阅读说明：本技术 一种钢带热浸镀方法 (Steel strip hot dipping method ) 是由 周涛 于 2021-10-09 设计创作，主要内容包括：本发明涉及金属材料的表面处理技术,具体涉及一种钢带热浸方法,以缓解现有技术中存在的镀层与基体金属的附着性能的问题。首先对钢带进行表面清洁,随后将钢带升温、油浴淬火,降温至室温,细化钢带表面晶粒尺寸,再次经过表面清洁后进行渗氮处理,在含氮气氛中进行,使得在经过淬火后的钢带表面晶界处析出氮化物,进一步细化钢带表面组织,为后续热浸镀提供较高表面能的表面,此外细化后的表面结构为后续镀层的制备过程提供更多的形核点位,有利于热浸镀镀层的附着性提高。(The invention relates to a surface treatment technology of a metal material, in particular to a hot dipping method of a steel strip, which is used for relieving the problem of the adhesion property of a coating and a base metal in the prior art. Firstly cleaning the surface of a steel strip, then heating the steel strip, carrying out oil bath quenching on the steel strip, cooling the steel strip to room temperature, refining the grain size of the surface of the steel strip, carrying out nitriding treatment after cleaning the surface of the steel strip again, and carrying out nitriding treatment in a nitrogen-containing atmosphere, so that nitrides are precipitated at the grain boundary position of the surface of the quenched steel strip, further refining the surface structure of the steel strip, providing a surface with higher surface energy for subsequent hot dip coating, and providing more nucleation sites for the preparation process of a subsequent coating by the refined surface structure, thereby being beneficial to improving the adhesiveness of the hot dip coating.)

1. The steel strip hot dip coating method as claimed in claim 1, wherein the steel strip is first subjected to surface cleaning, then the steel strip is heated to 850-; then carrying out hot dip galvanizing treatment on the treated steel strip; the galvanizing solution comprises the following chemical components: 13-20% of wt Al, 5-7% of wt Mg, 1-2% of wt Si, 3-5% of wt Zr, 0.1-0.2% of wt La and the balance of Zn; the plating temperature is 480-520 ℃, and the plating time is 1-3 min.

2. The method according to claim 1, characterized in that the specific surface cleaning method is sonication with 5% sodium hydroxide solution for 5-10 min.

3. The method of claim 1 wherein said nitrogen-containing atmosphere is N₂。

4. A method according to claim 1, characterized in that the plating temperature is 480 ℃ and the plating time is 2 min.

Technical Field

The invention relates to a surface treatment technology of a metal material, in particular to a steel strip hot dipping method.

Background

Metal corrosion refers to the damage of metallic materials by the action of the surrounding medium. Ordinary steel materials are extremely corrosive in most environments (such as atmosphere, seawater, factories, and the like). The iron and steel materials damaged by corrosion account for about one fifth of the total global production each year. The corrosion not only causes serious economic loss, but also endangers the life and property safety of people. There are many methods for protecting steel against corrosion, such as alloy steel protection, surface treatment protection, and electrochemical protection. The surface treatment protection method comprises the methods of hot dipping, electroplating, hot spraying, paint spraying and the like. Hot dip coating is a method in which a pretreated substrate (e.g., a steel material) is immersed in another low-melting metal bath in a molten state, and the bath metal is allowed to penetrate into the metal substrate for a certain period of time, thereby forming a metal film having a protective effect on the surface of the metal substrate. In recent years, Zn — Al — Mg alloy plating has been receiving wide attention for its excellent properties, and has been widely used in the fields of construction industry, household appliances, automobiles, and the like.

After hot dip coating, a protective film with good corrosion resistance can be formed on the metal surface, and the service life can be obviously prolonged. The traditional corrosion comprises chemical corrosion and electrochemical corrosion, and the formed oxide layer can prevent the substrate from being in direct contact with the environment, so that the protection effect is generated. If the zinc coating is damaged for some reason, and a small part of the iron surface is exposed and contacts with the electrolyte solution, the zinc can be used as the anode of the micro battery to protect the iron. However, if the iron surface is exposed too much to cover the damaged surface with electrolyte, the zinc protection is lost and the steel quickly corrodes as if it were not protected at all. Therefore, the corrosion resistance of the plating layer is further improved, and the adhesion performance of the plating layer and the base metal is also considered.

Disclosure of Invention

The present invention provides a hot dip method of steel strip to alleviate the problems of adhesion of the coating to the base metal in the prior art.

In order to alleviate the technical problems, the technical scheme provided by the invention is as follows:

firstly cleaning the surface of a steel strip, then heating the steel strip to 850-.

Nitrogen is used as a nitriding nitrogen source, and a hydrogen-containing nitrogen source is not used, so that hydrogen embrittlement of a matrix caused by introduction of an H element is avoided, and the usability is reduced. The selection of parameters such as nitriding temperature, nitriding time and the like can avoid the condition that the depth of a nitrogen source penetrating into the surface of a steel strip is too deep, mainly nitriding is carried out on the surface of the steel strip, permeation into the interior of the surface is not pursued, the combination property of a matrix and a coating is influenced on the contrary due to too high surface hardness caused by nitriding, the trend of cracking in the using process is increased due to hardness mismatching, and the corrosion phenomenon can be directly generated due to the occurrence of cracks.

The specific surface cleaning method is to adopt 5 percent sodium hydroxide solution for ultrasonic treatment for 5-10 min.

