Oxidation layer control and surface protection method in heat treatment process of stainless steel pipe fitting

Abstract

The invention relates to the technical field of heat treatment of stainless steel pipes, in particular to an oxide layer control and surface protection method in the heat treatment process of stainless steel pipes. Before heat treatment, the surface of the stainless steel pipe fitting is cleaned, in the heat treatment process, the outer side wall of the stainless steel pipe fitting is coated with a layer of fluorescent marking paint, the thickness change of the surface of the stainless steel pipe fitting is measured, whether the heat treatment temperature needs to be adjusted or not is judged, and effective judgment can be conducted according to point locations appearing on an oxide layer on the pipe fitting and the appearing speed of the oxide layer. The reason for the occurrence of the oxide layer is too high temperature, influences of other factors such as the oxidation environment problem, the stainless steel pipe fitting material problem and the oxide layer protection problem are eliminated, and the temperature environment during temperature rising / heat treatment and key technical data during heat treatment can be adjusted in a targeted mode according to the size and speed of the oxide layer. And in cooperation with an analysis and evaluation method, oxide layers are reduced, and the heat treatment efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment of stainless steel pipes, and in particular to a method for controlling an oxide layer and protecting a surface of a stainless steel pipe during heat treatment. Background Art

[0002] In the field of industrial manufacturing, stainless steel pipes are widely used in many industries such as petrochemicals, power generation and food processing due to their excellent corrosion resistance, high strength and durability. During the heat treatment of stainless steel pipes, a long-standing and challenging problem is the formation of an oxide layer on the pipe surface.

[0003] The presence of oxide scale on metal forgings can reduce the surface quality of steel structures, affecting the appearance and performance of the product. The formation of oxide scale can cause steel loss and reduce material utilization. The high hardness of the oxide scale can increase the difficulty and cost of subsequent processing steps.

[0004] Current industry methods, including spectroscopy, electron microscopy, and X-ray diffraction, have limitations. While these techniques can detect the presence and composition of the oxide layer to a certain extent, they cannot accurately determine whether the oxide layer is caused by excessive temperatures during heat treatment. This limitation fundamentally hinders the optimization of the heat treatment process.

[0005] If the temperature factors that lead to the formation of the oxide layer are not clear, it will be difficult to formulate targeted measures to optimize the heat treatment parameters and accurately control the growth of the oxide layer, and ultimately it will be difficult to improve product quality and production efficiency. Summary of the Invention

[0006] Technical problems solved

[0007] In view of the above-mentioned shortcomings of the prior art, the present invention provides a method for controlling the oxide layer and protecting the surface of stainless steel pipes during heat treatment, which can effectively solve the problems in the prior art.

[0008] Technical Solution

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0010] The present invention provides a method for controlling the oxide layer and protecting the surface of a stainless steel pipe during heat treatment, comprising: cleaning the surface of the stainless steel pipe before heat treatment; coating the outer wall of the stainless steel pipe with a layer of fluorescent marking paint during heat treatment; measuring the change in the surface thickness of the stainless steel pipe to determine whether the heat treatment temperature needs to be adjusted;

[0011] If necessary, the thickness information of the pipe is processed and analyzed to determine the thickness-time sequence table, and the heat treatment temperature is debugged and set with accuracy to complete the control of the oxide layer;

[0012] By processing and analyzing the pipe fittings after heat treatment, marking the pipe fitting thickness and the position of the oxide layer, and taking the temperature during heat treatment as a set of data pairs, analyzing multiple sets of data pairs, we can obtain the change data of temperature and pipe fitting thickness, and judge the risk degree of oxidation of the oxide layer based on the change data.

[0013] If the risk level is high, extract the points where the oxide layer appears quickly to determine whether the oxide layer on the pipe is caused by excessively high temperature. If so, readjust the heat treatment temperature and record the experimental data.

[0014] Furthermore, in the cleaning step before heat treatment, the surface of the stainless steel pipe is manually cleaned with acetone and alcohol to ensure that no impurities such as oil residue are left. It is then placed in an oven for drying. The titanium chips are collected and first soaked and cleaned with acetone to remove organic matter such as surface oil. Then, alkaline cleaning is performed to further remove impurities. Finally, it is rinsed with water and dried. Before each production, the titanium chips are placed in an environment not lower than the heating temperature and vacuum degree of the parts for degassing.

