CN109708939B - Simple erosion method for three-dimensional shape of MnS precipitate in sulfur-containing steel - Google Patents

Abstract

The invention relates to a method for detecting precipitates, in particular to a special display method for MnS of sulfur-containing microalloyed steel. The sulfur-containing microalloyed steel is a common non-quenched and tempered steel in the industry, and is mainly used in the manufacture of parts in the automobile industry. The method firstly adopts the traditional metallographic polishing method to prepare the metallographic sample of the sample, then adopts the special erosion method to carry out deep erosion, finally conducts the special wiping treatment to prepare the sample, and observes the three-dimensional morphology of MnS in the steel under the scanning electron microscope. The method has a very significant effect on the stereoscopic display of manganese sulfide precipitates in sulfur-containing microalloyed steels, and is of great significance for the accurate detection and analysis of manganese sulfide precipitates in sulfur-containing microalloyed steels.

Description

A Simple Erosion Method for Three-dimensional Morphology of MnS Precipitates in Sulfur-Containing Steel

technical field

The invention relates to a method for detecting precipitates, in particular to a special display method for MnS of sulfur-containing microalloyed steel.

Background technique

Sulfur-containing microalloyed steel is a common high-value-added steel product, widely used in the automotive industry and other important fields, mainly for the production of automotive crankshafts and connecting rods and other components. Metallographic analysis is a common analysis and detection method in the field of metal materials, which can display the microstructure of metal materials and provide guidance for subsequent analysis.

At present, picric acid is mainly used to erode the microscopic dendrite structure, and the erosion time is very short, generally 10s. If the erosion time is too long, the surface of the sample will turn black, and the dendrite structure will not be visible. In addition, the main method for the three-dimensional morphology detection of MnS precipitates in sulfur-containing steels is electrolytic erosion, so that MnS falls off from the matrix or the residual part remains in the matrix, but the electrolytic erosion process is cumbersome.

The patent number is: CN201610631231.1, a method for revealing austenite grain boundaries of microalloyed steel under vacuum hot corrosion conditions, which can realize the method and traditional process for revealing microalloy steel austenite grain boundaries under vacuum hot corrosion conditions In contrast, it combines the two experimental processes of the heating system simulation of the sample and the austenite grain hot corrosion visualization, which simplifies the experimental procedure, helps reduce energy consumption and emissions, and improves the experimental efficiency. But no effective display of manganese sulfide precipitates is involved.

The patent number is: CN201710639648.7, a method for extracting and separating nano-level precipitates in steel by using organic electrolyte. The invention discloses a method for extracting and separating nano-level precipitates in steel by using organic electrolyte, which can completely Non-destructively extracting and separating nano-level precipitates in steel, and solving the problem of easy agglomeration of nano-level precipitates in steel in traditional detection methods, so that the composition, size and three-dimensional morphology characteristics of nano-level precipitates in steel can be accurately detected. . However, the effective display of MnS precipitates is not involved. The method designed in this patent is an electrolytic method, and the extracted precipitates are nanoscale, and their characterization is separated from the matrix.

The patent number is: CN201310643630.6 patent, multi-stage sampling and systematic analysis method for analyzing non-metallic inclusions in steel, mainly through electrolytic corrosion method, all kinds of non-metallic inclusions in steel are completely extracted and weighed . In obtaining useful information, the patent requires complete separation of the precipitate and the matrix. During the separation process, agglomeration will inevitably occur. At the same time, the patent uses a combination of acid etching and electrolytic etching when obtaining the three-dimensional information of the inclusions, which may cause information distortion.

So far, the method for displaying the precipitates of sulfur-containing microalloyed steel is not perfect, especially for the displaying of the precipitates, almost all of them are electrolytic methods, and the electrolytic method is complicated. The manganese sulfide precipitate is a key component in the study of the product quality of sulfur-containing microalloyed steel, so a simple method that can effectively display the manganese sulfide precipitate is urgently needed. So far, the display of precipitates in sulfur-containing microalloyed steels is not perfect, and manganese sulfide precipitates are an important component in the study of sulfur-containing microalloyed steels. Therefore, there is an urgent need for a simple and effective three-dimensional display of manganese sulfide precipitates. morphological method.

SUMMARY OF THE INVENTION

Considering that the precipitates in the existing steel are small and the current metallographic polishing method can only observe the two-dimensional morphology, there is no simple display method that can effectively display the three-dimensional morphology of the manganese sulfide precipitates in the sulfur-containing microalloyed steel. The invention provides a special display method for the precipitates in the sulfur-containing microalloyed steel, which can effectively display the three-dimensional appearance of the manganese sulfide precipitates in the sulfur-containing microalloyed steel, and has good effect and simple operation.

