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CN117309543B - Iron-based powder oxygen content detection method - Google Patents

Iron-based powder oxygen content detection method Download PDF

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CN117309543B
CN117309543B CN202311302897.9A CN202311302897A CN117309543B CN 117309543 B CN117309543 B CN 117309543B CN 202311302897 A CN202311302897 A CN 202311302897A CN 117309543 B CN117309543 B CN 117309543B
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iron
based powder
sample
sintering
oxygen content
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CN117309543A (en
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尚德礼
廖相巍
康磊
吕春风
王铁
黄玉平
李广帮
李德军
常桂华
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Angang Steel Co Ltd
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    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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    • G01MEASURING; TESTING
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    • GPHYSICS
    • G01MEASURING; TESTING
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    • G01N1/00Sampling; Preparing specimens for investigation
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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    • G01MEASURING; TESTING
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    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17Systems in which incident light is modified in accordance with the properties of the material investigated
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    • G01N21/17Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3563Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing solids; Preparation of samples therefor
    • G01N2021/3572Preparation of samples, e.g. salt matrices

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Abstract

The invention relates to a method for detecting oxygen content of iron-based powder, which comprises the steps of firstly removing an oxidation layer on the surface of the iron-based powder, performing anti-oxidation treatment, then removing the oxidation layer through sintering, forming the iron-based powder, preparing a sample for detection by using a formed powder sintering material, and finally detecting the sample by using an oxygen analyzer to obtain the oxygen content of the iron-based powder. The whole detection process can avoid powder oxidation, is not influenced by external oxygen sources, and realizes accurate detection of the oxygen content of the iron-based powder.

Description

Iron-based powder oxygen content detection method
Technical Field
The invention relates to a metal powder oxygen content detection technology, in particular to an iron-based powder oxygen content detection method.
Background
Along with the development of technology, requirements on metal materials are more and more strict, such as requirements on high strength, long service life, corrosion resistance, use under severe conditions and the like, and one way of achieving the above properties is to improve the purity of the metal materials. The lower the oxygen content in the metal powder, the smaller the number of nonmetallic inclusions, the better the comprehensive properties of the metal material, the wider the application and the longer the service life. The higher oxygen content in the metallic material means that the number of nonmetallic inclusions is greater, and the inclusions significantly reduce the plasticity, toughness, fatigue properties, etc. of the material. It follows that an accurate assessment of the oxygen content of an iron-based powder is critical for its preparation and use. However, the existing detection method for the oxygen content of the iron-based powder is not perfect, and the problem of inaccurate oxygen content measurement results caused by powder oxidation and measurement methods cannot be effectively avoided, so that the method is further perfected, and the requirements of preparation and application of the high-purity iron-based powder are met.
Chinese patent application No. 201210188539.5 (publication No. CN103175777 a) discloses "a method for analyzing oxygen content in metal powder", comprising the steps of: firstly, placing metal powder to be tested into a high-purity nickel bag or nickel foil, wrapping the metal powder to be tested, compacting the metal powder, and removing air in the wrapping; secondly, placing the nickel bag or the nickel foil wrapped with the metal powder to be tested into a graphite crucible in a pulse heating furnace of an oxygen-nitrogen analyzer, and opening a power gas to enable a lower electrode to rise so that the graphite crucible is in contact with a fixed upper electrode; thirdly, electrifying to melt the powder to be tested in a nickel bag or nickel foil, and under the drive of helium flow, pulse heating the gas in the furnace (carbon monoxide or carbon dioxide formed after oxygen released in the melting process reacts with graphite enters a dust filter for filtration and dust removal; the method has three problems that when the powder is wrapped by the nickel bag or the nickel foil, the air between the powder cannot be discharged regardless of compaction, so that the measurement result can be influenced, the specific surface of the powder is very large, the powder is very easy to perform oxidation reaction with oxygen in the air during the sampling operation, the accuracy of the measurement result can be influenced, and the nickel bag or the nickel foil wrapping the powder can contain a certain amount of oxygen regardless of purity, so that the accuracy of the measurement result can be influenced.
