Method for measuring inflection point of growth temperature of oxide skin on surface of high alloy steel
By grinding, heating, cooling, and metallographic microscopy measurements on high-alloy steel samples, the problem of difficult removal of oxide scale on the surface of high-alloy steel was solved, the inflection point of oxide scale growth was determined, and the surface quality and shape control of steel plates were optimized.
Patent Information
- Application Number
- CN202511003028.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2025-11-18
AI Technical Summary
The oxide scale on the surface of high alloy steel has strong adhesion to the substrate and is difficult to remove, affecting the surface quality of the steel plate and making plate shape control difficult. There is currently no standardized method for measuring the inflection point of oxide scale growth temperature.
By processing high-alloy steel into cuboid samples, surface grinding and cleaning, heating and cooling using a muffle furnace, and measuring the oxide scale thickness using a metallographic microscope, growth curves were plotted to determine the inflection point of oxide scale growth.
A method for measuring the inflection point of oxide scale growth temperature in high alloy steel is provided, which helps to study the growth of oxide scale at various stages of rolling and provides reference data for production control of oxide scale surface quality.
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Figure CN120971118A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of steel rolling, in particular to a method for measuring the growth temperature inflection point of the surface oxide scale of high alloy steel. BACKGROUND
[0002] The surface oxide scale of high alloy steel is difficult to remove due to the strong adhesion between the surface oxide scale and the substrate, and the surface quality of the steel plate is poor, and the occurrence rate of surface defects such as pits and ripples is much higher than that of ordinary products. High alloy steel plates often have large rolling forces and are difficult to control the shape of the plate. It is difficult to solve the surface problem while optimizing the shape of the plate. It is necessary to study the growth law of the surface oxide scale of high alloy steel to eliminate the surface defect problem of high alloy steel.
[0003] The temperature at each stage of the production process of high alloy steel is one of the factors affecting the surface quality. The growth of the surface oxide scale of the steel is greatly related to the surface temperature. The more serious the high-temperature oxidation of the steel surface in the heating furnace, the more difficult it is to remove the oxide scale. Different types, combinations and compositions of alloying elements have different growth of the oxide scale. Therefore, a standard and universal method for measuring the growth temperature inflection point of the oxide scale of high alloy steel is needed. SUMMARY
[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a method for measuring the growth temperature inflection point of the surface oxide scale of high alloy steel.
[0005] To solve the above technical problems, the technical scheme of the present application is as follows: A method for measuring the growth temperature inflection point of the surface oxide scale of high alloy steel, comprising: The high alloy steel is processed into several cuboid samples, the surface of the sample is polished, and then the surface of the sample is cleaned with anhydrous ethanol, and then the sample is blown dry; Control the muffle furnace to heat to a preset temperature, place the upper surface of the sample upward in the muffle furnace, set several test temperature points for heating test, and take out the sample from the muffle furnace after the heating test is completed, immediately put it into water for cooling, then blow dry the sample; Use epoxy resin AB glue to package the upper surface of the sample, and use sandpaper to polish the side surface of the sample to the target mesh number, and then use W5, W2.5 and W1 metallographic polishing liquid to polish the sample in turn; Place the polished sample under a metallographic microscope to measure the thickness of the oxide scale on the upper surface of the sample, and plot the oxide scale growth curve under different heating temperatures with the heating temperature as the horizontal coordinate and the oxide scale thickness as the vertical coordinate; Determine the inflection point temperature of the oxide scale growth based on the oxide scale growth curve.
[0006] As a preferred solution of the method for measuring the growth temperature inflection point of the surface oxide scale of the high-alloy steel, wherein: the processing of the high-alloy steel into a plurality of cuboid samples comprises: The high-alloy steel is cut into a plurality of cuboid samples, and the sampling process avoids the heat affected zone.
[0007] As a preferred solution of the method for measuring the growth temperature inflection point of the surface oxide scale of the high-alloy steel, wherein: the polishing of the sample surface comprises: The sample surface is polished to a surface roughness of 0.8 μm.
[0008] As a preferred solution of the method for measuring the growth temperature inflection point of the surface oxide scale of the high-alloy steel, wherein: the length and width of the sample are both 40 mm, and the height is less than or equal to 20 mm.
