Multi-steel-grade online salt bath production process method and online salt bath device

Abstract

The invention relates to a multi-steel-grade online salt bath production process method and an online salt bath device.The method comprises the steps that a rolled finished wire rod is spun and laid to a Stelmor air cooling line, and the finished wire rod is cooled and pre-cooled to a first set temperature through the Stelmor air cooling line; the pre-cooled finished wire rod is conveyed to an online salt bath device for temperature control and isothermal phase transformation of the finished wire rod, and the temperature interval and the cooling rate in the online salt bath device can be adjusted; and the finished wire rod obtained after salt bath phase change is completed is conveyed back to the Stelmor air cooling line to be continuously cooled to the second set temperature. Isothermal phase transformation is completed through online salt bath, the sorbite rate and the structure property uniformity of the medium-high carbon steel are improved, and an offline salt bath process is replaced, so that energy-saving, emission-reducing and green production is realized; and by flexibly controlling the temperature interval and the cooling rate of structure transformation of the finished wire rod, the requirements of various different steel types can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of wire rod heat treatment, and in particular to an online salt bath production process method for multiple steel grades and an online salt bath device. Background Art

[0002] The Stelmor cooling process was jointly developed by Canada's Steyrco Steel Company and the United States' Morgan Company in 1964. It is currently the most commonly used wire rod controlled cooling process (see the layout diagram of the Stelmor cooling line area of ​​the conventional wire rod production line for details). Figure 6 After the finished wire rods rolled out of conventional high-speed wire production lines pass through the spinning machine, the high-temperature (about 900°C) single-layer coils are in a lapped state (the state of the coils on the Stelmor air-cooled line is shown in the figure). Figure 7 ) is laid flat on the Stelmor cooling line and transported by conveyor rollers to the coiling station for collection. The coil undergoes microstructural phase transformation during its transport along the cooling line, achieving its final mechanical properties. Because different steel grades require different mechanical properties, the cooling rate is controlled by adjusting the roller speed to control the coil spacing, the number of fans activated below the roller, the air volume of each fan, the air volume distribution between overlapped and non-overlapped points, and the opening and closing of the insulation hood to achieve the ideal metallographic structure.

[0003] The main disadvantages of this cooling process are as follows:

[0004] (1) The wind blown out by the fan flows out from the gap of the roller. This is often due to the limited air volume of the fan, the large wind resistance of the roller gap, and the unstable wind pressure, which leads to insufficient cooling rate. Especially when producing large-sized coils, the temperature difference between the core surface is large, the cooling is not thorough, the core tissue layer spacing is large, and the sorbite ratio is low.

[0005] (2) The coils overlap closely at the overlap points, the coil gaps at the non-overlap points are relatively large, the air volume distribution is uneven, the coil temperatures at the overlap points and the non-overlap points differ by 40 to 100°C, the coil pass performance is poorly uniform, and the strength fluctuates by about 80 MPa.

[0006] (3) In the face of the above-mentioned problems such as insufficient cooling capacity and difficulty in meeting performance standards, the only option is to use offline lead / salt bath heat treatment technology. However, offline treatment requires the coil that has been cooled to room temperature to be reheated to the austenitizing temperature and then subjected to controlled cooling treatment again, which results in high energy consumption, high carbon emissions, and serious environmental pollution.

[0007] In order to meet the cooling process requirements of high, medium and low carbon steel, especially to solve the shortcomings of large performance fluctuation and instability during production, a high-speed wire online heat treatment equipment and process (CN 116287664A) is disclosed in the prior art. Figure 8As shown, this technology performs online rapid cooling quenching-isothermal-controlled cooling-cleaning on the high-temperature wire rod to inhibit the precipitation of secondary network carbides of hypereutectoid steel and tertiary cementite of hypoeutectoid steel, and treats the bainite / bainite of the wire rod to achieve the goals of high-speed wire online production with high efficiency, good surface quality, high strength, good plasticity, good toughness, good uniformity of mechanical properties in the same circle, and energy saving and emission reduction.

[0008] Compared with the disadvantages of conventional Stelmor cooling lines, the aforementioned existing technical solution realizes the sorbite / bainite treatment, structural uniformity and surface quality control of wire rods by setting up online rapid cooling tanks and isothermal tanks. However, the following defects still exist: the lengths of the rapid cooling tanks and isothermal tanks remain unchanged, and the passing time is the same when producing different steel grades, making it impossible to achieve precise cooling rate control.

