CN113789432B - Method for improving local hardening of SA508-4 steel welded structure - Google Patents
Method for improving local hardening of SA508-4 steel welded structure Download PDFInfo
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- CN113789432B CN113789432B CN202111088080.7A CN202111088080A CN113789432B CN 113789432 B CN113789432 B CN 113789432B CN 202111088080 A CN202111088080 A CN 202111088080A CN 113789432 B CN113789432 B CN 113789432B
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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
- C21D1/78—Combined heat-treatments not provided for above
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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
- C21D1/26—Methods of annealing
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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
- C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
Abstract
The invention relates to a method for improving local hardening of an SA508-4 steel welded structure, and belongs to the technical field of welding. Heating SA508-4 steel to 600-680 ℃ at a heating rate of 40-80 ℃/min, preserving heat for 2-4 h, and cooling to room temperature along with the furnace; and then sequentially heating to a preset temperature at a heating rate of 10-20 ℃/s, preserving heat for 10-30 min, rapidly cooling to the preset temperature at a rate of 40-60 ℃/s, preserving heat for 10-60 min, and cooling to room temperature at a rate of 0.5-20 ℃/s. The invention obtains the balanced concentration distribution of elements in each phase through the distribution behavior of carbon and other alloy elements in the SA508-4 steel, improves the local hardening phenomenon of the welding structure of the SA508-4 steel, and is compared with the direct welding process adopted by the existing treatment method. The method can reduce the hardness of the welded structure, can improve the grain microstructure of the SA508-4 steel welded structure by adopting a reasonable element distribution process, and improves the mechanical property and the service performance of the welded structure.
Description
Technical Field
The invention relates to a method for improving local hardening of an SA508-4 steel welded structure, and belongs to the technical field of welding.
Background
The SA508-4 steel is a steel material which is developed for meeting the trend of large-scale and integrated development of nuclear power pressure vessels, and has the most development potential. Compared with the currently adopted SA508Gr.3 steel, the SA508-4 steel has higher mechanical properties such as toughness, hardenability and the like by increasing the element content of Cr and Ni and reducing the element content of Mn, so that the problems of hardenability, overweight raw materials and the like of the SA508Gr.3 steel in the manufacturing of a new-generation nuclear power pressure vessel are solved. However, the increase of the content of Cr and Ni elements in the SA508-4 steel causes the increase of carbon equivalent, thereby causing practical application problems of the SA508-4 steel, such as enhanced cold/hot crack sensitivity, increased cold/hot crack sensitivity coefficient, coarse welding structure grains, local hardening and the like. This is mainly caused by factors that the distribution and migration of carbon and alloy elements in different phases in the welded structure can affect the welded structure and the stability of mechanical properties due to the addition of elements capable of improving hardenability.
Disclosure of Invention
Aiming at the problem that the welding structure is locally hardened in the welding technology in the prior art, the invention provides a method for improving the local hardening of the welding structure of the SA508-4 steel, and the method can be used for obtaining the balanced concentration distribution of elements in each phase through the distribution behavior of carbon and other alloy elements in the SA508-4 steel and improving the local hardening phenomenon of the welding structure of the SA508-4 steel; compared with the direct welding process adopted by the existing treatment method, the method can reduce the hardness of the welded structure, can improve the grain microstructure of the SA508-4 steel welded structure by adopting a reasonable element distribution process, and improves the mechanical property and the service property of the welded structure.
A method for improving local hardening of a SA508-4 steel welded structure comprises the following specific steps:
(1) Heating the SA508-4 steel to 600-680 ℃ at the heating rate of 40-80 ℃/min, preserving the heat for 2-4 h, and then cooling the steel to room temperature along with the furnace; annealing the SA508-4 steel to eliminate the structural defects and residual stress in the forging process;
(2) Heating the SA508-4 steel treated in the step (1) to a preset temperature at a heating rate of 10-20 ℃/s, and preserving the heat for 10-30 min; rapidly completing the carbon element distribution at a preset higher temperature;
(3) Rapidly cooling the heat-preserved SA508-4 steel in the step (2) to a preset temperature at the speed of 40-60 ℃/s, and preserving the heat for 10-60 min; completing the distribution of alloy elements in a preset temperature interval;
(4) Cooling the heat-preserved SA508-4 steel in the step (3) to room temperature at the speed of 0.5-20 ℃/s; keeping the distribution of the tissues and elements to room temperature after the distribution;
the preset temperature of the step (2) is higher than Ac of SA508-4 steel 3 The temperature is lower than 1050 ℃.
The preset temperature in the step (3) is Ac of SA508-4 steel 1 ～Ac 3 The temperature is 714-773 ℃;
the invention improves the principle of local hardening of the SA508-4 steel welded structure:
the method has the advantages that the carbon element distribution is rapidly completed at a higher temperature, the distribution of other alloy elements is completed at a relatively lower temperature, the balanced concentration distribution of carbon and other alloy elements in each phase in the SA508-4 steel is promoted, the influence of the increase of carbon equivalent on the deterioration of welding performance is eliminated to a certain extent, and the local hardening phenomenon of the welding structure of the SA508-4 steel is improved.