[0009] As a preferred solution of the method for measuring the growth temperature inflection point of the surface oxide scale of the high-alloy steel, wherein: the control of the muffle furnace to be heated to a preset temperature, the placement of the upper surface of the sample upward in the muffle furnace, the setting of a plurality of test temperature points for heating test, and the removal of the sample from the muffle furnace after the heating test and the immediate cooling of the sample in water, followed by the drying of the sample comprises: The control of the muffle furnace to be heated to a first test temperature point at a predetermined heating rate, the taking of a sample, the placement of the upper surface of the sample upward on a heat-resistant metal support, the loading of the sample into the muffle furnace for heating test, and the removal of the sample from the muffle furnace after the heating test and the immediate cooling of the sample in water, followed by the drying of the sample; The control of the muffle furnace to be heated to a second test temperature point at a predetermined heating rate, the taking of a sample, the placement of the upper surface of the sample upward on a heat-resistant metal support, the loading of the sample into the muffle furnace for heating test, and the removal of the sample from the muffle furnace after the heating test and the immediate cooling of the sample in water, followed by the drying of the sample; The above steps are repeatedly performed until the heating test of all test temperature points is completed.
[0010] As a preferred solution of the method for measuring the growth temperature inflection point of the surface oxide scale of the high-alloy steel, wherein: the temperature difference between two adjacent test temperature points is equal.
[0011] As a preferred solution of the method for measuring the growth temperature inflection point of the surface oxide scale of the high-alloy steel, wherein: the test temperature interval of the heating test is 650℃-950℃, and the thirteen test temperature points are set, and the temperature difference between two adjacent test temperature points is 25℃.
[0012] In a preferred embodiment of the method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel as described in this invention, the target mesh size is 1000 mesh.
[0013] The beneficial effects of this invention are: This invention employs a laboratory heating test method to simulate the oxide scale growth rate of high alloy materials at different temperatures and holding times during various rolling stages after exiting the heating furnace. The thickness and morphology of the oxide scale are observed using a metallographic microscope after the experiment, and the growth rate of the oxide scale at different temperatures is obtained. This provides a basic research method for studying the growth of oxide scale at various rolling stages and provides effective reference data for controlling the surface quality of oxide scale in production. Attached Figure Description
[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0015] Figure 1 This is a growth curve of the oxide layer in Example 1. Detailed Implementation
[0016] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.
[0017] This application provides a method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel, which specifically includes the following steps: Step S101: Process the high alloy steel into several rectangular test specimens, grind the surface of the specimens, clean the surface of the specimens with anhydrous ethanol, and then blow the specimens dry.
[0018] Specifically, several cuboid samples are cut from the high-alloy steel along its upper surface. Each sample surface is then polished until the surface roughness Ra is 0.8 μm. The polished sample surfaces are then cleaned with anhydrous ethanol and dried with cold air.
[0019] It should be noted that when cutting high alloy steel, the heat-affected zone should be avoided, and work hardening caused by overheating should be avoided during processing.
[0020] To distinguish the upper surface of the sample, a notch is made on the upper surface of the sample using sandpaper during the polishing process.
[0021] Step S102: control the muffle furnace to heat up to a preset temperature, place the upper surface of the sample upward in the muffle furnace, set several test temperature points for heating test, and after the heating test is completed, take out the sample from the muffle furnace and immediately put it into water for cooling, and then dry the sample.
[0022] Specifically, when the heating test is performed, first, the muffle furnace is turned on, and the operating parameters are set so that the muffle furnace is heated to the required test temperature. After the temperature of the muffle furnace is stabilized, the sample is placed in the muffle furnace in turn for heating.
[0023] In this application, the test temperature range of the heating test is set to 650-950℃, and thirteen test temperature points are set, with a temperature difference of 25℃ between adjacent two test temperature points. The specific operation process is as follows: Step S102a: control the muffle furnace to heat up to the first test temperature point at a predetermined heating rate, take one sample, place its upper surface upward on a heat-resistant metal support, and put it into the muffle furnace for heating test, and after the heating test is completed, take out the sample from the muffle furnace, immediately put it into water for cooling using a long handle heat insulation clamp to minimize the regrowth of the oxide skin after taking out, and then dry it with a cold air blower.
