Measuring method for thermostability of residual austenite in steel

A technology of retained austenite and measurement method, applied in the direction of material magnetic variables, etc., can solve the problems of low magnetic field strength, material can not reach the magnetic saturation state, large sampling size, etc., to achieve the effect of saving material and accurate quantitative calculation results

Inactive Publication Date: 2009-08-12
HEBEI NORMAL UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, the magnetic measurement methods adopted, such as the impact measurement method, have the following problems: (1) the sampling size is large (greater than 50mm), and small samples cannot be measured; (2) the magnetic field strength is low, and the material cannot reach the magnetic saturation state, that is, The number of ferromagnetic phases and the magnetization deviate from the linear relationship, and the measurement results are affected by demagnetization factors, so the measurement results of retained austenite are not accurate; (3) the temperature change during measurement is difficult to accurately control

Method used

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  • Measuring method for thermostability of residual austenite in steel
  • Measuring method for thermostability of residual austenite in steel
  • Measuring method for thermostability of residual austenite in steel

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Experimental program
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Effect test

Embodiment 1

[0026] (1) Pretreatment of steel

[0027] Select 1.02C-1.35Cr-0.33Mn-0.26Si high-carbon steel, cast, roll, and soften annealing. The softening annealing process is: heating at 1093K for 1h, slowly cooling to 963K at a rate of 10K / h, and then air cooling to room temperature. The quenching heating temperature is 1133K, and the holding time is 30min.

[0028] (2) Magnetic high temperature test

[0029] The quenched and heated sample is directly quenched to room temperature, and the quenched steel is cut into block samples with a diameter of 2 mm and a length of 2 mm by electric discharge method. Magnetic measurements were performed on a vibrating sample magnetometer. The vibrating sample magnetometer was calibrated with a nickel standard prior to testing. The temperature cycle range of high temperature magnetic measurement is 300K-1173K, and the applied magnetic field strength is 0.79×10 6 A / m. The heating rate for high temperature magnetic measurement is 3-5K / min, and the c...

Embodiment 2

[0033] (1) Pretreatment of steel

[0034] Select 1.02C-1.35Cr-0.33Mn-0.26Si high-carbon steel, cast, roll, and soften annealing. The softening annealing process is: heating at 1093K for 1h, slowly cooling to 963K at a rate of 10K / h, and then air cooling to room temperature. The quenching heating temperature is 1133K, and the holding time is 30min.

[0035] (2) Magnetic high temperature test

[0036] The quenched and heated sample was quenched to 503K and kept for 40 minutes, and the austempered steel was cut into block samples with a diameter of 2 mm and a length of 2 mm by electric discharge method. Magnetic measurements were performed on a vibrating sample magnetometer. The vibrating sample magnetometer was calibrated with a nickel standard prior to testing. The temperature cycle range of high temperature magnetic measurement is 300K-1173K, and the applied magnetic field strength is 0.79×10 6 A / m. The heating rate for high temperature magnetic measurement is 3-5K / min, a...

Embodiment 3

[0040] (1) Pretreatment of steel

[0041] Select 1.02C-1.35Cr-0.33Mn-0.26Si high-carbon steel, cast, roll, and soften annealing. The softening annealing process is: heating at 1093K for 1h, slowly cooling to 963K at a rate of 10K / h, and then air cooling to room temperature. The quenching heating temperature is 1133K, and the holding time is 30min.

[0042] (2) Magnetic low temperature test

[0043] The quenched and heated sample was quenched to 503K and kept for 40 minutes, and the austempered steel was cut into block samples with a diameter of 2 mm and a length of 2 mm by electric discharge method. Magnetic measurements were performed on a vibrating sample magnetometer. The vibrating sample magnetometer was calibrated with a nickel standard prior to testing. The temperature cycle range of low temperature magnetic measurement is 300K-10K, and the applied magnetic field strength is 0.79×10 6 A / m. The heating and cooling rates for low temperature magnetic measurements are bot...

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Abstract

The invention discloses a method for measuring the thermal stability of remained austenite in quenching state steel. The measuring method comprises the following steps of quenching; sampling by wire cutting; making a high-temperature magnetic test(300K to 1,273K); making a low-temperature magnetic test (10K to 300K); and making a test on the thermal stability of the remained austenite by calculation. One or two samples are needed in the measuring process, and as for the size of the samples, the diameter is not more than 2mm, and the length is between 2 and 4mm; and the applied magnetic field strength is (1-3)*0.79*10 A / M. The method can measure the smallest magnetic moment which is 5*10-7emu, has the typical absolute accuracy better than 2 percent and the repeatability better than 1 percent. The method can be used for measuring the quantitative change conditions of the remained austenite when the quenching state samples (including the constant temperature quenching state) undergo high-temperature or low-temperature treatment, evaluating the thermal stability of the remained austenite, and providing basis of reasonably working out a tempering process and a cold treatment process of steel products.

Description

technical field [0001] The invention relates to a method for quantitatively measuring non-thermally stable phases in iron and steel materials, in particular to a method for measuring the thermal stability of retained austenite in steel. Background technique [0002] After the quenching treatment of steel materials, in addition to obtaining martensite and / or bainite, the structure often contains a certain amount of retained austenite. If it is tempered or cold-treated, the retained austenite will be transformed, which is a kind of The stability of the non-thermally stable phase has an important influence on the internal structure of the steel, so measuring its thermal stability is of great significance. Among the existing methods for measuring the thermal stability of retained austenite in steel, the X-ray diffraction method is widely used. This method observes the state of the diffraction peak and detects the state of the surface layer of the material. Influenced by many fa...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N27/72
Inventor 侯邓录孙世清潘成福
Owner HEBEI NORMAL UNIV
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