Method for treating abnormal structure of hot rolled wire rod

Abstract

The present invention discloses a method for processing abnormal tissue of hot-rolled wire rod, and relates to the technical field of steel production. It includes determining the source of abnormal tissue of hot-rolled wire rod: after heat-treating the hot-rolled wire rod with abnormal tissue, comparing the abnormal tissue changes in the microstructure metallographic diagram of the hot-rolled wire rod before and after the heat treatment; if the abnormal tissue after the heat treatment does not disappear, it means that the source of the abnormal tissue is the molten steel smelting process; if the abnormal tissue after the heat treatment is transformed into a normal tissue, it means that the source of the abnormal tissue is the rolling process; and then adjusting the rolling or molten steel smelting process method according to the different sources of the abnormal tissue to remove the abnormal tissue in the hot-rolled wire rod. The source of the abnormal tissue in the hot-rolled wire rod can be quickly determined by the heat treatment method, and then the process method and / or parameters are adjusted according to the different sources of the abnormal tissue, so that the abnormal tissue of the hot-rolled wire rod can be eliminated as soon as possible, saving the process adjustment time of the steel production process.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, and in particular to a method for processing abnormal structures of hot-rolled wire rods. Background Art

[0002] During the inspection process after the hot-rolled wire rods of medium and high carbon steel are rolled, the abnormal structure of local pearlite segregation in the transverse metallographic structure is often found, which seriously affects the processing and use of customers. If these hot-rolled wire rods with abnormal structures are directly processed, they may cause problems such as material cracking, wire breakage, tool damage, low efficiency and increased processing costs, affecting product quality. Therefore, solving the abnormal situation in the structure of hot-rolled wire rods is one of the problems that need to be solved urgently in this field.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The object of the present invention is to provide a method for treating abnormal structure of hot-rolled wire rod.

[0005] The present invention is achieved in that:

[0006] In a first aspect, the present invention provides a method for processing abnormal tissue of a hot-rolled wire rod, comprising determining the source of the abnormal tissue of the hot-rolled wire rod: subjecting the hot-rolled wire rod with the abnormal tissue to heat treatment, and comparing the changes in the abnormal tissue in the microstructure metallographic diagrams of the hot-rolled wire rod before and after the heat treatment; if the abnormal tissue after the heat treatment does not disappear, it indicates that the source of the abnormal tissue is the molten steel smelting process; if the abnormal tissue after the heat treatment is transformed into a normal tissue, it indicates that the source of the abnormal tissue is the rolling process; and then adjusting the rolling or molten steel smelting process according to the source of the abnormal tissue to remove the abnormal tissue in the hot-rolled wire rod.

[0007] In an alternative embodiment, the normal tissue includes a ferrite phase and a pearlite phase.

[0008] Preferably, in terms of volume percentage, the ferrite phase in the normal tissue is 25-40%, and the pearlite phase is 60-75%.

[0009] Preferably, the content of the ferrite phase in the abnormal structure is greater than 40% or the content of the pearlite phase is greater than 75%.

[0010] In an optional embodiment, the temperature of the heat treatment is the spinning temperature of the hot-rolled wire rod.

[0011] In an optional embodiment, when the hot rolled wire rod is S45C hot rolled wire rod, the heat treatment temperature is 840-860°C.

[0012] In an optional embodiment, the heat treatment process is carried out for a holding time of 30 to 60 minutes.

[0013] In an optional embodiment, the heat treatment further includes corroding the hot-rolled wire rod using an acid alcohol solution.

[0014] Preferably, the acid in the acid alcohol solution is nitric acid, and the concentration of the nitric acid is 3-5%.

[0015] In an optional embodiment, the method for adjusting the rolling process includes adjusting the parameters of the heating furnace. Preferably, the preheating section temperature of the heating furnace is ≤700°C, the heating section temperature is 700-1100°C, the soaking section temperature is 1000-1100°C, and the insulation time of the soaking section is ≥35min.

[0016] In an optional embodiment, the method for adjusting the rolling process further includes placing an insulating material between the walking beam of the heating furnace and the steel billet.

