CN-122016896-A - Determination of Cr in steel by X-ray diffraction method23C6Method of volume fraction

Abstract

The invention relates to the technical field of carbide detection, in particular to a method for determining Cr 23 C 6 volume fraction in steel by an X-ray diffraction method, which comprises the steps of mechanically processing a high-punch low-carbon quenched steel sample into a standard sample, measuring sample components, removing oxide skin on the surface of the standard sample, setting experimental parameters, placing the standard sample which is organized into martensite+austenite+Cr 23 C 6 in an instrument, carrying out systematic diffraction experiments to obtain diffraction lines, analyzing the diffraction lines to obtain peak position parameter information of martensite and austenite in the phases, searching Cr 23 C 6 data in a crystallographic database, fitting the obtained diffraction lines by a Rietveld refining method to obtain mass fractions of the martensite, cr 23 C 6 and austenite, establishing a model, converting the mass fractions into volume fractions, and determining the M 23 C 6 volume fractions of the samples with multiphase coexistence and preferred orientation.

Inventors

• WANG TING
• ZHONG LILI
• YAN PINGYUAN
• MA HUIXIA
• ZHAO BAOCHUN

Assignees

• 鞍钢股份有限公司

Dates

Publication Date

20260512

Application Date

20260209

Claims (4)

1. 1. A method for determining the volume fraction of Cr 23 C 6 in steel by an X-ray diffraction method, which is characterized by comprising the following steps: step one, mechanically processing a high-punch low-carbon quenched steel sample into a standard sample, and measuring the components of the standard sample; step two, removing oxide skin on the surface of the standard sample; Setting experimental parameters, placing a standard sample with a structure of martensite, austenite and Cr 23 C 6 in an instrument, and performing a diffraction experiment of the system to obtain a diffraction line; analyzing the diffraction spectrum line to obtain peak position parameter information of martensite and austenite in the phase; Searching data of martensite, austenite and Cr 23 C 6 in a crystallography database, and fitting the obtained diffraction lines by adopting a Rietveld refinement method to obtain mass fractions of martensite, cr 23 C 6 and austenite; Step six, establishing a model to convert the mass fraction into volume fraction; ; Wherein, the For the volume fraction of Cr 23 C 6 obtained after refinement, The mass fraction of Cr 23 C 6 is obtained after finishing; is the density of steel; The density of the ith element, g/cm 3 , n is the number of the elements in the alloy; Is Cr 23 C 6 density, g/cm 3 .
2. 2. The method for determining the volume fraction of Cr 23 C 6 in steel by using an X-ray diffraction method according to claim 1, wherein the standard sample is a high-punch low-carbon quenched steel sample with a length of 10-20 mm, a width of 10-20 mm and a height of 1-5 mm.
3. 3. The method for determining the volume fraction of Cr 23 C 6 in steel by using the X-ray diffraction method according to claim 1, wherein the experimental parameters are that an X' -PERT PRO X-ray diffractometer is used for experiment, a Cu target is adopted, the tube voltage is adjusted to 35-40 kV, and the tube current is set to 35-40 mA.
4. 4. The method for determining the volume fraction of Cr 23 C 6 in steel by using an X-ray diffraction method according to claim 1, wherein the obtained diffraction lines are fitted by using a Rietveld refinement method, and the fitting formula is as follows: ; Wherein Y 1 and Y bt are the intensity of the actually measured diffraction curve and the intensity of the back substrate, I pk 、J pk 、F pk is the multiple factor, the angle factor and the structural amplitude containing the temperature factor of the kth diffraction line of a certain phase in the standard sample to be measured respectively, G pki is a peak shape function; Is the weight factor of the P phase.

