403SS forge piece and heat treatment method thereof

Abstract

The invention discloses a 403SS forge piece and a heat treatment method thereof, and the heat treatment method comprises the following steps: quenching the 403SS forge piece for the first time, and cooling after quenching; then quenching for the second time, and cooling after quenching; and then tempering is carried out, cooling is carried out after tempering, and heat treatment of the 403SS forge piece is completed. According to the method, the 403SS material forge piece is subjected to primary complete austenitizing quenching treatment firstly, then the forge piece is heated at the temperature lower than the austenitizing temperature for secondary quenching and then is subjected to high-temperature tempering, a complex phase of acicular ferrite and fibrous tempered martensite can be obtained, and the toughness of steel can be remarkably improved; the method effectively solves the problem that the nuclear grade forge piece 403SS material forge piece is high in comprehensive mechanical property strength, low in impact and unstable in comprehensive mechanical property and cannot meet the requirements at the same time, improves the room temperature impact toughness of the forge piece 403SS material forge piece, improves the comprehensive mechanical property of the forge piece, and enables the forge piece 403SS material forge piece to be suitable for the nuclear power field.

Description

Technical Field

[0001] The invention belongs to the technical field of metal heat treatment, and in particular relates to a 403SS forging and a heat treatment method thereof. Background Art

[0002] 403SS material belongs to martensitic stainless steel. It is mainly used in the nuclear power field for forgings of reactor internal components such as compression springs that require high strength, high toughness, pressure resistance, and corrosion resistance. This type of forging is a ring-shaped part. The forging is relatively large, and the forging strength is higher than that of similar materials in national standards. The impact requirements are also high. In the production process, the impact is always low and unstable while ensuring the strength. Conventional heat treatment methods cannot simultaneously meet the requirements of high strength and high impact toughness. Therefore, it is very necessary to find a more convenient heat treatment method to improve the comprehensive mechanical properties of forgings.

[0003] The patent document with announcement number CN115612924A discloses a ferrite / martensitic heat-resistant steel for lead-bismuth stack and its preparation method, which is prepared through smelting, forging, normalizing, tempering and other steps. The appropriate rare earth content can purify the molten steel, refine the grains, modify the inclusions, improve the plasticity and strength of the steel, and improve the lead-bismuth corrosion resistance or radiation resistance or high-temperature oxidation resistance of the martensitic stainless steel. Rare earth elements are not added in this application, but the toughness of the material is improved by heat treatment process. It can be seen that the way this application solves the technical problem is different from that of the invention.

[0004] The patent document with the announcement number CN109913759A discloses a method for preparing a medium manganese steel material with a dual grain structure, which is carried out in the following steps: heating the medium manganese steel cold-rolled plate to a certain temperature to make it completely austenitized, and then quenching it to room temperature to obtain a complete martensitic structure; performing surface mechanical grinding treatment on the quenched medium manganese steel cold-rolled plate to form a certain thickness of a strong plastic deformation layer on the surface of the steel plate; performing austenite reverse phase transformation annealing on the medium manganese steel plate treated by SMAT to obtain a medium manganese steel with a dual grain structure. The method of the invention obtains a dual grain structure, which means that a certain thickness of the surface layer of the steel plate is submicron equiaxed crystals, which is different from the technical problem to be solved by the present application to obtain a complex structure of acicular ferrite and fibrous tempered martensite. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a 403SS forging and a heat treatment method thereof.

[0006] The present invention is achieved through the following technical solutions.

[0007] The invention provides a 403SS forging, which comprises the following components in mass percentage: C: 0.06-0.13%, Si: ≤0.50%, Mn: 0.25-0.80%, P: ≤0.015%, S: ≤0.015%, Cr: 11.50-13.00%, Ni: ≤0.50%, Co: ≤0.04%, and the rest is Fe.

[0008] Preferably, the following components are included in mass percentage: C: 0.095%, Si: 0.30%, Mn: 0.69%, P: 0.010%, S: 0.009%, Cr: 11.90%, Ni: 0.33%, Co: 0.028%, and the rest is Fe.