[0017] In an optional embodiment, the head temperature of the steel billet coming out of the heating furnace is 10-30°C higher than the temperature of the hot-rolled wire rod with abnormal structure coming out of the heating furnace, and the tail temperature is 20-30°C higher.

[0018] In an optional embodiment, the method for adjusting the rolling process also includes adjusting the rolling parameters. Preferably, the high-pressure water descaling pressure before rolling is ≥20MPa, the starting rolling temperature is Ac3+(70~130)℃, the finishing rolling temperature is Ac3+(40~80)℃, the sizing inlet temperature is Ac3+(30~70)℃, and the spinning temperature is Ac3+(60~80)℃.

[0019] The present invention has the following beneficial effects:

[0020] The present invention provides a method for processing abnormal tissue of a hot-rolled wire rod. The source of the abnormal tissue in the hot-rolled wire rod is determined by a heat treatment method, and the process method and / or parameters can be adjusted according to the different sources of the abnormal tissue, so that the abnormal tissue of the hot-rolled wire rod can be eliminated as soon as possible. Under the premise of ensuring product quality and product stability, the source of the abnormal tissue can be quickly confirmed, and the abnormal tissue generated in the rolling process can be quickly eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 The metallographic diagram of the S45C hot-rolled wire rod with abnormal structure provided in Example 1 of the present invention;

[0023] Figure 2 The metallographic image of the S45C hot-rolled wire rod with the abnormal structure eliminated after the heat treatment provided in Example 1 of the present invention;

[0024] Figure 3 The metallographic diagram of the 45 hot-rolled wire rod with abnormal structure provided in Example 2 of the present invention;

[0025] Figure 4 The metallographic image of the 45 hot-rolled wire rod with the abnormal structure eliminated after the heat treatment provided in Example 2 of the present invention;

[0026] Figure 5 This is a carbon element surface scanning image of the S45C hot-rolled wire rod after heat treatment provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0028] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0029] During the inspection process after the hot-rolled wire rods of medium-high carbon steel are rolled, abnormal structures such as local pearlite segregation in the transverse metallographic structure are often found. If the source of the abnormal structure cannot be confirmed, various processes need to be adjusted continuously to obtain steel grades of qualified quality. This process requires continuous attempts and may not be able to directly solve the abnormal structure in the hot-rolled wire rods, which will result in a large number of unqualified hot-rolled wire rods being produced, resulting in cost waste. Therefore, if you want to quickly deal with the abnormal structure in the hot-rolled wire rod, you need to first determine the source of the abnormal structure to achieve accurate regulation of the process. Therefore, the inventor proposes the following solution.

[0030] In a first aspect, the present invention provides a method for processing abnormal tissue of a hot-rolled wire rod, comprising determining the source of the abnormal tissue of the hot-rolled wire rod: subjecting the hot-rolled wire rod with the abnormal tissue to heat treatment, and comparing the changes in the abnormal tissue in the microstructure metallographic diagrams of the hot-rolled wire rod before and after the heat treatment; if the abnormal tissue after the heat treatment is not eliminated, it indicates that the source of the abnormal tissue is the molten steel smelting process; if the abnormal tissue after the heat treatment is transformed into a normal tissue, it indicates that the source of the abnormal tissue is the rolling process; and then adjusting the rolling or molten steel smelting process according to the source of the abnormal tissue to remove the abnormal tissue in the hot-rolled wire rod.

[0031] Through heat treatment, it can be quickly confirmed whether the abnormal structure of the hot-rolled wire rod appears during the rolling process or has already appeared during the molten steel smelting process. If it appears during the rolling process, then after the hot-rolled wire rod is heat-treated, the abnormal structure can be heated up and then cooled again to transform into a normal structure. If the cause of the abnormal structure has already appeared during the molten steel smelting process, the morphology of the abnormal structure cannot be changed even after heat treatment of the hot-rolled wire rod. This method can quickly confirm the source of the abnormal structure, thereby quickly adjusting the corresponding process, reducing the output of hot-rolled wire rods with abnormal structures, and reducing cost losses.