[0024] Step S102b: control the muffle furnace to heat up to the second test temperature point at a predetermined heating rate, take one sample, place its upper surface upward on a heat-resistant metal support, and put it into the muffle furnace for heating test, and after the heating test is completed, take out the sample from the muffle furnace, immediately put it into water for cooling using a long handle heat insulation clamp to minimize the regrowth of the oxide skin after taking out, and then dry it with a cold air blower.
[0025] Step S102c: cyclically execute the above steps until the heating test of all test temperature points is completed.
[0026] It should be noted that the holding time of the sample in the muffle furnace is determined according to the specific material of the sample, and is generally 2-10 min.
[0027] Step S103: encapsulate the upper surface of the sample using epoxy resin AB glue, and polish the side surface of the sample to the target mesh number using sandpaper, and then polish the sample in turn using W5, W2.5, and W1 metallographic polishing liquid.
[0028] Specifically, the upper surface of the sample is encapsulated using epoxy resin AB glue, and the cross section of the sample is polished to 1000 mesh in stages using a metallographic water sandpaper, and then polished in turn using W5, W2.5, and W1 metallographic polishing liquid.
[0029] Step S104: The polished sample is placed under a metallographic microscope to measure the oxide scale thickness on the upper surface of the sample, and an oxide scale growth curve at different heating temperatures is plotted with the heating temperature as the horizontal coordinate and the oxide scale thickness as the vertical coordinate.
[0030] Specifically, the polished sample is placed under a metallographic microscope for 500 times magnification to measure the oxide scale thickness. It can be understood that when the oxide scale thickness is less than 5 μm, 1000 times magnification can be used for measurement. Then an oxide scale growth curve at different heating temperatures is plotted with the heating temperature as the horizontal coordinate and the oxide scale thickness as the vertical coordinate.
[0031] Step S105: The inflection point temperature of the oxide scale growth is determined based on the oxide scale growth curve.
[0032] Specifically, the lowest heating temperature when the oxide scale thickness is greater than 5 μm is called the inflection point of the oxide scale growth temperature. When the temperature is lower than the inflection point, the oxide scale grows slowly; when the temperature is higher than the inflection point, the oxide scale grows significantly faster.
[0033] The application will be further described in detail below in combination with the drawings and specific examples.
[0034] This example is a test of the inflection point of the oxide scale growth temperature of a certain high alloy steel surface. The composition of the steel (wt%) is: C: 0.07, Mn: 1.0, P: 0.006, S: 0.0007, Si: 0.39, Ni: 1.5, Cr: 0.6, Cu: 0.02, and the balance is Fe. The thickness of the steel plate is 8 mm.
[0035] The experiment is divided into the following six steps: Step S101: Sample preparation.
[0036] The material is cut along the upper surface of the high alloy steel and processed into a sample of 40 mm x 40 mm x 8 mm, and the surface roughness is Ra 0.8 μm. Avoid the heat affected zone when sampling, and avoid work hardening caused by overheating during processing. In order to distinguish the upper surface of the sample, a notch is ground on the upper surface using sandpaper. The sample surface is cleaned with anhydrous ethanol and dried with cold air.
[0037] Step S102: Heating test.
[0038] The muffle furnace is turned on and the parameters are set. The temperature is raised to the required test temperature at a rate of 10℃ / min.
[0039] After the temperature of the muffle furnace is stabilized, the upper surface of the sample is placed upward on a heat-resistant metal support and placed in the muffle furnace for heating test. The experimental temperature setting range is 650℃-950℃, and there are 13 temperature points every 25℃. The holding time is 2 min.
[0040] After the heating test, the sample was taken out of the muffle furnace. In order to minimize the re-growth of the oxide skin after being taken out of the furnace, the sample was immediately placed in water for cooling using a long handle heat insulating clamp, and then dried using a hair dryer.
[0041] Step S103: oxide skin thickness measurement.
[0042] The upper surface of the sample was packaged using epoxy-based AB glue, and the cross section of the sample was polished to 1000 mesh using a metallographic sandpaper, and then polished using W5, W2.5, and W1 metallographic polishing liquid in sequence.
