure the quality of heat treatment. The heating temperature varies with the metal material being processed and the purpose of the heat treatment, but it is generally heated to above the phase transformation temperature to obtain a high-temperature structure. In addition, the transformation requires a certain amount of time. Therefore, when the surface of the metal workpiece reaches the required heating temperature, it must be maintained at this temperature for a certain period of time to make the internal and external temperatures consistent and the microstructure transformation to be complete. This period of time is called the holding time. When using high-energy-density heating and surface heat treatment, the heating speed is extremely fast and there is generally no holding time, while the holding time for chemical heat treatment is often longer.(3)Cooling
Cooling is also an indispensable step in the heat treatment process. The cooling methods vary depending on the process, mainly controlling the cooling rate. Generally, annealing has the slowest cooling rate, normalizing has a faster cooling rate, and quenching has a faster cooling rate. However, there are different requirements due to different steel types. For example, air-hardened steel can be hardened at the same cooling rate as normalizing.
3. Methods of heat treatment of square and rectangular tubes
(1) Annealing
Annealing is to heat the workpiece to an appropriate temperature, adopt different holding times according to the material and workpiece size, and then slowly cool it. The purpose is to make the internal structure of the metal reach or approach an equilibrium state, obtain good process performance and usability, or provide further quenching Make organizational preparations.(2)Normalizing
Normalizing is to heat the workpiece to a suitable temperature and then cool it in the air. The effect of normalizing is similar to that of annealing, except that the obtained structure is finer. It is often used to improve the cutting performance of materials, and is sometimes used for parts with low requirements. as final heat treatment.(3)Quenching
Quenching is to heat and preserve the workpiece and then rapidly cool it in quenching media such as water, oil, other inorganic salts, and organic aqueous solutions. After quenching, the steel parts become hard but brittle at the same time. In order to eliminate the brittleness in time, it generally needs to be tempered in time.(4)Tempering
In order to reduce the brittleness of steel parts, the quenched steel parts are kept for a long time at an appropriate temperature above room temperature and below 650°C, and then cooled. This process is called tempering. Annealing, normalizing, quenching, and tempering are the "four fires" in overall heat treatment. Among them, quenching and tempering are closely related and are often used together and are indispensable. "Four Fires" have evolved different heat treatment processes with different heating temperatures and cooling methods. In order to obtain a certain strength and toughness, the process of combining quenching and high-temperature tempering is called quenching and tempering. After some alloys are quenched to form a supersaturated solid solution, they are kept at room temperature or a slightly higher temperature for a longer period of time to improve the hardness, strength or electromagnetic properties of the alloy. This heat treatment process is called aging treatment.The method of effectively and closely combining pressure processing deformation and heat treatment to obtain good strength and toughness of the workpiece is called deformation heat treatment; heat treatment performed in a negative pressure atmosphere or vacuum is called vacuum heat treatment, which not only enables The workpiece will not be oxidized or decarburized, and the surface of the treated workpiece will be kept smooth and clean, improving the performance of the workpiece. It can also be chemically heat treated by penetrating agent.
Surface heat treatment is a metal heat treatment process that only heats the surface layer of the workpiece to change the mechanical properties of its surface layer. In order to only heat the surface of the workpiece without transferring too much heat into the interior of the workpiece, the heat source used must have a high energy density, that is, a large amount of heat energy is given to the workpiece per unit area, so that the surface or part of the workpiece can be heated for a short or instant. reach high temperatures. The main methods of surface heat treatment include flame quenching and induction heating heat treatment. Commonly used heat sources include oxygen acetylene or oxygen propane and other flames, induced current, laser and electron beam.
Chemical heat treatment is a metal heat treatment process that changes the chemical composition, structure and properties of the surface of the workpiece. The difference between chemical heat treatment and surface heat treatment is that the former changes the chemical composition of the surface layer of the workpiece. Chemical heat treatment is to heat the workpiece in a medium (gas, liquid, solid) containing carbon, salt medium or other alloying elements, and keep it warm for a long time, so that the surface of the workpiece can penetrate elements such as carbon, nitrogen, boron and chromium. After the elements are infiltrated, other heat treatment processes such as quenching and tempering are sometimes performed. The main methods of chemical heat treatment include carburizing, nitriding, and metalizing.
Heat treatment is one of the important processes in the manufacturing process of mechanical parts and tools and molds. Generally speaking, it can ensure and improve various properties of the workpiece, such as wear resistance, corrosion resistance, etc. It can also improve the structure and stress state of the blank to facilitate various cold and hot processing.
