WO2023232159A1 - Method for heat treatment of austenitic stainless steel bar by means of induction heating - Google Patents

Abstract

The present invention provides a method for the heat treatment of an austenitic stainless steel bar by means of induction heating. The method comprises: placing a hot-rolled austenitic stainless steel bar on a conveying roller, and then subjecting same to a high-temperature solution treatment and a rapid cooling treatment to obtain a completely austenitized stainless steel bar, wherein in the high-temperature solution treatment, the hot-rolled austenitic stainless steel bar is subjected to induction heating by means of an induction heating device. The method for the heat treatment of an austenitic stainless steel bar by means of induction heating of the present invention realizes online continuous transmission production, and has the advantages of a high automation degree, a fast heating speed and a short heat preservation time after the solid solution temperature is reached. In the present invention, the temperature of the austenitic stainless steel bar can be made uniform in the heating depth and the radial direction by adjusting the induction heating frequency, such that the whole cross section of the austenitic stainless steel bar is uniformly heated, and complete austenitization is achieved.

Description

An induction heating heat treatment method for austenitic stainless steel rods Technical field

The invention belongs to the technical field of heat treatment of metal materials, and specifically relates to an induction heating heat treatment method of austenitic stainless steel rods.

Background technique

1Cr18Ni9Ti is one of the most commonly used austenitic stainless steels. It has good heat resistance, corrosion resistance, welding, plasticity, strength and other properties. It is widely used in the preparation of aviation instruments and precision non-magnetic parts. Due to the precipitation of carbides on the grain boundaries of 1Cr18Ni9Ti in the hot-rolled state, the material hardness is relatively high and the plasticity and corrosion resistance are reduced. It needs to be solid solution treated before subsequent processing. The currently commonly used solution treatment method is to use a trolley furnace/roller hearth furnace to heat to the austenite range and then water-cool it to eliminate rolling stress, roll strips, carbides, etc. to obtain a complete austenite structure; for rolling As for the bars, since the bars are long (usually more than 5m) and the bars are stacked together, the cooling speeds in each section of the water cooling process vary greatly, and the bars are severely bent and deformed; on the one hand, the deformed bars have increased correction It is difficult to straighten; on the other hand, the large deformation of the bar during the straightening process leads to martensitic transformation, and the material hardness increases rapidly, which increases the difficulty of subsequent processing (Figure 1 shows the hot-rolled bar passing through the trolley furnace/ The metallographic structure of the austenitic stainless steel bar obtained after solution treatment and straightening treatment in the roller hearth furnace. The metallographic structure has obvious deformation texture, and the measured surface hardness is as high as 297HBW); therefore, the solid solution of the long bar The bending problem is a major problem that plagues on-site production.

Contents of the invention

In view of the shortcomings and defects of the existing technology, the present invention aims to provide an induction heating heat treatment method for austenitic stainless steel rods, wherein the induction heating heat treatment specifically uses an induction heating device to heat the hot-rolled austenitic stainless steel rods. The material is subjected to high-temperature solution treatment; the induction heating heat treatment method in the present invention is an online continuous transmission production, which has the advantages of high degree of automation, fast heating speed, and short holding time after reaching the solid solution temperature; in the present invention, by adjusting the induction heating frequency , can make the austenitic stainless steel rod achieve uniform temperature in the heating depth and radial direction, thereby ensuring that the entire cross-section of the austenitic stainless steel rod is heated evenly and achieving complete austenitization.

In order to achieve the above object, the present invention provides an induction heating heat treatment method for austenitic stainless steel rods, adopting the following technical solution:

An induction heating heat treatment method for austenitic stainless steel rods, including: placing the hot-rolled austenitic stainless steel rods on a transfer roller, and then performing high-temperature solution treatment and rapid cooling to obtain completely austenitized stainless steel rods;

Wherein, in the high-temperature solution treatment, an induction heating device is used to conduct induction heating on the hot-rolled austenitic stainless steel bar.

