CN111235367A - Heat treatment method for improving strength of laser additive manufacturing 12CrNi2 alloy steel - Google Patents
Heat treatment method for improving strength of laser additive manufacturing 12CrNi2 alloy steel Download PDFInfo
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- CN111235367A CN111235367A CN201811445752.3A CN201811445752A CN111235367A CN 111235367 A CN111235367 A CN 111235367A CN 201811445752 A CN201811445752 A CN 201811445752A CN 111235367 A CN111235367 A CN 111235367A
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- alloy steel
- laser additive
- additive manufacturing
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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
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
-
- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F2003/248—Thermal after-treatment
Abstract
The invention belongs to the field of metal laser additive manufacturing, and particularly relates to a heat treatment method for improving the strength of laser additive manufacturing 12CrNi2 alloy steel, which is suitable for improving the mechanical properties such as strength, hardness and the like of various laser additive manufactured complex-structure alloy steel components. The method comprises a quenching treatment step and a tempering treatment step. The quenching treatment steps are as follows: heating the alloy steel sample subjected to laser additive manufacturing and forming to 850-960 ℃ at the heating rate of 10-30 ℃/min, preserving heat for 0.5-2 h, and then putting the alloy steel sample into water to cool to room temperature. The tempering treatment step comprises: and heating the quenched sample to 200-400 ℃ at a heating rate of 10-30 ℃/min, preserving heat for 0.5-3 h, and then cooling in air to room temperature. The method can obviously improve the properties of the 12CrNi2 alloy steel, such as strength, hardness and the like, which are manufactured by laser additive manufacturing.
Description
Technical Field
The invention belongs to the field of metal laser additive manufacturing, and particularly relates to a heat treatment method for improving the strength of laser additive manufacturing 12CrNi2 alloy steel, which is suitable for improving the mechanical properties such as strength, hardness and the like of various laser additive manufactured complex-structure alloy steel components.
Background
With the continuous development of nuclear power utilities, people pay more attention to the safety problem of nuclear power. The emergency diesel generator of the nuclear power station is an emergency power supply of the nuclear power station, can be quickly started under the condition of unexpected power failure, and ensures that the operation of the nuclear power station is not influenced. The 12CrNi2 alloy steel is low-carbon alloy carburized structural steel, has better toughness performance matching, and is a preparation material of the camshaft of the current nuclear power emergency diesel engine. The camshaft is the main part that control diesel engine valve opened and shut, bears certain impact load, for guaranteeing emergency diesel engine's steady operation, all has higher requirement to the dimensional accuracy and the material of camshaft. However, the camshaft of the nuclear power emergency diesel engine is complex in structure and complex in processing technology, and at present, the manufacturing and the maintenance of the camshaft of the nuclear power emergency diesel engine depend on foreign technologies.
Laser Additive Manufacturing (LAM) is a new material rapid forming technology that uses Laser as an energy source to directly manufacture parts by melting material powder or wire layer by layer, and can perform precise forming and high-performance forming on complex parts. Currently, members such as a Ti alloy, a Ni-based alloy, and stainless steel formed by LAM have been used. However, the LAM alloy steel member is slow in development, and the main reasons are that the unbalanced solidification process of LAM easily causes uneven distribution of elements and poor structure controllability in the formed alloy steel member, which results in poor stability of mechanical properties of the LAM formed alloy steel member. Therefore, the formed member needs to be heat-treated to improve its properties by regulating its microstructure through solid-state phase transformation.
The invention content is as follows:
in order to solve the problem of low strength of an LAM formed 12CrNi2 alloy steel member, the invention aims to provide a heat treatment method for improving the strength of laser additive manufacturing 12CrNi2 alloy steel, and the tensile property of the LAM alloy steel is improved by regulating and controlling a microstructure through a quenching and tempering method.
The technical scheme of the invention is as follows:
a heat treatment method for improving the strength of laser additive manufacturing 12CrNi2 alloy steel comprises a quenching treatment step and a tempering treatment step, and specifically comprises the following steps:
(1) quenching step
Heating a laser additive manufacturing formed alloy steel sample to 850-960 ℃ at a heating rate of 10-30 ℃/min, preserving heat for 0.5-2 h, and then putting the alloy steel sample into water to cool to room temperature;
(2) tempering step
And heating the quenched sample to 200-400 ℃ at a heating rate of 10-30 ℃/min, preserving heat for 0.5-3 h, and then cooling in air to room temperature.
The heat treatment method for improving the strength of the 12CrNi2 alloy steel manufactured by the laser additive manufacturing is characterized in that the laser additive manufacturing is a laser melting deposition technology or a laser selective melting technology.
