CN113981186B - Atmosphere protection heat treatment process for preventing decarburization and carburetion - Google Patents
Atmosphere protection heat treatment process for preventing decarburization and carburetion Download PDFInfo
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- CN113981186B CN113981186B CN202111115107.7A CN202111115107A CN113981186B CN 113981186 B CN113981186 B CN 113981186B CN 202111115107 A CN202111115107 A CN 202111115107A CN 113981186 B CN113981186 B CN 113981186B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C21D1/76—Adjusting the composition of the atmosphere
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention discloses an atmosphere protection heat treatment process for preventing decarburization and carburetion, which mainly comprises the following steps: introducing N3-4 times of the volume of the heat treatment furnace 2 Discharging air in the heat treatment furnace; introducing a protective atmosphere into the heat treatment furnace, and monitoring the oxygen potential value in the heat treatment furnace, wherein the protective atmosphere comprises CO in percentage by volume 2 0.7％、CO 19.27％、CH 4 2.47% and H 2 77.56%; when the oxygen potential value in the heat treatment furnace reaches 1050, continuously introducing protective atmosphere and simultaneously introducing N 2 Maintaining the pressure, controlling the temperature of the heat treatment furnace to be 750-770 ℃, and keeping the temperature for 10-12h; after the heat preservation time is over, controlling the heat treatment furnace to cool down, stopping introducing the protective atmosphere and continuously introducing N 2 Discharging the protective atmosphere in the heat treatment furnace until the temperature of the heat treatment furnace is reduced to 540-560 ℃ or below, and taking out the steel to finish the heat treatment process. The invention avoids the unstable components of protective atmosphere, decarburization and carburetion, and ensures the heat treatment quality of steel.
Description
Technical Field
The invention relates to the technical field of heat treatment, in particular to an atmosphere protection heat treatment process for preventing decarburization and carburetion.
Background
The cold heading wire rod, namely the coil material leaving the factory from the steel mill, needs to go through the processes of factory spheroidizing annealing, pickling phosphorus saponification, wire drawing and the like, improves the plasticity and toughness of the material, meets the individualized requirements of customers on specifications, and simultaneously improves the cold heading performance of the material. In the spheroidizing annealing process of the key working procedure, the steel is extremely easy to generate decarburization under the high-temperature condition. Decarburization of steel has two processes: firstly, the C atoms of the surface are oxidized; secondly, the loss of C atoms on the surface causes the concentration of C on the surface to be reduced, wherein O2, H2O and the like belong to oxidizing gas, can be subjected to oxidation and decarburization reaction with the C atoms in the steel, and causes decarburization on the surface of the steel; CO, H2 and the like are reducing gases, so that an oxide layer and a decarburized layer on the surface of the steel can be reduced, and the original component state of the surface of the steel can be restored. According to the balance principle of chemical reaction, the oxidation reaction and the reduction reaction on the surface of the steel are carried out simultaneously, and if the oxidation reaction speed is higher than the reduction reaction, the decarburization on the surface of the material can be caused; otherwise, carburetion phenomenon, namely, phenomenon of enriching carbon content on the surface of the material, occurs.
After the surface of the steel is oxidized and decarbonized, the surface state is very rough, the luster is lost, pitting surfaces are easy to form, and the surface quality of the product is affected. When cold heading is carried out, the decarburized surface can be adhered to a die to lead to product galling, the subsequent heat treatment can lead to conditions of quenching cracks, soft spots, insufficient hardness and the like, carburetion can lead to cracking of the product during cold heading, and if the product is a high-strength bolt, the hydrogen embrittlement sensitivity of the product can be increased.