The main structure of the hot-rolled stainless steel bar in the present invention is an austenite structure, but there are more carbides precipitated at the grain boundaries (carbides are not austenite structures), which results in high hardness, plasticity and corrosion resistance. Performance decline; the present invention can achieve complete austenitization by performing high-temperature solid solution treatment and rapid cooling treatment on the hot-rolled austenitic stainless steel bar through an induction heating device (including an induction coil and a matching intermediate frequency power supply). The stainless steel rods can be delivered without straightening, thereby avoiding problems such as further increase in hardness caused by straightening deformation.

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, in the high temperature solid solution treatment, the induction heating is divided into a temperature increasing section and a heat preservation section; preferably, the induction Heating is divided into heating section I, heating section II, and heating section III. The heating section I and heating section II are the temperature increasing section, and the heating section III is the heat preservation section.

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, in the high temperature solid solution treatment, the holding temperature (solid solution temperature) of the heating section III is 1040-1060°C ( For example, 1042℃, 1045℃, 1050℃, 1053℃, 1055℃, 1058℃), the holding time is 30-60s (such as 32s, 35s, 40s, 45s, 50s, 55s).

In the high-temperature solution treatment of the present invention, a relatively high heating rate can be used in the temperature increasing section to make the surface temperature of the rod reach the solid solution temperature when entering the heat preservation section. The temperature increasing section is set to heating section I and heating section II. It is helpful to adjust the heating rate of the rod according to the specifications of the rod. If the holding temperature of the heating section III, that is, the solid solution temperature, is lower than 1040°C, the solid solution will be insufficient and a complete austenite structure will not be obtained; if the holding temperature of the heating section III, that is, the solid solution temperature, is higher than 1060°C, Then the grain growth trend is obvious, and the grain size is easily unqualified.

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, in the high temperature solid solution treatment, the induction heating device includes a plurality of induction coils and an intermediate frequency power supply adapted to them, The induction coil surrounds the hot-rolled austenitic stainless steel bar in the shape of a spring. The intermediate frequency power supply controls the induction coil to the hot-rolled austenitic stainless steel bar through the output voltage, output current and induction heating frequency. Perform induction heating.

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, in the high temperature solid solution treatment, in the heating section I, the output voltage of the intermediate frequency power supply is 500-700V (such as 550V , 600V, 620V, 650V), the output current is 80-300A (such as 100A, 150A, 200A, 250A), and the induction heating frequency is 2000-4000Hz (such as 2500Hz, 2700Hz, 3000Hz, 3500Hz); in the heating section II, The output voltage of the intermediate frequency power supply is 500-700V (such as 550V, 600V, 620V, 650V), the output current is 80-300A (such as 100A, 150A, 200A, 250A), and the induction heating frequency is 2000-4000Hz (such as 2500Hz, 2700Hz, 3000Hz, 3500Hz); in the heating section III, the output voltage of the intermediate frequency power supply is 400-600V (such as 450V, 480V, 520V, 550V), the output current is 30-150A (such as 50A, 80A, 100A, 120A), and the induction The heating frequency is 2000-4000Hz (such as 2500Hz, 2700Hz, 3000Hz, 3500Hz); more preferably, the induction heating frequencies in the heating section I, heating section II and heating section III are the same.

In the present invention, the heating power of the induction coil is further controlled by controlling the output voltage and output current of the intermediate frequency power supply (i.e. P=UI). The greater the heating power, the faster the heating speed; the induction heating frequency causes the induction heating coil to generate an alternating magnetic field. Then, the hot-rolled stainless steel bar is heated by generating eddy current. The induction heating frequency affects the heating depth of the bar and the temperature uniformity in the radial direction; and the present invention limits the induction heating frequency to the range of 2000-4000Hz, which can make The austenitic stainless steel rod achieves uniform temperature in the heating depth and radial direction, thereby ensuring uniform heating of the entire cross-section of the austenitic stainless steel rod and achieving complete austenitization.

The use of induction coils for induction heating mainly follows the basic principles of electromagnetic induction, skin effect and heat conduction. The material has two forms of penetration heating and conductive heating during the heating process. Since the high-temperature solid solution treatment of the present invention is an online continuous transmission In production, the holding time after reaching the solid solution temperature is short. Therefore, in order to ensure uniform solid solution, the current penetration depth needs to be greater than the radius of the rod, and the current penetration depth is inversely proportional to the induction heating frequency, so the higher the induction heating frequency. If the induction heating frequency is higher than 4000Hz, the current penetration depth will be small, resulting in uneven temperature inside and outside the rod. The austenite structure of the material is uneven.