According to the heat treatment method for improving the strength of the laser additive manufacturing 12CrNi2 alloy steel, the technical indexes of the laser additive manufacturing 12CrNi2 alloy steel are as follows: the tensile strength range is 670-690 MPa, the yield strength range is 620-640 MPa, and the microhardness range is 240-280 HV.
According to the heat treatment method for improving the strength of the laser additive manufactured 12CrNi2 alloy steel, after quenching and tempering treatment, the structure nonuniformity of the laser additive manufactured 12CrNi2 alloy steel disappears, and a uniform tempered martensite structure is formed, and the technical indexes are as follows: the tensile strength range is 1050-1250 MPa, the yield strength range is 900-1100 MPa, and the microhardness range is 330-420 HV.
The design idea of the invention is as follows: when LAM is formed, the rapid solidification and rapid cooling process of a molten pool and the complex thermal cycle effect generated by layer-by-layer forming cause the uneven distribution of internal tissues of alloy steel, and the mechanical property of the alloy steel is seriously influenced. Therefore, proper heat treatment is required to eliminate the uneven structure and regulate the proportion and the form of strengthening phases (such as martensite, carbide and the like) so as to improve the mechanical property of the LAM alloy steel.
The invention has the advantages and beneficial effects that:
1. the heat treatment method for improving the strength of the laser additive manufacturing 12CrNi2 alloy steel enables the improvement of the mechanical property of an LAM forming alloy steel component to be possible, and provides a new solution for optimizing the performance in the aspect of laser additive manufacturing alloy steel components.
2. The LAM formed alloy steel treated by the method has uniform structure and obviously improved tensile strength, yield strength and hardness.
Drawings
FIGS. 1(a) - (b) are metallographic micrographs of the microstructure of laser fusion deposited 12CrNi2 alloy steel in an example of the invention. Wherein (b) is an enlarged view of a dotted line box in (a).
FIG. 2 is a stress-strain curve of a laser fusion deposited 12CrNi2 alloy steel in accordance with an embodiment of the present invention. In the figure, the abscissa Engineering strain represents Engineering strain (%), and the ordinate Engineering strain represents Engineering stress (MPa).
FIGS. 3(a) - (b) are metallographic photographs of microstructures of laser melting deposition 12CrNi2 alloy steel after quenching at 860 ℃ and tempering at 200 ℃ in the examples of the invention. Wherein (b) is an enlarged view of a dotted line box in (a).
FIG. 4 is a stress-strain curve of a laser melting deposited 12CrNi2 alloy steel after quenching at 860 ℃ and tempering at 200 ℃ in an embodiment of the invention. In the figure, the abscissa Engineering strain represents Engineering strain (%), and the ordinate Engineering strain represents Engineering stress (MPa).
FIGS. 5(a) - (b) are metallographic photographs of the microstructure of laser melting deposited 12CrNi2 alloy steel after quenching at 950 ℃ and tempering at 300 ℃ in the example of the invention. Wherein (b) is an enlarged view of a dotted line box in (a).
FIG. 6 is a stress-strain curve of a laser melting deposited 12CrNi2 alloy steel after quenching at 950 ℃ and tempering at 300 ℃ in the embodiment of the invention. In the figure, the abscissa Engineering strain represents Engineering strain (%), and the ordinate Engineering strain represents Engineering stress (MPa).
Detailed Description
In the specific implementation process, the 12CrNi2 alloy steel manufactured by laser additive manufacturing is heated to 850-960 ℃ in a heating furnace at a certain heating rate, the temperature is kept for 0.5-2 h, then the alloy steel is taken out and rapidly put into water for cooling, then the alloy steel is heated to 200-400 ℃ at a certain heating rate, the temperature is kept for 0.5-3 h, and then the alloy steel is taken out and cooled to room temperature in the air.
The following description of the preferred embodiments of the present invention is provided for the purpose of illustration and description, and is in no way intended to limit the invention.
The present invention is further illustrated by the following examples.
Example 1
In this embodiment, the heat treatment method for improving the strength of the laser additive manufacturing 12CrNi2 alloy steel is as follows:
1. in this embodiment, the laser additive manufacturing of the 12CrNi2 alloy steel is performed by a laser melting deposition technology which is technically characterized by synchronous powder feeding, and the adopted laser is a semiconductor laser.
2. The quenching treatment steps are as follows: the laser additive manufacturing 12CrNi2 alloy steel is heated to 860 ℃ at the heating rate of 20 ℃/min and is kept for 0.5h, and then is cooled to the room temperature in water.
3. The tempering treatment step comprises: the quenched 12CrNi2 alloy steel is heated to 200 ℃ at the heating rate of 30 ℃/min and is kept for 2h, and then is cooled to room temperature in the air.
