A mist cooling device for super long round steel and normalizing process for SA182F11 super long round steel

Abstract

The present invention provides a mist cooling device for super-long round steel and a normalizing treatment process of SA182F11 super-long round steel using the mist cooling device. The mist cooling device is arranged behind an induction heating furnace. The mist cooling device is in the shape of a gyroscopic body as a whole and a through hole is arranged in the center of the mist cooling device along its axial direction for super-long round steel to pass through. The mist cooling device has multiple mist cooling rings evenly distributed along its axial direction, and the mist cooling ring has multiple nozzles evenly distributed along its circumference, and the spray medium of the nozzle is water mist. By adding a mist cooling unit after the induction heating furnace, the cooling intensity is improved. In the normalizing treatment process of the present invention, the steel is heated to 930-950°C in an induction heating furnace for insulation, and a continuous spray cooling method is adopted at the same time to obtain a pearlite + ferrite structure in equilibrium, which exhibits higher high-temperature endurance strength.

Description

Technical Field

[0001] The invention belongs to the field of super-long round steel, and in particular relates to a mist cooling device for super-long round steel and a normalizing process for SA182F11 super-long round steel. Background Art

[0002] Among the super-long steel varieties, SA182F11 material is often used to make boiler hangers. Boiler hangers are important load-bearing parts used in high-temperature environments. Their function is to hang the boiler body on the boiler top beam. They bear a large load and the operating temperature is 400-600℃, which requires higher high-temperature endurance strength.

[0003] During the processing, SA182F11 material is generally treated with normalizing to obtain a balanced pearlite + ferrite structure, which has little effect on the structural transformation when used in a high temperature environment; while annealing treatment cannot meet the strength requirements for use. As for quenching and tempering treatment, although it can achieve better mechanical properties, the high temperature environment has a greater impact on the structural transformation. Therefore, normalizing treatment is still a commonly used processing method for SA182F11 material.

[0004] The main specifications of SA182F11 super-long round steel are within 90mm in diameter and 9 to 12m in length. Traditional normalizing treatment is generally carried out in a trolley furnace, using gas flame heating, which has high requirements on the length and temperature uniformity of the furnace, huge investment and high production cost; at the same time, due to the long length of SA182F11 round steel, the steel is placed on the pad for heating and insulation, which is easy to bend. The bent steel needs to be straightened, which increases the waste of manpower and material costs; after the steel is air-cooled after being taken out of the furnace, it is impossible to ensure that the cooling rate of each part of such a long steel is consistent, resulting in a large dispersion of various performance indicators such as the organization and hardness of SA182F11 round steel, and local performance defects seriously affect the high-temperature endurance strength. Summary of the invention

[0005] In order to overcome the problems in the prior art of normalizing SA182F11 ultra-long round steel, such as high production cost, easy bending of steel and large dispersion of performance indicators of various parts of the steel, one of the purposes of the present invention is to propose a mist cooling device for ultra-long round steel, by adding a mist cooling unit after the induction heating furnace, thereby improving the cooling intensity.

[0006] The second purpose of the present invention is to propose a normalizing treatment process for SA182F11 ultra-long round steel. In the normalizing treatment process, the steel is heated to 930-950°C in an induction heating furnace and simultaneously a continuous spray cooling method is adopted to obtain a balanced pearlite + ferrite structure, which exhibits higher high temperature endurance strength.

[0007] In order to achieve the first object of the present invention, the present invention provides the following technical solutions:

[0008] A mist cooling device for super-long round steel, the mist cooling device is in the shape of a hollow gyroscope as a whole, and comprises:

[0009] A plurality of mist cooling rings are evenly distributed along the axial direction, and the axial center line of the mist cooling ring is on the same straight line as the axial center line of the mist cooling device. The through holes in the middle of the mist cooling ring are connected to form a cavity for the extra-long round steel to pass through. The inner side of the mist cooling ring is evenly provided with a plurality of nozzles along its circumference for spraying cooling medium onto the extra-long round steel.

[0010] The roller table penetrates the mist cooling device along the axial direction of the mist cooling device and is used for running the super-long round steel from one end to the other end of the mist cooling device.