[0009] A heat treatment method for a 403SS forging comprises the following steps:

[0010] S1, quenching the 403SS forging for the first time to obtain a first quenched forging;

[0011] S2, cooling after quenching;

[0012] S3, performing a second quenching on the first quenched forging to obtain a second quenched forging;

[0013] S4, cooling after quenching;

[0014] S5, tempering the secondary quenched forging to obtain a tempered forging;

[0015] S6. After tempering, cool down to complete the heat treatment of 403SS forgings.

[0016] Preferably, the first quenching in step S1 is to heat the 403SS forging to 950-970° C. over 2-4 hours and keep the temperature for 1-2 hours.

[0017] Preferably, after the first quenching in step S2 is completed, the forging is taken out of the furnace and water-cooled to room temperature.

[0018] Preferably, the second quenching in step S3 is to heat the once quenched forging to 830-850° C. for 1-3 hours and keep the temperature for 1-2 hours.

[0019] Preferably, after the second quenching in step S4 is completed, the second quenched forging is taken out of the furnace and water-cooled to room temperature.

[0020] Preferably, the tempering in step S5 is to heat the secondary quenched forging to 600-650° C. for 1-3 hours and keep the temperature for 3.5-4.5 hours.

[0021] Preferably, after tempering in step S6 is completed, the tempered forging is taken out of the furnace and water-cooled to room temperature.

[0022] The beneficial effects of the present invention are:

[0023] Compared with the prior art, the present invention first performs a complete austenitizing quenching treatment, and then performs a secondary quenching at a quenching temperature lower than the austenitizing temperature and then performs high-temperature tempering, that is, after the forging is completely austenitized and then quenched at a temperature lower than the austenitizing temperature, the acicular ferrite and fibrous tempered martensite complex phases are obtained after high-temperature tempering, which can significantly improve the toughness of the steel; effectively solves the problem that the comprehensive mechanical properties of the nuclear-grade forging 403SS material forgings, namely, high strength and low impact instability, cannot meet the requirements at the same time, improves the room temperature impact toughness of the 403SS material forgings, improves the comprehensive mechanical properties of the forgings, and enables the 403SS forgings to be suitable for the nuclear power field. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a heat treatment flow chart of an embodiment of the present invention;

[0025] Figure 2 is a heat treatment flow chart of an embodiment of the present invention;

[0026] Figure 3 It is a heat treatment flow chart of a comparative example of the present invention;

[0027] Figure 4 is the metallographic structure diagram of Example 3 of the present invention;

[0028] Figure 5 It is the metallographic structure diagram of comparative example 1 of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0030] Embodiment 1:

[0031] like Figure 1 , 2 As shown, a 403SS forging includes the following components, in mass percentage: C: 0.06%, Si: 0.10%, Mn: 0.40%, P: 0.006%, S: 0.004%, Cr: 11.50%, Ni: 0.10%, Co: 0.020%, and the remainder is Fe.

[0032] A heat treatment method for a 403SS forging comprises the following steps:

[0033] S1. Perform the first quenching on the 403SS forging. After 2 hours of heating, heat the 403SS forging to 950°C and keep it at this temperature for 1 hour to obtain a first quenching forging.

[0034] S2, after quenching, take out of the furnace and water cool the once quenched forging to room temperature;

[0035] S3, performing a second quenching on the first quenched forging, heating the first quenched forging to 830° C. after 1 hour of heating, and keeping the temperature for 1 hour to obtain a second quenched forging;

[0036] S4, after quenching, take out of the furnace and water cool the secondary quenched forging to room temperature;

[0037] S5, tempering the secondary quenched forging, heating the secondary quenched forging to 600° C. after 1 hour of heating, and keeping the temperature for 3.5 hours to obtain a tempered forging;

[0038] S6. After tempering, take the forging out of the furnace and water cool it to room temperature to complete the heat treatment of 403SS forgings.

[0039] The mechanical properties of the obtained 403SS forgings were tested twice at room temperature, and the test data are shown in the following table.

[0040] Table 1 - Room temperature mechanical properties of 403SS forgings of Example 1

[0041] project <![CDATA[R P0.2 (MPa)]]> <![CDATA[R m (MPa)]]> A(％) Z(％) Akv(J) Required value ≥620 ≥758 ≥16 ≥50 Average value ≥ 60J; Single value ≥ 50J Detection value 1 658 777 21 75.5 183、219、185 Detection value 2 650 764 20 76 198、201、199

[0042] Embodiment 2:

[0043] like Figure 1 , 2 As shown, a 403SS forging includes the following components, in mass percentage: C: 0.13%, Si: 0.50%, Mn: 0.78%, P: 0.012%, S: 0.010%, Cr: 13%, Ni: 0.50%, Co: 0.030%, and the remainder is Fe.

