CN112609056A - Decarburization-preventing steel through type heat treatment system and heat treatment method - Google Patents
Decarburization-preventing steel through type heat treatment system and heat treatment method Download PDFInfo
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- CN112609056A CN112609056A CN202110017326.5A CN202110017326A CN112609056A CN 112609056 A CN112609056 A CN 112609056A CN 202110017326 A CN202110017326 A CN 202110017326A CN 112609056 A CN112609056 A CN 112609056A
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- heat treatment
- protective gas
- type heat
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0056—Furnaces through which the charge is moved in a horizontal straight path
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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
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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
Abstract
The invention relates to a through type heat treatment system for decarburization-proof steel, which comprises a conveying device and a through type heat treatment furnace, wherein the conveying device penetrates through the through type heat treatment furnace, the through type heat treatment system also comprises a protective gas generating device, the output end of the protective gas generating device is provided with a plurality of connecting pipes, a plurality of air inlets are arranged on the through type heat treatment furnace along the whole length, each air inlet is connected with one connecting pipe, a gas composition analyzer is arranged in the through type heat treatment furnace and is used for analyzing CO and CO in protective gas introduced into the through type heat treatment furnace2The protective gas generating device comprises a controller which is in signal connection with the gas component analyzer to receive CO and CO in the protective gas2The controller judges the carbon potential Cp of the protective gas in the furnace and the carbon potential Cs of the steel material through an internal calculation programWhether the output protective gas component is balanced or not is automatically fed back and adjusted if the output protective gas component is unbalanced, so that Cp and Cs are balanced; the invention improves the quality and efficiency of the heat treatment of the steel.
Description
Technical Field
The invention relates to the technical field of stepping furnaces, in particular to a through type heat treatment system and a through type heat treatment method for decarburization-resistant steel.
Background
With the rapid development of industrial technology, the quality requirement and cost control of mechanical pipe products are higher and higher, and at present, a roller hearth type heat treatment furnace with a protective atmosphere is widely adopted in the steel heat treatment industry, so that the purpose of non-oxidation heat treatment of steel is achieved.
At present, in the non-oxidation heat treatment process of domestic steel, the ammonia decomposition (nitrogen-hydrogen) protective atmosphere is mainly adopted, so that the oxidation burning loss on the surface of the steel can be effectively reduced, and the heat treatment processes of non-oxidation annealing, recrystallization annealing, spheroidizing annealing, tempering, normalizing and the like of the steel are realized.
The ammonia decomposition protective atmosphere is adopted, and the main components of the protective atmosphere are N2 and H2. Although the protective atmosphere can effectively prevent the oxidation reaction of the steel in the high-temperature state in the heat treatment process, the surface of the discharged steel has no oxide layer. However, H2 and the cementite Fe3C in the steel material undergo a decarburization reaction at a high temperature. The reaction formula is as follows:
。
the decarburized layer is usually 0.005 to 0.015mm or more in depth depending on the difference in the outer diameter and wall thickness of the steel and the time and temperature of the heat treatment. The presence of a decarburized layer has a great influence on the wear resistance, fatigue limit and tensile strength of the steel.
In order to ensure the performance index and specification precision of subsequent pipe processing pieces and consider the purpose of reducing the cost of continuous production, the method of increasing the outer diameter and the wall thickness of a pipe fitting is generally adopted, the processing allowance is reserved for the subsequent processing, and the surface of the pipe fitting is turned to remove a decarburized layer and then is subjected to finish processing.
However, the method of removing the decarburized layer by subsequent processing not only increases the raw material demand and reduces the final yield, but also increases the turning process, and occupies certain cost in the pipe processing industry.
Disclosure of Invention
The invention aims to solve the problem of decarburization in the non-oxidation heat treatment process of steel, and provides a through-type heat treatment system and a heat treatment method for steel, which are used for preventing decarburization.