[0011] In the mist cooling device for super-long round steel as described above, preferably, the nozzle is connected to a cooling water source and a pressurized air source at the same time, and the cooling water source and the pressurized air source are mixed in the nozzle to form the cooling medium.

[0012] In the mist cooling device for super-long round steel as described above, preferably, the mist cooling ring is in the shape of a square ring, and the nozzles are arranged at the four corners of the mist cooling ring.

[0013] In the mist cooling device for super-long round steel as described above, preferably, the two diagonal lines of the mist cooling ring extend in the vertical direction and the horizontal direction respectively.

[0014] The mist cooling device for super-long round steel as described above preferably further comprises: four spray pipes, which are arranged on the outer wall of the mist cooling device along the axial direction of the mist cooling device, and the nozzle is connected to the spray pipes adjacent to the nozzle;

[0015] Preferably, four injection pipes pass through the four corners of all the mist cooling rings.

[0016] As described above, the mist cooling device of the extra-long round steel, preferably, the mist cooling device further comprises a plurality of supporting feet, the supporting feet are evenly distributed along the axial direction of the mist cooling device and are arranged at the bottom end of the mist cooling device.

[0017] In order to achieve the second object of the present invention, the present invention provides the following technical solutions:

[0018] A normalizing process for SA182F11 super-long round steel comprises: normalizing heating the round steel rolled piece in a single linear operation mode in an induction heating furnace, and then cooling the super-long round steel at a cooling rate of 3-7°C / s using the mist cooling device.

[0019] In the normalizing treatment process of SA182F11 ultra-long round steel as described above, preferably, during the normalizing heating, the round steel rolled piece runs in the induction heating furnace and sequentially passes through the heating section and the insulation section in the induction heating furnace, the heating temperature of the heating section is 900-950°C, the insulation temperature of the insulation section is 930-950°C, and the insulation time is 4-10 minutes.

[0020] In the normalizing process of SA182F11 ultra-long round steel as described above, preferably, the round steel rolled piece is obtained through a rolling process, and the rolling process includes heating treatment, rolling treatment and post-rolling cooling treatment of the billet, wherein the holding temperature of the heating treatment is 1150-1250°C, the starting temperature of the rolling treatment is ≤1100°C, preferably 1000-1100°C, the final rolling temperature is ≤1000°C, preferably 830-1000°C, and the cooling rate of the post-rolling cooling treatment is 0.5-1°C / s.

[0021] In the normalizing process of SA182F11 super-long round steel as described above, preferably, when the round steel rolled piece is cooled to below 200° C. by the mist cooling device, the round steel rolled piece is taken out of the mist cooling device and then air-cooled.

[0022] Compared with the closest prior art, the technical solution provided by the present invention has the following beneficial effects:

[0023] The present invention is the first to create a super-long round steel mist cooling device. After the round steel is normalized, it is cooled by mist cooling. Specifically, the mist cooling device of the present invention has a plurality of mist cooling rings evenly distributed along the axial direction, and the mist cooling ring has a plurality of nozzles evenly distributed along the circumferential direction. While the round steel runs along the axial direction of the mist cooling device, the nozzle sprays cooling medium on the surface of the round steel, thereby cooling the round steel. Therefore, the mist cooling device of the present invention can achieve uniform cooling of the entire round steel, the cooling rate of each part of the round steel is consistent, and the uniformity of various performance indicators such as the structure and hardness of the produced round steel is high. In addition, the cooling medium sprayed by the nozzle is composed of a cooling water source and a pressurized air source, and has a good cooling effect and a high cooling intensity.

