阅读说明：本技术 马氏体时效不锈钢枝晶腐蚀剂及腐蚀方法 (Dendritic crystal corrosive agent and corrosion method for maraging stainless steel ) 是由 白青青 张志宏 于 2019-10-25 设计创作，主要内容包括：本发明涉及马氏体时效不锈钢枝晶腐蚀剂及腐蚀方法,属于钢铁金相分析技术领域。本发明腐蚀剂为分析纯硝酸水溶液,由分析纯硝酸与水配制而成,枝晶腐蚀方法为a.切取铸态试样进行研磨、抛光处理；b.配制枝晶腐蚀剂；c.以不锈钢片作为阴极,试样作为阳极,将铸态试样放入腐蚀剂中进行常温电解浸蚀。本发明腐蚀剂配方简单,操作步骤简单,枝晶腐蚀的检测结果清晰准确,通过清晰的枝晶形貌可以准确地计算树枝晶间距等数据及采用能谱测定枝晶间以及枝晶干的偏析程度,用于评价铸态组织质量以及辅助评价均匀化热处理对于枝晶偏析的消除作用。(The invention relates to a dendritic corrosive agent and a corrosion method for maraging stainless steel, and belongs to the technical field of steel metallographic analysis. The corrosive is an analytically pure nitric acid aqueous solution and is prepared by analytically pure nitric acid and water, and the dendritic crystal corrosion method is that a, an as-cast sample is cut and ground and polished; b. preparing a dendritic crystal corrosive; c. and (3) putting the cast sample into a corrosive agent for normal-temperature electrolytic etching by taking the stainless steel sheet as a cathode and the sample as an anode. The corrosive disclosed by the invention is simple in formula, simple in operation steps, clear and accurate in detection result of dendritic crystal corrosion, and can accurately calculate data such as dendritic crystal spacing and the like through clear dendritic crystal morphology and determine the segregation degree between dendrites and dendrite trunks by adopting an energy spectrum, so that the corrosive is used for evaluating the cast structure quality and assisting in evaluating the elimination effect of homogenization heat treatment on dendritic crystal segregation.)

1. The dendritic corrosive agent for maraging stainless steel is characterized in that: the corrosive is an analytically pure nitric acid aqueous solution and is prepared from analytically pure nitric acid and water.

2. The maraging stainless steel dendritic etchant of claim 1, wherein: the volume fraction of the analytically pure nitric acid in the analytically pure nitric acid aqueous solution is 40-50%.

3. The maraging stainless steel dendritic etchant of claim 1, wherein: the mass fraction of the analytically pure nitric acid is 65-68%.

4. The method for corroding dendritic corrosive agent of maraging stainless steel as recited in any one of claims 1 to 3, characterized by comprising the steps of:

a. cutting an as-cast sample, and grinding and polishing the sample;

b. preparing a dendritic crystal corrosive;

c. and (3) taking the stainless steel sheet as a cathode and the as-cast sample as an anode, and putting the as-cast sample into a corrosive agent for normal-temperature electrolytic etching.

5. The dendritic corrosion method of maraging stainless steel according to claim 4, characterized in that: step a, mechanically grinding one plane of the cast test sample on 180#, 500# and 1000# sandpaper respectively, polishing with 2.5 mu m diamond polishing paste until the mirror surface is free of scratches, and then cleaning and drying.

6. The dendritic corrosion method of maraging stainless steel according to claim 4, characterized in that: and c, controlling the voltage of the electrolytic etching process to be 2-3V and the time to be 15-20 s.

Technical Field

The invention belongs to the technical field of steel metallographic analysis, and particularly relates to a dendritic crystal corrosive agent and a corrosion method for maraging stainless steel.

Background

The PH13-8Mo maraging stainless steel is a novel high-strength stainless steel, has high strength, high hardness and excellent corrosion resistance, and can be used in the industries of aerospace, nuclear reactors, petrochemical engineering and the like. In actual production, dendritic segregation is easily generated in the solidification process of molten steel, the higher the alloying degree is, the more easily the crystal segregation characteristics are left in a rolled material, and the mechanical property, the corrosion property and the like of a finished product are influenced, so that the corresponding dendritic detection technology is very important. The solidification condition is judged by observing the solidification dendritic crystal structure of the casting blank and measuring the primary and secondary dendrite spacing, and the quality of the cast ingot is improved by changing the solidification condition. Patent document CN 109295456a discloses a dendritic crystal corrosive liquid for precipitation-strengthened martensitic stainless steel and a use method thereof, the method requires many kinds of drugs, is complex in preparation method and not ideal in corrosion effect, is not suitable for corrosion of dendritic crystals of maraging stainless steel cast blanks, cannot clearly display the morphology of the dendritic crystals, and is not beneficial to measurement of dendrite spacing and evaluation of element segregation between dendrite trunk and dendrite through energy spectrum measurement. Therefore, in order to observe the dendritic structure of the maraging stainless steel ingot, it is necessary to develop a simple, effective, stable and reliable corrosive agent and a corrosion method.