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, the roller speed of the conveyor roller is 1-2 m/min (such as 1.2 m/min, 1.4 m/min, 1.5 m/min, 1.8 m/min, 1.9 m/min).

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, water cooling treatment is used in the rapid cooling treatment; preferably, the water cooling treatment is: after the high-temperature solid solution treatment is completed , the bar enters the spray ring under the transmission of the transmission roller for water spraying. The spray direction of the spray ring is perpendicular to the transmission direction of the transmission roller.

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, in the water cooling treatment, the flow rate of water spray is 30-80m³/h (such as 40m³/h, 45 m³/h, 50 m³/h, 55 m³/h, 60 m³/h, 65 m³/h, 70 m³/h, 75 m³/h), the duration of water spraying on the bar at the same position is 15-30s (such as 18s, 20s ,22s,25s,27s,29s).

In the water cooling treatment of the present invention, if the water spray flow rate is lower than 30 m³/h, the bar will be insufficiently cooled, resulting in an increase in the hardness of the bar, and a fully austenitized stainless steel bar cannot be obtained; if the water spray flow rate is greater than 80 m³/h, the cooling rate will be too fast and the bar will easily bend.

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, the grade of the hot-rolled austenitic stainless steel rods is 1Cr18Ni9Ti, and the chemical composition in mass percentage is: C≤0.12%, Si≤0.80%, Mn≤2.00%, P≤0.035%, S≤0.020%, Cr 17.0-19.0% (such as 17.3%, 17.5%, 18.0%, 18.2%, 18.5%), Ni 8.0-11.0% (such as 8.2%, 8.5%, 9.0%, 9.5%, 10.0%), Ti 5*(C-0.02)~0.80% (where C is the carbon content in the steel), and the rest are iron and inevitable impurity elements.

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, the diameter of the hot-rolled austenitic stainless steel rods is 20-50mm (such as 25mm, 30mm, 35mm, 40mm, 45mm , 48mm), length 5m-9m (such as 5.5m, 6m, 6.5m, 7m, 8m, 8.5m).

In the above induction heating heat treatment method of austenitic stainless steel rods, as a preferred embodiment, the hardness of the fully austenitized stainless steel rods is ≤187HBW, the flatness is ≤4mm/m, and the grain size is ≥ Level 5.

Compared with the prior art, the present invention has the following advantages:

(1) The induction heating heat treatment method in the present invention has the advantages of high degree of automation, fast heating speed, and short holding time after reaching the solid solution temperature;

(2) The fully austenitized stainless steel rod obtained by the induction heating heat treatment method of the present invention has a hardness ≤ 187 HBW, a flatness ≤ 4 mm/m, and a grain size ≥ level 5.

(3) The fully austenitized stainless steel rod obtained by the induction heating heat treatment method of the present invention has a short heating time, no burning loss on the surface, no heating defects, and good surface quality; the rod has small thermal deformation and does not need to be straightened. This can meet the requirements of the agreement and avoid surface hardening problems caused by straightening processing.

Description of the drawings

Figure 1 is a metallographic structure diagram of an austenitic stainless steel bar obtained after solid solution treatment and straightening treatment in the prior art;

Figure 2 is a schematic structural diagram of the induction heating heat treatment method of the present invention;

Figure 3 is a metallographic structure diagram of the surface of the fully austenitized stainless steel rod obtained in Example 4 of the present invention;

Fig. 4 is a metallographic structure diagram of the core portion of the fully austenitized stainless steel rod obtained in Example 4 of the present invention.

Explanation of reference signs: 1. Transfer roller; 2. Induction heating device; 21. First induction coil; 22. Second induction coil; 23. Third induction coil; 24. First intermediate frequency power supply; 25. Second intermediate frequency power supply ; 26. The third intermediate frequency power supply; 3. Spray ring; 4. Hot-rolled austenitic stainless steel bars.

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art fall within the scope of protection of the present invention.