Chinese patent application No. 201911134123.3 (publication No. CN111089947 a) discloses a device and a method for detecting high oxygen content in metal powder, which includes the steps of: (1) Accurately weighing a certain amount of high-oxygen-content metal powder and excessive carbon powder, mixing, wrapping the mixture with nickel sheets to form blocks, putting the blocks into a stainless steel crucible in a ceramic crucible, and then putting the ceramic crucible into a heating ring of a high-frequency heater connected with a reaction box through an operation port of the reaction box; (2) A fan arranged in the reaction box is started, an operation port of the reaction box is closed, a vent valve is opened, and inert gas nitrogen is used for replacing air in the reaction box; (3) Stopping nitrogen gas inlet and closing an emptying valve of an outlet of the reaction box when the detection value of the oxygen concentration detector in the reaction box is 0ppm, and starting the heating time and the heat preservation time set by the reaction high-frequency induction heater; (4) The powder in the stainless steel crucible in the ceramic crucible is subjected to high-temperature reaction to generate carbon monoxide gas or a small amount of carbon dioxide gas, and the concentration of carbon monoxide and carbon dioxide in the gas is obtained through a carbon monoxide detector and a carbon dioxide detector; (5) And (5) calculating the concentration of carbon monoxide and carbon dioxide gas to obtain the oxygen content in the metal powder. The method also has the problem that the oxygen is increased by the nickel sheet wrapping the powder and the oxygen in the air are subjected to oxidation reaction, so that the oxygen content of the metal powder cannot be accurately detected by adopting the method.
As described above, the conventional metal powder oxygen content detection method has a certain limitation. The invention provides an analysis method which does not adopt a nickel bag or a nickel foil to wrap powder and can prevent the powder from oxidizing in the detection process, and is very suitable for detecting the oxygen content of iron-based powder.
Disclosure of Invention
The invention provides an iron-based powder oxygen content detection method, which comprises the steps of firstly removing an oxidation layer on the surface of powder, performing anti-oxidation treatment, then removing the oxidation layer through powder sintering, forming, preparing a sample for an oxygen analyzer, and finally detecting the oxygen content of the iron-based powder through the oxygen analyzer; the whole detection process can avoid powder oxidation, is not influenced by external oxygen sources, and realizes accurate detection of the oxygen content of the iron-based powder.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
The method for detecting the oxygen content of the iron-based powder comprises the steps of firstly removing an oxidation layer on the surface of the iron-based powder, performing oxidation prevention treatment, then removing the oxidation layer through sintering, forming the iron-based powder, preparing a sample for detection by using a formed powder sintering material, and finally detecting the sample by using an oxygen analyzer to obtain the oxygen content of the iron-based powder.
An iron-based powder oxygen content detection method comprises the following steps:
1) Surface treatment of iron-based powder; removing the oxide layer on the surface of the iron-based powder to be analyzed, placing the iron-based powder into a rotary furnace, introducing inert gas into the rotary furnace to replace air, heating, and introducing H 2 S gas to enable the surface of the iron-based powder to generate an anti-oxidation layer;
2) Sintering iron-based powder; filling the iron-based powder subjected to surface treatment into a graphite mold, and sintering in a sintering furnace to prepare a sample blank; the oxidation preventing layer is removed in the sintering process;
3) Machining; processing the sample embryo into a sample;
4) Analyzing the oxygen content; and polishing to remove an oxide layer on the surface of the sample, and then performing oxygen content analysis.
The method for detecting the oxygen content of the iron-based powder specifically comprises the following steps:
1) Surface treatment of iron-based powder;
a. Placing the iron-based powder to be analyzed in liquid nitrogen for quenching treatment, so that the surface oxide layer of the iron-based powder is cracked;
b. Pickling the quenched iron-based powder with dilute hydrochloric acid to remove an oxide layer on the surface;
c. Immediately placing the pickled iron-based powder into a cleaning solution for cleaning to remove residual hydrochloric acid on the surface of the iron-based powder;
d. placing the cleaned iron-based powder into a rotary furnace, introducing inert gas into the rotary furnace, heating the rotary furnace to 80-100 ℃, and preserving heat for 5-10 min;
e. Continuously heating the rotary furnace to 400-450 ℃, stopping introducing inert gas, introducing H 2 S gas, and preserving heat for 3-8 min; generating an oxidation preventing layer on the surface of the iron-based powder, and then cooling;
f. Stopping introducing H 2 S gas after the temperature of the rotary furnace is reduced to room temperature, taking out the iron-based powder, and filling the iron-based powder into a sealing bag for later use;
2) Sintering iron-based powder;
a. Placing the iron-based powder subjected to the surface treatment in the step 1) into a graphite mold, placing the graphite mold in an SPS sintering furnace for vacuumizing treatment, starting sintering when the vacuum degree is less than 1Pa, and removing an oxidation preventing layer in the sintering process;
b. sintering temperature is 1180-1220 ℃, sintering heat preservation time is 30-40 mm, sintering pressure is 40-50 MPa, and heating rate is 80-120 ℃/min;
c. After the sintering is finished and the temperature is reduced to the room temperature, taking out a sample blank formed by sintering the iron-based powder;
3) Machining;
machining the sample embryo into a sample in a machining mode;
4) Analyzing the oxygen content;
Polishing to remove an oxide layer on the surface of a sample, then placing the polished sample into a graphite crucible, and heating and melting the sample through a pulse furnace; oxygen in the sample is separated out in the form of carbon monoxide, and is carried by carrier gas to enter a pulse infrared thermal conductivity and oxygen analyzer, and the oxygen content value is obtained after data processing by software.