[0015] Furthermore, the process of determining whether the heat treatment temperature needs to be adjusted is:

[0016] Take any data pair of two pipe fittings;

[0017] Obtain the location of the oxide layer on the pipe and other information, and compare and analyze it with the two pipes;

[0018] If the points of any one set of oxidation layers of the two sets of pipe fittings overlap, they are marked as overlapping oxidation points SC. If the points of the two sets of pipe fittings do not overlap, they are marked as non-overlapping oxidation points SP. The overlapping oxidation points SC and non-overlapping oxidation points SP are processed and analyzed to obtain the oxidation overlap ratio SC and the oxidation deviation ratio, and then the detection overlap value is obtained. The detection overlap value is then compared with the detection overlap threshold.

[0019] If the detection coincidence value is greater than the detection coincidence threshold, it means that there is no need to adjust the heat treatment temperature of the pipe;

[0020] If the detection overlap value is less than or equal to the detection overlap threshold, it indicates that the heat treatment temperature of the pipe needs to be adjusted.

[0021] Furthermore, the oxidation overlap ratio SC and the oxidation deviation ratio SP are obtained by counting the number of overlapping oxidation points in the two groups of pipe fittings data and comparing them with the number of oxide layers in the two groups of pipe fittings. The oxidation overlap ratio SC is obtained after ratio processing, and the oxidation deviation ratio SP is obtained by obtaining the distance D between the non-overlapping oxidation damage point and the nearest overlapping oxidation point on the two groups of pipe fittings, summing and averaging the proximity distances of all non-oxidation overlapping points to obtain the proximity distance mean, and ratio processing the proximity distance mean with the proximity distance reference value to obtain the oxidation deviation ratio, which is marked as SP.

[0022] Furthermore, the thickness-time sorting table is determined as follows: the thickness information of the oxide layer of each group of pipe fittings is obtained, and attached marks are made according to the heat treatment time, the oxidation and treatment time series information of each stainless steel pipe fitting is obtained, and the oxide layer thickness is arranged in order from small to large per unit time to obtain the thickness-time sorting table. The heat treatment temperature debugging accuracy setting process is as follows: in the thickness-time sorting table, non-overlapping oxidation points are selected in turn, and new detection points are added and set at the positions of the selected non-overlapping oxidation points. After setting, the detection overlap value is recalculated until the detection overlap value is greater than the detection overlap threshold, then the selection is stopped, and the setting of the detection points is finally completed.

[0023] Furthermore, the point where the oxidation layer appears quickly is obtained by measuring the initial thickness of the outside of the pipe and the thickness after heat treatment to obtain the thickness of the oxidation layer, and performing ratio processing on the thickness and heat treatment time to obtain the oxidation deformation rate. If the deformation rate at the detection point is greater than the oxidation deformation rate threshold, the detection point is marked as a rapid oxidation deformation point.

[0024] Furthermore, the step of determining whether the appearance of the oxide layer on the pipe fitting is caused by excessive temperature is as follows: extracting data pairs from the group of pipe fittings, extracting the heat treatment time, temperature curve, and the point where the oxide layer appears, counting the heat treatment time and the total area of ​​the oxide layer in the heating range, and performing ratio processing T1, counting the heat treatment time and the total area of ​​the oxide layer in the insulation range, and performing ratio processing T2, comparing the two sets of ratios, if T1 is greater than T2, it indicates that the oxide layer appears in the heating stage, and the heating time and temperature need to be adjusted; if T2 is greater than T1, it indicates that the oxide layer appears in the insulation stage, and the insulation time and temperature need to be adjusted, and anti-oxidation material is applied to the outside of the pipeline.