Description

Method for measuring Cr 23C6 volume fraction in steel by X-ray diffraction method Technical Field The invention relates to the technical field of carbide detection, in particular to a method for measuring Cr 23C6 volume fraction in steel by an X-ray diffraction method. Background The M 23C6 carbide (such as Cr 23C6、(Cr,Fe)23C6) in the steel is used as a key strengthening phase of stainless steel, heat-resistant steel and high alloy steel, and the components, the size, the distribution and the volume fraction of the carbide have decisive influence on the high-temperature strength, the corrosion resistance and the toughness of the material. The nano-scale intragranular dispersion precipitation can improve strength through an Orowan mechanism, and the continuous precipitation of grain boundaries can form a brittle network and induce a Cr-depleted region, so that the corrosion rate is increased. In the existing determination method, a chemical analysis method (acid-soluble extraction and a weight method) needs to destroy a sample and takes 8-24 hours, an original sample cannot be reserved, nano carbide is difficult to identify by a metallographic method, the area fraction conversion error is large, and the M 23C6 quantitative requirement cannot be met by a traditional XRD method (K value method/internal standard method) due to insufficient matrix absorption correction, difficult peak separation of multiphase coexistence (such as martensite and carbide), preferred orientation interference and low content detection limit. Disclosure of Invention The invention provides a method for determining Cr 23C6 volume fraction in steel by an X-ray diffraction method, which is used for determining M 23C6 mass fraction of a multiphase coexisting sample with preferred orientation, simultaneously establishing a conversion relation between XRD data acquisition and actual sample volume fraction based on the X-ray diffraction method, automatically converting the refined mass fraction into volume fraction required by mechanism analysis, and solving the parameter matching problem of a precipitation strengthening model. In order to achieve the above purpose, the invention is realized by adopting the following technical scheme: a method for determining Cr 23C6 volume fraction in steel by an X-ray diffraction method, which comprises the following steps: step one, mechanically processing a high-punch low-carbon quenched steel sample into a standard sample, and measuring the components of the standard sample; step two, removing oxide skin on the surface of the standard sample; Setting experimental parameters, placing a standard sample with a structure of martensite, austenite and Cr 23C6 in an instrument, and performing a diffraction experiment of the system to obtain a diffraction line; analyzing the diffraction spectrum line to obtain peak position parameter information of martensite and austenite in the phase; Searching data of martensite, austenite and Cr 23C6 in a crystallography database, and fitting the obtained diffraction lines by adopting a Rietveld refinement method to obtain mass fractions of martensite, cr 23C6 and austenite; Step six, establishing a model to convert the mass fraction into volume fraction; ; Wherein, the For the volume fraction of Cr 23C6 obtained after refinement,The mass fraction of Cr 23C6 is obtained after finishing; is the density of steel; The density of the ith element, g/cm 3, n is the number of the elements in the alloy; Is Cr 23C6 density, g/cm 3. Further, the standard sample is a high-punch low-carbon quenched steel sample with the length of 10-20 mm, the width of 10-20 mm and the height of 1-5 mm. Further, the experimental parameters are that an X' PERTPROX optical diffractometer is used for experiment, a Cu target is adopted, the tube voltage is adjusted to be 35-40 kV, and the tube current is set to be 35-40 mA. Further, the obtained diffraction lines are fitted by using a Rietveld refinement method, and a fitting formula is as follows: ; Wherein Y 1 and Y bt are the intensity of the actually measured diffraction curve and the intensity of the back substrate, I pk、Jpk、Fpk is the multiple factor, the angle factor and the structural amplitude containing the temperature factor of the kth diffraction line of a certain phase in the standard sample to be measured respectively, G pki is a peak shape function; Is the weight factor of the P phase. Compared with the prior art, the invention has the beneficial effects that: The non-destructive determination method based on Rietveld full spectrum refinement is provided, namely M 23C6 mass fraction determination is carried out on a sample with multi-phase coexistence and preferred orientation, meanwhile, conversion connection between XRD data acquisition and actual sample volume fraction is established, the refinement mass fraction is automatically converted into volume fraction required by mechanism analysis, and the problem of parameter matching of a