Further, in the step 1), before the iron-based powder is processed, the ambient temperature and humidity are adjusted to ensure that the temperature is 20-25 ℃ and the humidity is not more than 10%.
Further, in the step 1), dilute hydrochloric acid with the concentration of 8-17% is adopted for pickling, the temperature of the dilute hydrochloric acid is 60-80 ℃, and the pickling time is 0.1-0.3 min; the cleaning liquid is absolute ethyl alcohol.
In the step 1), the inert gas is argon or nitrogen, and the flow rate is 50-60L/h.
Further, in the step 1), the flow rate of the H 2 S gas is 10-20L/H.
Further, in the step 2), the sample embryo is a round bar with a diameter of 8-12 mm.
Further, in the step 3), the sample is a small round bar having a diameter of 5mm and a length of 30mm.
Further, in the step 4), a grinding wheel is used to polish the surface of the sample to remove the oxide layer.
Compared with the prior art, the invention has the beneficial effects that:
1) The invention provides an analysis method which does not adopt a nickel bag or a nickel foil to wrap powder and can prevent the powder from oxidizing in the detection process; firstly, removing a surface oxide layer generated in the processes of preparation, storage and transportation of powder, performing powder anti-oxidation treatment, and preventing the powder from being oxidized after contacting air; then removing an oxidation-preventing layer through powder sintering, forming, preparing a sample with the specification required by an oxygen analyzer through machining, and finally detecting the oxygen content of the iron-based powder through the oxygen analyzer;
2) The whole analysis process is not influenced by external oxygen sources (other raw materials which can be oxygenated are not introduced, such as nickel capsules or nickel foils), so that the accurate detection of the oxygen content of the iron-based powder is realized.
Detailed Description
The invention relates to an oxygen content detection method of an iron-based powder, which comprises the steps of firstly removing an oxidation layer on the surface of the iron-based powder and performing anti-oxidation treatment, then removing the oxidation layer through sintering and forming the iron-based powder, preparing a sample for detection by using a formed powder sintering material, and finally detecting the sample by using an oxygen analyzer to obtain the oxygen content of the iron-based powder.
The invention discloses a method for detecting oxygen content of iron-based powder, which comprises the following steps:
1) Surface treatment of iron-based powder; removing the oxide layer on the surface of the iron-based powder to be analyzed, placing the iron-based powder into a rotary furnace, introducing inert gas into the rotary furnace to replace air, heating, and introducing H 2 S gas to enable the surface of the iron-based powder to generate an anti-oxidation layer;
2) Sintering iron-based powder; filling the iron-based powder subjected to surface treatment into a graphite mold, and sintering in a sintering furnace to prepare a sample blank; the oxidation preventing layer is removed in the sintering process;
3) Machining; processing the sample embryo into a sample;
4) Analyzing the oxygen content; and polishing to remove an oxide layer on the surface of the sample, and then performing oxygen content analysis.