[0025] Furthermore, the method of readjusting the heat treatment temperature is: obtaining the heat treatment time and the total area of ​​the oxidation layer in the heating range, and ratioing them to obtain the oxidation heating rate result as T1, ratioing the total area of ​​the oxidation layer to the total external area of ​​the pipe fitting to obtain the oxidation ratio as T3, ratioing the oxidation ratio and the oxidation heating rate result to obtain T4, ratioing T4 and T1 to obtain T5, and the heating rate is increased according to the rate of T5.

[0026] Beneficial effects

[0027] Compared with the known public technologies, the technical solution provided by the present invention has the following beneficial effects:

[0028] The present invention heats RLHY-33 steel with an anti-oxidation coating, namely an environmentally friendly water-based coating, which has an operating temperature range of -60°C to 1700°C. After application, the coating is dense, and a dense and continuous oxide film is generated on the metal surface. The oxide film can prevent oxygen from further diffusing into the metal, and can reduce the generation of oxide scale and decarburization layer during the heating process of the steel ingot, thereby achieving self-protection and reducing the overall oxidation rate of the metal. In addition, the heating temperature and atmosphere of the forging heat treatment are reasonably controlled by controlling the temperature and atmosphere, thereby reducing the generation of oxide scale.

[0029] RLHY-33 steel heating anti-oxidation coating effectively solves the problem of scale during steel structure forging heat treatment, improving product quality, reducing material loss, and increasing material utilization. Effectively controlling scale reduces the difficulty of subsequent processing and reduces production costs.

[0030] In this solution, the original thickness information of the pipe fittings is first recorded, and then the thickness of the oxide layer is recorded, processed and analyzed, and a ranking table of thickness and time is determined. The data in the ranking table is processed and analyzed to obtain the range of temperature adjustment during the heat treatment process, improve the accuracy, and by adding an oxide coating, the control of the oxide layer and its surface protection are achieved. A series of key technical data on stainless steel pipe fittings during heat treatment are obtained, and combined with analysis and evaluation methods, the appearance of the oxide layer is reduced and the efficiency of heat treatment is improved.

[0031] In this application, by observing the points where the oxide layer appears on the pipe fittings and the rate at which it appears, it is possible to effectively determine whether the cause of the oxide layer is excessive temperature, and to exclude the influence of other factors, such as the oxidation environment problem, the material problem of the stainless steel pipe fittings, and the oxide layer protection problem, etc., and the temperature environment during heating / heat treatment can be adjusted in a targeted manner according to the size and speed of the oxide layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0033] Figure 1 It is a flowchart of the present invention. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] The present invention will be further described below with reference to the embodiments.

[0036] Example: A method for controlling the oxide layer and protecting the surface of stainless steel pipes during heat treatment, see the attached Figure 1 , Step 1: Before heat treatment, the surface of the stainless steel pipe is cleaned first. During the heat treatment process, a layer of fluorescent marking paint is applied on its outer wall. In the cleaning step before heat treatment, the surface of the stainless steel pipe is manually cleaned with acetone and alcohol to ensure that there is no oil or other impurities remaining. Then it is placed in an oven for drying. Titanium chips are collected and first soaked and cleaned with acetone to remove organic matter such as oil on the surface. Then, alkaline cleaning is performed to further remove impurities. Finally, it is rinsed with water and dried. Before each production, the titanium chips are placed in an environment not lower than the heating temperature and vacuum degree of the parts for degassing. Fluorescent marking paint is a common high-temperature resistant marking material;

[0037] Step 2: Measure the thickness change of the stainless steel pipe surface to determine whether the heat treatment temperature needs to be adjusted. If necessary, the thickness information of the pipe is processed and analyzed to determine the thickness-time sequence table, and the heat treatment temperature is debugged and set with accuracy to complete the control of the oxide layer.

[0038] The process of determining whether the heat treatment temperature needs to be adjusted is as follows:

[0039] Take any data pair of two pipe fittings;

[0040] Obtain the location of the oxide layer on the pipe and other information, and compare and analyze it with the two pipes;

[0041] If the points of any one set of oxidation layers of the two sets of pipe fittings overlap, they are marked as overlapping oxidation points SC. If the points of the two sets of pipe fittings do not overlap, they are marked as non-overlapping oxidation points SP. The overlapping oxidation points SC and non-overlapping oxidation points SP are processed and analyzed to obtain the oxidation overlap ratio SC and the oxidation deviation ratio, and then the detection overlap value is obtained. The detection overlap value is then compared with the detection overlap threshold.

