Frozen earth steel bar heat treatment process

Abstract

The invention discloses a frozen earth steel bar heat treatment process and belongs to the technical field of steel bar heat treatment. The method specifically comprises the following steps: preheating; carrying out austenitizing treatment; quenching treatment; carrying out tempering treatment; performing low-temperature treatment; and natural cooling: after the low-temperature treatment is finished, taking out the steel bar, and naturally cooling the steel bar to the ambient temperature at room temperature. The invention aims to provide the frozen soil reinforcing steel bar heat treatment process, and the yield strength and the tensile strength of the reinforcing steel bar in a frozen soil environment are effectively improved through the specific steps of heating, heat preservation, cooling and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment of steel bars, and in particular relates to a heat treatment process of frozen soil steel bars. Background Art

[0002] Construction projects in frozen soil regions place extremely stringent demands on the performance of steel bars. Frozen soil environments are characterized by low temperatures and freeze-thaw cycles. Ordinary steel bars are susceptible to embrittlement and a decrease in mechanical properties in such environments, seriously impacting the safety and durability of the structures. φ12mm steel bars are widely used in frozen soil projects, such as small building foundations and pipe supports in frozen soil areas. However, existing heat treatment processes for this size of steel bars are difficult to meet the special requirements of frozen soil environments.

[0003] Currently, common heat treatment processes for steel bars include normalizing, quenching, and tempering. However, these conventional processes have limitations in improving the low-temperature toughness and freeze-thaw resistance of steel bars. While normalizing can refine grain size, its effect on improving low-temperature performance is limited. Quenching can increase hardness, but it can increase the brittleness of the steel bar, making it prone to brittle fracture in frozen soil environments. Tempering can improve the brittleness of steel bars after quenching to a certain extent, but it is difficult to fully meet the comprehensive performance requirements of steel bars in frozen soil areas.

[0004] Therefore, developing a heat treatment process specifically for frozen soil steel bars with a specification of φ12mm to improve their mechanical properties in frozen soil environments has important practical significance and engineering application value. Summary of the Invention

[0005] The purpose of the present invention is to provide a heat treatment process for frozen soil steel bars, which effectively improves the yield strength and tensile strength of steel bars in frozen soil environments through specific heating, insulation, cooling and other steps.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a frozen soil steel bar heat treatment process, comprising:

[0008] Preheating treatment: Place the steel bar in a heating furnace and heat it to 200±10℃ at a heating rate of 34-6℃ / min, and keep it warm for 240±10min;

[0009] Austenitizing treatment: After preheating, heat the steel bar to 900-950℃ at a heating rate of 15-20℃ / min and keep it at this temperature for 45-60min to fully austenitize the steel bar;

[0010] Quenching treatment: The quenching is carried out by rapid cooling. The austenitized steel bars are quickly immersed in a quenching medium with a temperature of 10-20°C. The quenching medium is a special water-soluble quenching liquid. During the quenching process, the cooling rate is strictly controlled. In the range of 650-550°C, the cooling rate is maintained at 60-80°C / s; in the range of 550-300°C, the cooling rate is maintained at 20-30°C / s.

[0011] Tempering treatment: After quenching, the steel bars are tempered at a temperature of 180-220°C with a holding time of 90-120 minutes;

[0012] Low temperature treatment: The tempered steel bars are placed in a low temperature box and cooled to -40°C to -30°C at a cooling rate of 5-10°C / min, and kept at this temperature for 60-90 minutes;

[0013] Natural cooling: After the low-temperature treatment, take out the steel bars and allow them to cool naturally to ambient temperature at room temperature.

[0014] Furthermore, hot-rolled steel bars that meet national standards are selected as raw materials, and their chemical composition should meet the requirements of relevant standards to ensure the basic quality of the steel bars.

[0015] Furthermore, the preheating treatment is specifically as follows: placing the steel bar into a heating furnace, heating it to 200° C. at a heating rate of 5° C. / min, and keeping the temperature for 240 minutes.

[0016] Furthermore, the austenitizing treatment is specifically: heating to 900° C. at a heating rate of 15° C. / min and keeping the temperature for 45 minutes.

[0017] Furthermore, the quenching treatment is specifically as follows: the steel bar is quickly immersed in a water-soluble quenching liquid with a temperature of 10°C and a concentration of 15%; in the range of 650-550°C, the cooling rate is controlled at 60°C / s; in the range of 550-300°C, the cooling rate is controlled at 20°C / s.

[0018] Furthermore, the tempering treatment is specifically as follows: the quenched steel bars are tempered at 200° C. and kept warm for 90 minutes.

[0019] Furthermore, the low temperature treatment is specifically as follows: the tempered steel bars are placed in a low temperature box, cooled to -40°C at a cooling rate of 5°C / min, and kept warm for 60 minutes.