[0009] Therefore, the inventors, relying on their many years of experience and practice in related industries, have proposed an online salt bath production process method and an online salt bath device for multiple steel grades to overcome the defects of the prior art. Summary of the Invention

[0010] The purpose of the present invention is to provide an online salt bath production process method and an online salt bath device for multiple steel grades. The present invention completes isothermal phase transformation through an online salt bath, improves the sorbite rate and uniformity of microstructure and performance of medium and high carbon steels, and replaces the offline salt bath process, thereby achieving energy conservation, emission reduction and green production. By flexibly controlling the temperature range and cooling rate of the finished wire rod microstructure transformation, the present invention can meet the needs of various different steel grades.

[0011] The object of the present invention is achieved in this way. A multi-grade steel online salt bath production process method is provided. The finished wire rod after rolling is laid on a Stelmore air cooling line, and the finished wire rod is pre-cooled to a first set temperature through the Stelmore air cooling line. The pre-cooled finished wire rod is transported to an online salt bath device for temperature control and isothermal phase transformation of the finished wire rod. The temperature range and cooling rate in the online salt bath device are adjustable; the finished wire rod after the salt bath phase transformation is completed is transported back to the Stelmore air cooling line to continue cooling to a second set temperature.

[0012] In a preferred embodiment of the present invention, the finished wire rod after pre-cooling is transported to an online salt bath device for temperature control and isothermal phase transformation of the finished wire rod, comprising:

[0013] Step S1: After pre-cooling, the finished wire rod enters the pre-cooling zone of the online salt bath device, where a molten salt solution for cooling is provided. The finished wire rod is cooled to the phase change starting temperature by the molten salt solution in the pre-cooling zone;

[0014] Step S2: After cooling, the finished wire rod enters the uniform temperature zone of the online salt bath device. The uniform temperature zone is provided with a uniform temperature salt solution. The finished wire rod is temperature-homogenized in the uniform temperature zone. The travel speed and travel length of the finished wire rod in the uniform temperature zone are regulated to complete the isothermal phase transition of the structure; thus, the finished wire rod is subjected to sorbitization.

[0015] Step S3: The finished wire rod that has completed the phase change rises and leaves the uniform temperature zone of the online salt bath device.

[0016] In a preferred embodiment of the present invention, the finished wire rod after completing the salt bath phase change is returned to the Stelmor air cooling line for surface treatment, including: after the finished wire rod leaves the uniform temperature zone, it is transported into the surface washing area of ​​the online salt bath device to completely wash away the residual salt solution on the surface and blow it dry with high-pressure air.

[0017] In a preferred embodiment of the present invention, after the finished wire rod is transported back to the Stelmor air cooling line, the air cooling line fan is turned on to cool the finished wire rod after the salt bath phase change to a second set temperature, and the second set temperature is less than or equal to 400°C.

[0018] In a preferred embodiment of the present invention, the finished wire rod is spun by a spinning machine, and a pre-cooling fan is provided below the outlet of the spinning machine on the Stelmore air cooling line. The pre-cooling fan cools the finished wire rod to a first set temperature, and the first set temperature range is 730°C to 770°C.

[0019] The object of the present invention can also be achieved by providing an online salt bath device for implementing the aforementioned multi-grade steel online salt bath production process, the online salt bath device comprising:

[0020] A pre-cooling tank, wherein the inner cavity of the pre-cooling tank constitutes a pre-cooling zone, and the pre-cooling tank is arranged below the spinning head for spinning finished wire rods; the pre-cooling tank contains a molten salt solution for cooling; the pre-cooling tank is provided with a first roller group for supporting and driving the finished wire rods;

[0021] At least two temperature-equalizing salt baths connected in series, the inner cavity of the temperature-equalizing salt bath forming a temperature-equalizing zone; the inlet of the temperature-equalizing salt bath is connected to the outlet of the pre-cooling tank, and the temperature-equalizing salt bath is filled with temperature-equalizing salt liquid; a second roller group that can be connected to the first roller group and can swing and rise is provided in the temperature-equalizing salt bath, and the second roller group is used to support and drive the finished wire rod to move;

[0022] The surface flushing section is used to flush and clean the surface of the finished wire rod.