The specific scheme of the invention is as follows: the through type heat treatment system for the decarburization-resistant steel comprises a conveying device, a through type heat treatment furnace and a protective gas generating device, wherein the conveying device penetrates through the through type heat treatment furnace, a plurality of connecting pipes are arranged at the output end of the protective gas generating device, a plurality of air inlets are formed in the through type heat treatment furnace along the whole length, each air inlet is connected with one connecting pipe, a gas composition analyzer is arranged in the through type heat treatment furnace and used for analyzing CO and CO in protective gas introduced into the through type heat treatment furnace2The protective gas generating device comprises a controller which is in signal connection with the gas component analyzer to receive CO and CO in the protective gas2The controller judges whether the carbon potential Cp of the protective gas in the furnace and the carbon potential Cs of the steel are balanced or not through an internal calculation program, and if the carbon potential Cp of the protective gas in the furnace and the carbon potential Cs of the steel are unbalanced, the controller automatically feeds back and adjusts the components of the protective gas output by the protective gas generating device so as to balance the Cp and the Cs.
The protective gas generating device is provided with at least two raw material gas input ends, each raw material gas input end is provided with a flow control valve, all the flow control valves are in signal connection with the controller, and the controller changes CO and CO in the output protective gas by controlling the mixing proportion of the raw material gases2Volume fraction of (a).
The invention also provides a heat treatment method adopting the decarburization-preventing steel through-type heat treatment system, which comprises the following steps:
1) determining the carbon potential Cs of the steel to be heat-treated at the heat treatment temperature;
2) calculating the theoretical carbon potential Cp of the protective gas according to the following formula:
cp-protective gas carbon potential
t-temperature in the furnace
P-total pressure in furnace
r-coefficient of influence of alloy factors
K is a constant;
3) calculating an equilibrium constant Kp, wherein the Kp is calculated according to the following formula:
kp-equilibrium constant
k-coefficient of balance
t-the temperature in the furnace;
4) calculating a theoretical process factor PF, wherein the PF is calculated according to the following formula:
5) real-time detection of CO and CO in protective gas in furnace through gas analyzer2And calculating the actual process factor PF ', PF' according to the following formula:
6) and comparing the PF ' with the PF, and if the PF ' is not equal to the PF, enabling the controller to enable the protective gas generating device to adjust the components of the protective gas output so as to enable the PF ' to be equal to the PF, thereby achieving the purpose of balancing the carbon potential Cp of the protective gas and the carbon potential Cs of the steel.
Further, k in step 3) is calculated according to the following formula:
thereby obtaining
The working principle of the invention is as follows: the steel is conveyed forwards slowly by the conveying device, and the protective gas generating device is arranged in a through type in the process of passing through the through type heat treatment furnacePositive pressure protective gas is input into the heat treatment furnace along the full length range, and the protective gas comprises the following components: 15-25% of CO and 30-60% of H20.5% CO2The rest is N2(ii) a Controlling CO and CO by a controller2The carbon potential of the protective gas is changed according to the content proportion, so that the carbon potential Cp of the protective gas and the carbon potential Cs of the steel are balanced, the surface of the steel can be prevented from being decarburized and not being carburized, and the original performance of the steel is not changed.
Compared with the prior art, the invention has the following advantages: 1. the steel is not added with a decarburized layer after heat treatment, so that the uniformity of performance indexes such as wear resistance, fatigue limit and tensile strength of the steel is ensured; 2. the raw material steel before heat treatment does not need to reserve the turning allowance, so that the raw material is saved, the turning loss does not exist, and the yield of the product is finally improved; 3. and a decarburized layer is not added, so that the aim of removing the decarburized layer is fulfilled without turning in a subsequent process, the subsequent processing procedures are reduced, the processing time is saved, and the processing efficiency is improved.
Drawings
FIG. 1 is a perspective view of the present invention;
FIG. 2 is a front view of the present invention;
FIG. 3 is a view A-A of FIG. 2;
in the figure: 1-through heat treatment furnace, 2-conveying device, 3-controller, 4-gas component analyzer, 5-connecting pipe, 6-protective gas generating device and 7-flow control valve.