As shown in figure 1, the 12CrNi2 alloy steel prepared by laser melting deposition has uneven structure, and the structure between deposited layers is relatively coarse. The microhardness is 252.8 HV. As shown in FIG. 2, the tensile strength of the laser fused deposition 12CrNi2 alloy steel is 683.6MPa, and the yield strength is 626.6 MPa. As shown in FIG. 3, the microstructure morphology shows that the structural inhomogeneity of the laser melting deposition 12CrNi2 alloy steel after quenching and tempering treatment disappears, and a uniform tempered martensite structure is formed. The microhardness is 401.5HV, which is improved by 58.8% compared with the alloy steel in a deposition state. As shown in FIG. 4, the stress-strain curve shows that the tensile strength and yield strength of the laser melting deposition 12CrNi2 alloy steel after quenching and tempering treatment are remarkably improved, and are 1213.1MPa and 1050.6MPa respectively.
Example 2
In this embodiment, the heat treatment method for improving the strength of the laser additive manufacturing 12CrNi2 alloy steel is as follows:
1. in this embodiment, the laser additive manufacturing of the 12CrNi2 alloy steel is performed by a laser melting deposition technology which is technically characterized by synchronous powder feeding, and the adopted laser is a semiconductor laser.
2. The quenching treatment steps are as follows: the laser additive manufacturing 12CrNi2 alloy steel is heated to 950 ℃ at the heating rate of 30 ℃/min and is kept for 0.5h, and then is cooled to room temperature in water.
3. The tempering treatment step comprises: the quenched 12CrNi2 alloy steel is heated to 300 ℃ at the heating rate of 30 ℃/min and is kept for 2h, and then is cooled to room temperature in the air.
As shown in FIG. 5, the structure unevenness of the 12CrNi2 alloy steel after the quenching and tempering treatment disappeared, and a uniform tempered martensite structure was formed. The microhardness is 342.3HV through detection, and is improved by 35.4 percent compared with the alloy steel in a deposition state. As shown in FIG. 6, the stress-strain curve shows that the tensile strength and yield strength of the laser melting deposition 12CrNi2 alloy steel after quenching and tempering treatment are remarkably improved to 1113.4MPa and 992.1MPa respectively.
The example results show that the method can obviously improve the properties of strength, hardness and the like of the 12CrNi2 alloy steel manufactured by laser additive manufacturing through a specific quenching treatment step and a specific tempering treatment step.
Finally, it should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and not intended to limit the present invention, and although the present invention is described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications and equivalents can be made in the technical solutions described in the foregoing embodiments, or some technical features of the present invention may be equivalently replaced. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A heat treatment method for improving the strength of laser additive manufacturing 12CrNi2 alloy steel is characterized by comprising a quenching treatment step and a tempering treatment step, and specifically comprises the following steps:
(1) quenching step
Heating a laser additive manufacturing formed alloy steel sample to 850-960 ℃ at a heating rate of 10-30 ℃/min, preserving heat for 0.5-2 h, and then putting the alloy steel sample into water to cool to room temperature;
(2) tempering step
And heating the quenched sample to 200-400 ℃ at a heating rate of 10-30 ℃/min, preserving heat for 0.5-3 h, and then cooling in air to room temperature.
2. The heat treatment method for improving the strength of the laser additive manufactured 12CrNi2 alloy steel according to claim 1, wherein the laser additive manufacturing is a laser melting deposition technology or a laser selective melting technology.
3. The heat treatment method for improving the strength of the laser additive manufactured 12CrNi2 alloy steel according to claim 1, wherein the technical indexes of the laser additive manufactured 12CrNi2 alloy steel are as follows: the tensile strength range is 670-690 MPa, the yield strength range is 620-640 MPa, and the microhardness range is 240-280 HV.
4. The heat treatment method for improving the strength of the laser additive manufactured 12CrNi2 alloy steel according to claim 1, wherein after quenching and tempering treatment, the structure nonuniformity of the laser additive manufactured 12CrNi2 alloy steel disappears, and a uniform tempered martensite structure is formed, and the technical indexes are as follows: the tensile strength range is 1050-1250 MPa, the yield strength range is 900-1100 MPa, and the microhardness range is 330-420 HV.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112719296A (en) * | 2020-12-29 | 2021-04-30 | 中国人民解放军陆军装甲兵学院 | Method for regulating and controlling mechanical properties of 4Cr5MoSiV1 alloy steel |
| CN113185304A (en) * | 2021-05-13 | 2021-07-30 | 大连理工大学 | Method for regulating and controlling structure and performance of melt authigenic ceramic component manufactured by laser additive based on heat treatment method |
| CN113399780A (en) * | 2021-06-30 | 2021-09-17 | 华中科技大学 | Method for manufacturing 300M steel based on arc fuse additive manufacturing and 300M steel |
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