[0032] In an alternative embodiment, the normal tissue includes a ferrite phase and a pearlite phase.

[0033] Preferably, in terms of volume percentage, the ferrite phase in the normal tissue is 25-40%, and the pearlite phase is 60-75%.

[0034] Preferably, the content of the ferrite phase in the abnormal structure is greater than 40% or the content of the pearlite phase is greater than 75%.

[0035] More preferably, the content of the pearlite phase in the abnormal structure is greater than 75%.

[0036] It can be understood that in order to compare the abnormal structure changes in the microstructure metallographic diagram of the hot-rolled wire rod before and after heat treatment, the abnormal structure observed before heat treatment needs to be marked at the location of the abnormal structure before heat treatment.

[0037] In an optional embodiment, the heat treatment temperature is the spinning temperature of the hot-rolled wire rod. According to different grades of hot-rolled wire rod steel, the corresponding heat treatment temperature can be adjusted to ensure that the abnormal tissue can be re-cooled and crystallized to form the morphology of normal tissue.

[0038] For example, in an optional embodiment, when the hot-rolled wire rod is S45C hot-rolled wire rod, the heat treatment temperature is 840-860° C. When the hot-rolled wire rod is other grades of steel, the heat treatment temperature can also be adjusted accordingly.

[0039] For example, the heat treatment temperature of the S45C hot-rolled wire rod may be any value among 840°C, 845°C, 850°C, 855°C or 860°C, or a range value between any two values.

[0040] In an optional embodiment, the holding time of the heat treatment process is 30 to 60 minutes, for example, it can be any value among 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, or a range value between any two values.

[0041] By controlling the heat treatment temperature and holding time within the above range, uniform heating of the hot-rolled wire rod can be ensured, which is beneficial to the re-austenization of abnormal structures and phase transformation.

[0042] In an optional embodiment, the heat treatment further includes corroding the hot-rolled wire rod using an acid alcohol solution.

[0043] Preferably, after heat treatment, the hot-rolled wire rod is cooled according to the cooling rate after spinning until the temperature of the hot-rolled wire rod drops to room temperature, and then the hot-rolled wire rod is corroded with an acid alcohol solution to reveal its metallographic structure.

[0044] Preferably, the acid in the acid alcohol solution is nitric acid, and the volume concentration of nitric acid is 3-5%. More preferably, the acid alcohol solution is 4% nitric alcohol.

[0045] Regarding the abnormal structure that appears during the rolling process, the inventors found that the main reason is the uneven temperature of the billet during the rolling process and the temperature during the cooling process, which leads to local pearlite segregation in some areas of the hot-rolled wire rod, thus forming an abnormal structure. Therefore, the inventors proposed the following solution.

[0046] In an optional embodiment, the method for adjusting the rolling process includes adjusting the parameters of the heating furnace. Preferably, the preheating section temperature of the heating furnace is ≤700°C, the heating section temperature is 700-1100°C, the soaking section temperature is 1000-1100°C, and the insulation time of the soaking section is ≥35min.

[0047] By increasing the temperature in the heating furnace, ensuring the uniformity of the temperature in the heating furnace, and / or extending the insulation time of the heating furnace, the temperature of the steel billet is made more uniform, avoiding abnormal structure caused by uneven cooling in the subsequent rolling process.

[0048] In an optional embodiment, the method for adjusting the rolling process further includes arranging a heat insulating material between the walking beam of the heating furnace and the steel billet. Since cooling water flows through the walking beam, direct contact between the steel billet and the walking beam will also cause uneven temperature of the steel billet, thereby causing the appearance of abnormal tissue. The present invention arranges a heat insulating material on the surface of the walking beam to reduce the influence of the cooling water in the walking beam on the temperature of the steel billet, thereby avoiding the occurrence of local uneven temperature of the steel billet.

[0049] In an optional embodiment, the head temperature of the steel billet coming out of the heating furnace is 10-30°C higher than the temperature of the hot-rolled wire rod with abnormal structure, and the tail temperature is 20-30°C higher, so as to ensure uniform temperature of the hot-rolled wire rod.