[0042] If the detection coincidence value is greater than the detection coincidence threshold, it means that there is no need to adjust the heat treatment temperature of the pipe;

[0043] If the detection coincidence value is less than or equal to the detection coincidence threshold, it means that the heat treatment temperature of the pipe needs to be adjusted;

[0044] The oxidation overlap ratio SC and the oxidation deviation ratio SP are obtained by counting the number of overlapping oxidation points in the two groups of pipe fittings data and comparing them with the number of oxide layers in the two groups of pipe fittings. The oxidation overlap ratio SC is obtained after ratio processing, and the oxidation deviation ratio SP is obtained by obtaining the distance D between the non-overlapping oxidation damage point and the nearest overlapping oxidation point on the two groups of pipe fittings, summing and averaging the proximity distances of all non-oxidation overlapping points to obtain the proximity distance mean, and then ratio processing the proximity distance mean with the proximity distance reference value to obtain the oxidation deviation ratio, which is marked as SP.

[0045] By observing the location and rate of the oxide layer on the pipe fittings, it is possible to effectively determine whether the cause of the oxide layer is excessive temperature and eliminate other factors such as the oxidizing environment, the material of the stainless steel pipe fittings, and the oxide layer protection. In addition, the temperature environment during heating / heat treatment can be adjusted in a targeted manner according to the size and rate of the oxide layer.

[0046] Example 2:

[0047] Step 3: by processing and analyzing the pipe fittings after heat treatment, marking the thickness of the pipe fittings and the position of the oxide layer, and taking the temperature during heat treatment as a set of data pairs, analyzing multiple sets of data pairs to obtain the change data of temperature and pipe fitting thickness, and judging the risk degree of oxidation of the oxide layer according to the change data; the thickness-time sorting table is determined as follows: obtaining the thickness information of the oxide layer of each group of pipe fittings, and attaching marks according to the heat treatment time, obtaining the oxidation and treatment time series information of each stainless steel pipe fitting, and arranging them in order from small to large in unit time according to the oxide layer thickness, to obtain the thickness-time sorting table, the heat treatment temperature debugging accuracy setting process is as follows: in the thickness-time sorting table, non-overlapping oxidation points are selected in turn, and in the selected New detection points are added to the positions of non-overlapping oxidation points, and after setting, the detection overlap value is recalculated until the detection overlap value is greater than the detection overlap threshold, then the selection is stopped, and the setting of the detection points is finally completed. If the risk level is high, the points where the oxidation layer appears quickly are extracted to determine whether the oxidation layer on the pipe is caused by excessively high temperature. If so, the heat treatment temperature is readjusted and the experimental data is recorded. The method for obtaining the points where the oxidation layer appears quickly is as follows: the thickness of the oxide layer is obtained by measuring the initial thickness of the outside of the pipe and the thickness after heat treatment, and the ratio of the thickness to the heat treatment time is processed to obtain the oxidation deformation rate. If the deformation rate of the detection point is greater than the oxidation deformation rate threshold, the detection point is marked as a rapid oxidation deformation point.

[0048] First, the original thickness information of the pipe fittings is recorded, and then the thickness of the oxide layer is recorded, processed and analyzed, and a ranking table of thickness and time is determined. The data in the ranking table is processed and analyzed to obtain the range of temperature adjustment during the heat treatment process, improve the accuracy, and by adding an oxide coating, the oxide layer is controlled and its surface is protected. A series of key technical data on stainless steel pipe fittings during heat treatment are obtained, and combined with analysis and evaluation methods, the appearance of the oxide layer is reduced and the efficiency of heat treatment is improved.

