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Method for measuring high-silicon high-carbon steel wire rod austenite grain size

A technology of austenite grains and measurement methods, which is applied in measurement devices, particle size analysis, particle and sedimentation analysis, etc. Clear and successful results

Active Publication Date: 2018-05-11
INST OF RES OF IRON & STEEL JIANGSU PROVINCE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When the carbon content of the steel grade exceeds 0.87, the presence of high Si, Cr and other elements in the steel will significantly affect the oxidation and decarburization process during the heat treatment of the wire rod. Si will accelerate the decarburization of high-carbon steel, and Cr will be in the The enrichment of oxide scale and matrix interface affects the ferrite grains on the interface between the original austenite grains and the interface, and the accuracy of the oxidation method to determine the grain size of the original austenite becomes poor
At the same time, with the development of steelmaking technology, the purity of molten steel continues to increase, and the success rate of observing the grain boundaries of prior austenite by corroding martensite by direct hardening is getting lower and lower.
[0004] At the same time, only a local area of ​​the sample prepared by the above two methods can be clearly displayed, so as to determine the average grain size of the entire sample, the results are not representative

Method used

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  • Method for measuring high-silicon high-carbon steel wire rod austenite grain size
  • Method for measuring high-silicon high-carbon steel wire rod austenite grain size
  • Method for measuring high-silicon high-carbon steel wire rod austenite grain size

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0023] Process the wire rod into a round bar with a length of 10cm and a diameter of 6mm; heat the round bar on a thermal simulation testing machine to 980°C, keep it for 10 minutes, then cool it to 700°C at a speed of 30K / s, keep it for 10 minutes, and finally cool it down to room temperature quickly ; cut the heat-treated sample along the cross-section at the position of the welding thermocouple, then inlay, grind and polish it into a metallographic sample; rinse and dry it after corroding with sodium picrate aqueous solution for 2 minutes at 50°C; use a metallographic microscope to measure the crystal grain size, such as figure 1 As shown, the average grain size of the grains was measured to be 50 μm.

Embodiment 2

[0025] Process the wire rod into a round bar with a length of 10cm and a diameter of 6mm; heat the round bar on a thermal simulation testing machine to 1050°C, keep it for 10 minutes, then cool it to 720°C at a speed of 30K / s, keep it for 10 minutes, and finally cool it down to room temperature quickly ; cut the heat-treated sample along the cross-section at the position of the welding thermocouple, then inlay, grind and polish it into a metallographic sample; rinse and dry it after corroding with sodium picrate aqueous solution for 2 minutes at 50°C; use a metallographic microscope to measure the crystal grain size, such as figure 2 As shown, the average grain size of the grains was measured to be 56 μm.

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Abstract

The invention discloses a method for measuring high-silicon high-carbon steel wire rod austenite grain size. The method comprises the following steps: S1 sample preparation, processing a steel wire rod into a round rod with a length of 10cm and a diameter of 6mm; S2 sample processing, heating the round rod on a thermal simulation tester to 850-1200 DEG C and keeping at a temperature for 10 to 60 minutes, then cooling to 700-720 DEG C at a rate of 30K / s and keeping at a temperature for 10 minutes, and then rapidly cooling to room temperature; S3, sample observation, cutting, inlaying and polishing samples processed by S2 sample processing, corroding the samples with aqueous solution of sodium picrate, and using a metallographic microscope for measuring the grain size. The method can clearlydisplay original austenite grains, images of the samples are very clear in the entire cross section, success rate is high, and the method can meet the needs of scientific research.

Description

technical field [0001] The application relates to metallographic analysis, in particular to a method for measuring the austenite grain size of high-silicon and high-carbon steel wire rods. Background technique [0002] High-carbon steel generally has a pearlite structure in the hot-rolled state, and the austenite grain size is difficult to measure directly. Ordinary direct corrosion method, network ferrite method, etc. are not suitable for the measurement of austenite grains of high carbon steel. With the increase of carbon content, especially the addition of alloying elements in high carbon steel, the difficulty of showing grain boundaries by corrosion method also increases. [0003] At present, there are mainly two methods for the detection of austenite grain size of high carbon steel wire rod: oxidation method and direct quenching method. When the carbon content of the steel grade exceeds 0.87, the presence of high Si, Cr and other elements in the steel will significant...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N15/02
CPCG01N15/0205
Inventor 王雷胡磊麻晗胡显军施一新
Owner INST OF RES OF IRON & STEEL JIANGSU PROVINCE
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