At present, the common decarbonization-preventing atmosphere process is methanol instilling pyrolysis as a protective atmosphere, the pyrolysis principle is that CH3OH is directly instilled into a hearth heated at high temperature, and organic matters are subjected to high-temperature pyrolysis and cracking to generate reducing mixed gas containing CO, H2 and the like, so that the aim of preventing decarbonization is achieved, but the methanol instilling pyrolysis as the protective atmosphere usually requires other organic liquids such as ethanol and isopropanol due to lower carbon potential of pyrolysis products when the pyrolysis gas is generated. The dropping amount and dropping agent are easily affected by the factors of materials, furnace loading amount, furnace volume, temperature and the like. In addition, the methanol instillation cracking can cause carbon deposition on the furnace wall, heat radiation conduction is hindered, the methanol cracking is insufficient, the cracking gas component is unstable, the phenomenon of uncontrolled decarburization and carburetion on the surface of the material is caused, and then the product is scrapped.
Disclosure of Invention
The invention provides a heat treatment process for preventing decarburization and carburetion under the protection of protective atmosphere, which aims to avoid the defects existing in the prior art.
The invention solves the technical problems by adopting the following technical scheme:
the invention provides an atmosphere protection heat treatment process for preventing decarburization and carburetion, which comprises the following steps:
s100, placing the steel into a heat treatment furnace, controlling the temperature of the heat treatment furnace, and simultaneously introducing N3-4 times of the volume of the heat treatment furnace into the heat treatment furnace 2 Discharging air in the heat treatment furnace, and monitoring the oxygen potential value in the heat treatment furnace; s200, when the oxygen potential value in the heat treatment furnace reaches 900-910, introducing a protective atmosphere into the heat treatment furnace, and monitoring the oxygen potential value in the heat treatment furnace, wherein the protective atmosphere comprises CO in percentage by volume 2 0.7％、CO 19.27％、CH 4 2.47% and H 2 77.56%; s300, when the oxygen potential value in the heat treatment furnace reaches 1050, continuously introducing protective atmosphere and simultaneously introducing N 2 Maintaining the pressure, controlling the temperature of the heat treatment furnace to be 750-770 ℃, and keeping the temperature for 10-12h; s400, after the heat preservation time is finished, controlling the heat treatment furnace to cool down, stopping introducing the protective atmosphere and continuously introducing N 2 Discharging the protective atmosphere in the heat treatment furnace until the temperature of the heat treatment furnace is reduced to 540-560 ℃ or below, and taking out the steel to finish the heat treatment process.
In several embodiments, the steel is specifically SCM435 alloy steel.
In several embodiments, in S300, the N 2 The feed rate of (2) is 4-10m 3 /h。
In several embodiments, in S300, the oxygen potential value is controlled to stabilize at 1050 during the soak time.
In several embodiments, in S100 to S400, the oxygen potential value in the heat treatment furnace is monitored by a detection probe.
The invention has the following beneficial effects:
the invention is realized by feeding N 2 Discharging the oxidizing gas in the furnace to prevent the material from reacting with oxygen at high temperature to cause decarburization of the material; second by CO 2 0.7％、CO 19.27％、CH 4 2.47% and H 2 77.56% of specific protective atmosphere ratio, combined with the condition of oxygen potential value in the furnace, can protect the steel, so that the oxidation reaction and the reduction reaction on the surface of the steel are carried out simultaneously, the conditions of decarburization and carburetion are avoided, and the condition of unstable components of the protective atmosphere is avoided due to the fixed proportion of the protective atmosphere, so that the heat treatment quality of the steel is ensured.
Drawings
The drawings described herein are for illustration purposes only of selected embodiments and are not intended to represent all possible implementations and should not be construed as limiting the scope of the present invention.
FIG. 1 schematically shows a plot of nitrogen feed versus oxygen potential;
FIG. 2 schematically illustrates decarburization and carburetion of a steel at an oxygen potential value of 900;
FIG. 3 schematically illustrates decarburization and carburetion of a steel at 980 oxygen potential;
FIG. 4 schematically illustrates decarburization and carburetion of a steel at 1050 oxygen potential;
FIG. 5 schematically shows decarburization and carburetion of a steel at an oxygen potential value of 1100.
Detailed Description
In the following, embodiments of the present invention will be described in detail, for the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, and in the following, technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments.