[0044] A heat treatment method for a 403SS forging comprises the following steps:

[0045] S1. Perform the first quenching on the 403SS forging. After 4 hours of heating, heat the 403SS forging to 970°C and keep it at this temperature for 2 hours to obtain a first quenching forging.

[0046] S2, after quenching, take out of the furnace and water cool the once quenched forging to room temperature;

[0047] S3, performing a second quenching on the first quenched forging, heating the first quenched forging to 850°C after 3 hours of heating, and keeping the temperature for 2 hours to obtain a second quenched forging;

[0048] S4, after quenching, take out of the furnace and water cool the secondary quenched forging to room temperature;

[0049] S5, tempering the secondary quenched forging, heating the secondary quenched forging to 650°C after 3h of heating, and keeping the temperature for 4.5h to obtain a tempered forging;

[0050] S6. After tempering, take the forging out of the furnace and water cool it to room temperature to complete the heat treatment of 403SS forgings.

[0051] The mechanical properties of the obtained 403SS forgings were tested twice at room temperature, and the test data are shown in the following table.

[0052] Table 2 - Room temperature mechanical properties of 403SS forgings of Example 2

[0053] project <![CDATA[R P0.2 (MPa)]]> <![CDATA[R m (MPa)]]> A(％) Z(％) Akv(J) Required value ≥620 ≥758 ≥16 ≥50 Average value ≥ 60J; Single value ≥ 50J Detection value 1 660 777 20.5 74.5 202、210、183 Detection value 2 656 764 21 73 200、190、195

[0054] Embodiment 3:

[0055] like Figure 1 , 2 As shown, a 403SS forging includes the following components, in mass percentage: C: 0.095%, Si: 0.30%, Mn: 0.69%, P: 0.010%, S: 0.009%, Cr: 11.90%, Ni: 0.33%, Co: 0.028%, and the rest is Fe.

[0056] A heat treatment method for a 403SS forging comprises the following steps:

[0057] S1. Perform the first quenching on the 403SS forging. After heating for 3 hours, heat the 403SS forging to 950°C and keep it at this temperature for 1.5 hours to obtain a first quenching forging.

[0058] S2, after quenching, take out of the furnace and water cool the once quenched forging to room temperature;

[0059] S3, performing a second quenching on the first quenched forging, heating the first quenched forging to 840°C after 2h of heating, and keeping the temperature for 1.5h to obtain a second quenched forging;

[0060] S4, after quenching, take out of the furnace and water cool the secondary quenched forging to room temperature;

[0061] S5, tempering the secondary quenched forging, heating the secondary quenched forging to 610° C. after 2 h of heating, and keeping the temperature for 245 min to obtain a tempered forging;

[0062] S6. After tempering, take the forging out of the furnace and water cool it to room temperature to complete the heat treatment of 403SS forgings.

[0063] The mechanical properties of the obtained 403SS forgings were tested twice at room temperature, and the test data are shown in the following table.

[0064] Table 3 - Room temperature mechanical properties of 403SS forgings of Example 3

[0065]

[0066] Comparative Example 1:

[0067] like Figure 3 As shown, a 403SS forging includes the following components, in mass percentage: C: 0.095%, Si: 0.30%, Mn: 0.69%, P: 0.010%, S: 0.009%, Cr: 11.90%, Ni: 0.33%, Co: 0.028%, and the rest is Fe.

[0068] A heat treatment method for a 403SS forging comprises the following steps:

[0069] S1. Perform the first quenching on the 403SS forging. After 2 hours of heating, heat the 403SS forging to 950°C and keep it at this temperature for 1.5 hours to obtain a first quenching forging.

[0070] S2, after quenching, take out of the furnace and water cool the once quenched forging to room temperature;

[0071] S3, tempering the first quenched forging, heating the second quenched forging to 610°C after 2h of heating, and keeping the temperature for 245min to obtain a tempered forging;

[0072] S4. After tempering, the tempered forgings are taken out of the furnace and water-cooled to room temperature to complete the heat treatment of 403SS forgings.