[0024] Based on the above-mentioned mist cooling device, the present invention also provides a normalizing treatment method for SA182F11 ultra-long round steel by induction heating and then mist cooling. The induction heating furnace is used for heating, which avoids the problems of large investment and high cost caused by using a trolley furnace. At the same time, the induction heating furnace can achieve uniform heating. The round steel is heated in the induction heating furnace at a single uniform speed and rotates uniformly, which avoids bending of the steel and does not require straightening treatment. After induction heating, the present invention adopts mist cooling, which has high cooling intensity and can achieve uniform cooling of the entire round steel. The cooling rate of each part of the round steel is consistent. The uniformity of various performance indicators such as the structure and hardness of the produced round steel is high, which solves the problems of uneven steel structure and large performance fluctuations. Products that meet the structure and performance requirements can be obtained, the product quality is improved, the production efficiency is improved, and the equipment investment is small and the production cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the mist cooling device of the present invention;

[0026] Figure 2 for Figure 1 A schematic diagram of the structure of the mist cooling ring;

[0027] Figure 3 Metallographic photograph of the extra-long round steel produced by the production process of the present invention;

[0028] Figure 4 This is a metallographic photograph of the extra-long round steel produced in Comparative Example 1;

[0029] Figure 5 This is a metallographic photograph of the extra-long round steel produced in Comparative Example 2;

[0030] Figure 6 This is a schematic diagram of sampling for round steel performance testing;

[0031] Figure 1 and 2 Middle: 1. Mist cooling ring; 2. Spray pipe; 3. Nozzle; 4. Support foot. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0033] like Figure 1 and 2As shown, according to an embodiment of the present invention, a mist cooling device for super-long round steel is provided. The super-long round steel has a large size along its length direction, and is usually more than 3 meters in length. The air cooling or wind cooling cooling method used in the prior art cannot ensure that the cooling rate of each part of the round steel is consistent, which will lead to uneven internal structure of the steel and large performance dispersion, and local performance defects will seriously restrict the performance of the entire super-long round steel. The mist cooling device of the present invention is in the shape of a hollow gyroid as a whole, such as a hollow cylinder, a hollow regular quadrangular prism, etc. The mist cooling device includes: a plurality of mist cooling rings 1 evenly distributed along its axial direction, and the axial center line of the mist cooling ring 1 is on the same straight line as the axial center line of the mist cooling device, the through hole in the middle of the mist cooling ring 1 is connected to form a cavity for the super-long round steel to pass through, and the inner side of the mist cooling ring 1 is evenly provided with a plurality of nozzles 3 along its circumference, which are used to spray cooling medium to the super-long round steel; a roller, which runs through the mist cooling device along the axial direction of the mist cooling device, is used to run the super-long round steel from one end of the mist cooling device to the other end. When in use, the super-long round steel runs axially in the center of the mist cooling ring 1, that is, the center of the mist cooling device. Under the spraying action of the evenly arranged nozzles 3, each part of the super-long round steel evenly exchanges heat with the cooling medium, thereby ensuring that the cooling rate of each part of the round steel is consistent, the organization is highly uniform, and the performance is also uniform and consistent.

[0034] In a specific embodiment of the present invention, the nozzle 3 is connected to a cooling water source and a pressurized air source at the same time, and the cooling water source and the pressurized air source are mixed in the nozzle 3 to form the cooling medium. The temperature of the cooling water source is 20-25°C, and the flow rate is 0.01-0.03m 3 / min, the pressure of the pressurized air source is 0.45-0.55Mpa, and the flow rate is 8-12m 3 / min.

[0035] In a specific embodiment of the present invention, the mist cooling ring 1 is in a square ring shape, and the nozzles 3 are arranged at the four corners of the mist cooling ring 1. Preferably, the two diagonal lines of the mist cooling ring 1 extend in the vertical direction and the horizontal direction respectively (so that the placement and fixation are more secure). The present invention adopts the shape of a square ring so that the steel can be evenly cooled during the cooling process, so that the entire cross-section of the steel has a uniform structure;

[0036] In a specific embodiment of the present invention, it also includes: four injection pipes 2, which are arranged on the outer wall of the mist cooling device along the axial direction of the mist cooling device, and the nozzle 3 is connected to the injection pipe 2 adjacent to the nozzle 3; preferably, the four injection pipes 2 pass through all four corners of the mist cooling ring 1, and the inlet ends of the injection pipes 2 are simultaneously connected to the cooling water source and the pressurized air source; it should be noted that, according to the concept of uniform cooling of the present invention, the four injection pipes 2 should be connected to the same cooling water source and the same pressurized air source.

