Radiant tube heat treatment furnace with protective atmosphere circulating low-temperature heating function

Abstract

The invention belongs to the technical field of high-strength steel plate heat treatment equipment and production, and discloses a radiant tube heat treatment furnace with a protective atmosphere circulating low-temperature heating function. A radiant tube heating system and a protective atmosphere circulating low-temperature heating system are arranged on the same heat treatment furnace at the same time; the radiant tube heating system is arranged at a heating section, a soaking section and a heat preservation section of the heat treatment furnace; the protective atmosphere circulating low-temperature heating system is arranged at a soaking section and a heat preservation section of the heat treatment furnace; the two heating systems are evenly arranged on furnace rollers on the two sides of a hearth of the heat treatment furnace up and down. The furnace profile can meet the capacity of all heat treatment processes of normalizing, quenching, high-temperature tempering and medium-low temperature tempering of the high-strength steel plate under the protective atmosphere, the flexible adaptability of products is provided, one furnace profile can be built to adapt to production of different orders, investment is reduced, and productivity is improved. The use temperature of the heat treatment furnace can be changed from conventional 500-1000 DEG C to 100-1000 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment equipment and production technology for high-strength steel plates, and particularly to a radiant tube heat treatment furnace with a protective atmosphere circulation and low-temperature heating, which solves the technical bottleneck in the process compatibility of traditional heat treatment furnaces in a wide temperature range. Background Art

[0002] High-strength steel plates are widely used in fields such as automobiles, aviation, marine, nuclear power, and military. They have the advantages of high strength, high plasticity, high toughness, and high wear resistance. Heat treatment is an important processing process for high-strength steel. The heat treatment process includes normalizing, quenching, tempering, low-temperature tempering, etc. Through heat treatment, the organizational structure and various properties of steel can be improved. The continuous heat treatment furnace is the core equipment in the heat treatment process of high-strength steel plates.

[0003] At present, the continuous heat treatment furnaces applied in production are mainly divided into two types. One is a protective atmosphere continuous heat treatment furnace heated by radiant tubes, and the other is a continuous heat treatment furnace heated by open flames. The radiant tube heating heat treatment furnace can introduce nitrogen as a protective atmosphere to prevent the oxidation of steel plates and improve the surface quality, but it does not have the ability of low-temperature heat treatment and can only be applied to processes such as quenching, normalizing, and high-temperature tempering. On the contrary, the open flame heating heat treatment furnace does not have the function of a protective atmosphere (nitrogen) and is only suitable for the high, medium, and low-temperature tempering functions of steel plates. Currently, enterprises generally equip a heat treatment furnace heated by radiant tubes and a heat treatment furnace heated by open flames. In the actual production process, for some enterprises, due to the demand of customer products, the production orders of normalized plates are much more than those of medium and low-temperature tempering orders, resulting in insufficient production capacity of the radiant tube heating heat treatment furnace equipped by the enterprise, while the open flame heating heat treatment furnace is in a low production capacity state, causing low production line efficiency and energy waste.

[0004] Some enterprises will use the open flame heating heat treatment furnace for normalizing production to meet the order requirements, but it will cause problems such as oxidation of the steel plate surface and coking of furnace rolls, resulting in low product qualification rate and large use and maintenance amount of the heat treatment furnace. Summary of the Invention

[0005] The purpose of the present invention is to address the limitations of the above two furnace types and provide a radiant tube heat treatment furnace with a protective atmosphere circulation and low-temperature heating. This heat treatment furnace can not only achieve the heat treatment ability of a single furnace type to meet a large temperature span, including high-temperature normalizing and quenching above 900°C and low-temperature tempering below 200°C, but also meet the ability to heat under a protective atmosphere to prevent the oxidation of steel plates and improve the surface quality, and can achieve high-uniformity quenching, normalizing, high-temperature tempering, and low-temperature tempering below 200°C of heat-treated steel plates.