The raw materials described in the following examples can be obtained from public commercial channels; the grade of hot-rolled austenitic stainless steel rod used in the following examples is 1Cr18Ni9Ti, and the mass percentage of each element component is as shown in Table 1;

Table 1 The mass percentage of each element component in the hot-rolled austenitic stainless steel bar grade 1Cr18Ni9Ti (the balance is Fe and inevitable impurities)

A specific embodiment of the present invention provides an induction heating heat treatment method for austenitic stainless steel rods. The schematic structural diagram is shown in Figure 2 and includes: driving the hot-rolled austenitic stainless steel rods 4 along their length direction. The moving transfer roller 1, the induction heating device 2 and the spray ring 3 are arranged in sequence along the transmission direction of the hot-rolled austenitic stainless steel bar 4; the spray direction of the spray ring 3 is perpendicular to the direction of the transfer roller 1 In the transmission direction, the induction heating device 2 includes a plurality of spring-shaped induction coils surrounding the stainless steel rod and an intermediate frequency power supply adapted to the induction coils; in the embodiment of the present invention, three induction coils are used to heat the hot-rolled Austrian steel rods. The stainless steel rod 4 is subjected to induction heating (multiple induction coils can also be used for induction heating), which are respectively marked as the first induction coil 21, the second induction coil 22 and the third induction coil 23, and the matching intermediate frequency power supply Marked as the first intermediate frequency power supply 24, the second intermediate frequency power supply 25, and the third intermediate frequency power supply 26, the first induction coil 21 corresponds to the heating section I in the induction heating, and the second induction coil 22 corresponds to the heating section II in the induction heating. The third induction coil 23 corresponds to the heating section III (solid solution temperature) in induction heating;

The induction heating heat treatment specifically includes the following steps:

(1) Place the hot-rolled austenitic stainless steel bar 4 (diameter 20-50mm, length 5m-9m) on the transfer roller 1. The roller speed of the transfer roller 1 is 1-2 m/min.

(2) The induction heating device 2 is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel bar 4. The induction heating is divided into heating section I, heating section II and heating section III. The heating section I and the heating section II are: Heating temperature raising section, heating section III is the heat preservation section, in which the temperature (solid solution temperature) of the heating section III is 1040-1060°C, and the heat preservation time is 30-60s; in the heating section I, the output voltage of the first intermediate frequency power supply 24 is 500-700V, the output current is 80-300A, and the induction heating frequency is 2000-4000Hz; in the heating section II, the output voltage of the second intermediate frequency power supply 25 is 500-700V, the output current is 80-300A, and the induction heating frequency is 2000 -4000Hz; in the heating section III, the output voltage of the third intermediate frequency power supply 26 is 400-600V, the output current is 30-150A, and the induction heating frequency is 2000-4000Hz; in order to ensure the uniformity of heating, it is preferred to set the Induction heating frequency is consistent.

(3) After the high-temperature solution treatment is completed, the bar is transported by the transfer roller 1 and enters the spray ring 3 for water cooling treatment. The spray direction of the spray ring 3 is perpendicular to the transmission direction of the transfer roller 1, and the flow rate of the water spray is The temperature is 30-80m³/h, and the duration of water spraying on the rod at the same position is 15-30s. After water-cooling treatment, a fully austenitized stainless steel rod is obtained.

Embodiment 1 An induction heating heat treatment method for austenitic stainless steel rods, including:

(1) Place the hot-rolled austenitic stainless steel bar (diameter 20mm, length 9m) on the transfer roller. The roller speed of the transfer roller is 1.8m/min.

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Warm section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1050°C, and the insulation time is 33s; the output voltage of the first intermediate frequency power supply is 600V, the output current is 100A, and the induction heating frequency is 3000Hz; the output voltage of the second intermediate frequency power supply is 620V, the output current is 110A, and the induction heating frequency is 3000Hz; the output voltage of the third intermediate frequency power supply is 450V, the output current is 50A, and the induction heating frequency is 3000Hz.

(3) After the high-temperature solution treatment is completed, the bar immediately enters the spray ring under the transmission of the conveyor roller for water spraying. The flow rate of the water spray is 40m³/h. The duration of water spraying on the bar at the same position is 17 seconds. Completely austenitized stainless steel rods were obtained.