[0049] Example 3:

[0050] When protecting stainless steel pipe fittings, the cause of the oxide layer on the pipe fittings is first determined. The steps for determining whether the oxide layer on the pipe fittings is caused by excessive temperature are as follows: extract the data pairs from the group of pipe fittings, extract the heat treatment time, temperature curve and the point where the oxide layer appears, calculate the heat treatment time and the total area of ​​the oxide layer in the heating range, and perform ratio processing T1, calculate the heat treatment time and the total area of ​​the oxide layer in the insulation range, and perform ratio processing T2, compare the two groups of ratios, if T1 is greater than T2, it indicates that the oxide layer appears in the heating stage, and the heating time and temperature need to be adjusted. Adjustment is performed. If T2 is greater than T1, it indicates that the oxide layer appears in the insulation stage. The insulation time and temperature need to be adjusted, and anti-oxidation material should be applied to the outside of the pipeline. The method of re-adjusting the heat treatment temperature is: obtain the heat treatment time and the total area of ​​the oxide layer in the heating range, and compare them to obtain the oxidation heating rate result as T1, and compare the total area of ​​the oxide layer with the total external area of ​​the pipe to obtain the oxidation ratio as T3. Ratio the oxidation ratio and the oxidation heating rate results to obtain T4, and compare T4 and T1 to obtain T5. The heating rate is increased according to the rate of T5.

[0051] Specifically, RLHY-33 steel heating anti-oxidation coating, an environmentally friendly water-based coating with an operating temperature range of -60°C to 1700°C, forms a dense, continuous oxide film on the metal surface. This film prevents further oxygen diffusion into the metal, reducing the formation of scale and decarburization during the heating process, achieving self-protection and lowering the overall oxidation rate of the metal. Furthermore, by controlling the temperature and atmosphere during the forging heat treatment, the formation of scale is reduced. RLHY-33 steel heating anti-oxidation coating effectively solves the problem of scale during the forging heat treatment of steel structures, improving product quality, reducing material loss, and increasing material utilization. Effectively controlling scale reduces subsequent processing difficulties and lowers production costs.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for controlling the oxide layer and protecting the surface of stainless steel pipes during heat treatment, characterized in that: Including: before heat treatment, first clean the surface of the stainless steel pipe fittings, and during the heat treatment process, apply a layer of fluorescent marking paint on the outer wall of the stainless steel pipe fittings to measure the thickness change of the surface of the stainless steel pipe fittings to determine whether the heat treatment temperature needs to be adjusted; If necessary, the thickness information of the pipe is processed and analyzed to determine the thickness-time sequence table, and the heat treatment temperature is debugged and set with accuracy to complete the control of the oxide layer; By processing and analyzing the pipe fittings after heat treatment, marking the pipe fitting thickness and the position of the oxide layer, and taking the temperature during heat treatment as a set of data pairs, analyzing multiple sets of data pairs, we can obtain the change data of temperature and pipe fitting thickness, and judge the risk degree of oxidation of the oxide layer based on the change data. If the risk level is high, extract the points where the oxide layer appears quickly to determine whether the oxide layer on the pipe is caused by excessively high temperature. If so, readjust the heat treatment temperature and record the experimental data.

2. The method for controlling the oxide layer and protecting the surface of a stainless steel pipe during heat treatment according to claim 1, characterized in that: In the cleaning step before heat treatment, the surface of the stainless steel pipe is manually cleaned with acetone and alcohol to ensure that no impurities such as oil residue are left. It is then placed in an oven for drying. The titanium chips are collected and first soaked and cleaned with acetone to remove organic matter such as surface oil. Then, alkaline cleaning is performed to further remove impurities. Finally, the chips are rinsed with water and dried. Before each production, the titanium chips are placed in an environment not lower than the heating temperature and vacuum degree of the parts for degassing.

3. The method for controlling the oxide layer and protecting the surface of a stainless steel pipe during heat treatment according to claim 1, characterized in that: The process of determining whether the heat treatment temperature needs to be adjusted is as follows: Take any data pair of two pipe fittings; Obtain the location of the oxide layer on the pipe and other information, and compare and analyze it with the two pipes; If the points of any one set of oxidation layers of the two sets of pipe fittings overlap, they are marked as overlapping oxidation points SC. If the points of the two sets of pipe fittings do not overlap, they are marked as non-overlapping oxidation points SP. The overlapping oxidation points SC and non-overlapping oxidation points SP are processed and analyzed to obtain the oxidation overlap ratio SC and the oxidation deviation ratio, and then the detection overlap value is obtained. The detection overlap value is then compared with the detection overlap threshold. If the detection coincidence value is greater than the detection coincidence threshold, it means that there is no need to adjust the heat treatment temperature of the pipe; If the detection overlap value is less than or equal to the detection overlap threshold, it indicates that the heat treatment temperature of the pipe needs to be adjusted.