[0023] In a preferred embodiment of the present invention, the side of the pre-cooling groove close to the laying head is connected to the connecting groove, the end of the connecting groove close to the laying head is closed, and the end of the connecting groove away from the laying head is connected to the pre-cooling groove; a transition conveying roller group arranged downwardly inclined is provided in the connecting groove, and the two ends of the transition conveying roller group are respectively connected to the outlet roller group and the first roller group of the laying head;

[0024] The surface flushing part includes a liquid receiving tank, the end of the liquid receiving tank away from the uniform temperature salt bath tank is closed, and the end of the liquid receiving tank close to the uniform temperature salt bath tank is connected to the adjacent uniform temperature salt bath tank; a cleaning conveying roller group is arranged in the liquid receiving tank, and the two ends of the cleaning conveying roller group are respectively connected to the second roller group and the Stelmor air cooling line, and a flushing and drying device is arranged above the cleaning conveying roller group.

[0025] In a preferred embodiment of the present invention, the position state of the second roller group includes a low position state, a climbing state and a high position state, the low position state is flush with the first roller group, the low position state is lower than the liquid level in the temperature-equalizing salt bath; the high position state is higher than the liquid level in the temperature-equalizing salt bath, and the climbing state is a transitional state between the low position state and the high position state; the second roller group includes a plurality of second rollers, a plurality of the second rollers in at least one temperature-equalizing salt bath are in the low position state, and a plurality of the second rollers in at least one temperature-equalizing salt bath are in the climbing state.

[0026] In a preferred embodiment of the present invention, a roller lifting device is connected to the second rollers located at both ends of each of the temperature-equalizing salt baths, and the roller lifting device is used to change the position state of the second roller group.

[0027] In a preferred embodiment of the present invention, the first roller group includes a plurality of first rollers, and the axial ends of each first roller are sealed and pass through the side wall of the pre-cooling tank respectively. The plurality of first rollers are driven in groups, and the axial end of one first roller in each group is connected to a drive motor. The first rollers in each group are driven by a chain, and the drive motor and the chain are located on the outside of the pre-cooling tank.

[0028] As described above, the multi-grade steel online salt bath production process and online salt bath device provided by the present invention have the following characteristics:

[0029] Beneficial effects:

[0030] The present invention utilizes the "post-rolling waste heat + online salt bath quenching / isothermal transformation" process route to improve the sorbite rate and uniformity of microstructure and performance of medium and high carbon steel, replacing the offline salt bath process, thereby achieving energy conservation, emission reduction and green production; by flexibly controlling the temperature range and cooling rate of the microstructure transformation of the finished wire rod, it can adapt to the needs of various different types of steel such as steel for bridge cables, high-strength cord steel, steel for cutting wires, spring steel, etc.; after treatment, the sorbite rate of the finished wire rod is high, the network carbides and martensite bands in the core can be eliminated, the microstructure and performance of the finished wire rod are uniform, the added value of the product is increased, and the overall competitiveness of the production line is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0032] in:

[0033] Figure 1 This is a state diagram of the online salt bath device of the present invention when producing high carbon steel.

[0034] Figure 2 This is a state diagram of the online salt bath device of the present invention when producing medium carbon steel.

[0035] Figure 3 Schematic diagram of the cross section of the pre-cooling tank of the present invention.

[0036] Figure 4 This is an overall process flow chart of the wire rod in Example 3 of the present invention.

[0037] Figure 5 Schematic diagram of the TTT curve in S1 in Example 2 of the present invention.

[0038] Figure 6 This is the layout diagram of the Stelmor cooling line area of ​​a conventional wire rod production line.

[0039] Figure 7 This is the state of the coil on the Stelmore air-cooled line.

[0040] Figure 8 This is a schematic diagram of a high-speed wire online heat treatment device disclosed in the prior art.

[0041] In the picture:

[0042] 100. Online salt bath device;

[0043] 1. Pre-cooling tank; 11. First roller group; 111. First roller;

[0044] 2. Temperature-equalizing salt bath; 21. Second roller table group; 22. Roller table lifting device;

[0045] 3. Surface flushing unit; 31. Liquid receiving tank; 32. Cleaning conveyor roller set; 33. Flushing and drying device;

[0046] 4. Connecting groove; 41. Transition conveyor roller group;

[0047] 200, laying machine; 201, exit roller group;