[0006] The technical solution of the present invention is as follows: A radiant tube heat treatment furnace with a protective atmosphere circulating low-temperature heating system arranges a radiant tube heating system 4 and a protective atmosphere circulating low-temperature heating system 5 on the same heat treatment furnace at the same time; the radiant tube heating system is arranged in the heating section 1, soaking section 2, and heat preservation section 3 of the heat treatment furnace; the protective atmosphere circulating low-temperature heating system 5 is arranged in the soaking section 2 and heat preservation section 3 of the heat treatment furnace; the two heating systems are evenly arranged up and down on the furnace rolls on both sides of the furnace chamber of the heat treatment furnace.

[0007] Further, for the two heating systems at the soaking section 2 and heat preservation section 3, they are alternately arranged in the upper and lower layers of the furnace rolls on both sides of the furnace chamber of the heat treatment furnace.

[0008] Further, the radiant tube heating system 4 mainly consists of a burner a6, pipelines, and a closed radiant tube 7; the pipelines are divided into a gas pipeline 8, an air pipeline 9, and an exhaust pipeline 10; the gas pipeline 8 and the air pipeline 9 are respectively connected to the burner a6, and gas and air are sent into the burner a6 for combustion; the burner a6 is connected to the closed radiant tube 7, and the closed radiant tube 7 extends into the heat treatment furnace; the exhaust pipeline 10 is connected to the closed radiant tube 7, and after the high-temperature flue gas transfers heat to the steel plate through the closed radiant tube 7, it is discharged through the exhaust pipeline 10, and the closed radiant tube 7 is used to ensure that the protective atmosphere in the furnace chamber is not affected by the flue gas.

[0009] Further, the protective atmosphere circulating low-temperature heating system 5 mainly consists of a sealed circulation fan 11, a cut-off valve 14, a protective atmosphere nozzle group 12, a radiant tube heating box 13, and a pipeline 15; one end of the cut-off valve 14 is connected to the outlet at the top of the heat treatment furnace, and the other end is connected to the radiant tube heating box 13; the cut-off valve 14 is closed in the high-temperature mode and opened in the low-temperature mode;

[0010] The inlet of the sealed circulation fan 11 is connected to the radiant tube heating box 13, and the outlet of the sealed circulation fan 11 is connected to the pipeline 15; the pipeline 15 arranges a main pipeline along the furnace length of the heat treatment furnace, and several branch pipelines are divided on the main pipeline, and the ends of the branch pipelines are connected to the protective atmosphere nozzle group 12; the protective atmosphere nozzle group 12 is connected to the heat treatment furnace through an opening in the furnace wall.

[0011] Further, the radiant tube heating box 13 mainly consists of a burner b17, a closed radiant tube 18, a cold nitrogen regulating valve 19, and a thermocouple 16; the burner b17 is connected to the closed radiant tube 18, and the closed radiant tube 18 extends into the radiant tube heating box 13 from one end to heat the protective atmosphere; several cold nitrogen regulating valves 19 are arranged in the radiant tube heating box 13 for releasing cold nitrogen; the thermocouple 16 is located at the other end of the radiant tube heating box 13.

[0012] Further, the protective atmosphere is sucked out and pressurized by the sealed circulating fan 11 from the heat treatment furnace hearth. After the temperature of the protective atmosphere is adjusted by the radiant tube heating box 13, it is sprayed into the heat treatment furnace hearth by the protective atmosphere nozzle group 12 through the pipeline 15; the protective atmosphere is cyclically adjusted to the target temperature to enhance the convective heat transfer amount between the heat treatment furnace hearth and the steel plate.

[0013] Further, the working state is divided into a high-temperature mode and a low-temperature mode; the high-temperature mode is used for normalizing, quenching, and high-temperature tempering; the low-temperature mode is used for medium-temperature tempering and low-temperature tempering.

[0014] Further, in the high-temperature mode, only the radiant tube heating system 4 is used for heating; in the low-temperature mode, the radiant tube heating system 4 and the protective atmosphere circulating low-temperature heating system 5 are used for combined heating; the boundary temperature between the high-temperature mode and the low-temperature mode is 400°C.

[0015] Further, the heating section 1 is heated by the radiant tube heating system 4, and the furnace temperature of the heat treatment furnace is set higher than the target temperature of the steel plate, and the temperature of the steel plate is calculated according to the in-furnace time and the length of the heating section 1.