Embodiment 2 An induction heating heat treatment method for austenitic stainless steel rods, including:

(1) Place the hot-rolled austenitic stainless steel bar (diameter 25mm, length 8m) on the transfer roller. The roller speed of the transfer roller is 1.7m/min.

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Warm section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1045°C, and the insulation time is 35s; the output voltage of the first intermediate frequency power supply is 610V, the output current is 110A, and the induction heating frequency is 2800Hz; the output voltage of the second intermediate frequency power supply is 630V, the output current is 120A, and the induction heating frequency is 2800Hz; the output voltage of the third intermediate frequency power supply is 460V, the output current is 60A, and the induction heating frequency is 2800Hz.

(3) After the high-temperature solution treatment is completed, the bar immediately enters the spray ring under the transmission of the conveyor roller for water spraying. The flow rate of the water spray is 45m³/h. The duration of water spraying on the bar at the same position is 18 seconds. Completely austenitized stainless steel rods were obtained.

Embodiment 3 An induction heating heat treatment method for austenitic stainless steel rods, including:

(1) Place the hot-rolled austenitic stainless steel bar (diameter 30mm, length 7.5m) on the transfer roller. The roller speed of the transfer roller is 1.6m/min.

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Temperature section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1048°C, and the insulation time is 38s; the output voltage of the first intermediate frequency power supply is 625V, the output current is 125A, and the induction heating frequency is 2600Hz; the output voltage of the second intermediate frequency power supply is 650V, the output current is 135A, and the induction heating frequency is 2600Hz; the output voltage of the third intermediate frequency power supply is 475V, the output current is 65A, and the induction heating frequency is 2600Hz.

(3) After the high-temperature solution treatment is completed, the bar immediately enters the spray ring under the transmission of the conveyor roller for water spraying. The flow rate of the water spray is 50m³/h. The duration of water spraying on the bar at the same position is 19 seconds. Completely austenitized stainless steel rods were obtained.

Embodiment 4 An induction heating heat treatment method for austenitic stainless steel rods, including:

(1) Place the hot-rolled austenitic stainless steel bar (diameter 35mm, length 7m) on the transfer roller. The speed of the transfer roller is 1.5m/min.

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Temperature section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1052°C, and the insulation time is 40s; the output voltage of the first intermediate frequency power supply is 640V, the output current is 140A, and the induction heating frequency is 2400Hz; the output voltage of the second intermediate frequency power supply is 660V, the output current is 155A, and the induction heating frequency is 2400Hz; the output voltage of the third intermediate frequency power supply is 480V, the output current is 70A, and the induction heating frequency is 2400Hz.

(3) After the high-temperature solution treatment is completed, the bar immediately enters the spray ring under the transmission of the conveyor roller for water spraying. The flow rate of the water spray is 55m³/h. The duration of water spraying on the bar at the same position is 20s. A fully austenitized stainless steel rod was obtained, and the metallographic structure diagrams of its surface and core are shown in Figures 3 and 4 respectively.

Embodiment 5 An induction heating heat treatment method for austenitic stainless steel rods, including:

(1) Place the hot-rolled austenitic stainless steel bar (diameter 40mm, length 6.5m) on the transfer roller. The roller speed of the transfer roller is 1.4m/min.

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Temperature section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1055°C, and the insulation time is 43s; the output voltage of the first intermediate frequency power supply is 650V, the output current is 145A, and the induction heating frequency is 2300Hz; the output voltage of the second intermediate frequency power supply is 670V, the output current is 160A, and the induction heating frequency is 2300Hz; the output voltage of the third intermediate frequency power supply is 485V, the output current is 75A, and the induction heating frequency is 2300Hz.

(3) After the high-temperature solution treatment is completed, the bar immediately enters the spray ring under the transmission of the transfer roller for water spraying. The flow rate of the water spray is 58m³/h. The duration of water spraying on the bar at the same position is 21s. Completely austenitized stainless steel rods were obtained.

