CN116949270A - Heat treatment method of P24 steel pipe - Google Patents
Heat treatment method of P24 steel pipe Download PDFInfo
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- CN116949270A CN116949270A CN202310375136.XA CN202310375136A CN116949270A CN 116949270 A CN116949270 A CN 116949270A CN 202310375136 A CN202310375136 A CN 202310375136A CN 116949270 A CN116949270 A CN 116949270A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 82
- 239000010959 steel Substances 0.000 title claims abstract description 82
- 238000010438 heat treatment Methods 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 55
- 238000004321 preservation Methods 0.000 claims abstract description 57
- 238000005496 tempering Methods 0.000 claims abstract description 20
- 238000001816 cooling Methods 0.000 claims abstract description 19
- 238000003723 Smelting Methods 0.000 claims description 3
- 238000005242 forging Methods 0.000 claims description 3
- 238000005096 rolling process Methods 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 238000007599 discharging Methods 0.000 claims description 2
- 238000005098 hot rolling Methods 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims 1
- 238000010606 normalization Methods 0.000 abstract description 2
- 230000008520 organization Effects 0.000 abstract description 2
- 239000013078 crystal Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 2
- 239000003779 heat-resistant material Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000011534 incubation Methods 0.000 description 1
- 230000002045 lasting effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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Abstract
The application discloses a heat treatment method of a P24 steel pipe, which comprises the steps of sequentially carrying out normalizing treatment and tempering treatment on the P24 steel pipe, wherein the normalizing treatment comprises the following steps: (1) Heating the P24 steel pipe in a cold state to a first-stage heat preservation area at a heating rate lower than 600 ℃/hour for heat preservation, wherein the heat preservation temperature is 880-940 ℃; (2) After the first-stage heat preservation is finished, rapidly heating to the heat preservation temperature of the second-stage heat preservation for heat preservation, wherein the heat preservation temperature is 980-1020 ℃; the rapid temperature rise speed is greater than the heating rate of the first-stage heat preservation step; and (3) cooling to room temperature after the second-stage heat preservation is finished. The P24 steel pipe suppresses grain growth at a low temperature Duan Baowen higher than the austenitizing critical temperature; preserving heat in a high temperature section to ensure that steel pipes with qualified performances are obtained; proper organization and performance is achieved at a particular cooling rate using controlled cooling rate techniques during normalization.
Description
Technical Field
The application belongs to the field of manufacturing of heat-resistant steel pipes, and relates to a heat treatment method of a P24 steel pipe.
Background
The P24 steel is a high temperature heat resistant material, the Mo content of which is equivalent to that of P22, the creep strength of the steel is improved by adding V, ti and B, and the allowable stress in the creep temperature range of 550-620 ℃ is more than 1.5 times that of the P22 steel. The P24 steel has excellent oxidation resistance, corrosion resistance and high-temperature mechanical properties, and is mainly used for manufacturing components such as water-cooled walls, headers and the like of the ultra-supercritical boiler. The P24 steel is a major breakthrough to the P22 steel, not only has high-temperature lasting strength, but also can be applied to replace the P91 steel in a certain temperature range, and the material does not need preheating before welding and post-welding heat treatment after welding, so that the manufacturing cost of a boiler can be saved, and the application prospect is considerable.
As bainitic steel, a large number of experimental data show that the size effect of the P24 steel pipe is obvious, when the wall thickness is less than or equal to 10mm, a structure with excellent comprehensive performance can be obtained through normalizing air cooling, and when the wall thickness is more than or equal to 50mm, a structure with qualified performance is difficult to obtain through quenching. In addition, as the thickness increases, the difficulty of heat treatment increases. In the prior art, the normalizing temperature of the P24 steel pipe is up to 1000 ℃, the normalizing heat preservation time is longer and longer along with the increase of the thickness of the steel pipe, the tendency of austenite grain growth is obviously increased, and the bainite grain size is larger in the subsequent normalizing cooling process. Finally, the product performance is presented, the structure is uneven, the grains are coarse, and the impact toughness is poor. In addition, for thick-walled pipes having a wall thickness/outside diameter of > 0.10, conventional heat treatment methods, i.e. tempering after normalizing, are employed. After normalizing and tempering, the obtained P24 steel pipe has coarse grains, uneven structure and unqualified impact energy.