[0037] In a specific embodiment of the present invention, the mist cooling device further comprises a plurality of legs 4, the legs 4 are evenly distributed along the axial direction of the mist cooling device and are arranged at the bottom end of the mist cooling device, and the legs 4 are used to support the mist cooling device to ensure that it is stably placed.

[0038] Example 1

[0039] like Figure 1 and 2 As shown, the total length of the mist cooling device in this embodiment is 3000mm (the length of the mist cooling device is adjusted according to the actual need of the round steel length), which is arranged behind the induction heating furnace, and the distance between the mist cooling device and the induction heating furnace is 300mm, and the induction heating furnace and the mist cooling device share the same roller, which is composed of rollers arranged at equal intervals along the axial direction of the induction heating furnace, and the rollers are placed at an angle of 30°, thereby driving the steel to rotate at a uniform speed, and the round steel passes through the induction heating furnace and the mist cooling device in sequence during the rotation process.

[0040] The side length of the mist cooling ring 1 is 480 mm, the ring width (ring thickness) of the mist cooling ring 1 is 40 mm, the diameter of the nozzle is 50 mm, the mist cooling ring 1 has a total of 16 sections (the number of sections of the mist cooling ring is adjusted according to the actual needs of the round steel length), and the support legs 4 are a total of 4, and the support legs 4 include a base plate horizontally arranged on the ground and the extension direction of the base plate is perpendicular to the axial direction of the mist cooling device, and vertical plates are symmetrically arranged at both ends of the base plate, and the top ends of the two vertical plates are respectively connected to the two symmetrical corners of the mist cooling ring 1 along the horizontal direction, thereby supporting the mist cooling device.

[0041] On the basis of the above-mentioned mist cooling device, an embodiment of the present invention also provides a normalizing treatment process for SA182F11 super-long round steel. SA182F11 material is often used to make boiler hangers, which are important load-bearing parts used in high-temperature environments and require high high-temperature endurance strength. The existing normalizing treatment process easily leads to uneven internal structure of the steel and large performance dispersion, and local performance defects will seriously restrict the performance of the entire super-long round steel. To this end, the embodiment of the present invention includes the following steps:

[0042] Rolling process: The round steel rolled piece is obtained by a rolling process, and the rolling process includes heating treatment, rolling treatment and cooling treatment after rolling of the billet, the holding temperature of the heating treatment is 1150-1250°C (such as 1155°C, 1180°C, 1200°C, 1220°C, 1230°C, 1245°C), the starting temperature of the rolling treatment is below 1100°C, preferably 1000-1100°C (such as 1090°C, 1050°C, 1000°C), and the final rolling temperature is below 1000°C, preferably 8 30~1000℃ (such as 995℃, 970℃, 930℃, 905℃, 850℃), the cooling rate of the post-rolling cooling treatment is 0.5~1.5℃ / s (the rolled steel is placed on a cooling bed and a heat preservation cover is put down for heat preservation, and the cooling rate is controlled to be 0.5~1.5℃ / s, such as 0.8℃ / s, 1℃ / s, 1.2℃ / s), when cooled to below 400℃ (such as 390℃, 380℃, 370℃, 350℃), leave the cooling bed, perform stack cooling, cool to room temperature and then transfer to the heat treatment furnace;

[0043] The present invention adopts a high temperature heating temperature of 1150-1250° C. in the rolling process, which can ensure that the C, Mn, Cr and Mo elements are fully and evenly diffused, so that the austenite grain size exceeds the width of the original banded strip; at the same time, the start rolling temperature is controlled at 1000-1100° C., and the final rolling temperature is controlled at 830-1000° C., and a relatively high final rolling deformation temperature is maintained, so that the rolled steel enters cooling in the two-phase region, and at a cooling rate of 0.5-1° C. / s, the long-distance diffusion of C on the original banded base is suppressed, the formation of ferrite and pearlite banded structures is controlled, and finally a material with uniform structure is obtained.