[0050] In an optional embodiment, the method for adjusting the rolling process also includes adjusting the rolling parameters. Preferably, the high-pressure water descaling pressure before rolling is ≥20MPa, the starting rolling temperature is Ac3+(70~130)℃, the finishing rolling temperature is Ac3+(40~80)℃, the sizing inlet temperature is Ac3+(30~70)℃, and the spinning temperature is Ac3+(60~80)℃.

[0051] It should be noted that Ac3 is the temperature at which all ferrite is transformed into austenite when hypoeutectoid steel is heated. Different grades of hot-rolled wire rod steel have different Ac3s, and the temperature at various locations during the rolling process can be adjusted according to the Ac3 of different grades according to the above method to avoid the occurrence of abnormal structures during the rolling process.

[0052] For example, if the Ac3 of a certain brand of hot-rolled wire rod steel is 780℃, then the starting rolling temperature of the hot-rolled wire rod steel of this brand is 850~910℃, the finishing temperature is 820~860℃, the sizing inlet temperature is 810~850℃, and the wire drawing temperature is 840~860℃.

[0053] In an optional embodiment, the method of adjusting the molten steel smelting process includes but is not limited to: adjusting the molten steel composition, adjusting the amount of protective slag during the refining process, adjusting the power supply and / or air blowing process parameters of the refining, etc.

[0054] Example 1

[0055] This embodiment provides a method for treating abnormal structure of hot-rolled wire rod, and the specific steps are as follows:

[0056] First, determine the source of the abnormal structure. The S45C hot-rolled wire rods obtained during the production process were tested and photographed using image analysis software. S45C hot-rolled wire rods with abnormal metallographic structure (pearlite segregation) were observed, such as Figure 1 As shown, the contents of ferrite and pearlite phases in normal and abnormal tissues are measured, and the location of the abnormal tissue is marked.

[0057] Then the hot-rolled wire rod with abnormal structure is heat treated. The furnace temperature is raised to 845℃, and the sample is placed in a 310S high temperature resistant stainless steel plate box and placed in a heat treatment furnace with protective atmosphere. After keeping warm for 40 minutes, it is taken out and the hot-rolled wire rod is cooled according to the cooling rate after spinning until the temperature of the hot-rolled wire rod cools to room temperature. The metallographic observation surface is well protected during the heat treatment process.

[0058] The hot-rolled wire rod cooled to room temperature was lightly polished, corroded with 4% nitric acid alcohol solution, and then cleaned with alcohol. Metallographic photographs were taken using image analysis software to obtain the metallographic structure of the hot-rolled wire rod after heat treatment, which was compared with the metallographic structure of the hot-rolled wire rod before heat treatment, and the ferrite and pearlite content of the two were compared.

[0059] By comparison, it is found that after heat treatment, the metallographic images of abnormal tissue and normal tissue are consistent, such as Figure 2 As shown, it is believed that the abnormal structure comes from the rolling process. By adjusting the parameters of the rolling process, the abnormal structure of the hot-rolled wire rod can be solved. The specific adjustment process is as follows:

[0060] Heat insulation material is set on the surface of the walking beam of the heating furnace so that the billet does not directly contact the surface of the walking beam. The preheating section temperature of the heating furnace is adjusted to 650℃, the heating section temperature to 1000℃, the soaking section temperature to 1050℃ and the soaking section insulation time to 40min, and the billet is heated according to the above parameters. After heating, the head temperature of the billet is increased by 20℃ compared with the head temperature of the hot-rolled wire rod with abnormal structure when it leaves the heating furnace, and the tail temperature is increased by 25℃ accordingly, and then the billet is sent to the rolling mill for rolling.

[0061] The rolling process controls the high-pressure water descaling pressure to 20.7 MPa, the starting rolling temperature to 890°C, the finishing rolling temperature to 840°C, the sizing inlet temperature to 830°C, and the wire laying temperature to 840°C. During the rolling process, the water tank on the rolling mill side is opened first to ensure that the temperature of the billet meets the temperature requirements of the above rolling stages.