Disclosure of Invention
Aiming at the problems in the prior art, the application provides a heat treatment method of a P24 steel pipe.
In order to achieve the above object, the following technical scheme is adopted.
The heat treatment method of the P24 steel pipe comprises the steps of sequentially carrying out normalizing treatment and tempering treatment on the P24 steel pipe, wherein the normalizing treatment comprises the following steps:
(1) First stage incubation (low temperature Duan Baowen):
heating the cold P24 steel pipe to a first-stage heat-preserving zone at a heating rate of less than 600 ℃/hr (e.g., 100 ℃/hr, 200 ℃/hr, 300 ℃/hr, 500 ℃/hr, 550 ℃/hr) and at a heat-preserving temperature of 880 ℃ -940 ℃ (e.g., 890 ℃, 900 ℃, 910 ℃, 920 ℃, 930 ℃);
(2) Second-stage heat preservation (high-temperature heat preservation)
After the first-stage heat preservation is finished, rapidly heating to a heat preservation temperature of the second-stage heat preservation for heat preservation, wherein the heat preservation temperature of the second-stage heat preservation is 980 ℃ -1020 ℃ (for example, 985 ℃, 990 ℃, 1000 ℃, 1010 ℃, 1015 ℃); the rapid temperature rise speed is greater than the heating rate of the first-stage heat preservation step;
(3) And cooling to room temperature after the second-stage heat preservation is finished.
In the above heat treatment method, in the step (1), the first-stage heat preservation time is 60 minutes to 120 minutes (for example, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes).
In the application, the heat preservation at the low temperature section has the functions of making the structure uniform and completely austenitizing, and simultaneously avoiding the growth of crystal grains.
In the above heat treatment method, in the step (1), the heating rate is 300 to 500 ℃/hr (for example, 320 ℃/hr, 350 ℃/hr, 400 ℃/hr, 450 ℃/hr, 480 ℃/hr), preferably 350 to 450 ℃/hr (for example, 360 ℃/hr, 380 ℃/hr, 400 ℃/hr, 420 ℃/hr, 440 ℃/hr).
In the above heat treatment method, as a preferred embodiment, the normalizing treatment is performed by heating using a step heat treatment furnace.
In the above heat treatment method, as a preferred embodiment, in the step (2), the second stage heating rate is 10℃C/min or more (for example, 11℃C/min, 12℃C/min, 13℃C/min, 14℃C/min, 15℃C/min)
In the application, the second-stage heat preservation is a temperature range required by the process, and mainly ensures that indexes such as strength, hardness and the like meet standard requirements.
In the above heat treatment method, in the step (2), the second-stage heat preservation time is 60 minutes to 120 minutes (for example, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes).
In the above heat treatment method, as a preferred embodiment, in the step (3), the cooling rate is not less than 500 ℃/h (for example, 520 ℃/h, 550 ℃/h, 600 ℃/h, 650 ℃/h, 700 ℃/h).
In the above heat treatment method, as a preferred embodiment, the tempering treatment includes loading the steel pipe into a tempering furnace in a cold state, heating to a process heat preservation temperature, and discharging the steel pipe from the furnace for air cooling after a period of heat preservation.
In the above heat treatment method, as a preferred embodiment, the tempering treatment is performed at a temperature of 730 to 770 ℃ (e.g., 735 ℃, 740 ℃, 750 ℃, 760 ℃, 765 ℃) and a tempering time of 3 to 4 minutes per 1mm wall thickness.