[0043] The polished sample was placed under a metallographic microscope at 500 times magnification to measure the thickness of the oxide skin. When the oxide skin thickness was less than 5 μm, 1000 times magnification was used for measurement.
[0044] Step S104: oxide skin growth curve drawing.
[0045] The heating temperature was taken as the abscissa, and the thickness of the oxide skin after the heating test was taken as the ordinate, and the oxide skin growth curve under different heating temperatures was drawn, which was Figure 1 .
[0046] Step S105: results The lowest heating temperature when the oxide skin thickness was greater than 5 μm was called the inflection point of the oxide skin growth temperature. The oxide skin growth temperature inflection point of the high alloy steel material used in the test was 825℃. Below the inflection point temperature, the oxide skin grew slowly; above the inflection point temperature, the oxide skin grew significantly faster.
[0047] Thus, by using different temperatures to carry out heating tests on high alloy steel, the oxide skin growth temperature inflection point of the high alloy steel surface was effectively evaluated, which provided a basic research method for studying the growth of oxide skin at each stage of rolling, and provided effective reference data for production to control the surface quality of oxide skin.
[0048] In addition to the above embodiments, the present application can have other implementation manners; any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.
Claims
1. A method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel, characterized in that: include: The high alloy steel was processed into several rectangular test specimens. After the surface of the test specimens was polished, the surface of the test specimens was cleaned with anhydrous ethanol and then the test specimens were dried. Control the muffle furnace to heat up to the preset temperature, place the sample with the upper surface facing up inside the muffle furnace, set several test temperature points for heating test, and after the heating test is completed, take the sample out of the muffle furnace, put it into water for cooling, and then blow the sample dry. The upper surface of the sample was sealed with epoxy resin AB glue, and the sides of the sample were sanded to the target mesh size. Then, the sample was polished with W5, W2.5 and W1 metallographic polishing liquids in sequence. The thickness of the oxide layer on the upper surface of the polished sample was measured under a metallographic microscope. The growth curve of the oxide layer at different heating temperatures was plotted with the heating temperature as the abscissa and the oxide layer thickness as the ordinate. The inflection point temperature of oxide scale growth was determined based on the oxide scale growth curve.
2. The method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel according to claim 1, characterized in that: The process of machining high-alloy steel into several rectangular parallelepiped samples includes: Several cuboid samples were cut from high-alloy steel, and the sampling process avoided the heat-affected zone of the cut.
3. The method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel according to claim 1, characterized in that: The grinding of the sample surface includes: The sample surface was polished to a surface roughness of 0.8 μm.
4. The method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel according to claim 1, characterized in that: The length and width of the sample are both 40 mm, and the height is less than or equal to 20 mm.
5. The method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel according to claim 1, characterized in that: The process of controlling the muffle furnace to heat to a preset temperature, placing the sample with its upper surface facing upwards inside the muffle furnace, setting several test temperature points for heating tests, and after the heating tests are completed, removing the sample from the muffle furnace, immediately immersing it in water for cooling, and then drying the sample includes: Control the muffle furnace to heat up to the first test temperature point at a predetermined heating rate. Take a sample, place it on a heat-resistant metal support with its upper surface facing up, put it into the muffle furnace for heating test, and after the heating test is completed, take the sample out of the muffle furnace, put it into water for cooling, and then blow the sample dry. Control the muffle furnace to heat up to the second test temperature point at a predetermined heating rate. Take a sample, place it on a heat-resistant metal support with its upper surface facing up, put it into the muffle furnace for heating test, and after the heating test is completed, take the sample out of the muffle furnace, put it into water for cooling, and then blow the sample dry. Repeat the above steps until the heating test at all test temperature points is completed.
6. The method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel according to claim 1, characterized in that: The temperature difference between two adjacent test temperature points is equal.
7. The method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel according to claim 6, characterized in that: The heating test has a test temperature range of 650℃ to 950℃, and there are thirteen test temperature points. The temperature difference between two adjacent test temperature points is 25℃.
8. The method for measuring the inflection point of oxide scale growth temperature on the surface of high alloy steel according to claim 1, characterized in that: The target mesh size is 1000 mesh.