[0062] Example 2

[0063] This embodiment provides a method for treating abnormal structure of hot-rolled wire rod, and the specific steps are as follows:

[0064] First, determine the source of the abnormal structure. The 45 hot-rolled wire rods obtained during the production process were tested and photographed using image analysis software. 45 hot-rolled wire rods with abnormal metallographic structure (pearlite segregation) were observed, such as Figure 3 As shown, the contents of ferrite and pearlite phases in normal and abnormal tissues are measured, and the location of the abnormal tissue is marked.

[0065] Then the hot-rolled wire rod with abnormal structure is heat treated. The furnace temperature is raised to 850℃, and the sample is placed in a 310S high temperature resistant stainless steel plate box and placed in a heat treatment furnace with protective atmosphere. After keeping warm for 45 minutes, it is taken out and the hot-rolled wire rod is cooled according to the cooling rate after spinning until the hot-rolled wire rod reaches room temperature. The metallographic observation surface is well protected during the heat treatment process.

[0066] The hot-rolled wire rod cooled to room temperature was lightly polished, corroded with 4% nitric acid alcohol solution, and then cleaned with alcohol. Metallographic photographs were taken using image analysis software to obtain the metallographic structure of the hot-rolled wire rod after heat treatment, which was compared with the metallographic structure of the hot-rolled wire rod before heat treatment, and the ferrite and pearlite content of the two were compared.

[0067] By comparison, it is found that after heat treatment, the metallographic images of abnormal tissue and normal tissue are consistent, such as Figure 4 As shown, it is believed that the abnormal structure comes from the rolling process. By adjusting the parameters of the rolling process, the abnormal structure of the hot-rolled wire rod can be solved. The specific adjustment process is as follows:

[0068] Heat-insulating materials are set on the surface of the walking beam of the heating furnace so that the billet does not directly contact the surface of the walking beam. The preheating section temperature of the heating furnace is adjusted to 600°C, the heating section temperature to 1050°C, the soaking section temperature to 1080°C, and the soaking section insulation time to 45 minutes, and then the billet is heated. After heating, the head temperature of the billet increases by 25°C compared with the head temperature of the hot-rolled wire rod with abnormal structure when it leaves the heating furnace, and the tail temperature increases by 27°C accordingly, and then the billet is sent to the rolling mill for rolling.

[0069] The rolling process controls the high-pressure water descaling pressure of 21.2MPa, the starting rolling temperature of 900℃, the finishing rolling temperature of 850℃, the sizing inlet temperature of 840℃, and the wire laying temperature of 850℃. During the rolling process, the water tank on the rolling mill side is opened first to ensure that the temperature of the billet meets the temperature requirements of the above rolling stages.

[0070] Comparative Example 1

[0071] This comparative example provides a method for treating abnormal structures of hot-rolled wire rods, wherein the method for determining the source of the abnormal structures is: electron probe method, which is as follows:

[0072] First, the S45C hot-rolled wire rod cooled to room temperature was lightly polished, then shallowly etched with 4% nitric acid alcohol solution, then cleaned with alcohol and dried. The metallographic structure was observed under a metallographic microscope and the abnormal tissue area was marked.

[0073] Then, place the sample into the electron probe and locate the abnormal tissue through the optical eyepiece. The scanning area is set to 4mm 2 , the scanning area includes abnormal tissue locations and normal locations.

[0074] Select the surface scanning mode, select the C element, the acceleration voltage is 15KV, the current is 100nA, the beam diameter is MIN, the step size is 2um, the dwell time is 2s, and the scanning is started until it is completed. The surface scanning results are shown in Figure 5 However, carbon is an ultra-light element, and has the common characteristics and difficulties of ultra-light element testing. Carbon contamination is easily introduced during sample preparation and testing, which affects the accuracy of the detected carbon content and further affects the judgment of the C element distribution.

[0075] Comparative Example 2

[0076] This comparative example provides a method for processing abnormal structure of hot-rolled wire rod, which is different from Example 1 only in that the high-pressure water descaling pressure is controlled at 20.7 MPa, the starting rolling temperature is 900°C, the finishing rolling temperature is 810°C, the sizing inlet temperature is 800°C, and the spinning temperature is 830°C during the rolling process. During the rolling process, all water tanks are activated.