[0048] 300. Finished wire rod. DETAILED DESCRIPTION

[0049] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0050] The specific embodiments of the present invention described herein are intended only to illustrate the present invention and are not to be construed as limiting the present invention in any way. In light of the present invention, a skilled person may conceive of any possible variations based on the present invention, all of which should be considered to fall within the scope of the present invention. It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be an intermediate element at the same time. The terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to mechanical or electrical connections, or to internal communication between two elements, and may be directly connected or indirectly connected through an intermediate medium. A person of ordinary skill in the art can understand the specific meanings of the above terms based on the specific circumstances. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended only to describe specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0052] The present invention provides a multi-grade steel online salt bath production process method, such as Figure 1 、 Figure 2As shown, the finished wire rod after rolling is spun onto the Stelmore air cooling line, and the finished wire rod is pre-cooled to a first set temperature through the Stelmore air cooling line. The pre-cooled finished wire rod is transported to an online salt bath device for temperature control and isothermal phase transformation of the finished wire rod. The temperature range and cooling rate in the online salt bath device are adjustable; the finished wire rod after the salt bath phase transformation is transported back to the Stelmore air cooling line to continue cooling to a second set temperature.

[0053] The present invention is suitable for producing alloy steel wires with specifications of 5.0 to 25 mm; the types of steel produced mainly include steel for bridge cables, high-strength cord steel, steel for cutting wires, spring steel, etc.

[0054] The present invention utilizes the "post-rolling waste heat + online salt bath quenching / isothermal transformation" process route to improve the sorbite rate and uniformity of microstructure and performance of medium and high carbon steel, replacing the offline salt bath process, thereby achieving energy conservation, emission reduction and green production; by flexibly controlling the temperature range and cooling rate of the microstructure transformation of the finished wire rod, it can meet the needs of various different types of steel such as steel for bridge cables, high-strength cord steel, cutting wire steel, spring steel, etc.; after treatment, the sorbite rate of the finished wire rod is high, the sorbite rate is ≥90%, the core network carbide and martensite band can be eliminated, the microstructure and performance of the finished wire rod are uniform, the strength deviation of the same circle is ≤25MPa, the added value of the product is increased, and the overall competitiveness of the production line is enhanced.

[0055] Example 1

[0056] like Figure 1 、 Figure 2 As shown, the present invention provides an online salt bath device 100 for implementing the aforementioned multi-grade steel online salt bath production process method. The online salt bath device 100 includes:

[0057] The pre-cooling tank 1 has an inner cavity forming a pre-cooling zone. The pre-cooling tank 1 is arranged below the spinning head 200 for spinning the finished wire rod 300. The pre-cooling tank 1 contains a molten salt solution for cooling. The pre-cooling tank 1 is provided with a first roller set 11 for supporting and driving the finished wire rod 300.

[0058] At least two temperature-equalizing salt baths 2 are connected in series, and the inner cavity of the temperature-equalizing salt bath 2 constitutes a temperature-equalizing zone; the inlet of the temperature-equalizing salt bath 2 is connected to the outlet of the pre-cooling tank 1, and the temperature-equalizing salt solution is contained in the temperature-equalizing salt bath 2; a second roller group 21 that can be connected to the first roller group 11 and can swing and rise is set in the temperature-equalizing salt bath 2, and the second roller group 21 is used to support and drive the finished wire rod 300 to move;

[0059] The surface flushing portion 3 is used to flush and clean the surface of the finished wire rod 300 .

[0060] Further, if Figure 1 、 Figure 2As shown, the side of the pre-cooling tank 1 close to the spinning head is connected to the connecting tank 4, the end of the connecting tank 4 close to the spinning head 200 is closed, and the end of the connecting tank 4 away from the spinning head 200 is connected to the pre-cooling tank 1; a downwardly inclined transition conveying roller group 41 is provided in the connecting tank 4, and the two ends of the transition conveying roller group 41 are respectively connected to the outlet roller group 201 of the spinning head 200 and the first roller group 11.

[0061] The exit roller group 201 can directly adopt the conveying roller of the Stelmor air cooling line. A pre-cooling fan is set on the lower side of the exit roller group 201. During the conveying process, the pre-cooling fan can perform preliminary cooling on the high-temperature coil (finished wire rod). Finally, the exit roller group 201 conveys the high-temperature coil (finished wire rod) into the online salt bath device 100.