The invention discloses a method for detecting oxygen content of iron-based powder, which specifically comprises the following steps:
1) Surface treatment of iron-based powder;
a. Placing the iron-based powder to be analyzed in liquid nitrogen for quenching treatment, so that the surface oxide layer of the iron-based powder is cracked;
b. Pickling the quenched iron-based powder with dilute hydrochloric acid to remove an oxide layer on the surface;
c. Immediately placing the pickled iron-based powder into a cleaning solution for cleaning to remove residual hydrochloric acid on the surface of the iron-based powder;
d. placing the cleaned iron-based powder into a rotary furnace, introducing inert gas into the rotary furnace, heating the rotary furnace to 80-100 ℃, and preserving heat for 5-10 min;
e. Continuously heating the rotary furnace to 400-450 ℃, stopping introducing inert gas, introducing H 2 S gas, and preserving heat for 3-8 min; generating an oxidation preventing layer on the surface of the iron-based powder, and then cooling;
f. Stopping introducing H 2 S gas after the temperature of the rotary furnace is reduced to room temperature, taking out the iron-based powder, and filling the iron-based powder into a sealing bag for later use;
2) Sintering iron-based powder;
a. Placing the iron-based powder subjected to the surface treatment in the step 1) into a graphite mold, placing the graphite mold in an SPS sintering furnace for vacuumizing treatment, starting sintering when the vacuum degree is less than 1Pa, and removing an oxidation preventing layer in the sintering process;
b. sintering temperature is 1180-1220 ℃, sintering heat preservation time is 30-40 mm, sintering pressure is 40-50 MPa, and heating rate is 80-120 ℃/min;
c. After the sintering is finished and the temperature is reduced to the room temperature, taking out a sample blank formed by sintering the iron-based powder;
3) Machining;
machining the sample embryo into a sample in a machining mode;
4) Analyzing the oxygen content;
Polishing to remove an oxide layer on the surface of a sample, cutting the polished sample into particles, placing the particles in a graphite crucible, and heating and melting the sample through a pulse furnace; oxygen in the sample is separated out in the form of carbon monoxide, and is carried by carrier gas to enter a pulse infrared thermal conductivity and oxygen analyzer, and the oxygen content value is obtained after data processing by software.
Further, in the step 1), before the iron-based powder is processed, the ambient temperature and humidity are adjusted to ensure that the temperature is 20-25 ℃ and the humidity is not more than 10%.
Further, in the step 1), dilute hydrochloric acid with the concentration of 8-17% is adopted for pickling, the temperature of the dilute hydrochloric acid is 60-80 ℃, and the pickling time is 0.1-0.3 min; the cleaning liquid is absolute ethyl alcohol.
In the step 1), the inert gas is argon or nitrogen, and the flow rate is 50-60L/h.
Further, in the step 1), the flow rate of the H 2 S gas is 10-20L/H.
Further, in the step 2), the sample embryo is a round bar with a diameter of 8-12 mm.
Further, in the step 3), the sample is a small round bar having a diameter of 5mm and a length of 30mm.
Further, in the step 4), a grinding wheel is used to polish the surface of the sample to remove the oxide layer.
The principle of the method for detecting the oxygen content of the iron-based powder provided by the invention is as follows: firstly, removing a surface oxide layer generated in the processes of iron-based powder preparation, storage and transportation and the like through acid washing, performing anti-oxidation treatment to prevent the iron-based powder from being oxidized after contacting air, then sintering the iron-based powder to remove the anti-oxidation layer and enable the iron-based powder to be formed (sample embryo), preparing a sample (small round bar) with the specification required by an oxygen analyzer through machining, and finally detecting the oxygen content in the iron-based powder through the oxygen analyzer.
The detection process (preferred scheme) is as follows:
1. surface treatment of iron-based powder;
1) Firstly, the temperature and humidity of the environment where the iron-based powder is treated are regulated, the temperature is regulated to 20-25 ℃, and the humidity is ensured to be not more than 10%.
2) Placing iron-based powder (weight is 200-300 g) to be analyzed into liquid nitrogen for quenching treatment, so that an oxide layer on the surface of the iron-based powder is cracked;
3) The quenched iron-based powder is cleaned by adopting dilute hydrochloric acid with the concentration of 10 to 15 percent, the temperature of the dilute hydrochloric acid is controlled between 60 and 80 ℃, and the pickling time is controlled between 0.1 and 0.3min.
4) And rapidly putting the pickled iron-based powder into absolute ethyl alcohol within 4min, and removing residual hydrochloric acid on the surface of the iron-based powder.
5) Placing the iron-based powder cleaned by the absolute ethyl alcohol into a rotary furnace, introducing argon into the rotary furnace, wherein the flow rate of the argon is 50-60L/h, heating the rotary furnace to 80-100 ℃, and preserving heat for 5-10 min.
6) Stopping introducing argon after the rotary furnace continues to the temperature of 400-450 ℃, introducing H 2 S gas instead, keeping the flow of H 2 S gas at 10-20L/H, preserving heat for 3-8 min, and cooling.
7) And after the temperature is reduced to room temperature, stopping introducing H 2 S gas, taking out the iron-based powder, and filling the iron-based powder into a sealing bag for standby.