[0044] Induction heating normalizing process: heating is carried out in a single straight line operation mode in an induction heating furnace (the operation speed is generally 0.7-1.3 m / min), the working frequency of the induction heating furnace is 3000-4000 Hz, the round steel rolled piece runs in the induction heating furnace and passes through the heating section and the insulation section in the induction heating furnace in sequence (the induction heating furnace includes multiple sections of inductors, and generally the first several sections of inductors that the steel enters are used for heating and heating, so the several sections of inductors used for heating and heating are recorded as the heating section; the several sections of inductors that pass through subsequently are used for insulation, so the several sections of inductors used for insulation are recorded as the insulation section), the heating temperature of the heating section is 900-950°C, the insulation temperature of the insulation section is 930-950°C, and the insulation time is 4-10 min.

[0045] The Ac3 temperature of SA182F11 material is about 890°C. Normalizing needs to be heated to 30-50°C above Ac3 to make the steel completely austenitized. Too high a temperature wastes resources, and too low a temperature cannot completely transform the structure. Therefore, the present invention selects a normalizing holding temperature of 930-950°C.

[0046] Cooling process: The mist cooling device of the super long round steel as described above is used for cooling. If the cooling speed is too slow, the cooling effect cannot be achieved. If it is too fast, it will transform into martensite structure, affecting the high temperature service life. Therefore, the cooling speed of the present invention is 3-7°C / s.

[0047] The air cooling speed varies according to the temperature of the original steel. Generally, the higher the temperature, the faster the cooling. According to actual on-site measurements, for steel with a steel temperature of 600°C, air cooling is placed for about 30 minutes, the temperature drops by about 200-250°C, and the cooling speed is less than 0.2°C / s, which is very slow. The air cooling speed is about 0.5-1°C / s, but air cooling is difficult to control and cannot be cooled evenly. The present invention adopts a mist cooling method with a cooling speed of 3-7°C / s, a high cooling intensity, and can achieve uniform cooling of the entire round steel, and the cooling rate of each part of the round steel is consistent.

[0048] In a specific embodiment of the present invention, as a preferred embodiment, in the rolling process, the start rolling temperature is 1000-1100°C.

[0049] In a specific embodiment of the present invention, as a preferred embodiment, in the rolling process, the final rolling temperature is 830-1000°C.

[0050] In a specific embodiment of the present invention, as a preferred scheme, in the cooling process, the cooling speed is controlled by adjusting the flow rate of the cooling water source, the pressure and flow rate of the pressurized air source, and the travel speed of the round steel. When the round steel rolled piece is cooled to below 200°C, preferably 180-200°C, by the mist cooling device, the round steel rolled piece is taken out of the mist cooling device and then air-cooled.

[0051] In a specific embodiment of the present invention, as a preferred solution, the diameter of the produced super-long round steel is Φ20-90 mm and the length is more than 3 m.

[0052] Example 2

[0053] This embodiment is used to produce extra-long round steel for SA182F11 boiler suspension rod. The round steel specification is The specific production process is as follows:

[0054] (1) Rolling process: The raw material is SA182F11 continuous casting 240mm wide * 240mm high * 9m long square billet, which is rolled into φ50mm * 10000mm round steel on a three-roller sizing mill. The specific rolling process parameters are: heating temperature 1200℃, starting rolling temperature 1050℃, final rolling temperature 900℃, placed on a cooling bed for cooling after rolling, and a heat preservation cover can be put down for heat preservation. The cooling rate is controlled at 0.8-1.0℃ / s. When cooled to below 400℃, it leaves the cooling bed and is pile-cooled. After cooling to room temperature, it is transferred to a heat treatment furnace;

[0055] (2) Medium frequency induction heating normalizing process: A seven-section medium frequency induction heating furnace is used (the first three sections are used for heating, and the last four sections are used for heat preservation). Each section of the induction heating furnace is 1200 mm long, and the spacing between adjacent induction heating furnaces is 300 mm. The induction coil is fixed on the roller table. A single round steel is linearly moved and rotated in the induction coil for heating. The round steel running speed is 1 m / min, the induction coil working frequency is 4000 Hz, the total power is 1600 kW, the round steel heating temperature is 930°C, the heat preservation temperature is 950°C, and the heat preservation time is 5.7 min.