The present invention is a simple erosion method for the three-dimensional morphology of MnS precipitates in sulfur-containing steel; the sulfur-containing steel is a sulfur-containing and manganese-containing microalloy steel; the simple erosion method comprises the following steps:

step one

The samples are ground and polished;

Step 2

The sample is eroded by non-electrolytic method; the erosive agent used for erosion is composed of 100ml water, 3-5g picric acid and 0.5-1ml detergent;

When eroding, the control temperature is 60-80℃ and the time is 10-20min;

Step 3

The finished etched sample was wiped to yield the product.

As a preferred solution, the present invention provides a simple erosion method for the three-dimensional morphology of MnS precipitates in sulfur-containing steel; the non-quenched and tempered steel contains Fe, C, Si, Mn, P, S, Nb, V, Ti, Ni, Cr, N.

As a further preferred solution, the present invention provides a simple erosion method for the three-dimensional morphology of MnS precipitates in sulfur-containing steel; the microalloyed steel includes the following components in mass percentage:

C 0.3-0.6%,

Si0.2-0.5%,

Mn0.6-0.9%,

P0.005-0.01%,

S0.04-0.07%,

Nb0.01-0.03%,

V0.08-0.12%,

Ti0.02-0.05%,

Ni0.1-0.3%,

Cr0.1-0.3%,

N0.1-0.2%,

Fe balance.

As a further preferred solution, a simple erosion method for the three-dimensional morphology of MnS precipitates in a sulfur-containing steel of the present invention; the microalloyed steel includes the following components by mass percentage:

C0.4-0.5%,

Si0.3-0.4%,

Mn0.7-0.8%,

P0.006-0.008%,

S0.05-0.06%,

Nb0.015-0.025%,

V0.09-0.11%,

Ti0.03-0.04%,

Ni0.15-0.25%,

Cr0.15-0.25%,

N0.12-0.18%,

Fe: surplus.

As a preferred solution, the present invention is a simple erosion method for the three-dimensional morphology of MnS precipitates in sulfur-containing steel; when grinding, metallographic sandpaper is used for smoothing; the sandpaper is 160#, 400#, 800#, 1200# in turn. , 1500#, 2000# for grinding; when polishing, use a metallographic turntable, the number of revolutions is 300-1000r/min; the polishing cloth is flannel, and the time is 3-6min. Hand grinding or sample grinding can be used for sample grinding.

As a preferred solution, the present invention is a simple erosion method for the three-dimensional morphology of MnS precipitates in sulfur-containing steel; the wiping treatment described in step 3 is: using the same kind of flannel for polishing, under the condition of water flow, in the same direction Wipe until the eroded black surface is visibly brighter and cannot be brighter. Wiping includes manual.

As a preferred solution, the present invention is a simple erosion method for the three-dimensional morphology of MnS precipitates in sulfur-containing steel; the obtained product is used for metallographic detection or scanning electron microscope detection. Especially suitable for scanning electron microscope detection.

The invention provides a simple erosion method for the three-dimensional morphology of MnS precipitates in sulfur-containing steel. The sulfur-containing microalloy steel is mainly used for hot forgings of automobiles, specifically, crankshafts and connecting rods.

In the process of technical development of the present invention, it was accidentally discovered that, for the sulfur-containing steel with special components, the non-electrolytic method is used to carry out appropriate long-term erosion, and then cooperate with the wiping process, so that the MnS precipitates in the sulfur-containing steel can be well removed. The three-dimensional morphology is fully displayed. For subsequent characterization, the characterization includes metallographic characterization, scanning electron microscope detection, electron probe detection, and the like. The present invention is very effective for characterizing the three-dimensional morphology of manganese sulfide precipitates in sulfur-containing microalloyed steels. In particular, when the method developed in the present invention is used to study blanks with larger thickness, there are natural advantages for the distribution of the precipitates in the product and the size of the precipitates.

The invention provides a simple erosion method for the three-dimensional morphology of MnS precipitates in sulfur-containing steel, regardless of whether the precipitates in sulfur-containing steel are nano-level or micro-level; through the treatment of the invention, combined with the subsequent characterization process, it can be objectively characterized come out.

The present invention is mainly aimed at the precipitation MnS in the sulfur-containing steel, and does not involve the inclusions in the steel, and the precipitation phase MnS is three-dimensionally observed on the matrix without electrolysis and extraction. For thick parts, the distribution and size information of MnS precipitates in the matrix can be basically determined by surface and cross-section treatment. Compared with the existing method, the efficiency of the present invention is greatly improved. Excluding the time for subsequent characterization, the pre-treatment time is only 1/3 of the prior art, or even less than that.

Description of drawings

Accompanying drawing 1 is the SEM image of the product obtained in Example 1;

Figure 2 shows the characterization diagram of the product obtained in Comparative Example 1.

