Composite etchant for 409L ferritic stainless steel and use method thereof

Abstract

The invention discloses a composite etchant used for 409L ferritic stainless steel and a using method of the composite etchant. The etchant comprises: an etchant (1): the weight ratio of the etchant (1) is: the weight ratio of trinitrophenol is in the range of 4.4% to 4.7%; the weight ratio of aqueous hydrochloric acid solution with a concentration of 37% is in the range of 5.2% to 14.9%; the weight ratio of benzalkonium chloride is in the range of 1.0% to 6.0%; and the weight ratio of ethanol is in the range of 74.4% to 89.4%; an etchant (2): the weight ratio of the etchant (2) is : the weight ratio of hydrochloric acid is in the range of 12% to 35%; the rest is distilled water. The using method comprises: after polishing, sample is firstly dipped into the etchant (1), and is taken out after 40 to 70 seconds and directly put into the etchant (2), and is taken out after 60 seconds and washed, parched and observed corrosion condition; in each cycle, residence time of the sample in the etchant 1 declines 10 seconds than last cycle, and the minimum residence time of the sample is 10 seconds, and the residence time of the sample in the etchant (1) is unchanged. The invention has the advantages of keeping surface of the 409L ferritic stainless steel sample clear after being corroded, high display quality of grain boundary and grain, and long preservation time for the etchant. And the invention can be used repeatedly so as to reduce discharging of waste liquid and be in favor of environment protection.

Description

technical field [0001] The invention relates to stainless steel technology, in particular to the ratio of metallographic etchant for 409L ferritic stainless steel and its supporting use method. Background technique [0002] The microstructure of cold-rolled 409L ferritic stainless steel after annealing is an important means to judge whether the cold-rolling and annealing process is reasonable, and it is also the main factor affecting the final performance of the product. How can it truly and quickly reflect the microstructure of 409L ferritic stainless steel? Structure is one of the key technologies. [0003] To display the microstructure of metallic materials, the first condition must be to corrode the different colors of grain boundaries and grains of different phases. The vast majority of ferritic stainless steels have a single-phase structure at room temperature, so the electrochemical micro-battery effect cannot be used in the erosion process, but chemical corrosion (d...

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Problems solved by technology

[0011] 1. The etchant works slowly (destroying the passivation film), but the erosion (grain boundary) speed is fast, which makes it difficult to grasp the erosion time of the sample, and the quality of the metallographic display is unstable, (see figure 2 )

[0012] 2. Since the grain boundary is not clearly displayed, if the erosion time is prolonged, it is easy to form over-corrosion, resulting in the failure of the erosion process, (see image 3)

[0013] 3. The solution has a fast failure rate and a short duration of use (3 days to 1 week)

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