Embodiment 6 An induction heating heat treatment method for austenitic stainless steel rods, including:

(1) Place the hot-rolled austenitic stainless steel bar (diameter 45mm, length 6m) on the transfer roller. The roller speed of the transfer roller is 1.3m/min.

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Temperature section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1055°C, and the insulation time is 46s; the output voltage of the first intermediate frequency power supply is 665V, the output current is 170A, and the induction heating frequency is 2200Hz; the output voltage of the second intermediate frequency power supply is 680V, the output current is 185A, and the induction heating frequency is 2200Hz; the output voltage of the third intermediate frequency power supply is 490V, the output current is 78A, and the induction heating frequency is 2200Hz.

(3) After the high-temperature solution treatment is completed, the bar immediately enters the spray ring under the transmission of the conveyor roller for water spraying. The flow rate of the water spray is 65m³/h. The duration of water spraying on the bar at the same position is 23s. Completely austenitized stainless steel rods were obtained.

Embodiment 7 An induction heating heat treatment method for austenitic stainless steel rods, including:

(1) Place the hot-rolled austenitic stainless steel bar (diameter 50mm, length 5m) on the transfer roller. The speed of the transfer roller is 1.2m/min.

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Warm section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1058°C, and the insulation time is 50s; the output voltage of the first intermediate frequency power supply is 675V, the output current is 185A, and the induction heating frequency is 2000Hz; the output voltage of the second intermediate frequency power supply is 690V, the output current is 190A, and the induction heating frequency is 2000Hz; the output voltage of the third intermediate frequency power supply is 495V, the output current is 85A, and the induction heating frequency is 2000Hz.

(3) After the high-temperature solution treatment is completed, the bar immediately enters the spray ring under the transmission of the conveyor roller for water spraying. The flow rate of the water spray is 75m³/h. The duration of water spraying on the bar at the same position is 25s. Completely austenitized stainless steel rods were obtained.

Comparative Example 1 An induction heating heat treatment method for austenitic stainless steel rods, including:

In Comparative Example 1, except that step (2) is different from Example 1, the rest are the same as Example 1;

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Temperature section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1020°C, and the insulation time is 33s; the output voltage of the first intermediate frequency power supply is 500V, the output current is 95A, and the induction heating frequency is 3000Hz; the output voltage of the second intermediate frequency power supply is 580V, the output current is 100A, and the induction heating frequency is 3000Hz; the output voltage of the third intermediate frequency power supply is 400V, the output current is 40A, and the induction heating frequency is 3000Hz.

Comparative Example 2 An induction heating heat treatment method for austenitic stainless steel rods, including:

In Comparative Example 2, except that step (2) is different from Example 1, the rest are the same as Example 1;

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Warm section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1070°C, and the insulation time is 33s; the output voltage of the first intermediate frequency power supply is 650V, the output current is 110A, and the induction heating frequency is 3000Hz; the output voltage of the second intermediate frequency power supply is 650V, the output current is 120A, and the induction heating frequency is 3000Hz; the output voltage of the third intermediate frequency power supply is 480V, the output current is 60A, and the induction heating frequency is 3000Hz.

Comparative Example 3 An induction heating heat treatment method for austenitic stainless steel rods, including:

In Comparative Example 3, except that step (2) is different from Example 1, the rest are the same as Example 1;

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Warm section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1050°C, and the insulation time is 33s; the output voltage of the first intermediate frequency power supply is 650V, the output current is 180A, and the induction heating frequency is 1800Hz; the output voltage of the second intermediate frequency power supply is 650V, the output current is 170A, and the induction heating frequency is 1800Hz; the output voltage of the third intermediate frequency power supply is 500V, the output current is 90A, and the induction heating frequency is 1800Hz.

Comparative Example 4 An induction heating heat treatment method for austenitic stainless steel rods, including:

In Comparative Example 4, except that step (2) is different from Example 1, the rest are the same as Example 1;

(2) An induction heating device is used to perform high-temperature solid solution treatment on the hot-rolled austenitic stainless steel rods. Induction heating is divided into heating section I, heating section II and heating section III. Heating section I and heating section II provide heating. Temperature section, heating section III is the insulation section, where the temperature (solid solution temperature) of heating section III is 1050°C, and the insulation time is 33s; the output voltage of the first intermediate frequency power supply is 580V, the output current is 90A, and the induction heating frequency is 5000Hz; the output voltage of the second intermediate frequency power supply is 590V, the output current is 100A, and the induction heating frequency is 5000Hz; the output voltage of the third intermediate frequency power supply is 400V, the output current is 50A, and the induction heating frequency is 5000Hz.