As can be seen from Figure 1, the present invention has a very obvious effect on the three-dimensional morphology display of MnS in the sulfur-containing microalloyed steel, and effectively shows the distribution and shape of the precipitates during the solidification of the microalloyed steel. It shows that this method is an effective and simple method for displaying the three-dimensional morphology of MnS precipitates in sulfur-containing microalloyed steels.

It can be seen from Figure 2 that the three-dimensional morphology of the precipitates can be seen at all after a short time of erosion.

Detailed ways

Example 1

In the present embodiment, the steps of the erosion method for the three-dimensional morphology of MnS precipitates in a simple sulfur-containing steel are as follows:

step one

The samples were ground and polished; the chemical composition was Fe-0.46C-0.35Si-0.71Mn-0.0075P-0.055S-0.022Nb-0.094V-0034Ti-0.21Ni-0.19Cr-0.014N in wt% containing Sulfur microalloyed steel is subjected to grinding treatment, using sandpaper in the order of 160#, 400#, 800#, 1200#, 150#0, 2000#; the polished samples are polished, and a metallographic turntable is used, and the number of revolutions is 800r. /min, the time is 5min; the polishing cloth is flannel.

Step 2

A special erosion method is used to deeply erode the sample; the etchant is an aqueous solution of picric acid (3-5g picric acid, 100ml water); 1-2 drops of detergent are also added; the temperature is controlled at 60-80 degrees Celsius; the erosion time is 10- 20min.

Step 3

Wipe the etched sample with the same flannel for polishing, and manually wipe in the same direction under the condition of water flow, until the black surface becomes significantly brighter and cannot be brighter.

The electron microscope photo of the three-dimensional morphology of the etched manganese sulfide precipitation phase of the obtained sample is shown in Figure 1.

Comparative Example 1

After picric acid erosion, the erosion time was 10s, and the surface of the sample showed a micro-dendritic structure, as shown in Figure 2, and the three-dimensional morphology of the precipitate could not be seen at all.

Comparative Example 2

If it is eroded for a long time, without special wiping treatment, the surface will be black and no precipitate can be seen at all.

Comparative Example 3

Other operations are the same as in Example 1, except that the erosion time is 25 minutes; when wiping in the later period, it is found that it is difficult to wipe brightly. As a result, the three-dimensional morphology of the manganese sulfide precipitation phase cannot be clearly identified in the subsequent scanning electron microscope observation.

Claims (5)

1. A simple erosion method for the three-dimensional shape of MnS educt in sulfur-containing steel; the method is characterized in that: the sulfur-containing steel is sulfur-containing and manganese-containing microalloyed steel; the microalloyed steel comprises the following components in percentage by mass:

C0.3-0.6％，

Si0.2-0.5％，

Mn0.6-0.9％，

P0.005-0.01％，

S0.04-0.07％，

Nb0.01-0.03％，

V0.08-0.12％，

Ti0.02-0.05％，

Ni0.1-0.3％，

Cr0.1-0.3％，

N0.1-0.2％,

the balance of Fe;

the simple erosion method comprises the following steps:

step one

Grinding and polishing the sample;

step two

Eroding the sample by adopting an electroless method; the etching agent is prepared by adding 3-5g picric acid and 0.5-1ml liquid detergent into 100ml water;

during erosion, the temperature is controlled to be 60-80 ℃ and the time is 10-20 min;

step three

Wiping the corroded sample to obtain a product; the wiping treatment is that the same kind of flannelette for polishing is adopted to wipe towards the same direction under the condition of water flow until the corroded black surface becomes obviously bright and can not become brighter.

2. The simple erosion method for the three-dimensional morphology of MnS precipitates in the sulfur-containing steel according to claim 1; the method is characterized in that: the microalloyed steel comprises the following components in percentage by mass:

C0.4-0.5％,

Si0.3-0.4％，

Mn0.7-0.8％，

P0.006-0.008％，

S0.05-0.06％，

Nb0.015-0.025％，

V0.09-0.11％，

Ti0.03-0.04％，

Ni0.15-0.25％，

Cr0.15-0.25％，

N0.12-0.18％,

fe: and (4) the balance.

3. The simple erosion method for the three-dimensional morphology of MnS precipitates in the sulfur-containing steel according to claim 1; the method is characterized in that: during flattening, metallographic abrasive paper is adopted for flattening; the sand paper is sequentially polished by 160#, 400#, 800#, 1200#, 1500# and 2000 #; during polishing, a metallographic turntable is adopted, and the rotation speed is 300-; the polishing cloth is flannelette for 3-6 min.

4. The simple erosion method for the three-dimensional morphology of MnS precipitates in the sulfur-containing steel according to claim 1; the method is characterized in that: the obtained product is used for metallographic detection or scanning electron microscope detection.

5. The simple erosion method of the three-dimensional morphology of MnS precipitates in the sulfur-containing steel according to claim 4; the method is characterized in that: the obtained product is used for scanning electron microscope detection.

Images