The invention has the beneficial effects that:
(1) According to the invention, the balanced concentration distribution of elements in each phase is obtained through the distribution behavior of carbon and other alloy elements in the SA508-4 steel, and the local hardening phenomenon of the welding structure of the SA508-4 steel is improved;
(2) Compared with the direct welding process adopted by the existing treatment method, the method can reduce the hardness of the welded structure, can improve the grain microstructure of the SA508-4 steel welded structure by adopting a reasonable element distribution process, and improves the mechanical property and the service property of the welded structure.
Drawings
FIG. 1 is a process diagram for improving local hardening of a SA508-4 steel weld structure;
FIG. 2 is a diagram of a welding simulation process;
FIG. 3 is a metallographic structure of a welded structure in a direct welding process;
FIG. 4 is a metallographic structure diagram of a weld structure in example 1;
FIG. 5 is a metallographic structure diagram of a weld structure in example 2;
FIG. 6 is a metallographic structure diagram of a weld structure in example 3;
FIG. 7 is a graph comparing the micro-hardness of the weld structure of examples 1 to 3, which were obtained by the direct welding process.
Detailed Description
The alloy composition of the SA508-4 steel in the embodiment of the invention is within the standard composition range specified by ASME; shooting a metallographic sample of a welded structure under an optical microscope to obtain a microstructure photo; the microhardness of the welded structure is detected by an HVS- (50) type digital Vickers hardness tester, and a metallographic structure diagram of the welded structure under the direct welding process of SA508-4 steel is shown in a figure 3.
The present invention will be described in further detail with reference to specific embodiments, but the scope of the present invention is not limited to the description.
Example 1: a method for improving local hardening of a SA508-4 steel welded structure (see figure 1) comprises the following specific steps:
(1) Heating the SA508-4 steel to 600 ℃ at the heating rate of 40 ℃/min, preserving the heat for 2 hours, and then cooling the steel to room temperature along with the furnace; annealing the SA508-4 steel at 600 ℃ to eliminate the structural defects and residual stress in the forging process;
(2) Heating the SA508-4 steel treated in the step (1) to a preset temperature (880 ℃) at a heating rate of 10 ℃/s and preserving heat for 10min; rapidly completing the carbon element distribution at the temperature of 880 ℃;
(3) Rapidly cooling the heat-preserved SA508-4 steel in the step (2) to a preset temperature (700 ℃) at the speed of 40 ℃/s, and preserving heat for 10min; completing the distribution of alloy elements at the temperature of 700 ℃;
(4) Cooling the heat-preserved SA508-4 steel in the step (3) to room temperature at the rate of 0.5 ℃/s; keeping the distribution of the tissues and elements to room temperature after the distribution is finished;
after the welding simulation process shown in FIG. 2, the obtained metallographic structure photograph and the grain size distribution chart are shown in FIG. 4, the microhardness of the welded structure is shown in FIG. 7, and after the treatment of the method for improving the local hardening of the welded structure of the SA508-4 steel, the average grain size is reduced by 24 μm, and the microhardness is reduced by 42.9HV.
Example 2: a method for improving local hardening of a SA508-4 steel welded structure (see figure 1) comprises the following specific steps:
(1) Heating the SA508-4 steel to 640 ℃ at a heating rate of 60 ℃/min, preserving heat for 3 hours, and then cooling to room temperature along with the furnace; annealing the SA508-4 steel at 640 ℃ to eliminate the structural defects and residual stress in the forging process;
(2) Heating the SA508-4 steel treated in the step (1) to a preset temperature (800 ℃) at a heating rate of 15 ℃/s and preserving heat for 20min; rapidly completing the carbon element distribution at the temperature of 800 ℃;
(3) Rapidly cooling the heat-preserved SA508-4 steel in the step (2) to a preset temperature (720 ℃) at a speed of 50 ℃/s, and preserving the heat for 60min; completing the distribution of alloy elements at the temperature of 720 ℃;
(4) Cooling the heat-preserved SA508-4 steel in the step (3) to room temperature at the speed of 8 ℃/s; keeping the distribution of the tissues and elements to room temperature after the distribution is finished;
after the welding simulation process shown in FIG. 2, the obtained metallographic structure photograph and the grain size distribution graph are shown in FIG. 5, the microhardness of the welded structure is shown in FIG. 7, and after the treatment of the method for improving the local hardening of the SA508-4 steel welded structure, the average grain size is reduced by 33 μm, and the microhardness is reduced by 36.5HV.
