Evaluation method of weathering resistant steel

Abstract

The invention discloses an evaluation method of weathering resistant steel. The evaluation method comprises the following steps: processing a sample; treating the sample; before a corrosion test is carried out, the metal hanging pieces need to be weighed and recorded, the metal hanging pieces are hung on a storage rack of a periodic infiltration test box through thin wires, and the hanging heights of the hanging pieces are kept consistent; a solution used in the periodic infiltration corrosion test is a NaHSO3 solution prepared by using deionized water, the initial concentration is (1.0 + / -0.05) * 10 <-2 > mol / L, the concentration of a replenishment solution is (2.0 + / -0.05) * 10 <-2 > mol / L, and the Ph is 4.4-4.8; a periodic infiltration test is conducted for 72 h; after the test is finished, taking out the sample, drying and storing, and pickling to remove surface corrosion products; the method comprises the following steps: soaking a sample in a pickling solution for 2 minutes, sequentially soaking and cleaning with deionized water and absolute ethyl alcohol, blow-drying and weighing; and calculating the weight loss ratio, the corrosion depth and the annual corrosion depth according to a formula.

Description

Technical Field

[0001] The invention belongs to the technical fields of analysis and measurement control technology and material performance characterization, and in particular relates to an evaluation method for weathering steel. Background Art

[0002] Atmospheric corrosion is one of the main failure modes of steel materials. The economic losses caused by atmospheric corrosion account for about 50% of the total corrosion losses. Weathering steel is a low-alloy steel series between ordinary steel and stainless steel, also known as atmospheric corrosion resistant steel. It is a plain carbon steel with a small amount of copper and corrosion-resistant elements such as phosphorus, chromium, and nickel added to form a protective layer on the surface of the substrate to improve its atmospheric corrosion resistance. Using weathering steel as a building structure has the advantages of reducing pollution, reducing construction costs, reducing building weight, increasing building safety, shortening construction periods, and increasing the effective space of buildings.

[0003] It is generally believed that it takes several years for the formation of a stable rust layer of weathering steel in the atmosphere, which is too long. In order to quickly and timely evaluate the corrosion behavior of weathering steel, laboratory acceleration methods are usually used. The current accelerated corrosion test methods for metal materials mainly include salt spray test, corrosion paste test and periodic immersion corrosion test. In contrast, the periodic immersion corrosion test is most suitable for evaluating weathering steel. Summary of the invention

[0004] The purpose of the present invention is to provide an evaluation method for weathering steel based on the current periodic immersion corrosion test, so as to solve the problem that the existing metal materials and corrosion evaluation methods are only applicable to a single corrosion environment and cannot be applied to complex environments such as vehicles and railways, and no evaluation standards can be provided for weathering steels with specific contents of Ni and V.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for evaluating weathering steel, comprising:

[0007] The sample was processed into a 60×40×4mm cuboid, and the sample was polished from coarse to fine until the surface was smooth; each time the sandpaper was changed for polishing, the polishing direction was perpendicular to the previous polishing direction until no trace of the previous polishing could be seen; a circular hole with a diameter of 3mm was opened at the same position at both ends of the sample to hang the sample, and 5 parallel samples were taken from each group;

[0008] The polished metal coupons need to be cleaned in an ultrasonic machine filled with anhydrous ethanol, blown dry with cold air, and placed in a dryer to dry for 24 hours;

[0009] Before the corrosion test, the metal coupons need to be weighed and recorded, and the metal coupons are hung on the rack of the periodic immersion test box with a thin wire. The hanging height of each coupon is kept consistent.