[0020] Further, frozen soil reinforcement.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The 12 mm steel bars treated by the heat treatment process of the present invention exhibit excellent performance in terms of yield strength and tensile strength, and can meet the engineering construction requirements in frozen soil environments. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the embodiments.

[0024] A heat treatment process for frozen soil steel bars with a specification of φ12mm:

[0025] Raw material preparation: 12mm hot-rolled steel bars are selected, and their chemical composition has been tested to meet national standards.

[0026] Preheating treatment: Place the steel bars in a heating furnace, heat to 200°C at a heating rate of 5°C / min, and keep warm for 120 minutes.

[0027] Austenitizing treatment: then heated to 900°C at a heating rate of 15°C / min and kept at this temperature for 45 minutes.

[0028] Quenching: Quickly immerse the steel bar in a 15% aqueous quenching solution at a temperature of 10°C. Control the cooling rate at 60°C / s in the 650-550°C range and 20°C / s in the 550-300°C range.

[0029] Tempering treatment: The quenched steel bars are tempered at 200℃ for 90 minutes.

[0030] Low temperature treatment: The tempered steel bars are placed in a low temperature box and cooled to -40°C at a cooling rate of 5°C / min and kept warm for 60 minutes.

[0031] Natural cooling: Cool naturally at room temperature after low temperature treatment.

[0032] The mechanical properties of each embodiment before heat treatment are shown in Table 1:

[0033] Table 1: Mechanical properties of φ12mm frozen soil steel bars before heat treatment

[0034]

[0035] The mechanical properties of each embodiment after heat treatment are shown in Table 2:

[0036] Table 2: Mechanical properties of φ12mm frozen soil steel bars after heat treatment

[0037]

[0038] It can be seen from the test results that the 12 mm steel bars treated by the heat treatment process of the present invention exhibit excellent performance in terms of yield strength and tensile strength, and can meet the requirements of engineering construction in frozen soil environments.

[0039] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A frozen soil steel bar heat treatment process, characterized in that: include: Preheating treatment: Place the steel bar in a heating furnace and heat it to 200±10℃ at a heating rate of 34-6℃ / min, and keep it warm for 240±10min; Austenitizing treatment: After preheating, heat the steel bar to 900-950℃ at a heating rate of 15-20℃ / min and keep it at this temperature for 45-60min to fully austenitize the steel bar; Quenching treatment: The quenching is carried out by rapid cooling. The austenitized steel bars are quickly immersed in a quenching medium with a temperature of 10-20°C. The quenching medium is a special water-soluble quenching liquid. During the quenching process, the cooling rate is strictly controlled. In the range of 650-550°C, the cooling rate is maintained at 60-80°C / s; in the range of 550-300°C, the cooling rate is maintained at 20-30°C / s. Tempering treatment: After quenching, the steel bars are tempered at a temperature of 180-220°C with a holding time of 90-120 minutes; Low temperature treatment: The tempered steel bars are placed in a low temperature box and cooled to -40°C to -30°C at a cooling rate of 5-10°C / min, and kept at this temperature for 60-90 minutes; Natural cooling: After the low-temperature treatment, take out the steel bars and allow them to cool naturally to ambient temperature at room temperature.

2. The frozen soil steel bar heat treatment process according to claim 1, characterized in that: Hot-rolled steel bars that meet national standards are selected as raw materials, and their chemical composition should meet the requirements of relevant standards to ensure the basic quality of the steel bars.

3. The frozen soil steel bar heat treatment process according to claim 1, characterized in that: The preheating treatment is specifically as follows: the steel bars are placed in a heating furnace, heated to 200° C. at a heating rate of 5° C. / min, and kept warm for 240 minutes.

4. The frozen soil steel bar heat treatment process according to claim 1, characterized in that: The austenitizing treatment is specifically as follows: heating to 900° C. at a heating rate of 15° C. / min and keeping the temperature for 45 minutes.

5. The frozen soil steel bar heat treatment process according to claim 1, characterized in that: The quenching treatment is specifically as follows: the steel bar is quickly immersed in a water-soluble quenching liquid with a temperature of 10°C and a concentration of 15%; in the range of 650-550°C, the cooling rate is controlled at 60°C / s; in the range of 550-300°C, the cooling rate is controlled at 20°C / s.

6. The frozen soil steel bar heat treatment process according to claim 1, characterized in that: The tempering treatment is specifically as follows: the quenched steel bars are tempered at 200° C. and kept warm for 90 minutes.

7. The frozen soil steel bar heat treatment process according to claim 1, characterized in that: The low temperature treatment is specifically as follows: the tempered steel bars are placed in a low temperature box, cooled to -40°C at a cooling rate of 5°C / min, and kept warm for 60 minutes.

8. The frozen soil steel bar heat treatment process according to claim 1, characterized in that: The specification of the frozen soil steel bars is φ12mm.

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