[0056] (3) Cooling process:

[0057] Due to the high temperature of the induction heating furnace, in order to ensure safe production, the position of the mist cooling device and the induction heating furnace cannot be too close. According to the distance between the mist cooling device and the induction heating furnace in Example 1, the round steel enters the mist cooling device about 18 seconds after being heated in the induction heating furnace. By adjusting the flow rate of the cooling water source and the pressure and flow of the pressurized air source, in this embodiment, the temperature of the cooling water source is 25°C and the flow rate is 0.01m 3 / min, the pressure of the pressurized air source is 0.45Mpa, and the flow rate is 9m 3 / min, the round steel still adopts a single linear and rotating operation mode in the mist cooling device, and the operation speed of the round steel is generally 0.7-1.3m / min, and specifically 1m / min in this embodiment, thereby controlling the cooling rate within the range of 3-4℃ / s. When the temperature of the round steel drops to 200℃, it exits the mist cooling device and then is air-cooled.

[0058] Example 3

[0059] This embodiment is used to produce extra-long round steel for SA182F11 boiler suspension rod. The round steel specification is The specific production process is as follows:

[0060] (1) Rolling process: the raw material is SA182F11 continuous casting 240*240mm high*9m long square billet, the heating temperature is 1210℃, the starting rolling temperature is 1060℃, the final rolling temperature is 910℃, and it is placed on the cooling bed for cooling after rolling. The heat preservation cover can be put down for heat preservation. The cooling rate is controlled at 1.0~1.3℃ / s. When it is cooled to below 400℃, it leaves the cooling bed and is pile-cooled. After cooling to room temperature, it is transferred to the heat treatment furnace;

[0061] (2) Medium frequency induction heating normalizing process: The induction coil of the induction heating furnace has an operating frequency of 3500 Hz, a total power of 1500 kW, a round steel running speed of 1.3 m / min, a round steel heating temperature of 925°C, a holding temperature of 945°C, and a holding time of 4.5 min;

[0062] (3) Cooling process:

[0063] The mist cooling device of Example 1 is used, and the flow rate of the cooling water source and the pressure and flow rate of the pressurized air source are adjusted. In this embodiment, the temperature of the cooling water source is 25°C, the flow rate is 0.02m 3 / min, the pressure of the pressurized air source is 0.50Mpa, and the flow rate is 8m 3 / min, the round steel still adopts a single linear and rotating operation mode in the mist cooling device, and the round steel running speed is 1.3m / min, thereby controlling the cooling rate within the range of 4-5℃ / s. When the temperature of the round steel drops to 160℃, it exits the mist cooling device and then is air-cooled.

[0064] Example 4

[0065] This embodiment is used to produce extra-long round steel for SA182F11 boiler suspension rod. The round steel specification is The specific production process is as follows:

[0066] (1) Rolling process: the raw material is SA182F11 continuous casting 240*240mm high*9m long square billet, the heating temperature is 1220℃, the starting rolling temperature is 1100℃, the final rolling temperature is 930℃, and it is placed on the cooling bed for cooling after rolling. The heat preservation cover can be put down for heat preservation. The cooling rate is 0.5~0.8℃ / s. When it is cooled to below 400℃, it leaves the cooling bed and is pile-cooled. After cooling to room temperature, it is transferred to the heat treatment furnace;

[0067] (2) Medium frequency induction heating normalizing process: The induction coil of the induction heating furnace has an operating frequency of 4000 Hz, a total power of 1600 kW, a round steel running speed of 0.8 m / min, a round steel heating temperature of 935°C, a holding temperature of 955°C, and a holding time of 8.5 min;

[0068] (3) Cooling process:

[0069] The mist cooling device of Example 1 is used, and the flow rate of the cooling water source and the pressure and flow rate of the pressurized air source are adjusted. In this embodiment, the temperature of the cooling water source is 22°C, the flow rate is 0.03m 3 / min, the pressure of the pressurized air source is 0.55Mpa, and the flow rate is 10m 3 / min, the round steel still adopts a single straight line operation mode in the mist cooling device, and the round steel running speed is 0.8m / min, thereby controlling the cooling rate to be 2.5-3.5℃ / s. When the temperature of the round steel drops to 180℃, it leaves the mist cooling device and then is air-cooled.