Performance testing

[Amended in accordance with Rule 26 26.07.2023]
The rods obtained in Examples 1-7 and Comparative Examples 1-4 of the present invention were subjected to hardness testing (performed with reference to GBT231.1-2018), flatness testing (performed with reference to T/SSEA 0069-2020), and metallographic Microstructure testing was performed using a microscope, and the test results are shown in Table 2.

Among them, A refers to austenite and F refers to ferrite.

Although Comparative Example 2 is qualified, the grain size is close to the required lower limit, and there is a risk of failure during mass production.

The above descriptions are only preferred embodiments of the present invention and are 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 the pending rights of the present invention. within the scope of protection required.

Claims (5)

1. An induction heating heat treatment method for austenitic stainless steel rods, which is characterized by: placing the hot-rolled austenitic stainless steel rods on a transfer roller, and then performing high-temperature solution treatment and rapid cooling to obtain a completely austenitic stainless steel bar. Tempered stainless steel rods;

   Wherein, in the high-temperature solution treatment, an induction heating device is used to conduct induction heating on the hot-rolled austenitic stainless steel bar;

   In the high-temperature solution treatment, the induction heating is divided into a temperature increasing section and a heat preservation section;

   The induction heating is divided into heating section I, heating section II, and heating section III. The heating section I and heating section II are the temperature increasing section, and the heating section III is the heat preservation section;

   The heat preservation temperature of the heating section III is 1040-1060°C, and the heat preservation time is 30-60s;

   In the high-temperature solution treatment, in the heating section I, the output voltage of the intermediate frequency power supply is 500-700V, the output current is 80-300A, and the induction heating frequency is 2000-4000Hz; in the heating section II, the intermediate frequency power supply The output voltage is 500-700V, the output current is 80-300A, and the induction heating frequency is 2000-4000Hz; in the heating section III, the output voltage of the intermediate frequency power supply is 400-600V, the output current is 30-150A, and the induction heating frequency is 2000-4000Hz;

   The induction heating frequencies in the heating section I, heating section II and heating section III are the same;

   In the rapid cooling process, water cooling is used;

   In the water cooling treatment, the flow rate of water spraying is 30-80m³/h, and the duration of water spraying on the rod at the same position is 15-30s;

   The grade of the hot-rolled austenitic stainless steel bar is 1Cr18Ni9Ti, and its chemical composition in mass percentage is: C≤0.12%, Si≤0.80%, Mn≤2.00%, P≤0.035%, S≤0.020%, Cr 17.0 -19.0%, Ni 8.0-11.0%, Ti 5*(C-0.02)~0.80%, the rest is iron and inevitable impurity elements;

   The hot-rolled austenitic stainless steel rod has a diameter of 20-50mm and a length of 5m-9m.
2. The heat treatment method according to claim 1, characterized in that, in the high-temperature solid solution treatment, the induction heating device includes a plurality of induction coils and a matching intermediate frequency power supply, and the induction coils are surrounded by springs. For the hot-rolled austenitic stainless steel bar, the intermediate frequency power supply controls the induction coil to conduct induction heating of the hot-rolled austenitic stainless steel bar through the output voltage, output current and induction heating frequency.
3. The heat treatment method according to claim 1, characterized in that the roller speed of the conveying roller is 1-2 m/min.
4. The heat treatment method according to claim 1, characterized in that the water cooling treatment specifically includes: after the high-temperature solution treatment is completed, the bar enters the spray ring under the transmission of the transmission roller to spray water, and the spray ring sprays water. The shower direction is perpendicular to the transmission direction of the conveyor roller.
5. The heat treatment method according to claim 1, characterized in that the hardness of the fully austenitized stainless steel rod is ≤187HBW, the flatness is ≤4mm/m, and the grain size is ≥5 levels.