4. The method for controlling the oxide layer and protecting the surface of a stainless steel pipe during heat treatment according to claim 3, characterized in that: The oxidation overlap ratio SC and the oxidation deviation ratio SP are obtained by counting the number of overlapping oxidation points in the two groups of pipe fittings data and comparing them with the number of oxide layers in the two groups of pipe fittings. The oxidation overlap ratio SC is obtained after ratio processing, and the oxidation deviation ratio SP is obtained by obtaining the distance D between the non-overlapping oxidation damage point and the nearest overlapping oxidation point on the two groups of pipe fittings, summing and averaging the proximity distances of all non-oxidation overlapping points to obtain the proximity distance mean, and then ratio processing the proximity distance mean with the proximity distance reference value to obtain the oxidation deviation ratio, which is marked as SP.

5. The method for controlling the oxide layer and protecting the surface of a stainless steel pipe during heat treatment according to claim 4, characterized in that: The thickness-time sorting table is determined in the following manner: the thickness information of the oxide layer of each group of pipe fittings is obtained, and attached marks are made according to the heat treatment time, so as to obtain the oxidation and treatment time series information of each stainless steel pipe fitting, and the oxide layer thickness is arranged in order from small to large per unit time to obtain the thickness-time sorting table. The heat treatment temperature debugging accuracy setting process is as follows: non-overlapping oxidation points are selected in sequence in the thickness-time sorting table, new detection points are added and set at the positions of the selected non-overlapping oxidation points, and after setting, the detection overlap value is recalculated until the detection overlap value is greater than the detection overlap threshold, then the selection is stopped, and the setting of the detection points is finally completed.

6. The method for controlling the oxide layer and protecting the surface of a stainless steel pipe during heat treatment according to claim 1, characterized in that: The method for obtaining the point where the oxidation layer appears quickly is: measuring the initial thickness of the outside of the pipe and the thickness after heat treatment to obtain the thickness of the oxidation layer, and performing ratio processing on the thickness and heat treatment time to obtain the oxidation deformation rate. If the deformation rate at the detection point is greater than the oxidation deformation rate threshold, the detection point is marked as a rapid oxidation deformation point.

7. The method for controlling the oxide layer and protecting the surface of a stainless steel pipe during heat treatment according to claim 1, characterized in that: The step of determining whether the oxide layer on the pipe fitting is caused by excessive temperature is as follows: extracting data pairs from the group of pipe fittings, extracting the heat treatment time, temperature curve and the point where the oxide layer appears, counting the heat treatment time and the total area of ​​the oxide layer in the heating range, and performing ratio processing T1, counting the heat treatment time and the total area of ​​the oxide layer in the insulation range, and performing ratio processing T2, comparing the two sets of ratios, if T1 is greater than T2, it indicates that the oxide layer appears in the heating stage, and the heating time and temperature need to be adjusted; if T2 is greater than T1, it indicates that the oxide layer appears in the insulation stage, and the insulation time and temperature need to be adjusted, and anti-oxidation material is applied to the outside of the pipe.

8. The method for controlling the oxide layer and protecting the surface of a stainless steel pipe during heat treatment according to claim 7, characterized in that: The method for readjusting the heat treatment temperature is: obtaining the heat treatment time and the total area of ​​the oxidation layer in the heating range, and performing ratio processing to obtain the oxidation heating rate result as T1, performing ratio processing on the total area of ​​the oxidation layer and the total external area of ​​the pipe fitting to obtain the oxidation ratio as T3, performing ratio processing on the oxidation ratio and the oxidation heating rate result to obtain T4, performing ratio processing on T4 and T1 to obtain T5, and the heating rate is increased according to the rate of T5.

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