A heat treatment method for ultra-supercritical steam turbine castings above 620°C

A heat treatment method and ultra-supercritical technology, applied in the field of heat treatment, can solve problems such as the inability to meet the requirements of grain refinement and comprehensive performance, and achieve the effect of weakening the heritability of the structure, reducing the processing difficulty, and reducing the grain size.

Active Publication Date: 2019-10-08
TIANJIN HEAVY EQUIP ENG RES +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Existing heat treatment methods cannot meet the requirements of ultra-supercritical ZG08Cr9W3Co3VNbNB material castings for grain refinement and comprehensive performance

Method used

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  • A heat treatment method for ultra-supercritical steam turbine castings above 620°C
  • A heat treatment method for ultra-supercritical steam turbine castings above 620°C
  • A heat treatment method for ultra-supercritical steam turbine castings above 620°C

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] Heat treatment of ZG08Cr9W3Co3VNbNB castings smelted by vacuum induction furnace, ZG08Cr9W3Co3VNbNB casting components are C: 0.09, Si: 0.31, Mn: 0.53, Cr: 9.11, Nb: 0.05, W: 2.96, Co: 2.98, V: 0.18, B: 0.014, N: 0.0068, the balance is Fe and unavoidable impurities.

[0037] The specific steps and process parameters are as follows:

[0038] S1. Homogenization heat treatment: put the casting in a high-temperature furnace at 200°C for 5 hours, then raise the temperature to 800°C at a rate of 50°C / h for 5 hours, then raise the temperature to 1140°C at a rate of 80°C, and hold for 10 hours for homogenization Heat treatment to dissolve boron carbides and delta ferrite and eliminate component segregation of large castings. After heat preservation, furnace cool at a rate of 30°C / h to below 150°C.

[0039] S2. Low-temperature annealing heat treatment: put the casting into a 150°C waiting furnace, hold it for 5 hours, then raise the temperature to 800°C at a rate of 50°C / h, and...

Embodiment 2

[0043] The ZG08Cr9W3Co3VNbNB castings melted in a vacuum induction furnace are heat treated. The components of the ZG08Cr9W3Co3VNbNB castings are C: 0.07, Si: 0.29, Mn: 0.48, Cr: 9.0, Nb: 0.04, W: 2.7, Co: 3.3, V: 0.24, B: 0.012, N: 0.008, the balance is Fe and unavoidable impurities.

[0044] The specific steps and process parameters are as follows:

[0045] S1. Homogenization heat treatment: hold at 210°C for 5 hours in a high-temperature furnace, raise the temperature at a rate of 40°C / h to 800°C for 5 hours, then raise the temperature at a rate of 70°C to 1180°C, and hold for 12 hours for homogenization heat treatment. After the heat preservation is over, furnace cool at a rate of 25°C / h to below 150°C.

[0046] S2. Low-temperature annealing heat treatment: put the casting into the 80°C waiting furnace, hold it for 5 hours, then raise the temperature to 700°C at a rate of 40°C / h, and after holding it for 40 hours, cool it in the furnace at a rate of 40°C / h to below 150°C,...

Embodiment 3

[0050] The ZG08Cr9W3Co3VNbNB castings melted in a vacuum induction furnace are heat treated. The components of the ZG08Cr9W3Co3VNbNB castings are C: 0.08, Si: 0.33, Mn: 0.54, Cr: 8.8, Nb: 0.05, W: 2.9, Co: 3.3, V: 0.24, B: 0.013, N: 0.008, the balance is Fe and unavoidable impurities.

[0051] The specific steps and process parameters are as follows:

[0052] S1. Homogenization heat treatment: Put the casting in a high-temperature furnace at 250°C for 5 hours, then raise the temperature to 800°C at a rate of 30°C / h for 5 hours, then raise the temperature to 1200°C at a rate of 60°C, and hold it for 14 hours for homogenization heat treatment. After the heat preservation is over, furnace cool at a rate of 20°C / h to below 150°C.

[0053] S2. Low-temperature annealing heat treatment: put the casting into a 110°C waiting furnace, hold it for 5 hours, then raise the temperature to 850°C at a rate of 30°C / h, and after holding it for 50 hours, cool it in the furnace at a rate of 45°...

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Abstract

The invention discloses a heat treatment method of more than 620 DEG C ultra-supercritical turbine casting, and belongs to the technical field of heat treatment. The heat treatment method disclosed bythe invention comprises the following steps of S1, homogenizing heat treatment; S2, low-temperature annealing heat treatment; S3, normalizing heat treatment; and S4, tempering heat treatment; a low-temperature annealing heat treatment technology comprises the following steps of putting the ultra-supercritical turbine casting in an idle furnace of 80 to 150 DEG C, performing heat preservation for5 h, then heating to 650 to 850 DEG C at a rate not higher than 50 DEG C / h, and performing heat preservation for 30 to 100 h. By making a reasonable process system of homogenizing heat treatment, normalizing heat treatment and tempering heat treatment, and meanwhile, performing low-temperature annealing heat treatment between homogenizing heat treatment and normalizing heat treatment, a ferrite and carbide structure nearly balanced is obtained; structure heredity is eliminated, and crystal grains are refined, so that a problem that the crystal grains of the casting of a ZG08Cr9W3Co3VNbNB material are coarse due to the structure heredity is solved, and the requirement of the product on combination property is met.

Description

technical field [0001] The invention belongs to the technical field of heat treatment, in particular to a heat treatment method for castings of ultra-supercritical steam turbines above 620°C. Background technique [0002] The composition of ultra-supercritical thermal power plants has become the main development direction of clean coal-fired technology in major countries in the world. The ferritic heat-resistant steel used in the casting materials of ultra-supercritical units has the advantages of high thermal conductivity, small linear expansion coefficient, high corrosion resistance and good manufacturability. With the improvement of unit parameters, 9Cr ferritic heat-resistant steel suitable for temperatures above 620 °C has been continuously developed and applied, and ZG08Cr9W3Co3VNbNB material has been used as one of the candidate materials for large steam turbine castings of 630-650 °C ultra-supercritical thermal power units. [0003] Since large-scale castings cannot...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D1/18C21D1/26C21D1/28C21D6/00C21D9/00C22C38/02C22C38/04C22C38/22C22C38/24C22C38/26C22C38/30C22C38/32
Inventor 朱琳张留军宋肖阳李康常军委
Owner TIANJIN HEAVY EQUIP ENG RES
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