[0016] Further, the protective atmosphere nozzle group 12 adopts pulse jet control; the pulse jet frequency is closed-loop automatically controlled with the furnace temperature and the furnace pressure to ensure that the furnace is under positive pressure control of 10 Pa - 30 Pa.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] Since this heat treatment furnace has a dual heating function of a radiant tube heating system and a protective atmosphere circulating low-temperature heating system, the radiant tube heating system can meet the capabilities of normalizing, quenching, and high-temperature tempering of the steel plate under a protective atmosphere, and the protective atmosphere circulating low-temperature heating system can achieve medium and low-temperature tempering capabilities. At medium and low temperatures, the protective atmosphere nozzle group makes the furnace gas stir more violently, realizing the furnace temperature uniformity; at the same time, the flue gas at a fixed temperature impacts the steel plate through the jet of the protective atmosphere nozzle group, enhancing the convective heat transfer coefficient and improving the heating efficiency.

[0019] The present invention has the ability to meet all heat treatment processes of normalizing, quenching, high-temperature tempering, medium and low-temperature tempering of high-strength steel plates under a protective atmosphere with one furnace type, providing flexible adaptability for products. One furnace type can be built to adapt to the production of different orders, reducing investment and increasing production capacity. The use temperature of the heat treatment furnace can be changed from the conventional 500 - 1000°C to 100 - 1000°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0021] Figure 1 Schematic structural diagram of a radiant tube heat treatment furnace with a protective atmosphere circulating low-temperature heating

[0022] Figure 2 Schematic structural diagram of the heating section of the heat treatment furnace

[0023] Figure 3 Schematic structural diagram of the soaking section and heat preservation section of the heat treatment furnace

[0024] Figure 4 Schematic partial structural diagram of the radiant tube heating system

[0025] Figure 5 Schematic partial structural diagram of the protective atmosphere circulating low-temperature heating system

[0026] In the figure: 1 - heating section; 2 - soaking section; 3 - heat preservation section; 4 - radiant tube heating system; 5 - protective atmosphere circulating low-temperature heating system; 6 - burner a; 7 - closed radiant tube; 8 - gas pipeline; 9 - air pipeline; 10 - exhaust pipeline; 11 - sealed circulating fan; 12 - protective atmosphere nozzle group; 13 - radiant tube type heating box; 14 - cut-off valve; 15 - pipeline; 16 - thermocouple; 17 - burner b; 18 - closed radiant tube; 19 - cold nitrogen gas regulating valve. Specific implementation mode

[0027] The present invention provides a radiant tube heat treatment furnace with a protective atmosphere circulating low-temperature heating. The radiant tube heating system is arranged in the heating section, soaking section, and heat preservation section of the heat treatment furnace, and the protective atmosphere circulating low-temperature heating system is arranged in the soaking section and heat preservation section of the heat treatment furnace.

[0028] As Figure 1 shown, the heat treatment furnace of the present invention is divided into three heating sections, namely heating section 1, soaking section 2, and heat preservation section 3. A radiant tube heating system and a protective atmosphere circulating low-temperature heating system are arranged on the same heat treatment furnace. The radiant tube heating system 4 is arranged in heating section 1, soaking section 2, and heat preservation section 3, and the protective atmosphere circulating low-temperature heating system 5 is arranged in soaking section 2 and heat preservation section 3. The two heating systems are evenly arranged up and down on the furnace rolls on both sides of the furnace chamber of the heat treatment furnace. The two heating systems can not only meet the working range of 100 - 1000 degrees, but also have the ability to heat under a protective atmosphere in terms of structure.

[0029] The working state of the heat treatment furnace of the present invention is divided into a high-temperature mode (including normalizing, quenching, and high-temperature tempering) and a low-temperature mode (including medium-temperature and low-temperature tempering). In the high-temperature mode, the heat treatment furnace of the present invention only uses the radiant tube heating system 4 for heating. In the low-temperature mode, the radiant tube heating system 4 and the protective atmosphere circulating low-temperature heating system 5 are used for combined heating. The boundary temperature between the high-temperature mode and the low-temperature mode can be adjusted as needed, generally 400 °C.

[0030] As Figure 2 shown, radiant tube heating systems 4 are respectively arranged on the upper and lower layers of the heating section 1. The above-mentioned radiant tube heating systems 4 are used to heat the steel plate in the high-temperature mode and the low-temperature mode.