[0062] like Figure 1 、 Figure 2 As shown, the spinning machine 200 can adopt a high-speed oil film bearing spinning machine, which is horizontally arranged and has an outlet inclination angle of 20 degrees. A pair of bevel gears are driven by a motor to rotate the core shaft, forming the high-speed linear motion wire into a coil of predetermined diameter (finished wire rod) and dropping it onto the conveying roller of the Stelmor cooling line (i.e., the outlet roller group 201).

[0063] The surface flushing part 3 includes a liquid receiving tank 31, which is closed at one end away from the uniform temperature salt bath 2, and is connected to the adjacent uniform temperature salt bath 2 at one end of the liquid receiving tank 31 close to the uniform temperature salt bath 2; a cleaning conveying roller group 32 is arranged in the liquid receiving tank 31, and the two ends of the cleaning conveying roller group 32 are respectively connected to the second roller group 21 and the Stelmor air cooling line; a flushing and drying device 33 is arranged above the cleaning conveying roller group 32.

[0064] Furthermore, the position states of the second roller group 21 include a low state, a climbing state and a high state. The low state is flush with the first roller group 11 and lower than the liquid level in the temperature-equalizing salt bath 2, so that the finished wire rod 300 can be immersed in the salt solution; the high state is higher than the liquid level in the temperature-equalizing salt bath 2, and the climbing state is a transitional state between the low state and the high state; the second roller group 21 includes multiple second rollers, and the multiple second rollers in at least one temperature-equalizing salt bath are in the low state, and the multiple second rollers in at least one temperature-equalizing salt bath 2 are in the climbing state.

[0065] Further, if Figure 1 、 Figure 2 As shown, the second rollers located at both ends of each temperature-equalizing salt bath 2 are connected to roller lifting devices 22 , and the roller lifting devices 22 are used to change the position state of the second roller group 21 .

[0066] Further, if Figure 3As shown, the first roller group 11 includes a plurality of first rollers 111, and the axial ends of each first roller 111 are sealed and pass through the side wall of the pre-cooling tank 1 respectively. The plurality of first rollers 111 are driven in groups, and the axial end of a first roller 111 in each group is connected to the drive motor. The first rollers 111 in each group are driven by a chain, and the drive motor and the chain are located on the outside of the pre-cooling tank 1.

[0067] In the present embodiment, after the transition conveying roller group 41, there is provided with a section of pre-cooling groove 1 to form a pre-cooling zone. This section is about 6m long and can quickly cool the finished wire rod (forming a coil of predetermined diameter through a laying head) at high temperature to the temperature at which the phase change begins; the pre-cooling groove 1 is a 3-sided (two side surfaces and a bottom surface) closed trough structure, with a row of high-temperature and corrosion-resistant first rollers 111 (i.e., the first roller group 11) passing through the middle. The coupling at the axial end of the first roller 111 passes through the sidewall of the pre-cooling groove 1 and adopts high-temperature resistant sealing to prevent the salt solution from leaking. The first roller group 11 adopts AC variable frequency reduction motor drive, grouped centralized transmission, and the chain used for transmission is a double-row chain. The drive motor and chain are all on the outside of the pre-cooling groove 1 and will not be eroded by the salt bath.

[0068] After the pre-cooling zone, there are 4 sections of equalizing salt baths 2 with hydraulic lifting devices. The number of equalizing salt baths 2 to be used is determined according to the isothermal transformation time of different steel grades. The liquid level of the salt solution in the equalizing salt baths 2 remains unchanged.

[0069] like Figure 1 As shown, when producing high carbon steel, the second rollers in the three sections (the first three sections) of the temperature-equalizing salt bath tank 2 close to the pre-cooling tank 1 are lowered to a low position (low state), and the second rollers in the last section of the temperature-equalizing salt bath tank 2 are in an inclined climbing position (climbing state). The finished wire rod is temperature-homogenized in the first three sections of the temperature-equalizing salt bath tank 2 to complete the isothermal phase change of the structure.

[0070] like Figure 2 As shown, when producing medium carbon steel, the second rollers in the two sections (the first two sections) of the temperature-equalizing salt bath 2 close to the pre-cooling tank 1 are lowered to a low position (low state), the second rollers in the third section of the temperature-equalizing salt bath 2 are in an inclined climbing position (climbing state), and the second rollers in the last section of the temperature-equalizing salt bath 2 are raised to a high position (high state). The finished wire rod is temperature-homogenized in the first two sections of the temperature-equalizing salt bath 2, completes the isothermal phase change of the structure, and then climbs out of the molten salt.