In the above step 1), the humidity is ensured to be not more than 10% in order to prevent the iron-based powder from being oxidized to be intensified due to the excessively high humidity.
In the step 2), the iron-based powder is placed in liquid nitrogen for quenching treatment, so that the oxide layer on the surface of the iron-based powder is cracked, and the dilute hydrochloric acid is easy to use in the next pickling process to rapidly and stably remove the iron oxide layer on the surface of the iron-based powder.
In the step 3), the concentration of the dilute hydrochloric acid is 8% -17%, the temperature is controlled at 60-80 ℃, and the pickling time is controlled at 0.1-0.3 min, so as to ensure that the ferric oxide on the surface layer of the iron-based powder can be uniformly removed through the dilute hydrochloric acid, and a large amount of metallic iron is not reacted with the hydrochloric acid.
In the step 5), the temperature of the rotary furnace is raised to 80-100 ℃ so as to remove the residual ethanol on the surface of the iron-based powder.
In the step 6), the rotary kiln is continuously heated to 400-450 ℃ and then is filled with H 2 S gas so as to enable Fe element on the surface of the iron-based powder to react with the H 2 S gas to generate an oxidation-resistant layer (ferrous sulfide), and the iron-based powder can be prevented from reacting with oxygen in the air, so that oxygen increasing of the powder caused by oxidation of the iron-based powder in the next step is prevented.
2. Sintering iron-based powder;
1) The iron-based powder after the surface treatment is put into a graphite mold (the diameter of the mold cavity is preferably 10 mm), and placed in an SPS sintering furnace (a discharge plasma sintering furnace) for vacuum treatment, and sintering is started when the vacuum degree is less than 1 Pa.
2) The sintering temperature is 1180-1220 ℃, the sintering heat preservation time is 30-40 mm, the sintering pressure is 40-50 MPa, and the heating rate is 80-120 ℃/min.
3) After the sintering is completed and the temperature is reduced to room temperature, a sample embryo (round bar) formed by sintering the iron-based powder is taken out.
In the step 1), sintering is started when the vacuum degree is below 1Pa, so that on one hand, the sintering process is ensured to be beneficial to decomposing ferrous sulfide and removing sulfur element; on the other hand, ensures that the iron-based powder is not oxidized during sintering.
In the step 2), the limiting range of the sintering temperature is 1180-1220 ℃, and the temperature higher than 1180 ℃ can ensure that ferrous sulfide is fully decomposed and sulfur element is removed; below 1220 ℃ in order to avoid melting of the iron-based powder; the sintering pressure is 40-50 MPa, so that the iron-based powder can be ensured to have higher density after sintering, and the internal oxidation of a sample embryo in the later processing process is avoided; the sintering heat preservation time is 30-40 mm, which is favorable for the higher density of the sintered iron-based powder.
3. Machining;
the sample blank (round bar) formed after sintering the iron-based powder was machined into a sample (small round bar) having a diameter of 5mm and a length of 30 mm.
4. Analyzing the oxygen content;
The test process of the oxygen content in the sample comprises the following steps: firstly, polishing the surface of a small round bar by using a grinding wheel to remove an oxide layer, and placing a sample (metal bar particles for short) cut into particles by using the small round bar into a sample inlet of a pulse furnace; opening a furnace door of the pulse furnace, placing the graphite crucible on a lower electrode of the pulse furnace, and lifting the lower electrode; after the graphite crucible and the metal rod particles are degassed, the metal rod particles fall into the graphite crucible and are heated and melted; oxygen in the sample is separated out in the form of carbon monoxide, and is carried by carrier gas to enter a pulse infrared thermal conductivity and oxygen analyzer, and the oxygen content value is obtained after software data processing.
In the process, the grinding wheel is used for polishing the surface of the small round bar to remove the oxide layer, and the accuracy of the analysis result can be ensured only by polishing the grinding wheel to remove the oxide layer on the surface of the small round bar mainly in consideration of the possible surface oxidation of the small round bar before the analysis of the oxygen content.
The following examples are given by way of illustration of detailed embodiments and specific procedures based on the technical scheme of the present invention, but the scope of the present invention is not limited to the following examples.
In the following comparative examples and examples, the test raw materials were iron-based powders.
