The quenching treatment of ERW Steel Pipe is an important heat treatment process, which aims to change the structure and performance of the pipe by controlling the heating temperature and cooling rate to improve the hardness and strength. Quenching treatment is a type of heat treatment for steel and plays a vital role in the entire process. This process results in steels with excellent mechanical properties suitable for use in many engineering fields, especially in applications requiring high strength and wear resistance.Quenching treatment is not just a simple heating and cooling of steel, but a precisely controlled heat treatment process to ensure that the structure and performance of the steel meet the design requirements. In this process, there are strict requirements and controls on heating temperature, holding time, cooling medium, cooling rate and other factors. Through quenching treatment, the structural structure of steel can undergo phase transformation, thereby significantly improving its hardness, strength and wear resistance.During the quenching process, the focus is on controlling the cooling rate. Rapid cooling causes a martensite transformation in the steel's microstructure, resulting in high hardness and strength, but may reduce toughness. Conversely, a slower cooling rate helps maintain some toughness, but may sacrifice some hardness and strength. Therefore, in practical applications, appropriate quenching process parameters need to be selected according to specific requirements and usage scenarios.
The surface quenching and tempering heat treatment of ERW steel pipes is usually carried out by induction heating or flame heating, mainly focusing on technical parameters such as surface hardness, local hardness and effective hardened layer depth. When testing hardness, you can use Vickers hardness tester, Rockwell hardness tester or surface Rockwell hardness tester. Each hardness tester has its applicable situations and characteristics.
Vickers hardness tester:
Scope of application: To test the surface hardness of straight seam welded pipes after heat treatment, a test force of 0.5 to 100kg can be used.
High precision: It can detect surface hardened layers as thin as 0.05mm thick, with high precision and resolution, and can distinguish small differences.
Detection of effective hardened layer depth: It can also be used to detect effective hardened layer depth.
Advantages: high precision, able to distinguish small differences, suitable for surface heat treatment processing or occasions requiring precise measurement.
Rockwell hardness:
Scope of application: It is also suitable for testing the hardness of surface quenched workpieces. Different scales can be used, such as HRC scales.
Detection of effective hardening depth: capable of testing surface-hardened straight seam welded pipes with an effective hardening depth exceeding 0.1mm.
Advantages: simple operation, low price, fast measurement, hardness value can be read directly, suitable for rapid non-destructive piece-by-piece inspection.
Surface Rockwell hardness tester:
Scope of application: also used to test the hardness of surface quenched workpieces, with three scales to choose from.
Advantages: simple operation, easy to use, low price, suitable for fast and non-destructive piece-by-piece inspection.
For parts with higher local hardness requirements, induction heating and other methods can be used for local quenching heat treatment. At this time, it is necessary to mark the location of the local quenching heat treatment and the local hardness value on the drawing, and ensure that the hardness testing instrument can perform detection in the designated area, such as using a Rockwell hardness tester to test the HRC hardness value or a surface Rockwell hardness tester to test HRN Hardness value.
Quenching treatment steps:
Heating: Place the ERW steel pipe into a heating furnace or other heating equipment to bring it to the quenching temperature. The quenching temperature depends on the composition of the steel pipe and the required hardness.
Control the heating speed and temperature uniformity to avoid excessive temperature gradient or local overheating.
Insulation: After reaching the quenching temperature, keep it for a certain period of time to ensure uniform temperature inside the steel pipe and cause corresponding changes in the organizational structure.
The holding time is determined according to the size and material of the steel pipe, usually between a few minutes and tens of minutes.
Quenching: The heated steel pipe is quickly placed in the quenching medium for rapid cooling. Commonly used quenching media include water, oil or polymer. Control the quenching speed and the temperature of the cooling medium to ensure that the steel pipe is rapidly cooled during the quenching process to form a martensite structure.
Tempering: Quenched steel pipes are usually too hard and brittle and need to be tempered to improve their toughness and strength. Put the steel pipe into the tempering furnace, heat it to a certain temperature and maintain it for a certain time, and then cool it to room temperature.
Surface treatment (optional): After completing the quenching and tempering treatment, surface treatment, such as rust removal, painting, etc., may be required to improve the appearance and anti-corrosion performance of the steel pipe.
Precautions:
Temperature control: The temperature must be strictly controlled during the heating process to ensure that the steel pipe reaches the required quenching temperature. The temperature of the quenching medium also needs to be noted. Too high or too low may affect the quenching effect.
Cooling rate: Ensure that the steel pipe is cooled quickly in the quenching medium, and control the cooling rate to form the required organizational structure.
Heating time: The holding time affects the phase transformation and stability of the internal structure of the steel pipe and needs to be reasonably determined based on the specific circumstances.
Quenching medium selection: Different quenching media have different quenching effects on steel pipes. The appropriate medium needs to be selected according to the steel pipe material and required performance.
Tempering treatment: The selection of tempering temperature and time affects the toughness and strength of the steel pipe. The tempering process parameters need to be determined according to specific requirements.
Surface treatment: Surface treatment can improve the appearance and anti-corrosion performance of the steel pipe, but it must avoid affecting the quenching and tempering effects of the steel pipe.
Quality control: During the entire quenching process, various process parameters must be strictly controlled to ensure that the steel pipe meets the hardness, strength and wear resistance required by the design.
Through the above steps and precautions, ERW steel pipes can be effectively quenched, improving their mechanical properties and service life, and ensuring that the steel pipes meet quality standards and customer needs.