In the application, tempering can eliminate the internal stress of the steel pipe, stabilize the structure, reduce brittleness and obtain the required mechanical property, thus obtaining the final product.
In the above heat treatment method, as a preferred embodiment, the heat treatment method is applied to a P24 thick-walled pipe having a wall thickness/outer diameter of 0.10 or more (e.g., 0.15, 0.20, 0.30, 0.35, 0.50).
In the above heat treatment method, as a preferable embodiment, the specification of the P24 steel pipe is (168 to 508) mm (30 to 120) mm, for example, the diameter of the P24 steel pipe is 180mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm or 500mm; the thickness of the P24 steel pipe is 40mm, 50mm, 70mm, 80mm, 90mm, 100mm or 110mm 。
In the above heat treatment method, as a preferred embodiment, the chemical components of the P24 steel pipe include, in mass percent: 0.05 to 0.10 percent of C, 0.15 to 0.45 percent of Si, 0.30 to 0.70 percent of Mn, 2.20 to 2.60 percent of Cr, 0.90 to 1.10 percent of Mo, 0.0015 to 0.007 percent of B, 0.20 to 0.30 percent of V, 0.06 to 0.10 percent of Ti, less than or equal to 0.02 percent of Al, less than or equal to 0.020 percent of P and less than or equal to 0.010 percent of S.
In the above heat treatment method, as a preferred embodiment, the P24 steel pipe is produced by a method of smelting a steel ingot, forging a round pipe blank, and hot rolling a seamless steel pipe, and preferably, an ASSEL unit is used as a rolling equipment.
In the prior art, fine grains can improve impact energy, but a large amount of test data show that the thick-wall P24 steel pipe cannot obtain fine grains through a conventional heat treatment method. The acceptable performance of the P24 steel pipe with the wall thickness/outer diameter smaller than 0.10 can be obtained by adopting the conventional method, but the acceptable performance of the P24 steel pipe with the wall thickness/outer diameter larger than or equal to 0.10 cannot be obtained by adopting the conventional method. The heat treatment method of the present application can be applied to a P24 steel pipe having a wall thickness/outer diameter of less than or equal to 0.10 to obtain acceptable performance, as well as to a P24 steel pipe having a wall thickness/outer diameter of less than or equal to 0.10 to obtain acceptable performance.
In the application, the normalizing heat treatment is carried out on the steel pipe by adopting two-section heat preservation of a low-temperature section and a high-temperature section, the P24 steel pipe is preserved above the austenitizing critical temperature of 820 ℃, after complete austenitization, the grain growth is restrained by slow heating, the heat preservation of the low-temperature section below 940 ℃ is carried out, the grains are refined, and the grain growth is controlled. Then preserving heat according to the temperature required by the process specified by ASME SA-335-2021 standard, finishing heat preservation within the allowable process range of 980-1020 ℃, and then rapidly cooling by water cooling to obtain the product with fine crystal grains and good comprehensive performance.
For the metal material, the finer the crystal grains are, the higher the strength and hardness in normal-temperature mechanical properties are, and the better the plasticity and toughness are. This is because the finer the grains, the more dispersed the plastic deformation can be within the grains, so that the more uniform the plastic deformation, the less the concentration of internal stress; and the finer the crystal grain, the more the grain boundary surface, the more the grain boundary is tortuous; the more chance that grains are staggered from grain to grain, the less favorable the crack propagation and development, the more tightly the grains are to each other, and the better the strength and toughness.
According to the application, the normal temperature mechanical property of the metal is improved by refining the crystal grains, so that the impact energy of the P24 steel pipe is improved. For thick-wall pipes with wall thickness/outer diameter more than or equal to 0.10, preserving heat for a period of time above the austenitizing critical temperature, refining grains and controlling the growth of the grains after complete austenitizing, then quickly heating to the process preserving temperature, and quickly cooling after reaching the preserving time specified by the process, thus obtaining the P24 steel pipe with fine grains and good mechanical properties.