[ Comparative example ]
The oxygen content of the iron-based powder is detected by adopting a conventional method, namely the iron-based powder is directly put into a high-purity nickel bag, the high-purity nickel bag is wrapped and compacted, air in the wrapping is removed, then the nickel bag wrapped with the iron-based powder is put into a graphite crucible in a pulse heating furnace of an oxygen-nitrogen analyzer, and finally the oxygen content of the iron-based powder is detected to be 98ppm.
The following examples were all tested using the test methods of the present invention.
[ Example 1]
In this example, the oxygen content of the iron-based powder was measured as follows:
1. surface treatment of iron-based powder;
1) The temperature and humidity of the room in which the sample was treated were adjusted to 22℃and 9%.
2) 240G of iron-based powder to be analyzed is placed into liquid nitrogen for quenching treatment, so that an oxide layer on the surface of the iron-based powder is cracked.
3) And (3) pickling the quenched iron-based powder by adopting dilute hydrochloric acid with the concentration of 11%, wherein the temperature of the dilute hydrochloric acid is controlled at 75 ℃, and the pickling time is controlled at 0.2min.
4) And rapidly putting the pickled iron-based powder into absolute ethyl alcohol within 4min, and removing residual hydrochloric acid on the surface of the iron-based powder.
5) Adding the iron-based powder cleaned by the absolute ethyl alcohol into a rotary furnace, introducing argon into the rotary furnace, wherein the flow rate of the argon is 52L/h, heating the rotary furnace to 85 ℃, and preserving heat for 6min.
6) And stopping introducing argon after the temperature of the rotary furnace is continuously increased to 420 ℃, introducing H 2 S gas instead, keeping the flow of H 2 S gas at 11L/H, keeping the temperature for 4min, and then cooling.
6) And after the temperature is reduced to room temperature, stopping introducing H 2 S gas, taking out the iron-based powder, and filling the iron-based powder into a sealing bag for standby.
2. Sintering iron-based powder;
1) Filling the iron-based powder subjected to the surface treatment into a graphite mold, wherein the diameter of a cavity of the graphite mold is 10mm, placing the graphite mold in an SPS sintering furnace for vacuumizing treatment, and starting sintering when the vacuum degree is less than 1 Pa;
2) Sintering temperature is 1190 ℃, sintering heat preservation time is 32 mm, sintering pressure is 42MPa, and heating rate is 88 ℃/min;
3) And taking out the round bar formed by sintering the iron-based powder after the sintering is finished and the temperature is reduced to the room temperature.
3. Machining;
the round bar was machined into a small round bar of 5mm diameter and 30mm length by a machine tool.
4. Analyzing the oxygen content;
firstly, polishing the surface of a small round bar by using a grinding wheel to remove an oxide layer, and placing a sample (metal bar particles for short) cut into particles by using the small round bar into a sample inlet of a pulse furnace; opening a furnace door of the pulse furnace, placing the graphite crucible on a lower electrode of the pulse furnace, and lifting the lower electrode; after the graphite crucible and the metal rod particles are degassed, the metal rod particles fall into the graphite crucible and are heated and melted; oxygen in the sample is separated out in the form of carbon monoxide, and is carried by carrier gas to enter a pulse infrared thermal conductivity and oxygen analyzer, and the oxygen content value is 48ppm through software data processing.
[ Example 2]
In this example, the oxygen content of the iron-based powder was measured as follows:
1. surface treatment of iron-based powder;
1) The temperature and humidity of the room in which the sample was treated were adjusted to 23℃and 8%.
2) 250G of iron-based powder to be analyzed is placed into liquid nitrogen for quenching treatment, so that an oxide layer on the surface of the iron-based powder is cracked.
3) And (3) pickling the quenched iron-based powder by adopting dilute hydrochloric acid with the concentration of 12%, wherein the temperature of the dilute hydrochloric acid is controlled at 74 ℃, and the pickling time is controlled at 0.1min.
4) And rapidly putting the pickled iron-based powder into absolute ethyl alcohol within 4min, and removing residual hydrochloric acid on the surface of the iron-based powder.
5) Adding the iron-based powder cleaned by the absolute ethyl alcohol into a rotary furnace, introducing argon into the rotary furnace, wherein the flow rate of the argon is 55L/h, heating the rotary furnace to 90 ℃, and preserving heat for 8min.
6) And stopping introducing argon after the rotary furnace is continuously heated to 425 ℃, introducing H 2 S gas instead, keeping the flow of H 2 S gas at 15L/H, and cooling after keeping the temperature for 5 min.
6) And after the temperature is reduced to room temperature, stopping introducing H 2 S gas, taking out the iron-based powder, and filling the iron-based powder into a sealing bag for standby.