[0073] The mechanical properties of the obtained 403SS forgings were tested twice at room temperature, and the test data are shown in the following table.

[0074] Table 4 - Room temperature mechanical properties of 403SS forgings of Comparative Example 1

[0075] project <![CDATA[R P0.2 (MPa)]]> <![CDATA[R m (MPa)]]> A(％) Z(％) Akv(J) Required value ≥620 ≥758 ≥16 ≥50 Average value ≥ 60J; Single value ≥ 50J Detection value 1 665 780 21.5 71.5 59、91、45 Detection value 2 650 765 21 70.5 48、73、51

[0076] It can be seen from Tables 1-4 that the strength and impact of the forgings obtained in Examples 1-3 meet the requirements, and are close to the strength of Comparative Example 1, but the impact is quite different.

[0077] Example 3 is the best example. In Example 3, Akv (187, 187, 224) and Akv (212, 182, 234) are much higher than the impact energy of the comparative example under the same experimental conditions, the impact toughness is increased by nearly 3 times, and the comprehensive mechanical properties are also very good. Therefore, the 403SS material forging adopts a single quenching and a secondary quenching below the austenitizing temperature and high temperature tempering to achieve high strength and high impact requirements, and has a good effect.

[0078] Figure 4 The structure is: acicular ferrite and fibrous tempered martensite duplex structure;

[0079] Figure 5The structure is: tempered martensite structure with martensite orientation maintained;

[0080] The process of the present application adopts quenching lower than austenitizing, and the obtained plastic phase acicular ferrite divides the brittle phase martensite to the maximum extent. During the crack propagation process, the acicular ferrite consumes a lot of energy due to plastic deformation and hinders the development of the crack, making the energy required for crack propagation work larger, thereby increasing the impact work.

Claims

1. A 403SS forging, characterized in that: In units of mass percentage, it includes the following components: C: 0.06-0.13%, Si: ≤0.50%, Mn: 0.25-0.80%, P: ≤0.015%, S: ≤0.015%, Cr: 11.50-13.00%, Ni: ≤0.50%, Co: ≤0.04%, and the rest is Fe.

2. A 403SS forging as claimed in claim 1, characterized in that: In units of mass percentage, it includes the following components: C: 0.095%, Si: 0.30%, Mn: 0.69%, P: 0.010%, S: 0.009%, Cr: 11.90%, Ni: 0.33%, Co: 0.028%, and the rest is Fe.

3. A heat treatment method for a 403SS forging according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1, quenching the 403SS forging for the first time to obtain a first quenched forging; S2, cooling after quenching; S3, performing a second quenching on the first quenched forging to obtain a second quenched forging; S4, cooling after quenching; S5, tempering the secondary quenched forging to obtain a tempered forging; S6. After tempering, cool down to complete the heat treatment of 403SS forgings.

4. A heat treatment method for 403SS forgings as claimed in claim 3, characterized in that: The first quenching in step S1 is to heat the 403SS forging to 950-970° C. over 2-4 hours and keep the temperature for 1-2 hours.

5. A heat treatment method for 403SS forgings as claimed in claim 3, characterized in that: After the first quenching in step S2 is completed, the forging is taken out of the furnace and water-cooled to room temperature.

6. A heat treatment method for 403SS forgings as claimed in claim 3, characterized in that: The second quenching in step S3 is to heat the first quenched forging to 830-850° C. over 1-3 hours and keep the temperature for 1-2 hours.

7. A heat treatment method for 403SS forgings as claimed in claim 3, characterized in that: After the second quenching in step S4 is completed, the second quenched forging is taken out of the furnace and water-cooled to room temperature.

8. A heat treatment method for 403SS forgings as claimed in claim 3, characterized in that: The tempering in step S5 is to heat the secondary quenched forging to 600-650° C. for 1-3 hours and keep the temperature for 3.5-4.5 hours.

9. A heat treatment method for 403SS forgings as claimed in claim 3, characterized in that: After tempering in step S6, the forged piece is taken out of the furnace and water-cooled to room temperature.

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