Compared with the prior art, the application has the following beneficial technical effects:
1. the P24 steel pipe is at a low temperature Duan Baowen which is higher than the austenitizing critical temperature, so that the growth of grains is inhibited; and (3) preserving heat in a process temperature, namely a high-temperature section, so as to ensure that the steel pipe with qualified performance is obtained.
2. At normalization, appropriate organization and performance are achieved at a particular cooling rate using controlled cooling rate techniques.
Drawings
Fig. 1 is a schematic diagram of a two-stage normalizing process for a P24 steel pipe according to the present application.
FIG. 2 is a structural diagram of a P24 steel pipe after heat treatment obtained in example 1 of the present application.
FIG. 3 is a structural diagram of a heat-treated P24 steel pipe obtained in comparative example 1 of the present application.
Detailed Description
The present application will be described in detail below with reference to the drawings and examples of the present application. The examples are provided by way of explanation of the application and not limitation of the application. Indeed, it will be apparent to those skilled in the art that modifications and variations can be made in the present application without departing from the scope or spirit of the application. For example, features illustrated or described as part of one embodiment can be used on another embodiment to yield still a further embodiment. Accordingly, it is intended that the present application encompass such modifications and variations as fall within the scope of the appended claims and their equivalents.
Examples 1 to 5
A heat treatment method of a high-temperature heat-resistant material P24 steel pipe, rolling to obtain a steel pipe with the specification of (168-508) mm (30-120) mm (diameter: wall thickness), adopting two-section heat preservation normalizing heat treatment, and then tempering, wherein the normalizing heat treatment process is shown in figure 1, and the heat treatment comprises the following steps:
(1) When the P24 steel pipe is normalized, heating to a first-stage heat preservation area at a heating rate of 300-450 ℃/h, wherein the heat preservation temperature is 880-940 ℃; preserving heat for 60-120 minutes;
(2) Quickly heating to a second-stage heat preservation area at a heating rate of 10-15 ℃/min, wherein the heat preservation temperature is 980-1020 ℃; preserving heat for 60-120 minutes in the temperature range;
(3) Rapidly cooling to room temperature at a rate of 650 ℃/hour by water cooling;
(4) Tempering according to a tempering process specified by ASME SA-335-2021 standard, wherein the tempering temperature is 730-770 ℃; and obtaining the P24 steel pipe after heat treatment.
Table 1 lists the main process parameters in examples 1-5.
TABLE 1 essential process parameters in examples 1-5
The mechanical properties, impact energy, hardness, texture and grain size of the heat-treated P24 steel pipes were measured according to standards ASTM a370, ASTM E23, ASTM E10, ASTM E112, respectively, and the measurement results are shown in table 2.
TABLE 2 structure and property of P24 Steel pipe after heat treatment in examples 1-5
Comparative examples 1 to 3
The comparative example adopts a conventional process to carry out heat treatment on a P24 steel pipe, the P24 steel pipe is obtained by smelting steel ingots, forging round pipe blanks and producing seamless steel pipes by an ASEEL unit, and the heat treatment comprises the following steps:
(1) When the P24 steel pipe is normalized, heating to the heat preservation temperature of 990-1020 ℃ at the heating rate of 7-8 ℃/min for heat preservation for 80-120 minutes;
(2) Air cooling after normalizing;
(3) Tempering according to a tempering process specified by ASME SA-335-2021 standard, wherein the temperature range is 750-770 ℃, and the heat preservation time is 150-300 minutes; and obtaining the P24 steel pipe after heat treatment.
Table 1 shows the main process parameters of the heat treatment of the P24 steel pipes in comparative examples 1-3. The structure and properties of the heat-treated P24 steel pipe are shown in table 2.
It should be understood that these examples are for the purpose of illustrating the application only and are not intended to limit the scope of the application. Furthermore, it is to be understood that various changes, modifications and/or variations may be made by those skilled in the art after reading the technical content of the present application, and that all such equivalents are intended to fall within the scope of the present application as defined in the appended claims.