2. Sintering iron-based powder;
1) Filling the iron-based powder subjected to the surface treatment into a graphite mold, wherein the diameter of a cavity of the graphite mold is 10mm, placing the graphite mold in an SPS sintering furnace for vacuumizing treatment, and starting sintering when the vacuum degree is less than 1 Pa;
2) The sintering temperature is 1200 ℃, the sintering heat preservation time is 35 mm, the sintering pressure is 45MPa, and the heating rate is 90 ℃/min;
3) And taking out the round bar formed by sintering the iron-based powder after the sintering is finished and the temperature is reduced to the room temperature.
3. Machining;
the round bar was machined into a small round bar of 5mm diameter and 30mm length by a machine tool.
4. Analyzing the oxygen content;
Firstly, polishing the surface of a small round bar by using a grinding wheel to remove an oxide layer, and placing a sample (metal bar particles for short) cut into particles by using the small round bar into a sample inlet of a pulse furnace; opening a furnace door of the pulse furnace, placing the graphite crucible on a lower electrode of the pulse furnace, and lifting the lower electrode; after the graphite crucible and the metal rod particles are degassed, the metal rod particles fall into the graphite crucible and are heated and melted; oxygen in the sample is separated out in the form of carbon monoxide, and is carried by carrier gas to enter a pulse infrared thermal conductivity and oxygen analyzer, and the oxygen content value is 47ppm after software data processing.
[ Example 3]
In this example, the oxygen content of the iron-based powder was measured as follows:
1. surface treatment of iron-based powder;
1) The temperature and humidity of the room in which the sample was treated were adjusted to 25℃and 8%.
2) 270G of iron-based powder to be analyzed is placed into liquid nitrogen for quenching treatment, so that an oxide layer on the surface of the iron-based powder is cracked.
3) And (3) pickling the quenched iron-based powder by adopting dilute hydrochloric acid with the concentration of 14%, wherein the temperature of the dilute hydrochloric acid is controlled at 76 ℃, and the pickling time is controlled at 0.3min.
4) And rapidly putting the pickled iron-based powder into absolute ethyl alcohol within 4min, and removing residual hydrochloric acid on the surface of the iron-based powder.
5) Adding the iron-based powder cleaned by the absolute ethyl alcohol into a rotary furnace, introducing argon into the rotary furnace, wherein the flow rate of the argon is 58L/h, heating the rotary furnace to 95 ℃, and preserving heat for 9min.
6) And stopping introducing argon after the temperature of the rotary furnace is continuously increased to 440 ℃, introducing H 2 S gas instead, keeping the flow of H 2 S gas at 19L/H, keeping the temperature for 7min, and then cooling.
6) And after the temperature is reduced to room temperature, stopping introducing H 2 S gas, taking out the iron-based powder, and filling the iron-based powder into a sealing bag for standby.
2. Sintering iron-based powder;
1) Filling the iron-based powder subjected to the surface treatment into a graphite mold, wherein the diameter of a cavity of the graphite mold is 10mm, placing the graphite mold in an SPS sintering furnace for vacuumizing treatment, and starting sintering when the vacuum degree is less than 1 Pa;
2) Sintering temperature is 1210 ℃, sintering heat preservation time is 36 mm, sintering pressure is 47MPa, and heating rate is 100 ℃/min;
3) And taking out the round bar formed by sintering the iron-based powder after the sintering is finished and the temperature is reduced to the room temperature.
3. Machining;
the round bar was machined into a small round bar of 5mm diameter and 30mm length by a machine tool.
4. Analyzing the oxygen content;
Firstly, polishing the surface of a small round bar by using a grinding wheel to remove an oxide layer, and placing a sample (metal bar particles for short) cut into particles by using the small round bar into a sample inlet of a pulse furnace; opening a furnace door of the pulse furnace, placing the graphite crucible on a lower electrode of the pulse furnace, and lifting the lower electrode; after the graphite crucible and the metal rod particles are degassed, the metal rod particles fall into the graphite crucible and are heated and melted; oxygen in the sample is separated out in the form of carbon monoxide, and is carried by carrier gas to enter a pulse infrared thermal conductivity and oxygen analyzer, and the oxygen content value is 49ppm through software data processing.