[0010] The solution used in the periodic immersion corrosion test is a NaHSO3 solution prepared with deionized water, with an initial concentration of (1.0±0.05)×10-2mol / L, a replenishment solution concentration of (2.0±0.05)×10-2mol / L, and a Ph of 4.4-4.8; the periodic immersion test lasts for 72h;

[0011] After the test, the sample was taken out, dried and stored, and then pickled to remove the surface rust products; the pickling solution was prepared by 500ml HCl and 500ml deionized water; the sample was soaked in the pickling solution for 2 minutes, then soaked and cleaned with deionized water and anhydrous ethanol in turn, and then dried and weighed;

[0012] Calculate the weight loss rate, corrosion depth and annual corrosion depth according to the following formula;

[0013] Corrosion rate: W = W t ×10 6 / [2(a·b+a·c+b·c+2πdc)-1 / 4πd 2 ]·t

[0014] Where: W--weight loss rate, unit: g / m 2 ·h; W t —Corrosion weight loss, unit: g; t-test time, unit: h; a, b, c are the length, width and height of the sample, unit: mm; d is the diameter of the hole in the sample hanging piece, mm;

[0015] Corrosion depth: D t =W t ×10 3 / ρA

[0016] Where: D t —Corrosion depth, unit: μm; wt—Corrosion weight loss in time t, unit: g; ρ—Density of the sample, unit: g·mm -3 ; ρ is 7.8X10 -3 g·mm -3 ; A—Exposed area of ​​the sample, unit: mm 2 ;

[0017] Annual corrosion depth: D = D t *365*24 / (t*1000)

[0018] Where: D—annual corrosion depth, unit: mm / a; D t —Corrosion depth, unit: μm; t--test time, unit: h.

[0019] Furthermore, the corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.12%~0.15%, Si 0.38%~0.48%, Mn 1.28%~1.38%, P≤0.025%, S≤0.015%, Cr 0.30%~0.35%, Cu 0.25%~0.30%, Ni 0.25%~0.35%, V 0.10%~0.12%, and the rest are Fe and impurities, with a total mass fraction of 100%.

[0020] Furthermore, the corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.12%, Si 0.38%, Mn 1.28%, P 0.0104%, S 0.007%, Cr 0.31%, Cu 0.28%, Ni 0.26%, V 0.11%, and the rest are Fe and impurities, with a total mass fraction of 100%.

[0021] Furthermore, the corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.14%, Si 0.40%, Mn 1.35%, P 0.0103%, S 0.008%, Cr 0.30%, Cu 0.29%, Ni 0.26%, V 0.12%, and the rest are Fe and impurities, with a total mass fraction of 100%.

[0022] Furthermore, the corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.13%, Si 0.39%, Mn 1.32%, P 0.0088%, S 0.008%, Cr 0.31%, Cu 0.30%, Ni 0.286%, V 0.12%, and the rest are Fe and impurities, with a total mass fraction of 100%.

[0023] Furthermore, the corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.15%, Si 0.39%, Mn 1.29%, P 0.009%, S 0.008%, Cr 0.32%, Cu 0.299%, Ni 0.287%, V 0.12%, and the rest are Fe and impurities, with a total mass fraction of 100%.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are:

[0025] It is applicable to the complex environments of vehicles, railways, etc., solves the problem of single corrosion evaluation method, and provides appropriate evaluation standards for weathering steels with specific Ni and V contents. DETAILED DESCRIPTION

[0026] Table 1 shows the chemical composition of each example steel grade, and Tables 2, 3 and 4 further illustrate the present invention in conjunction with each embodiment.

[0027] Table 1 Chemical composition of each example %

[0028] Examples C Si Mn P S Cr Ni Cu V Example 1 0.12 0.38 1.28 0.0104 0.007 0.31 0.26 0.28 0.11 Example 2 0.14 0.40 1.35 0.0103 0.008 0.30 0.26 0.29 0.12 Example 3 0.13 0.39 1.32 0.0088 0.008 0.31 0.286 0.300 0.12 Example 4 0.15 0.39 1.29 0.009 0.008 0.32 0.287 0.299 0.12

[0029] Table 2 Length, width and height of each instance

[0030]

[0031] Table 3 Corrosion rate of each example

[0032]

[0033]

[0034] Table 4 Corrosion depth and annual corrosion depth of each example

[0035]