Claims (10)
1. A heat treatment method of a P24 steel pipe, characterized in that the heat treatment method comprises subjecting the P24 steel pipe to a normalizing treatment and a tempering treatment in sequence, wherein the normalizing treatment comprises:
(1) First-stage heat preservation
Heating the P24 steel pipe in a cold state to a first-stage heat preservation area at a heating rate lower than 600 ℃/h for heat preservation, wherein the heat preservation temperature of the first-stage heat preservation area is 880-940 ℃;
(2) Second stage of heat preservation
After the first-stage heat preservation is finished, rapidly heating to the heat preservation temperature of the second-stage heat preservation for heat preservation, wherein the heat preservation temperature of the second-stage heat preservation is 980-1020 ℃; the rapid temperature rise speed is greater than the heating rate of the first-stage heat preservation step;
(3) And cooling to room temperature after the second-stage heat preservation is finished.
2. The method of heat treatment of P24 steel pipe according to claim 1, wherein in step (1), the heating rate is 300 to 500 ℃/hr, preferably 350 to 450 ℃/hr; and/or the number of the groups of groups,
in the step (2), the heating rate of the second stage is more than or equal to 10 ℃/min; and/or the number of the groups of groups,
in the step (3), the cooling speed is more than or equal to 500 ℃/h.
3. The heat treatment method for P24 steel pipe according to claim 1 or 2, wherein,
the normalizing treatment is performed by heating using a step heat treatment furnace.
4. A heat treatment method of P24 steel pipe according to any one of claims 1 to 3, wherein in the step (1), the first-stage heat preservation time is 60 minutes to 120 minutes; and/or the number of the groups of groups,
in the step (2), the heat preservation time of the second-stage heat preservation is 60-120 minutes.
5. The method of heat treatment of P24 steel pipe according to any one of claims 1 to 4, wherein the tempering treatment comprises loading the steel pipe into a tempering furnace in a cold state, heating to a process heat preservation temperature, and discharging the steel pipe from the furnace for air cooling after a period of heat preservation.
6. The heat treatment method of a P24 steel pipe according to any one of claims 1 to 5, wherein the tempering treatment is performed at a temperature of 730 ℃ to 770 ℃ for a tempering time of 3 to 4 minutes per 1mm wall thickness.
7. The heat treatment method of a P24 steel pipe according to any one of claims 1 to 6, wherein the chemical composition of the P24 steel pipe comprises, in mass percent: 0.05 to 0.10 percent of C, 0.15 to 0.45 percent of Si, 0.30 to 0.70 percent of Mn, 2.20 to 2.60 percent of Cr, 0.90 to 1.10 percent of Mo, 0.0015 to 0.007 percent of B, 0.20 to 0.30 percent of V, 0.06 to 0.10 percent of Ti, less than or equal to 0.02 percent of Al, less than or equal to 0.020 percent of P and less than or equal to 0.010 percent of S.
8. A method for heat treatment of P24 steel pipes according to any one of claims 1-7, characterized in that the P24 steel pipes are produced by smelting steel ingots, forging round pipe blanks, hot rolling seamless steel pipes, preferably the rolling equipment is an ASSEL unit.
9. The method for heat treatment of P24 steel pipe according to any one of claims 1 to 8, wherein the heat treatment method is applied to P24 thick-walled pipe having a wall thickness/outer diameter of 0.10 or more.
10. The method of heat treatment of P24 steel pipe according to any one of claims 1 to 9, wherein the specification of the P24 steel pipe is (168 to 508) mm x (30 to 120) mm.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310375136.XA CN116949270A (en) | 2023-04-10 | 2023-04-10 | Heat treatment method of P24 steel pipe |
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| CN202310375136.XA CN116949270A (en) | 2023-04-10 | 2023-04-10 | Heat treatment method of P24 steel pipe |
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