Detailed Description
Referring to fig. 1-3, the through type heat treatment system for decarburization-resistant steel of the embodiment includes a conveying device 2 and a through type heat treatment furnace 1, the conveying device 2 penetrates through the through type heat treatment furnace 1, the through type heat treatment system further includes a shielding gas generating device 6, the output end of the shielding gas generating device 6 is provided with a plurality of connecting pipes 5, a plurality of air inlets are arranged on the through type heat treatment furnace 1 along the whole length, each air inlet is connected to one connecting pipe 5, a gas composition analyzer 4 is arranged in the through type heat treatment furnace 1, and the gas composition analyzer 4 is used for analyzing CO and CO in the shielding gas introduced into the through type heat treatment furnace 12The protective gas generating device 6 comprises a controlA controller 3, wherein the controller 3 is in signal connection with the gas component analyzer 4 to receive CO and CO in the protective gas2The controller 3 judges whether the carbon potential Cp of the protective gas in the furnace and the carbon potential Cs of the steel are balanced or not through an internal calculation program, and if the carbon potential Cp of the protective gas in the furnace and the carbon potential Cs of the steel are unbalanced, the output protective gas components of the protective gas generating device are automatically fed back and adjusted so that the Cp and the Cs are balanced.
In this embodiment, the shielding gas generator 6 has two raw material gas input ends, each raw material gas input end is equipped with a flow control valve 7, all the flow control valves 7 are in signal connection with the controller 3, and the controller 3 changes CO and CO in the output shielding gas by controlling the mixing ratio of each raw material gas2Volume fraction of (a).
The embodiment also provides a method for carrying out heat treatment on bearing steel by adopting the decarburization-preventing steel through-type heat treatment system, which comprises the following steps:
1) the heat treatment temperature of the bearing steel is 795 ℃, and the carbon potential Cs =0.845 of the bearing steel at the temperature is obtained by looking up a table;
2) calculating the theoretical carbon potential Cp of the protective gas according to the following formula:
cp-protective gas carbon potential
t-temperature in the furnace
P-total pressure in furnace
r-coefficient of influence of alloy factors
K is a constant; from the calculation, Cp =0.29
3) Calculating an equilibrium constant Kp, wherein the Kp is calculated according to the following formula:
kp-equilibrium constant
k-coefficient of balance
t-the temperature in the furnace; calculating Kp =5.72
4) Calculating a theoretical process factor PF, wherein the PF is calculated according to the following formula:
substituting the steps Cp and Cs into the formula yields PF =196
5) Real-time detection of CO and CO in protective gas in furnace through gas analyzer2And calculating the actual process factor PF ', PF' according to the following formula:
6) and comparing the PF ' with the PF, and if the PF ' is not equal to the PF, enabling the controller to enable the protective gas generating device to adjust the components of the protective gas output so as to enable the PF ' to be equal to the PF, thereby achieving the purpose of balancing the carbon potential Cp of the protective gas and the carbon potential Cs of the steel.
Claims (4)
1. A through type heat treatment system for decarburization-proof steel comprises a conveying device and a through type heat treatment furnace, wherein the conveying device penetrates through the through type heat treatment furnace, and is characterized in that: the protective gas heat treatment furnace is characterized by further comprising a protective gas generating device, a plurality of connecting pipes are arranged at the output end of the protective gas generating device, a plurality of gas inlet holes are formed in the through type heat treatment furnace along the whole length, each gas inlet hole is connected with one connecting pipe, a gas composition analyzer is arranged in the through type heat treatment furnace and used for analyzing CO and CO in the protective gas introduced into the through type heat treatment furnace2The protective gas generating device comprises a controller which is in signal connection with the gas component analyzer to receive CO and CO in the protective gas2The controller judges whether the carbon potential Cp of the protective gas in the furnace and the carbon potential Cs of the steel are balanced or not through an internal calculation program, and if the carbon potential Cp of the protective gas in the furnace and the carbon potential Cs of the steel are unbalanced, the controller automatically feeds back and adjusts the components of the protective gas output by the protective gas generating device so as to balance the Cp and the Cs.