[0071] The structure of the temperature-equalizing salt bath tank 2 can be the same as that of the pre-cooling tank 1 .

[0072] A liquid receiving tank 31 is provided behind the temperature-averaging zone to constitute a flushing zone. This section is about 6 m long. The flushing and drying device 33 uses cold water to flush the salt solution remaining on the surface of the wire rod to prevent the salt solution from being carried out of the online salt bath device 100. After flushing, high-pressure air can be used to blow dry the finished wire rod 300 to prevent corrosion and rust on the surface of the finished wire rod.

[0073] Example 2

[0074] The main process route of the multi-grade steel online salt bath production process of the present invention includes:

[0075] A. The process before salt bath includes:

[0076] (1) The finished rolled wire rod 300 is laid out on a Stelmor air cooling line, specifically including:

[0077] The rolled piece enters the finishing mill at 900±20℃ to complete final rolling, and then is cooled in a water cooling box after rolling. The finished wire rod is spun at 860±20℃ and evenly spread on the Stelmor air cooling line (the exit roller group 201 of the spinning machine 200).

[0078] (2) The aforementioned pre-cooling of the finished wire rod 300 to the first set temperature through the Stelmore air cooling line specifically includes:

[0079] The finished wire rod 300 is spun by a spinning machine. A pre-cooling fan is provided below the outlet of the spinning machine on the Stelmore air cooling line. The pre-cooling fan cools the finished wire rod to a first set temperature, which is in the range of 730°C to 770°C.

[0080] Turn on the pre-cooling fan of the Stelmor air cooling line to quickly cool the finished wire rod to avoid grain growth. At this time, the fan air volume and the cooling rate of the rolled piece should be controlled according to the CCT curve of each steel grade, in order to control the formation of eutectoid cementite and avoid martensite and bainite.

[0081] B. Salt bath process:

[0082] The above-mentioned method of conveying the pre-cooled finished wire rod 300 to the online salt bath device 100 for temperature control and isothermal phase transformation of the finished wire rod specifically includes:

[0083] Step S1: After pre-cooling, the finished wire rod 300 enters the pre-cooling zone of the online salt bath device 100. The pre-cooling zone is provided with a molten salt solution for cooling. The finished wire rod is cooled to the phase change starting temperature by the molten salt solution in the pre-cooling zone;

[0084] Specifically, the pre-cooling fan cools the finished wire rod to above the Ac1 line, about 750±20℃, and then enters the pre-cooling tank 1 of the online salt bath device. The temperature of the molten salt in the pre-cooling tank 1 is 550~650℃. According to the CCT curve and TTT curve (such as Figure 5As shown), the finished wire rod 300 passes through the loop (overlap and non-overlap points) and is quickly cooled to the phase change start temperature in this groove. Considering the speed of the first roller is 0.8m / s, the length of this section is about 6m; the transportation speed and length can be determined according to actual needs.

[0085] Step S2: After cooling, the finished wire rod 300 enters the uniform temperature zone of the online salt bath device. The uniform temperature zone is provided with a uniform temperature salt solution. The finished wire rod 300 is temperature-homogenized in the uniform temperature zone. The travel speed and travel length of the finished wire rod 300 in the uniform temperature zone are regulated to complete the isothermal phase transition of the structure; thus, the finished wire rod 300 is subjected to sorbitization.

[0086] Specifically, the finished wire rod 300 (formed into a coil of predetermined diameter by a spinning machine) continues to be temperature-homogenized in the equalizing salt bath tank 2 of the online salt bath device to complete the isothermal phase change of the tissue, realize the sorbitization of the finished wire rod, avoid other tissue formation areas, and determine the time and distance of transportation of the finished wire rod 300 in the equalizing salt bath tank 2 based on the phase change completion time on the TTT curve.

[0087] The transportation time and distance can refer to the specific settings for producing high carbon steel and medium carbon steel described in Example 1.

[0088] The temperature range and cooling rate in steps S1 and S2 can be adjusted according to actual needs. By flexibly controlling the temperature range and cooling rate of the coil structure transformation, it can meet the needs of different steel grades such as bridge cable steel, high-strength cord steel, cutting wire steel, and spring steel.

[0089] Step S3 , the finished wire rod 300 that has completed the phase change rises along the second roller set 21 and leaves the uniform temperature zone of the online salt bath device 100 .

