Precipitation hardening type martensitic steel and process for producing same

By controlling the austenite phase amount and alloy composition, combined with appropriate heat treatment conditions, the deficiencies in tensile strength and energy absorption of precipitation-strengthened martensitic steel are solved, achieving a tensile strength of 1500MPa and an absorption of more than 30J. energy for efficient power generation turbines and lightweight aircraft components.

Inactive Publication Date: 2015-01-07
PROTERIAL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These alloys are low-alloy steels that can obtain a tensile strength of 1800 MPa class and an elongation of about 10%, but the amount of Cr that contributes to corrosion resistance and oxidation resistance is as little as about 1%, so they cannot be used as steel alloys for steam turbines. Moving blade use

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0057] The following examples illustrate the present invention in more detail.

[0058] A 10kg steel ingot is produced by vacuum melting, and a forging material having a square shape with a cross section of 45mm×20mm is produced by hot forging. Table 1 shows the composition of the molten steel ingot.

[0059] [Table 1]

[0060] (quality%)

[0061]

[0062] Note: The "-" in the table is not added.

[0063] For the raw material after forging, heat treatment was performed under various conditions shown in Table 2. The melt treatment is oil cooling after being kept at 927℃×1h. For some, for the purpose of reducing retained austenite, a cryogenic treatment of -75°C×2h is performed after the solution treatment. After that, the aging treatment of air cooling after keeping at 524℃×8h was carried out. The processed raw materials were subjected to test piece processing and characteristic evaluation. The tensile test was implemented in accordance with ASTM-E8. The Charpy impact test uses a ...

Embodiment 2

[0078] An example is shown in which the precipitation-strengthened martensitic steel of the present invention is manufactured on an industrial scale.

[0079] A test piece was collected from a round bar material of Φ220 mm made by hot forging a 1 ton steel ingot manufactured by vacuum induction melting and vacuum arc remelting, and the same characteristics evaluation as in Example 1 was performed. The composition of the steel ingot obtained by vacuum arc remelting is shown in Table 4.

[0080] In addition, the heat treatment conditions are: melt heat treatment: air cooling after 927℃×1h holding and air cooling after 880℃×1h holding; cryogenic treatment: -75℃×2h; aging treatment: 524℃×8h holding and air cooling.

[0081] The results of the characteristic evaluation are shown in Table 5. Regarding the amount of austenite of the raw material used for the characteristic evaluation, the test number 21 was 0.2% after the cryogenic treatment and 0.4% after the aging treatment. In addition...

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Abstract

Provided are a precipitation hardening type martensitic steel which combines a tensile strength in the 1500-MPa class with a Charpy absorption energy as high as 30 J or above and a process for producing the martensitic steel. The precipitation hardening type martensitic steel contains, in terms of mass%, up to 0.05% C, up to 0.2% Si, up to 0.4% Mn, 7.5-11.0% Ni, 10.5-13.5% Cr, 1.75-2.5% Mo, 0.9-2.0% Al, and less than 0.1% Ti, with the remainder comprising Fe and impurities, and contains austenite in an amount of 0.1-6.0% by volume.

Description

Technical field [0001] The present invention relates to a precipitation-strengthened martensitic steel with high strength and excellent impact characteristics and a method of manufacturing the same. Background technique [0002] In the past, high-strength iron-based alloys have been used for turbine parts for power generation and aircraft body parts. [0003] For turbine parts for power generation, high Cr steel is used for various parts. Among turbine parts, particularly for low-pressure final stage rotor blades of steam turbines that require strength, 12Cr steel containing approximately 12% by weight of Cr is used as an alloy that combines strength, oxidation resistance, and corrosion resistance. In order to improve the efficiency of power generation, the blade length is advantageous, and for 12Cr steel, due to the limitation of strength, the limit of the blade length is about 1 meter. [0004] In addition, low-alloy high-tensile steels such as AISI 4340 and 300M are known. Thes...

Claims

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Application Information

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Patent Type & AuthorityApplications(China)
IPC IPC(8): C22C38/00C22C38/50C21D6/00
CPCC22C38/00C22C38/50C21D6/00C22C38/06C22C38/02C22C38/04C22C38/44C21D6/004C21D2211/001C21D2211/004C21D2211/008C21D6/005C21D6/008C21D6/02
OwnerPROTERIAL LTD