As can be seen from the above examples, the oxygen content of the iron-based powder detected by the method of the invention is significantly reduced compared with that of the conventional detection method (comparative example), and the maximum reduction reaches 51ppm. The method provided by the invention has the advantages that not only is oxygen in the coating such as the nickel capsule effectively removed, but also oxygen in the surface oxide in the preparation, storage and transportation processes of the iron-based powder is effectively removed, and meanwhile, oxygenation caused by oxidation of the iron-based powder in the conventional detection process is avoided.
The oxygen content measurements for examples 1-3 were: the difference between 48ppm, 47ppm and 49ppm is small, which indicates that the detection method is stable and reliable, and the slight difference is caused by detection errors and does not influence the stability of the detection method.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.

Claims (8)

1. The method is characterized in that firstly, an oxidation layer on the surface of the iron-based powder is removed, oxidation prevention treatment is carried out, then the iron-based powder is sintered to remove the oxidation prevention layer, the iron-based powder is molded, a sample for detection is prepared by using the molded powder sintered material, and finally, an oxygen analyzer is adopted to detect the sample, so that the oxygen content of the iron-based powder is obtained; the method specifically comprises the following steps:
1) Surface treatment of iron-based powder;
a. Placing the iron-based powder to be analyzed in liquid nitrogen for quenching treatment, so that the surface oxide layer of the iron-based powder is cracked;
b. Pickling the quenched iron-based powder with dilute hydrochloric acid to remove an oxide layer on the surface;
c. Immediately placing the pickled iron-based powder into a cleaning solution for cleaning to remove residual hydrochloric acid on the surface of the iron-based powder;
d. placing the cleaned iron-based powder into a rotary furnace, introducing inert gas into the rotary furnace, heating the rotary furnace to 80-100 ℃, and preserving heat for 5-10 min;
e. Continuously heating the rotary furnace to 400-450 ℃, stopping introducing inert gas, introducing H 2 S gas, and preserving heat for 3-8 min; generating an oxidation preventing layer on the surface of the iron-based powder, and then cooling;
f. Stopping introducing H 2 S gas after the temperature of the rotary furnace is reduced to room temperature, taking out the iron-based powder, and filling the iron-based powder into a sealing bag for later use;
2) Sintering iron-based powder;
a. Placing the iron-based powder subjected to the surface treatment in the step 1) into a graphite mold, placing the graphite mold in an SPS sintering furnace for vacuumizing treatment, starting sintering when the vacuum degree is less than 1Pa, and removing an oxidation preventing layer in the sintering process;
b. sintering temperature is 1180-1220 ℃, sintering heat preservation time is 30-40 mm, sintering pressure is 40-50 MPa, and heating rate is 80-120 ℃/min;
c. After the sintering is finished and the temperature is reduced to the room temperature, taking out a sample blank formed by sintering the iron-based powder;
3) Machining;
machining the sample embryo into a sample in a machining mode;
4) Analyzing the oxygen content;
Polishing to remove an oxide layer on the surface of a sample, cutting the polished sample into particles, placing the particles in a graphite crucible, and heating and melting the sample through a pulse furnace; oxygen in the sample is separated out in the form of carbon monoxide, and is carried by carrier gas to enter a pulse infrared thermal conductivity and oxygen analyzer, and the oxygen content value is obtained after data processing by software.
2. The method according to claim 1, wherein in step 1), the ambient temperature and humidity are adjusted to ensure that the temperature is 20-25 ℃ and the humidity is not more than 10% before the iron-based powder is processed.
3. The method for detecting oxygen content of iron-based powder according to claim 1, wherein in the step 1), dilute hydrochloric acid with concentration of 8% -17% is used for pickling, the temperature of the dilute hydrochloric acid is 60-80 ℃, and the pickling time is 0.1-0.3 min; the cleaning liquid is absolute ethyl alcohol.
4. The method for detecting oxygen content of iron-based powder according to claim 1, wherein in the step 1), the inert gas is argon or nitrogen, and the flow rate is 50-60L/h.
5. The method for detecting oxygen content of iron-based powder according to claim 1, wherein in the step 1), the flow rate of the H 2 S gas is 10-20L/H.
6. The method for detecting oxygen content of iron-based powder according to claim 1, wherein in the step 2), the sample embryo is a round rod with a diameter of 8-12 mm.
7. The method for detecting oxygen content of iron-based powder according to claim 1, wherein in the step 3), the sample is a small round bar with a diameter of 5mm and a length of 30 mm.
8. The method for detecting oxygen content of iron-based powder according to claim 1, wherein in the step 4), a grinding wheel is used to polish the surface of the sample to remove the oxide layer.
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