And then carrying out hot dip galvanizing treatment on the treated steel strip. The galvanizing solution comprises the following chemical components: 13-20 wt% of Al, 5-7 wt% of Mg, 1-2 wt% of Si, 3-5 wt% of Zr, 0.1-0.2 wt% of La and the balance of Zn. The plating temperature is 480-520 ℃, and the plating time is 1-3 min. The obtained coating phase comprises an Al-rich phase, a Zn-rich phase and Mg₂Si phase, Si-rich phase, MgZn₂Phase, Mg₂Zn₁₁And (4) phase(s).

Influence of Al element on corrosion resistance of hot dip coating alloy: the addition of the Al element can obviously improve the corrosion resistance of the hot dip coating Zn, and during the corrosion process, Al can form a compact aluminum oxide passivation layer on the surface of the coating, and the layer has a better protection effect.

The addition of Mg element can improve the corrosion resistance of the coating, improve the morphology of the alloy structure and promote MgZn in the alloy structure₂And the corrosion products of the plating layer are more compact and have better corrosion resistance by adding the corrosion inhibitor. If the content of Mg element is too high, the viscosity of the zinc liquid can be obviously increased, so that the coating becomes brittle and the wettability of the zinc liquid is reduced.

Adding Zr element in proper content to form hot dip coating alloy coatingThe center is formed, thereby playing the role of refining the alloy structure of the plating layer. When Zr exists in the hot dip coating alloy liquid in the form of extremely fine precipitates, the addition of Zr can also break coarse MgZn continuously distributed in the alloy structure₂Phase, making it become a dispersed homogeneous MgZn₂Meanwhile, various primary phases and eutectic structures can be made finer and denser, so that the microstructure and the mechanical property of the Zn-Al-Mg alloy coating are obviously improved, and the properties of the hot dip coating product such as hardness, surface quality, corrosion resistance and the like can be improved.

Adding a certain amount of Si into the plating solution to generate Mg₂Si phase, presence of Mg₂Si vs MgZn₂The effect of relatively improving the corrosion resistance of the coating is better.

The rare earth element La is added into the plating solution, so that the viscosity of the plating solution can be reduced, the fluidity of the plating solution is improved, the uniformity of the components of the plating solution is facilitated, the corrosion resistance of the obtained plating layer is more uniform, and the phenomenon of local corrosion reduction caused by component segregation is avoided.

According to the method, the corrosion resistance of the steel strip is improved by adjusting the alloy elements and the content, the surface structure is refined by combining quenching and nitriding processes before hot dip coating, more nucleation points are provided for the subsequent coating preparation process, and the adhesion of the hot dip coating is improved.

Detailed Description

Example 1

Cleaning the surface of a steel strip, carrying out ultrasonic treatment for 8min by adopting a 5% sodium hydroxide solution, then heating the steel strip to 900 ℃, carrying out oil bath quenching, cooling to room temperature, carrying out surface cleaning again, and carrying out nitriding treatment, wherein the nitriding temperature is 520 ℃, and the nitriding atmosphere is N₂The nitrogen gas introduction rate is maintained at 0.3L/min, and the temperature is kept for 2 h.

The galvanizing solution comprises the following chemical components: 15% wt Al, 6% wt Mg, 2% wt Si, 4% wt Zr, 0.1% wt La, the balance Zn. The plating temperature was 480 ℃ and the plating time was 2 min.

And (5) after the preparation, testing the corrosion resistance and the adhesion of the steel strip. In the corrosion resistance test, the coated steel strip is loaded into a salt spray tester and is subjected to corrosion resistance testThe area where the tarnishing phenomenon occurs is measured according to the international standard (ASTM B117-11). At this time, 2ml/80cm per hour was sprayed with 5% saline (temperature: 35 ℃ C., pH: 6.8)²The saline water (D) was analyzed by an image analyzer (image analyzer) to determine the area of the generated rust, and when the area of the rust was 5% or less, it was evaluated as "O", and when the area of the rust exceeded 5%, it was evaluated as "X"

The adhesion test is carried out according to the test method in the national standard GB/T39130-2020, the adhesive force grade is judged by adopting a tape visual inspection method, wherein the grade 1 represents that no powdering or little powdering phenomenon is displayed on the tape, the grade 2 represents that a plurality of fine linear powdering phenomena are generated on the tape, the grade 3 represents that a plurality of linear or flaky powdering phenomena are generated in a narrow area on the tape, the grade 4 represents that a plurality of large linear or flaky powdering phenomena are generated in the whole area on the tape, and the grade 5 represents that the coating on the tape is basically completely peeled off.

Examples 2 to 11

The coating preparation process in the example 1 is adopted, the pretreatment quenching and carburizing process is adjusted, then the influence of the pretreatment process on the binding property of the hot-dip coating and the matrix is judged through an adhesion test, and the specific treatment parameters in the example are shown in the table 1.

In example 6, the pretreatment was carried out without quenching, and only nitriding was carried out, and the resulting plating showed many line-like or sheet-like powdering phenomena in a narrow region on the adhesive tape in the adhesion test. Example 7 only the quenching treatment was performed during the pretreatment, the subsequent nitriding operation was omitted, and the resulting plating layer showed many line-like or sheet-like powdering phenomena in the adhesion test in a narrow region on the tape. Examples 8 to 11 adjusted the nitriding parameters, resulting in different degrees of deterioration of the adhesion.

TABLE 1

Examples 12 to 24

The pretreatment method of example 1 was used to adjust the composition of the zinc plating bath, and then the corrosion resistance was measured to find the time when the corrosion phenomenon occurred in each example. See table 2 for bath composition for each example and table 3 for specific corrosion resistance test results. The surfaces of the examples 1, 12-15 showed no significant tarnishing after 900h of the salt spray test. While examples 16-24 exhibited partial rust after 750h or 900h of the salt spray test.

TABLE 2

TABLE 3