Thus, the following detailed description of the embodiments of the invention, which is provided herein, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention, based on which all other embodiments, as derived by a person of ordinary skill in the art without making any inventive effort, are within the scope of the invention.
The terminology used herein is for the purpose of describing embodiments and is not intended to be limiting and/or limiting of the invention.
In the invention, the steel material adopted is SCM435 alloy steel, and the structural steel of the SCM435 alloy has chemical composition (%): carbon C0.33-0.38, silicon Si 0.15-0.35, manganese Mn 0.60-0.90, S sulfur less than or equal to 0.030, P less than or equal to 0.030, cr 0.90-1.20, ni less than or equal to 0.25, mo 0.15-0.30, and SCM435 alloy steel production process is 'two-ball two-drawing', namely spheroidizing annealing-pickling phosphorus saponification-semi-finished wire drawing-spheroidizing annealing-pickling phosphorus saponification-finished wire drawing, wherein the purpose of the spheroidizing annealing process is to spheroidize carbide in the steel to obtain granular pearlite.
Specifically, the heat treatment process comprises the following steps:
firstly, placing steel into a heat treatment furnace, controlling the temperature of the heat treatment furnace, and simultaneously introducing N3-4 times of the volume of the heat treatment furnace into the heat treatment furnace 2 And discharging air containing oxidizing gas in the heat treatment furnace through the filled nitrogen, monitoring the oxygen potential value in the heat treatment furnace through a detection probe, and judging whether the air in the furnace is discharged or not through the oxygen potential value.
Secondly, when the oxygen potential value in the heat treatment furnace reaches 900-910, introducing a protective atmosphere into the heat treatment furnace, and monitoring the oxygen potential value in the heat treatment furnace through a detection probe, wherein the protective atmosphere comprises CO in percentage by volume 2 0.7％、CO 19.27％、CH 4 2.47% and H 2 77.56％。
When the oxygen potential value in the heat treatment furnace reaches 900-910, the residual quantity of the oxygen-containing gas in the furnace is less, and the standard is reached, and the volume of the nitrogen to be fed is judged through the oxygen potential value, wherein the relation between the feeding volume of the nitrogen and the oxygen potential value is shown in the table 1:
TABLE 1 relation between nitrogen gas feeding amount and oxygen potential value
| Nitrogen gas feed amount | 1 times of nitrogen | 2 times nitrogen | 3 times nitrogen | 3.5 times of nitrogen | 4 times of nitrogen |
| Oxygen potential value | 780 | 850 | 900 | 910 | 910 |
Wherein, 1-4 times of nitrogen gas refers to 1-4 times of the volume of the heat treatment furnace, and according to Table 1 and FIG. 1, when 3 times or more of nitrogen gas is introduced, the oxygen potential value tends to be stabilized around 900, whereby 3-4 times of the amount of nitrogen gas introduced is selected.
Then, continuously monitoring the oxygen potential value, when the oxygen potential value in the heat treatment furnace reaches 1050, continuously introducing protective atmosphere, and simultaneously introducing N 2 Pressure maintaining is carried out, N 2 The feed rate of (2) is 4-10m 3 And/h, controlling the temperature of the heat treatment furnace to be 750-770 ℃, keeping the temperature for 10-12h, and controlling the oxygen potential value in the heat treatment furnace to be 1050 stably within the heat treatment furnace.
When the protective atmosphere is introduced into the furnace, the oxygen-containing gas in the furnace is continuously reduced, the oxygen potential value is increased again, and the decarburization and carburetion conditions of the material are shown in table 2:
TABLE 2 Table SCM435 decarburization and carburetion Condition at different oxygen potential values
And FIGS. 1-3 show decarburization and carburetion at values of 900, 980, 1050, 1100, respectively, for oxygen potential.
In combination with Table 2 and FIGS. 2-5, when the oxygen potential in the furnace is 1050, the steel is not decarburized or carburised in combination with the protective atmosphere.