[0090] C. Surface cleaning process after salt bath: After completing the salt bath phase change, the finished wire rod 300 is returned to the Stelmor air cooling line for surface treatment, including: after the finished wire rod 300 leaves the uniform temperature zone, it is transported into the surface flushing area of ​​the online salt bath device 100 to completely rinse off the residual salt solution on the surface and blow dry with high-pressure air.

[0091] D. Finished wire rod 300 returns to Stelmor air cooling line:

[0092] After the finished wire rod 300 is transported back to the Stelmor air cooling line, the air cooling line fan is turned on appropriately to cool the finished wire rod 300 after the salt bath phase change to the second set temperature, which is less than or equal to 400°C, to prevent the formation of secondary iron oxide scale and reduce or eliminate the downstream steel wire pickling process.

[0093] Example 3

[0094] The overall process flow for producing alloy steel wire using the online salt bath device 100 and the multi-steel online salt bath production process method of the present invention is as follows:

[0095] Step a, cold billet loading;

[0096] Step b, heating in a heating furnace;

[0097] Step c, high-pressure water dephosphorization;

[0098] Step d, rolling by a roughing mill;

[0099] Step e, 1# flying shear;

[0100] Step f, rolling by the intermediate rolling mill;

[0101] Step g, 2# flying shear;

[0102] Step h, rolling in a pre-finishing mill;

[0103] Step i, pre-water cooling;

[0104] Step j, 3# flying shear;

[0105] Step k, rolling by a finishing mill;

[0106] Step 1, pre-water cooling;

[0107] Step m, reducing and sizing unit;

[0108] Step n: water cooling;

[0109] Step o, clamping and spinning; the spinning in this step adopts the process (1) before the salt bath in Example 2;

[0110] Step p, pre-cooling in the Stelmore air cooling line; this step adopts the process (2) before the salt bath in Example 2;

[0111] Step q, online salt bath; this step adopts the salt bath process and post-salt bath surface cleaning process of Example 2;

[0112] Step r, cooling in a Stelmore air cooling line; this step adopts the cooling step of returning the finished wire rod 300 of Example 2 to the Stelmore air cooling line;

[0113] Step s, collecting the papers;

[0114] Step t, PF line conveying;

[0115] Step u, compacting and bundling;

[0116] Step v, weighing the coil;

[0117] Step w, unloading the finished product roll;

[0118] Step x: Storage.

[0119] The overall process flow chart of wire is as follows Figure 4 shown.

[0120] As described above, the multi-grade steel online salt bath production process and online salt bath device provided by the present invention have the following characteristics:

[0121] Beneficial effects:

[0122] The present invention utilizes the "post-rolling waste heat + online salt bath quenching / isothermal transformation" process route to improve the sorbite rate and uniformity of microstructure and performance of medium and high carbon steel, replacing the offline salt bath process, thereby achieving energy conservation, emission reduction and green production; by flexibly controlling the temperature range and cooling rate of the microstructure transformation of the finished wire rod, it can adapt to the needs of various different types of steel such as steel for bridge cables, high-strength cord steel, steel for cutting wires, spring steel, etc.; after treatment, the sorbite rate of the finished wire rod is high, the network carbides and martensite bands in the core can be eliminated, the microstructure and performance of the finished wire rod are uniform, the added value of the product is increased, and the overall competitiveness of the production line is enhanced.

[0123] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A multi-grade steel online salt bath production process, characterized in that: The finished wire rods after rolling are laid out to the Stelmore air cooling line, where they are pre-cooled to a first set temperature and then transported to an online salt bath device for temperature control and isothermal phase transformation. The temperature range and cooling rate in the online salt bath device are adjustable. After the salt bath phase transformation is completed, the finished wire rods are transported back to the Stelmore air cooling line to continue cooling to a second set temperature.

2. The multi-grade steel online salt bath production process according to claim 1, characterized in that: The finished wire rod after pre-cooling is transported to the online salt bath device for temperature control and isothermal phase transformation of the finished wire rod, including: Step S1: After pre-cooling, the finished wire rod enters the pre-cooling zone of the online salt bath device, where a molten salt solution for cooling is provided. The finished wire rod is cooled to the phase change starting temperature by the molten salt solution in the pre-cooling zone; Step S2: After cooling, the finished wire rod enters the uniform temperature zone of the online salt bath device. The uniform temperature zone is provided with a uniform temperature salt solution. The finished wire rod is temperature-homogenized in the uniform temperature zone. The travel speed and travel length of the finished wire rod in the uniform temperature zone are regulated to complete the isothermal phase transition of the structure; thus, the finished wire rod is subjected to sorbitization. Step S3: The finished wire rod that has completed the phase change rises and leaves the uniform temperature zone of the online salt bath device.

