Method for displaying metallurgical structure of ultralow-carbon cold roll annealed interstitial-free steel

Abstract

The invention relates to a method for displaying the metallurgical structure of ultralow-carbon cold roll annealed interstitial-free steel, which belongs to the technical field of physical detection. The invention is used for realizing the aims of clear display and easy operation of the metallurgical structure of ultralow-carbon cold roll annealed interstitial-free steel. The method comprises the following steps: a. coarse grinding; b. polishing; c. erosion by a first reagent: eroding the polished sample in the first reagent for 10-20 seconds, wherein the first reagent is 5.5-6.5% nitric acid alcohol; d. erosion by a second reagent: eroding the sample in the second reagent immediately after taking out the sample from the first reagent, until the sample surface is evenly black, wherein the second reagent is prepared from 3-7g of sodium pyrosulfite, 9-12g of anhydrous sodium thiosulfate and 70-100ml of distilled water; and e. sample detection: wiping the sample with the first reagent to remove black on the surface, rinsing with alcohol, and blow-drying so that people can observe the sample. The method has the advantages of simpleness, simplified steps, easy master, resource conservation and high efficiency; the obtained structure has the advantages of clear grain boundary and no double grain boundary, and can properly reflect the annealing situation; and thus, the method is very suitable for field usage, and performs important functions on reasonably controlling technological parameters and ensuring product performance in the production field.

Description

technical field [0001] The invention relates to a metallographic structure display method, in particular to a method for clearly displaying the metallographic structure of ultra-low carbon cold-rolled annealed interstitial-free steel, and belongs to the technical field of physical detection. technical background [0002] The metallographic structure of ultra-low carbon cold-rolled annealed interstitial atom-free steel directly affects the performance of steel, especially the shape and size of ferrite grains can directly reflect the performance of steel, and can directly reflect the situation of mask annealing, By analyzing the metallographic structure of ultra-low carbon cold-rolled and annealed interstitial-free steel, the process parameters can be reasonably controlled to achieve the best performance of the steel. However, the microstructure display of ultra-low carbon cold-rolled and annealed interstitial-free steel has always been a difficult problem in actual production...

AI Technical Summary

Problems solved by technology

However, the microstructure display of ultra-low carbon cold-rolled and annealed interstitial-free steel has always been a difficult problem in actual production. At present, many companies still use the traditional method of using 4% nitric acid alcohol solution as an etchant to etch the test piece. If the etching time of this conventional method is short, the obtained metallographic structure is as follows: figure 1 As shown, the grains of the structure cannot be fully displayed; if the erosion time is prolonged, the grain boundaries cannot be fully displayed, and sometimes there will be double grain boundaries. For the metallographic structure, see figure 2

Since this method cannot correctly reflect the shape and size of ferrite grains, it affects the observation of the annealed structure, and thus cannot provide reliable information for production

[0003] At present, there are still several methods to display the metallographic structure of ultra-low carbon cold-rolled annealed interstitial-free steel. The first reagent erodes the sample, but before the second reagent erodes, the sample needs to be repeatedly polished 3-6 times. The operation process is cumbersome and time-consuming, and it is not easy for the operator to master it. So successful, poor operability

Chinese patent application 97119946.9 discloses a "metallographic structure display method of cold-rolled annealed interstitial atom-free steel". This method also uses two reagents to etch the sample, but hydrogen peroxide must be prepared before the erosion %, oxalic acid 1.5-10%, hydrofluoric acid 0.1-1%, and the rest is water to wipe the sample to remove the interference layer, and then to corrode. This method needs to prepare a variety of reagents, and there are also The problem of cumbersome operation, high cost and poor operability

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