Finally, after the heat preservation time is finished, controlling the heat treatment furnace to cool down, stopping introducing the protective atmosphere and continuously introducing N 2 And discharging the residual protective atmosphere in the heat treatment furnace until the temperature of the heat treatment furnace is reduced to 540-560 ℃ or below, taking out the steel, and preventing the high-temperature surface of the material from reacting with air to cause decarburization when the steel is discharged, thereby completing the heat treatment process, wherein the residual unreacted protective atmosphere is subjected to combustion treatment.
Example 1
An atmosphere protection heat treatment process for preventing decarbonization and carburetion comprises the following steps:
s100, placing the steel into a heat treatment furnace, controlling the temperature of the heat treatment furnace, and simultaneously introducing N3 times the volume of the heat treatment furnace into the heat treatment furnace 2 Monitoring the oxygen potential value in the heat treatment furnace through a detection probe;
s200, when the oxygen potential value in the heat treatment furnace reaches 900, introducing a protective atmosphere into the heat treatment furnace, and monitoring the oxygen potential value in the heat treatment furnace through a detection probe, wherein the protective atmosphere comprises CO in percentage by volume 2 0.7％、CO 19.27％、CH 4 2.47% and H 2 77.56％。
S300, when the oxygen potential value in the heat treatment furnace reaches 1050, continuously introducing protective atmosphere and simultaneously introducing N 2 Pressure maintaining is carried out, N 2 Is 6m 3 And/h, controlling the temperature of the heat treatment furnace to be 750-770 ℃ and the heat preservation time to be 11h.
S400, after the heat preservation time is finished, controlling the heat treatment furnace to cool down, and stopping introducing protectionAtmosphere is continuously introduced with N 2 And discharging the residual protective atmosphere in the heat treatment furnace until the temperature of the heat treatment furnace is reduced to 550 ℃ or below, and taking out the steel to finish the heat treatment.
Example 2
An atmosphere protection heat treatment process for preventing decarbonization and carburetion comprises the following steps:
s100, placing the steel into a heat treatment furnace, controlling the temperature of the heat treatment furnace, and simultaneously introducing N3 times the volume of the heat treatment furnace into the heat treatment furnace 2 Monitoring the oxygen potential value in the heat treatment furnace through a detection probe;
s200, when the oxygen potential value in the heat treatment furnace reaches 900, introducing a protective atmosphere into the heat treatment furnace, and monitoring the oxygen potential value in the heat treatment furnace through a detection probe, wherein the protective atmosphere comprises CO in percentage by volume 2 0.7％、CO 19.27％、CH 4 2.47% and H 2 77.56％。
S300, when the oxygen potential value in the heat treatment furnace reaches 1050, continuously introducing protective atmosphere and simultaneously introducing N 2 Pressure maintaining is carried out, N 2 Is 4m 3 And/h, controlling the temperature of the heat treatment furnace to be 750-770 ℃ and the heat preservation time to be 10h.
S400, after the heat preservation time is finished, controlling the heat treatment furnace to cool down, stopping introducing the protective atmosphere and continuously introducing N 2 And discharging the residual protective atmosphere in the heat treatment furnace until the temperature of the heat treatment furnace is reduced to 540 ℃ or below, and taking out the steel to finish the heat treatment.
Example 3
An atmosphere protection heat treatment process for preventing decarbonization and carburetion comprises the following steps:
s100, placing the steel into a heat treatment furnace, controlling the temperature of the heat treatment furnace, and simultaneously introducing N3 times the volume of the heat treatment furnace into the heat treatment furnace 2 Monitoring the oxygen potential value in the heat treatment furnace through a detection probe;
s200, when the oxygen potential value in the heat treatment furnace reaches 910, introducing a protective atmosphere into the heat treatment furnace, monitoring the oxygen potential value in the heat treatment furnace through a detection probe,wherein the protective atmosphere comprises CO in percentage by volume 2 0.7％、CO 19.27％、CH 4 2.47% and H 2 77.56％。
S300, when the oxygen potential value in the heat treatment furnace reaches 1050, continuously introducing protective atmosphere and simultaneously introducing N 2 Pressure maintaining is carried out, N 2 Is 10m 3 And/h, controlling the temperature of the heat treatment furnace to be 750-770 ℃ and the heat preservation time to be 12h.