Example 3: a method for improving local hardening of a SA508-4 steel welding structure (see figure 1) comprises the following specific steps:
(1) Heating the SA508-4 steel to 680 ℃ at a heating rate of 80 ℃/min, preserving heat for 4h, and cooling to room temperature along with the furnace; annealing the SA508-4 steel at 680 ℃ to eliminate the structural defects and residual stress in the forging process;
(2) Heating the SA508-4 steel treated in the step (1) to a preset temperature (1050 ℃) at a heating rate of 20 ℃/s, and preserving heat for 30min; rapidly completing the carbon element distribution at 1050 ℃;
(3) Rapidly cooling the heat-preserved SA508-4 steel in the step (2) to a preset temperature (750 ℃) at a speed of 60 ℃/s, and preserving heat for 30min; completing the distribution of alloy elements at the temperature of 750 ℃;
(4) Cooling the heat-preserved SA508-4 steel in the step (3) to room temperature at the rate of 20 ℃/s; keeping the distribution of the tissues and elements to room temperature after the distribution;
after the welding simulation process shown in FIG. 2, the obtained metallographic structure photograph and the grain size distribution chart are shown in FIG. 6, the microhardness of the welded structure is shown in FIG. 7, and after the treatment of the method for improving the local hardening of the welded structure of the SA508-4 steel, the average grain size is reduced by 19 μm, and the microhardness is reduced by 42.4HV.
While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit and scope of the present invention.
Claims (1)
1. A method for improving local hardening of an SA508-4 steel welded structure is characterized by comprising the following specific steps:
(1) Heating the SA508-4 steel to 600-680 ℃ at a heating rate of 40-80 ℃/min, preserving the heat for 2-4 h, and then cooling to room temperature along with the furnace;
(2) Heating the SA508-4 steel processed in the step (1) to a preset temperature at a heating rate of 10-20 ℃/s, and keeping the temperature for 10-30min; wherein the predetermined temperature is higher than Ac of SA508-4 steel 3 The temperature is lower than 1050 ℃;
(3) Rapidly cooling the SA508-4 steel subjected to heat preservation in the step (2) to a preset temperature at a speed of 40-60 ℃/s, and preserving heat for 10-60min; wherein the preset temperature is Ac of SA508-4 steel 1 ~Ac 3 (ii) temperature;
(4) And (4) cooling the heat-insulated SA508-4 steel in the step (3) to room temperature at the speed of 0.5-20 ℃/s.
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Citations (3)
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| CN102912108A (en) * | 2012-10-23 | 2013-02-06 | 鞍钢股份有限公司 | Heat treatment process for improving microstructure and properties of micro-alloy steel weld joint |
| CN106498146A (en) * | 2016-10-13 | 2017-03-15 | 北京科技大学 | A kind of method for improving slab multi-pass welding welding point low-temperature flexibility |
| CN107326160A (en) * | 2017-06-29 | 2017-11-07 | 山东建筑大学 | A kind of low-carbon C Mn Si systems steel C, Mn with TRIP effects integrate partition heat treatment method |
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| KR100261664B1 (en) * | 1997-10-21 | 2000-07-15 | 이종훈 | Intercritical heat treatment process for toughness improvement of sa508 gr.3 steel |
| CN103215491A (en) * | 2013-02-01 | 2013-07-24 | 河北联合大学 | Method for preparing carbon-silicon-manganese-series Q&P steel through alloy element partitioning |
| US9803256B2 (en) * | 2013-03-14 | 2017-10-31 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
| CN104532126B (en) * | 2014-12-19 | 2017-06-06 | 宝山钢铁股份有限公司 | A kind of super high strength hot rolled Q＆P steel of low yield strength ratio and its manufacture method |
| CN107287401B (en) * | 2017-06-10 | 2020-10-09 | 山东建筑大学 | Method for improving performance of traditional Q & P steel through carbon-manganese comprehensive distribution |
| ES2932501T3 (en) * | 2017-11-02 | 2023-01-20 | Cleveland Cliffs Steel Properties Inc | Pressure hardened steel with tailored properties after novel heat treatment |
| CN112899463A (en) * | 2021-01-15 | 2021-06-04 | 天津职业技术师范大学(中国职业培训指导教师进修中心) | Postweld low-temperature distribution method for improving toughness of low-phase-change deposited metal with dual-phase structure |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102912108A (en) * | 2012-10-23 | 2013-02-06 | 鞍钢股份有限公司 | Heat treatment process for improving microstructure and properties of micro-alloy steel weld joint |
| CN106498146A (en) * | 2016-10-13 | 2017-03-15 | 北京科技大学 | A kind of method for improving slab multi-pass welding welding point low-temperature flexibility |
| CN107326160A (en) * | 2017-06-29 | 2017-11-07 | 山东建筑大学 | A kind of low-carbon C Mn Si systems steel C, Mn with TRIP effects integrate partition heat treatment method |
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