Disclosure of Invention

The invention aims to solve the technical problems and provides a maraging stainless steel dendrite corrosive which is an analytically pure nitric acid aqueous solution and is prepared from analytically pure nitric acid and water.

Wherein the volume fraction of the analytically pure nitric acid in the analytically pure nitric acid aqueous solution is 40-50%.

Wherein the mass fraction of the analytically pure nitric acid is 65-68%.

The invention also provides a method for performing dendritic crystal corrosion on maraging stainless steel by using the corrosive, which comprises the following steps:

a. cutting an as-cast sample, and grinding and polishing the sample;

b. preparing a dendritic crystal corrosive;

c. and (3) putting the cast sample into a corrosive agent for normal-temperature electrolytic etching by taking the stainless steel sheet as a cathode and the sample as an anode.

In the step a, one plane of the cast test sample is mechanically ground on 180#, 500# and 1000# sandpaper respectively, and then polished by 2.5 mu m diamond polishing paste until the mirror surface is free of scratches, and then cleaned and dried.

Wherein, the voltage in the electrolytic etching process of the step c is controlled to be 2-3V, and the time is controlled to be 15-20S.

The invention has the beneficial effects that:

the corrosive agent has simple formula and is prepared by only adding a certain amount of deionized water into analytically pure nitric acid; the method has simple operation steps, can corrode and display the dendritic crystal structure characteristics of the maraging stainless steel ingot, can accurately calculate the data such as the dendritic crystal spacing and the like through the clear dendritic crystal morphology and determine the segregation degree between dendrites and dendrite trunks by adopting an energy spectrum, and is used for evaluating the cast structure quality and assisting in evaluating the elimination effect of homogenization heat treatment on the dendritic crystal segregation.

Drawings

FIG. 1 is a photograph of an optical mirror after corrosion of maraging stainless steel of example 1;

FIG. 2 is an SEM image of maraging stainless steel of example 1 after corrosion;

FIG. 3 is a photograph of an optical mirror after corrosion of maraging stainless steel of example 2;

FIG. 4 is an SEM image of maraging stainless steel of example 2 after corrosion;

FIG. 5 is a photograph of an optical mirror after corrosion of maraging stainless steel of comparative example 1;

FIG. 6 is a photograph of a light mirror after corrosion of maraging stainless steel of comparative example 2.

Detailed Description

The invention provides a maraging stainless steel dendrite corrosive which is an analytically pure nitric acid aqueous solution and is prepared from analytically pure nitric acid and water.

The invention provides a method for carrying out dendritic crystal corrosion on maraging stainless steel by adopting the corrosive, which comprises the following steps:

a. cutting an as-cast sample, and grinding and polishing the sample;

b. preparing a dendritic crystal corrosive;

c. and (3) putting the cast sample into a corrosive agent for normal-temperature electrolytic etching by taking the stainless steel sheet as a cathode and the sample as an anode.

The as-cast sample of the invention needs to be subjected to surface treatment before being corroded by the corrosive agent, so that the surface of the sample is in a mirror surface state without scratches.

Preferably, one flat surface of the sample is mechanically ground with 180#, 500#, and 1000# sandpaper, respectively, and then polished with 2.5 μm diamond polishing paste.

The dendritic crystal corrosion adopts an electrolytic etching method, the voltage in the electrolytic etching process is controlled to be 2-3V, and the time is controlled to be 15-20S.

The maraging stainless steel has stronger corrosion resistance, and the effect of corroding dendritic crystals by adopting a general weak acid corrosive is not obvious. The method solves the problem that the maraging stainless steel dendrite corrosion reagent cannot rapidly and clearly display the solidification structure of the dendrite of the casting blank, and has simple operation steps and clear and accurate detection result of dendrite corrosion.

The present invention is further illustrated by the following examples.