S400, after the heat preservation time is finished, controlling the heat treatment furnace to cool down, stopping introducing the protective atmosphere and continuously introducing N 2 And discharging the residual protective atmosphere in the heat treatment furnace until the temperature of the heat treatment furnace is reduced to 560 ℃ or below, and taking out the steel to finish the heat treatment.
The present invention describes preferred embodiments, including the best mode known to the inventors for carrying out the invention. Variations of these preferred embodiments will, of course, be apparent to those skilled in the art. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the claims. Moreover, unless indicated otherwise or clearly contradicted by context, the present invention includes any of the above-described factors and all possible variations thereof.
Claims (4)
1. An atmosphere protection heat treatment process for preventing decarburization and carburetion is characterized by comprising the following steps:
s100, placing the steel into a heat treatment furnace, controlling the temperature of the heat treatment furnace, and simultaneously introducing N3-4 times of the volume of the heat treatment furnace into the heat treatment furnace 2 Discharging air in the heat treatment furnace, and monitoring the oxygen potential value in the heat treatment furnace;
s200, when the oxygen potential value in the heat treatment furnace reaches 900-910, introducing a protective atmosphere into the heat treatment furnace, and monitoring the oxygen potential value in the heat treatment furnace, wherein the protective atmosphere comprises CO in percentage by volume 2 0.7%、CO 19.27%、CH 4 2.47% and H 2 77.56%；
S300, when the oxygen potential value in the heat treatment furnace reaches 1050, continuously introducing protective atmosphere and simultaneously introducing N 2 Maintaining pressure, controlling the temperature of the heat treatment furnace to be 750-770 ℃, keeping the temperature for 10-12h, and controlling the oxygen potential value to be 1050 in the heat preservation time;
s400, after the heat preservation time is finished, controlling the heat treatment furnace to cool down, stopping introducing the protective atmosphere and continuously introducing N 2 Discharging the protective atmosphere in the heat treatment furnace until the temperature of the heat treatment furnace is reduced to 540-560 ℃ or below, and taking out the steel to finish the heat treatment process.
2. The decarburization preventing and carbureting atmosphere protecting heat treating process according to claim 1, wherein the steel is SCM435 alloy steel.
3. The decarburization preventing and carbureting atmosphere protecting heat treating process according to claim 2, wherein in S300, the N 2 The feed rate of (2) is 4-10m 3 /h。
4. A decarburization-preventing and carbureting atmosphere protecting heat treating process according to claim 3, wherein in S100 to S400, the oxygen potential value in the heat treating furnace is monitored by a detecting probe.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003201512A (en) * | 2002-01-04 | 2003-07-18 | Chugai Ro Co Ltd | Method for stabilization of furnace atmosphere in batch- type annealing furnace |
| CN104988288A (en) * | 2015-07-29 | 2015-10-21 | 西安市北恒实业有限公司 | No-hydrogen atmosphere protection heat treatment process completely without decarburization for steel |
| EP3168314A1 (en) * | 2015-11-13 | 2017-05-17 | Air Liquide Deutschland GmbH | Method for heat treating metallic work pieces |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003201512A (en) * | 2002-01-04 | 2003-07-18 | Chugai Ro Co Ltd | Method for stabilization of furnace atmosphere in batch- type annealing furnace |
| CN104988288A (en) * | 2015-07-29 | 2015-10-21 | 西安市北恒实业有限公司 | No-hydrogen atmosphere protection heat treatment process completely without decarburization for steel |
| EP3168314A1 (en) * | 2015-11-13 | 2017-05-17 | Air Liquide Deutschland GmbH | Method for heat treating metallic work pieces |
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