3. The multi-grade steel online salt bath production process according to claim 2, characterized in that: After the salt bath phase change, the finished wire rod is returned to the Stelmor air cooling line for surface treatment, including: after the finished wire rod leaves the uniform temperature zone, it is transported into the surface washing area of ​​the online salt bath device to completely wash away the residual salt liquid on the surface and blow dry with high-pressure air.

4. The multi-grade steel online salt bath production process according to claim 2, characterized in that: After the finished wire rod is transported back to the Stelmor air cooling line, the air cooling line fan is turned on to cool the finished wire rod after the salt bath phase change to a second set temperature, which is less than or equal to 400°C.

5. The multi-grade steel online salt bath production process according to claim 1, characterized in that: The finished wire rod is spun by a spinning machine. A pre-cooling fan is provided below the outlet of the spinning machine on the Stelmore air cooling line. The pre-cooling fan cools the finished wire rod to a first set temperature, which is in the range of 730°C to 770°C.

6. An online salt bath device, characterized in that: For implementing the multi-grade steel online salt bath production process according to any one of claims 2 to 5, the online salt bath device comprises: A pre-cooling tank, wherein the inner cavity of the pre-cooling tank constitutes a pre-cooling zone, and the pre-cooling tank is arranged below the spinning head for spinning finished wire rods; the pre-cooling tank contains a molten salt solution for cooling; the pre-cooling tank is provided with a first roller group for supporting and driving the finished wire rods; At least two temperature-equalizing salt baths connected in series, the inner cavity of the temperature-equalizing salt bath forming a temperature-equalizing zone; the inlet of the temperature-equalizing salt bath is connected to the outlet of the pre-cooling tank, and the temperature-equalizing salt bath is filled with temperature-equalizing salt liquid; a second roller group that can be connected to the first roller group and can swing and rise is provided in the temperature-equalizing salt bath, and the second roller group is used to support and drive the finished wire rod to move; The surface flushing section is used to flush and clean the surface of the finished wire rod.

7. The online salt bath device according to claim 6, characterized in that The side of the pre-cooling groove close to the spinning machine is connected to the connecting groove, the end of the connecting groove close to the spinning machine is closed, and the end of the connecting groove away from the spinning machine is connected to the pre-cooling groove; a transition conveying roller group arranged downwardly inclined is provided in the connecting groove, and the two ends of the transition conveying roller group are respectively connected to the outlet roller group and the first roller group of the spinning machine; The surface flushing part includes a liquid receiving tank, the end of the liquid receiving tank away from the uniform temperature salt bath tank is closed, and the end of the liquid receiving tank close to the uniform temperature salt bath tank is connected to the adjacent uniform temperature salt bath tank; a cleaning conveying roller group is arranged in the liquid receiving tank, and the two ends of the cleaning conveying roller group are respectively connected to the second roller group and the Stelmor air cooling line, and a flushing and drying device is arranged above the cleaning conveying roller group.

8. The online salt bath device according to claim 7, characterized in that The position states of the second roller group include a low position state, a climbing state and a high position state. The low position state is flush with the first roller group and is lower than the liquid level in the temperature-equalizing salt bath; the high position state is higher than the liquid level in the temperature-equalizing salt bath, and the climbing state is a transitional state between the low position state and the high position state; the second roller group includes multiple second rollers, and the multiple second rollers in at least one temperature-equalizing salt bath are in the low position state, and the multiple second rollers in at least one temperature-equalizing salt bath are in the climbing state.

9. The online salt bath device according to claim 8, characterized in that The second rollers located at both ends of each of the temperature-equalizing salt baths are connected to roller lifting devices, and the roller lifting devices are used to change the position state of the second roller group.

10. The online salt bath device according to claim 8, characterized in that: The first roller group includes multiple first rollers, and the axial ends of each first roller are sealed and pass through the side walls of the pre-cooling tank. The multiple first rollers are driven in groups, and the axial end of one first roller in each group is connected to a drive motor. The first rollers in each group are driven by a chain, and the drive motor and the chain are located outside the pre-cooling tank.

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