[0036] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for evaluating weathering steel, characterized in that: include: The sample was processed into a 60×40×4mm cuboid, and the sample was polished from coarse to fine until the surface was smooth; each time the sandpaper was changed for polishing, the polishing direction was perpendicular to the previous polishing direction until no trace of the previous polishing could be seen; a circular hole with a diameter of 3mm was opened at the same position at both ends of the sample to hang the sample, and 5 parallel samples were taken from each group; The polished metal coupons need to be cleaned in an ultrasonic machine filled with anhydrous ethanol, blown dry with cold air, and placed in a dryer to dry for 24 hours; Before the corrosion test, the metal coupons need to be weighed and recorded, and the metal coupons are hung on the rack of the periodic immersion test box with a thin wire. The hanging height of each coupon is kept consistent. The solution used in the periodic immersion corrosion test is a NaHSO3 solution prepared with deionized water, with an initial concentration of (1.0±0.05)×10-2mol / L, a replenishment solution concentration of (2.0±0.05)×10-2mol / L, and a Ph of 4.4-4.8; the periodic immersion test lasts for 72h; After the test, the sample was taken out, dried and stored, and then pickled to remove the surface rust products; the pickling solution was prepared by 500ml HCl and 500ml deionized water; the sample was soaked in the pickling solution for 2 minutes, then soaked and cleaned with deionized water and anhydrous ethanol in turn, and then dried and weighed; Calculate the weight loss rate, corrosion depth and annual corrosion depth according to the following formula; Corrosion rate: W = W t ×10 6 / [2(a·b+a·c+b·c+2πdc)-1 / 4Πd 2 ]·t Where: W--weight loss rate, unit: g / m 2 ·h; W t —Corrosion weight loss, unit: g; t-test time, unit: h; a, b, c are the length, width and height of the sample, unit: mm; d is the diameter of the hole in the sample hanging piece, mm; Corrosion depth: D t =W t ×10 3 / ρA Where: D t —Corrosion depth, unit: μm; wt—Corrosion weight loss in time t, unit: g; ρ—Density of the sample, unit: g·mm -3 ; ρ is 7.8X10 -3 g·mm -3 ; A—Exposed area of ​​the sample, unit: mm 2 ; Annual corrosion depth: D = D t *365*24 / (t*1000) Where: D—annual corrosion depth, unit: mm / a; D t —Corrosion depth, unit: μm; t--test time, unit: h.

2. The method for evaluating weathering steel according to claim 1, characterized in that: The corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.12%-0.15%, Si 0.38%-0.48%, Mn 1.28%-1.38%, P≤0.025%, S≤0.015%, Cr 0.30%-0.35%, Cu 0.25%-0.30%, Ni 0.25%-0.35%, V0.10%-0.12%, and the rest are Fe and impurities, with a total mass fraction of 100%.

3. The method for evaluating weathering steel according to claim 2, characterized in that: The corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.12%, Si 0.38%, Mn 1.28%, P 0.0104%, S 0.007%, Cr 0.31%, Cu 0.28%, Ni 0.26%, V 0.11%, and the rest is Fe and impurities, with a total mass fraction of 100%.

4. The method for evaluating weathering steel according to claim 2, characterized in that: The corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.14%, Si 0.40%, Mn 1.35%, P 0.0103%, S 0.008%, Cr 0.30%, Cu 0.29%, Ni 0.26%, V 0.12%, and the rest is Fe and impurities, with a total mass fraction of 100%.

5. The method for evaluating weathering steel according to claim 2, characterized in that: The corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.13%, Si 0.39%, Mn 1.32%, P 0.0088%, S 0.008%, Cr0.31%, Cu 0.30%, Ni 0.286%, V 0.12%, and the rest is Fe and impurities, with a total mass fraction of 100%.

6. The method for evaluating weathering steel according to claim 2, characterized in that: The corrosion-resistant steel is composed of the following chemical components in weight percentage: C 0.15%, Si 0.39%, Mn 1.29%, P 0.009%, S 0.008%, Cr0.32%, Cu 0.299%, Ni 0.287%, V 0.12%, and the rest is Fe and impurities, with a total mass fraction of 100%.

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