[0070] Comparative Example 1

[0071] Except for the cooling process which is slightly different from that of Example 2, Comparative Example 1 is the same as Example 2. The cooling method adopted in Comparative Example 1 is air cooling, that is, air cooling is performed by a fan, and after cooling to around 300° C., air cooling is performed.

[0072] Comparative Example 2

[0073] Comparative Example 2 is the same as Example 2 except that the cooling process is slightly different from that of Example 2. The cooling method adopted in Comparative Example 2 is air cooling, that is, natural cooling in the air.

[0074] Organization comparison: Example 2 ( Figure 3 ) and Comparative Example 1 ( Figure 4 ) and Comparative Example 2 ( Figure 5 ) compared to round steel, the internal structure of round steel is ferrite + pearlite structure, with little difference.

[0075] The round steel produced in Examples 2 to 4 of the present invention is qualified after ultrasonic and magnetic particle testing, the ultrasonic testing meets the requirements of GB / T 4162A level, and the depth of surface defects is less than or equal to 0.2 mm;

[0076] The mechanical properties of Examples 2 to 4 and Comparative Examples 1 and 2 were tested at the same time. The performance tests of all lengths were carried out on Example 2, Comparative Examples 1 and 2. When sampling the round steel of Example 2, Comparative Examples 1 and 2, the round steel of Example 2, Comparative Examples 1 and 2 was tested according to Figure 6 As shown, the head and tail of the round steel are cut off, and then samples are taken from the front, middle and back of the round steel for performance testing. The mechanical properties of the remaining embodiments and comparative examples are tested as a whole, which are summarized in the following Table 1:

[0077] Table 1 Mechanical properties test results

[0078]

[0079] It can be seen from the mechanical property test results in Table 1 that, on the basis of the same normalizing process, the cooling methods of wind cooling and air cooling respectively adopted in Examples 1 and 2 have an important impact on the strength of the super-long round steel, especially the tensile strength which is crucial for the use of super-long round steel. The tensile strength of the entire length of Example 2 tested is 625 / 626 / 640, the tensile strength of the entire length of Example 1 tested is 492 / 526 / 554, and the tensile strength of the entire length of Example 2 tested is 534 / 508 / 517. It can be seen that the average tensile strength of Examples 1 and 2 is significantly lower than the average tensile strength of Example 2, and the tensile strength of the round steel at different positions of Examples 1 and 2 is quite different, which cannot meet customer requirements; in addition to tensile strength, the yield strength, hardness, etc. of Examples 1 and 2 have large differences in numerical distribution within the entire length of the round steel, with large fluctuations and unevenness. In comparison, the mechanical properties of the round steel obtained in Example 2 fluctuate less over the entire length (for the head, middle and tail material collection in Example 2, the full-length hardness fluctuation range is within 14HBW; the hardness difference of the same section is within 5HBW), and the full-length hardness deviation of Example 3 is also within 4HBW. This proves that the mist cooling method of the present invention can achieve uniform cooling of various parts of the round steel and obtain better mechanical properties, especially the tensile strength, which is increased by nearly 100Mpa, which is of great significance for the service life of the boiler boom under high load.

[0080] In summary, the present invention also has the following technical effects:

[0081] 1) SA182F11 round steel with a specification of Φ20-90mm can obtain a normalized structure of uniformly distributed blocky ferrite + lamellar pearlite by using the normalizing process of the present invention (such as Figure 3 ), the actual grain size can be controlled between 6 and 10 levels.

[0082] 2) The hardness of SA182F11 round steel with a specification of Φ20-90mm produced by the present invention is as follows: the cross-sectional hardness is 164-184HBW; for the same specification batch of steel, the full-length hardness dispersion can be controlled within ≤15HBW, and the cross-sectional hardness dispersion can be controlled within ≤10HBW.