[0031] As Figure 3 shown, radiant tube heating systems 4 and protective atmosphere circulation low-temperature heating systems 5 are respectively arranged on the upper and lower layers of the soaking section 2 and the heat preservation section 3. In the high-temperature mode, the above-mentioned radiant tube heating systems 4 are used to heat the steel plate. In the low-temperature mode, the above-mentioned radiant tube heating systems 4 and the protective atmosphere circulation low-temperature heating systems 5 work simultaneously to heat the steel plate. In both modes, the furnace is ensured to be in a protective atmosphere.

[0032] As Figure 4 shown, the radiant tube heating system 4 is composed of a burner a6, a closed radiant tube 7, a gas pipeline 8, an air pipeline 9 and an exhaust pipeline 10. The above-mentioned radiant tube heating system 4 is installed on the furnace wall. The closed radiant tube 7 is inside the furnace, and the burner a6 is installed inside the closed radiant tube 7.

[0033] In the high-temperature mode and the low-temperature mode, the radiant tube heating system 4 is involved in the work. Gas enters the burner a6 through the gas pipeline 8 and air enters through the air pipeline 9 to burn. The high-temperature flue gas generated by the combustion transfers heat to the furnace through the closed radiant tube 7 and is then discharged through the exhaust pipeline 10, completing the heating process of the steel plate.

[0034] As Figure 5 shown, the protective atmosphere circulation low-temperature heating system 5 is composed of a sealed circulation fan 11, a protective atmosphere nozzle group 12, a radiant tube heating box 13, a cut-off valve 14 and a pipeline 15. The above-mentioned cut-off valve 14 is installed on the top of the furnace and communicates with the furnace; the above-mentioned radiant tube heating box 13 is installed on the cut-off valve 14; the inlet of the above-mentioned sealed circulation fan 11 is connected to the radiant tube heating box 13, and the outlet is connected to the pipeline 15; one end of the above-mentioned protective atmosphere nozzle group 12 is connected to the pipeline 15 and the other end is installed on the furnace wall; a thermocouple 16, a burner b17, a closed radiant tube 18 and a cold nitrogen regulating valve 19 are installed on the above-mentioned radiant tube heating box 9.

[0035] When in the high-temperature mode (above 400 °C), the protective atmosphere circulating low-temperature heating system 5 does not participate in the operation. The above-mentioned cut-off valve 14 is in the closed state, and the sealed circulating fan 11 is in the shutdown state. When in the low-temperature mode (below 400 °C), the above-mentioned radiant tube heating system 4 and the protective atmosphere circulating low-temperature heating system 5 work simultaneously. Specifically, the above-mentioned cut-off valve 14 is opened, and the furnace protective atmosphere enters the temperature-adjusting heating box 13. The protective atmosphere is heated by the heating system composed of the burner b17 and the closed radiant tube 18 or cooled by supplying cold nitrogen through the cold nitrogen regulating valve 19 to adjust to a constant temperature. The constant temperature is detected by the thermocouple 16. The heating or cooling of the temperature-adjusting box is controlled by the temperature detected by the thermocouple 16. The protective atmosphere after reaching the constant temperature is pressurized by the above-mentioned sealed circulating fan 11 and enters the pipeline 15. The pressure of the protective atmosphere is pressurized to 2-8 kPa. The protective atmosphere with a certain pressure is sprayed into the furnace at high speed through the above-mentioned nozzle group 12 to heat the steel plate.

[0036] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating, characterized in that: A radiant tube heating system (4) and a protective atmosphere circulating low-temperature heating system (5) are arranged simultaneously on the same heat treatment furnace; the radiant tube heating system is arranged in the heating section (1), the soaking section (2), and the insulation section (3) of the heat treatment furnace; the protective atmosphere circulating low-temperature heating system (5) is arranged in the soaking section (2) and the insulation section (3) of the heat treatment furnace; the two heating systems are evenly arranged up and down on the furnace rollers on both sides of the heat treatment furnace.

2. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to claim 1, characterized in that: The two heating systems in the soaking section (2) and the heat preservation section (3) are alternately arranged in the upper and lower layers of furnace rollers on both sides of the furnace chamber of the heat treatment furnace.

3. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to claim 1, characterized in that: The radiant tube heating system (4) is mainly composed of a burner a (6), a pipeline, and a closed radiant tube (7); the pipeline is divided into a gas pipeline (8), an air pipeline (9), and a smoke exhaust pipeline (10); the gas pipeline (8) and the air pipeline (9) are respectively connected to the burner a (6), and the gas and air are sent into the burner a (6) for combustion; the burner a (6) is connected to the closed radiant tube (7), and the closed radiant tube (7) extends into the heat treatment furnace; the smoke exhaust pipeline (10) is connected to the closed radiant tube (7), and the high-temperature smoke passes through the closed radiant tube (7) to exchange heat with the steel plate and is then discharged through the smoke exhaust pipeline (10), and the closed radiant tube (7) is used to ensure that the protective atmosphere of the furnace is not affected by the smoke.

4. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to claim 1, characterized in that: The protective atmosphere circulation low-temperature heating system (5) is mainly composed of a sealed circulation fan (11), a shut-off valve (14), a protective atmosphere nozzle group (12), a radiation tube heating box (13) and a pipeline (15); one end of the shut-off valve (14) is connected to the top outlet of the heat treatment furnace, and the other end is connected to the radiation tube heating box (13); the shut-off valve (14) is closed in the high-temperature mode, and is opened in the low-temperature mode; The inlet of the sealed circulating fan (11) is connected to the radiation tube heating box (13), and the outlet of the sealed circulating fan (11) is connected to the pipeline (15); the pipeline (15) is arranged along the length of the heat treatment furnace as a main pipeline, and the main pipeline is divided into a plurality of branch pipelines, and the ends of the branch pipelines are connected to the protective atmosphere nozzle group (12); the protective atmosphere nozzle group (12) is connected to the heat treatment furnace through the furnace wall opening.

5. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to claim 4, characterized in that: The radiation tube type heating box (13) is mainly composed of a burner b (17), a closed radiation tube (18), a cold nitrogen regulating valve (19) and a thermocouple (16); the burner b (17) is connected to the closed radiation tube (18), and the closed radiation tube (18) extends from one end of the radiation tube type heating box (13) to heat the protective atmosphere; a plurality of cold nitrogen regulating valves (19) are arranged in the radiation tube type heating box (13) to release cold nitrogen; and the thermocouple (16) is located at the other end of the radiation tube type heating box (13).

6. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to claim 4, characterized in that: The protective atmosphere is sucked out from the furnace of the heat treatment furnace by a sealed circulation fan (11) and pressurized. After the protective atmosphere is temperature-controlled by a radiation tube heating box (13), it is sprayed into the furnace of the heat treatment furnace through a pipeline (15) and a protective atmosphere nozzle group (12). The protective atmosphere is circulated and adjusted to a target temperature, thereby enhancing the convection heat exchange between the furnace of the heat treatment furnace and the steel plate.

7. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to any one of claims 1 to 6, characterized in that: The working state is divided into a high temperature mode and a low temperature mode; the high temperature mode is used for normalizing, quenching, and high temperature tempering; the low temperature mode is used for medium temperature tempering and low temperature tempering.

8. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to claim 7, characterized in that: In the high temperature mode, only the radiation tube heating system (4) is used for heating; in the low temperature mode, a combination of the radiation tube heating system (4) and the protective atmosphere circulation low temperature heating system (5) is used for heating; the boundary temperature between the high temperature mode and the low temperature mode is 400°C.

9. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to any one of claims 1 to 6, characterized in that: The heating section (1) is heated by a radiant tube heating system (4), the temperature of the heat treatment furnace is set higher than the target temperature of the steel plate, and the temperature of the steel plate is calculated based on the time in the furnace and the length of the heating section (1).

10. The radiant tube heat treatment furnace with protective atmosphere circulation low temperature heating according to any one of claims 1 to 6, characterized in that: The protective atmosphere nozzle group (12) adopts pulse jet control; the pulse jet frequency is automatically controlled in a closed loop with the furnace temperature and the furnace pressure to ensure that the furnace is under positive pressure control of 10Pa-30Pa.

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