[0077] The S45C wire rod produced in this comparative example has pearlite segregation at the edge, which can be eliminated after heat treatment, indicating that abnormal structure will be produced under this rolling process.

[0078] The present invention provides a method for processing abnormal tissue of hot-rolled wire rods. Metallographic tissue analysis is performed by heat treatment method, which can solve the problem that the existing in-situ analysis method may have a detection blind spot. At the same time, the detection method can quickly determine the source of the abnormal tissue. Furthermore, the uniformity of the temperature of the billet is ensured by controlling the temperature and time of the heating furnace during the rolling process, the heating of the walking beam and the billet in the heating furnace, the temperature compensation of the head and tail of the billet, and the appropriate descaling water pressure; and then the appropriate starting rolling temperature, finishing rolling temperature, sizing temperature and spinning temperature are controlled, and the number and mode of water tank nozzle opening are optimized. The uniformity of the cooling of the hot-rolled wire rod can be effectively improved, thereby avoiding the occurrence of abnormal tissue in the hot-rolled wire rod.

[0079] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for treating abnormal structure of hot-rolled wire rod, characterized in that: The method includes determining the source of abnormal tissue of the hot-rolled wire rod: after heat-treating the hot-rolled wire rod with abnormal tissue, comparing the changes of abnormal tissue in the microstructure metallographic diagram of the hot-rolled wire rod before and after the heat treatment; if the abnormal tissue after the heat treatment does not change, it indicates that the source of the abnormal tissue is the molten steel smelting process; if the abnormal tissue after the heat treatment is transformed into a normal tissue, it indicates that the source of the abnormal tissue is the rolling process; Then, the rolling or steelmaking process is adjusted according to the source of the abnormal structure to remove the abnormal structure in the hot-rolled wire rod.

2. The method according to claim 1, characterized in that: The normal tissue includes a ferrite phase and a pearlite phase; Preferably, in terms of volume percentage, the ferrite phase in the normal tissue is 25-40%, and the pearlite phase is 60-75%; Preferably, the content of the ferrite phase in the abnormal structure is greater than 40% or the content of the pearlite phase is greater than 75%.

3. The method according to claim 1, characterized in that The temperature of the heat treatment is the spinning temperature of the hot-rolled wire rod.

4. The method according to claim 3, characterized in that When the hot-rolled wire rod is S45C hot-rolled wire rod, the heat treatment temperature is 840-860°C.

5. The method according to claim 1, characterized in that The heat treatment process has a holding time of 30 to 60 minutes.

6. The method according to claim 1, characterized in that The heat treatment further includes corroding the hot-rolled wire rod with an acid alcohol solution; Preferably, the acid in the acid alcohol solution is nitric acid, and the concentration of nitric acid is 3-5%.

7. The method according to claim 1, characterized in that The method for adjusting the rolling process includes adjusting the parameters of the heating furnace. Preferably, the preheating section temperature of the heating furnace is ≤700°C, the heating section temperature is 700-1100°C, the soaking section temperature is 1000-1100°C, and the insulation time of the soaking section is ≥35min.

8. The method according to claim 1, characterized in that The method of adjusting the rolling process also includes placing insulating material between the walking beam of the heating furnace and the steel billet.

9. The method according to claim 8, characterized in that The head temperature of the steel billet coming out of the heating furnace is 10-30°C higher than the temperature of the hot-rolled wire rod with abnormal structure coming out of the heating furnace, and the tail temperature is 20-30°C higher.

10. The method according to claim 1, characterized in that The method for adjusting the rolling process also includes adjusting the rolling parameters. Preferably, the high-pressure water descaling pressure before rolling is ≥20MPa, the starting rolling temperature is Ac3+(70~130)℃, the finishing rolling temperature is Ac3+(40~80)℃, the sizing inlet temperature is Ac3+(30~70)℃, and the spinning temperature is Ac3+(60~80)℃.

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