[0083] 3) The deformation of steel after induction normalizing is very small and no straightening is required. The curvature of the round steel produced by the induction heating normalizing treatment of the present invention is within 2 mm / m and no straightening is required.

[0084] 4) The present invention has no restrictions on the length of the steel material, and the steel material can be any length, preferably a steel material with a length of more than 3m.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the claims of the present invention.

Claims

1. A normalizing process for super-long round steel for SA182F11 boiler suspension rod, characterized in that: include: The round steel rolled piece is normalized and heated by a single round steel running linearly and rotating in a medium frequency induction heating furnace, and then cooled by a mist cooling device at a cooling rate of 3-4°C / s. During the normalizing heating, the round steel rolled piece runs in the induction heating furnace and sequentially passes through the heating section and the insulation section in the induction heating furnace, the running speed is 1m / min, the heating temperature of the heating section is 930°C, the insulation temperature of the insulation section is 950°C, and the insulation time is 5.7min. The round steel rolled piece is obtained by a rolling process, and the rolling process includes heating treatment, rolling treatment and post-rolling cooling treatment of the billet; the heating temperature of the heating treatment in the rolling process is 1200°C, the starting rolling temperature of the rolling treatment is 1050°C, the final rolling temperature is 900°C, and the cooling rate of the post-rolling cooling treatment is 0.8-1°C / s; The specification of round steel is Φ50mm*10000mm; The mist cooling device is in the shape of a hollow gyroscope as a whole, and comprises: A plurality of mist cooling rings are evenly distributed along the axial direction, and the axial center line of the mist cooling ring is on the same straight line as the axial center line of the mist cooling device. The through holes in the middle of the mist cooling ring are connected to form a cavity for the extra-long round steel to pass through. The inner side of the mist cooling ring is evenly provided with a plurality of nozzles along its circumference for spraying cooling medium onto the extra-long round steel. A roller conveyor is inserted into the mist cooling device along the axial direction of the mist cooling device, and is used to move the super-long round steel from one end of the mist cooling device to the other end. The roller conveyor is composed of rollers arranged at equal intervals, and the rollers are placed at an angle of 30 degrees, thereby being able to drive the steel to rotate at a uniform speed, and the induction heating furnace and the mist cooling device share the same roller conveyor. The mist cooling device is arranged behind the induction heating furnace, and the round steel passes through the induction heating furnace and the mist cooling device in sequence during the rotating process; The mist cooling ring is in a square ring shape, and the nozzles are arranged at the four corners of the mist cooling ring. The nozzles are connected to the cooling water source and the pressurized air source at the same time, and the cooling water source and the pressurized air source are mixed in the nozzle to form the cooling medium. The temperature of the cooling water source is 25°C and the flow rate is 0.01m 3 / min, the pressure of the pressurized air source is 0.45Mpa, and the flow rate is 9 m 3 / min; The two diagonal lines of the mist cooling ring extend in the vertical direction and the horizontal direction respectively. The mist cooling device further comprises a plurality of legs, which are evenly distributed along the axial direction of the mist cooling device and are arranged at the bottom end of the mist cooling device, the legs comprise a bottom plate horizontally arranged on the ground and the extension direction of the bottom plate is perpendicular to the axial direction of the mist cooling device, vertical plates are symmetrically arranged at both ends of the bottom plate, and the top ends of the two vertical plates are respectively connected to two symmetrical corners of the mist cooling ring along the horizontal direction, thereby supporting the mist cooling device; It also includes: four spray pipes, which are arranged on the outer wall of the mist cooling device along the axial direction of the mist cooling device, and the nozzle is connected to the spray pipes adjacent to the nozzle; Four injection pipes pass through the four corners of all the mist cooling rings; the inlet ends of the injection pipes are simultaneously connected to a cooling water source and a pressurized air source; the four injection pipes are connected to the same cooling water source and the same pressurized air source.

2. The normalizing process for the super-long round steel for SA182F11 boiler suspension rod according to claim 1, characterized in that: When the round steel rolled piece is cooled to below 200° C. by the mist cooling device, the round steel rolled piece is taken out from the mist cooling device and then air-cooled.

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