2. The through-type heat treatment system for a steel product against decarburization as set forth in claim 1, wherein: the protective gas generator is provided with at least two raw material gas input ends, each raw material gas input end is provided with a flow control valve, all the flow control valves are in signal connection with the controller, and the controller changes CO and CO in the output protective gas by controlling the mixing proportion of the raw material gases2Volume fraction of (a).
3. A heat treatment method using the through-type heat treatment system for a steel material prevented from being decarburized according to claim 1, characterized in that: the method comprises the following steps:
1) determining the carbon potential Cs of the steel to be heat-treated at the heat treatment temperature;
2) calculating the theoretical carbon potential Cp of the protective gas according to the following formula:
cp-protective gas carbon potential
t-temperature in the furnace
P-total pressure in furnace
r-coefficient of influence of alloy factors
K is a constant;
3) calculating an equilibrium constant Kp, wherein the Kp is calculated according to the following formula:
kp-equilibrium constant
k-coefficient of balance
t-the temperature in the furnace;
4) calculating a theoretical process factor PF, wherein the PF is calculated according to the following formula:
5) real-time detection of CO and CO in protective gas in furnace through gas analyzer2And calculating the actual process factor PF ', PF' according to the following formula:
6) and comparing the PF ' with the PF, and if the PF ' is not equal to the PF, enabling the controller to enable the protective gas generating device to adjust the components of the protective gas output so as to enable the PF ' to be equal to the PF, thereby achieving the purpose of balancing the carbon potential Cp of the protective gas and the carbon potential Cs of the steel.
4. A heat treatment method according to claim 3, wherein: k in step 3) is calculated according to the following formula:
thereby obtaining
。
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04259324A (en) * | 1991-02-08 | 1992-09-14 | Sumitomo Metal Ind Ltd | Method for controlling atmosphere in continuous type non-oxidizing heat treatment furnace |
| CN104099448A (en) * | 2014-07-31 | 2014-10-15 | 江苏力星通用钢球股份有限公司 | Roller heat treatment zero decarbonization control method for mesh belt 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 |
| CN105200368A (en) * | 2015-09-11 | 2015-12-30 | 北京北方车辆集团有限公司 | Controlled-atmosphere thermal treatment furnace carbon potential and temperature control system online calibration method |
| CN205062128U (en) * | 2015-07-29 | 2016-03-02 | 西安市北恒实业有限公司 | Heat treating complete protective atmosphere's of no hydrogen preparation facilities |
| CN111593292A (en) * | 2020-06-24 | 2020-08-28 | 南京高速齿轮制造有限公司 | Vacuum furnace carbon potential dynamic detection device and detection method thereof |
-
2021
- 2021-01-07 CN CN202110017326.5A patent/CN112609056B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04259324A (en) * | 1991-02-08 | 1992-09-14 | Sumitomo Metal Ind Ltd | Method for controlling atmosphere in continuous type non-oxidizing heat treatment furnace |
| CN104099448A (en) * | 2014-07-31 | 2014-10-15 | 江苏力星通用钢球股份有限公司 | Roller heat treatment zero decarbonization control method for mesh belt 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 |
| CN205062128U (en) * | 2015-07-29 | 2016-03-02 | 西安市北恒实业有限公司 | Heat treating complete protective atmosphere's of no hydrogen preparation facilities |
| CN105200368A (en) * | 2015-09-11 | 2015-12-30 | 北京北方车辆集团有限公司 | Controlled-atmosphere thermal treatment furnace carbon potential and temperature control system online calibration method |
| CN111593292A (en) * | 2020-06-24 | 2020-08-28 | 南京高速齿轮制造有限公司 | Vacuum furnace carbon potential dynamic detection device and detection method thereof |
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