CN111663091B

CN111663091B - Method for improving corrosion resistance of industrial pure copper

Info

Publication number: CN111663091B
Application number: CN201910174518.XA
Authority: CN
Inventors: 杨森; 陈子蕴; 黄鸣; 秦渊; 薛云飞; 冯文
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2019-03-08
Filing date: 2019-03-08
Publication date: 2021-12-10
Anticipated expiration: 2039-03-08
Also published as: CN111663091A

Abstract

The invention discloses a method for improving the corrosion resistance of industrial pure copper, which comprises the following steps of firstly carrying out homogenization treatment on the pure copper to homogenize the structure of a material; and then, carrying out compression deformation treatment on the material, wherein the deformation amount is 5-15%, so that stress is introduced into the material, and then regulating and controlling the characteristic distribution of the grain boundary in the material through annealing treatment. The invention adopts the thermomechanical treatment method of the above steps on the basis of not adding any alloy element to realize the optimization of the pure copper grain boundary characteristic distribution, thereby achieving the purpose of improving the corrosion resistance of the pure copper grain boundary.

Description

Method for improving corrosion resistance of industrial pure copper

Technical Field

The invention belongs to a technology for enhancing the performance of industrial pure copper, in particular to a method for improving the corrosion resistance of the industrial pure copper.

Background

The industrial pure copper and copper alloy not only have good comprehensive physical properties of heat conduction, electric conduction, bonding property, processability and the like, but also are not expensive. Therefore, the copper and the copper alloy have wide application in the fields of electronic appliances, transportation, electric power, instruments and traditional mechanical manufacture. However, with the development of the industry and the advent of new machinery, copper and copper alloys are required to have good performance in some special environments. At present, if copper and copper alloy are exposed to oxygen-containing water, oxidizing acid or some ocean atmospheric environments containing chloride ions, ammonium ions and high temperature and high salt, verdigris is easily generated on the surface of the copper and the copper alloy to form obvious corrosion, the performances of conductivity, strength, hardness and the like of the copper and the copper alloy can be greatly influenced, and particularly when stress exists in the use environment, the material is easy to lose efficacy, and extremely serious results are caused.

The traditional method for improving the corrosion resistance of copper and copper alloy generally comprises surface passivation treatment and surface coating preparation, and the mechanism is to isolate the metal surface from substances which are easy to cause material failure so as to achieve the corrosion resistance effect. However, these measures have certain limitations, for example, because copper is difficult to form a stable and compact oxide, a special passivating agent needs to be utilized, and waste liquid generated after passivation can pollute the environment; and introducing new impurity elements after treatment to influence the performances such as conductivity and the like. Therefore, there is a need to develop new methods for improving the corrosion resistance of copper and copper alloys. The grain boundary engineering can change the grain boundary performance, the form and the proportion in the material through the thermomechanical treatment, and improve the corrosion resistance of the material through improving the grain boundary performance. Compared with the traditional method, the method has the advantages of simpler and more economical process, no waste liquid generated in the processing process, and no other impurity elements introduced. At present, no thermomechanical treatment mode is utilized at home to improve the corrosion resistance of industrial pure copper.

In the literature (Kongping, university of Qingdao science and technology (Nature science edition), 2010 and 3), phytic acid and sodium molybdate are used as corrosion inhibitors to prepare a dense and ordered monomolecular self-assembled film on the surface of copper, so that the corrosion resistance of the copper is improved. But the process is complex, the cost of molybdate is high, and the molybdenum element in the corrosion inhibitor has certain influence on animals and plants.

Disclosure of Invention

The invention aims to provide a method for improving the corrosion resistance of industrial pure copper, thereby realizing the improvement of the corrosion resistance of the industrial pure copper under the condition of low cost.

The technical scheme for realizing the purpose of the invention is as follows: a method for improving the corrosion resistance of industrial pure copper comprises the following steps of firstly carrying out homogenization treatment on the pure copper to ensure that the internal structure of the material is uniform and stress-free; subsequently, the material is subjected to compressive deformation, thereby introducing stress into the interior of the material; finally, the distribution and control of the grain boundary characteristics in the material are realized through annealing treatment. The method specifically comprises the following steps:

(1) firstly, carrying out homogenization treatment on industrial pure copper, wherein the annealing temperature of the homogenization treatment is 700-;

(2) rapidly placing the homogenized industrial pure copper bar in a liquid cooling medium for rapid cooling to obtain a quenched structure;

(3) compressing the bar subjected to the treatment;

(4) repeating the operation of the step (3), and performing multi-time unidirectional compression until the final deformation is 5% -15%;

(5) placing the bar treated in the step (4) in a heat treatment furnace, and annealing the bar at 400-600 ℃ for 15 min;

(6) and (3) placing the bar subjected to annealing treatment in a liquid cooling medium for rapid cooling, thereby obtaining the industrial pure copper with good corrosion resistance.

Further, in the step (2), the liquid cooling medium is an ice-water mixture to obtain a faster cooling speed, so as to obtain a uniform quenching structure.

Furthermore, in the step (3), compression deformation is carried out at room temperature, and the compression speed is 0.08mm/s, so as to avoid the situation that the deformation amount is difficult to control due to too high speed.

Further, in the step (4), the final deformation amount is preferably 10%.

Further, in the step (5), the bar is annealed at 600 ℃.

Further, in the step (6), the liquid cooling medium is an ice-water mixture.

Compared with the prior art, the invention has the remarkable advantages that:

(1) the low sigma CSL crystal boundary proportion in the material is improved to more than 80 percent, and the corrosion resistance of the treated material is superior to that of the original material;

(2) simple operation, high production efficiency, no introduction of new elements and no chemical pollution.

Drawings

FIG. 1(a) is a plot of grain boundary characteristics of commercially pure copper without grain boundary engineering treatment of the starting material.

FIG. 1(b) is a distribution diagram of grain boundary characteristics of commercially pure copper after grain boundary engineering treatment.

FIG. 1(c) is a Tafel plot of the original material and the material after grain boundary engineering treatment.

Detailed Description

The principle of the invention is based on a grain boundary engineering process, the material is subjected to recovery and recrystallization through compression deformation and annealing treatment, a low sigma CSL grain boundary is generated, and the grain boundary characteristic distribution of the material is regulated, so that the corrosion resistance of the industrial pure copper is improved. The method comprises the following specific steps:

(1) placing the industrial pure copper bar in a heat treatment furnace, and carrying out homogenization treatment for 15min at the temperature of 750 ℃;

(2) quenching the homogenized sample by using an ice-water mixture;

(3) performing unidirectional compression on the quenched sample, wherein the compression temperature is 25 ℃, and the compression speed is 0.08 mm/s;

(4) repeating the operation of the step 3 until the deformation reaches 10 percent;

(5) placing the deformed sample in a heat treatment furnace for annealing treatment, wherein the annealing temperature is 400-600 ℃, and the annealing time is 15 min;

(6) and quenching the annealed sample by using an ice-water mixture.

In the following examples, the optimization effect of the material grain boundary characteristic distribution is expressed by low Σ CSL grain boundary proportion (%), and a higher value indicates a better optimization effect of the grain boundary; the intergranular corrosion tendency of the material is represented by the corrosion potential (Icorr) in a Tafel curve and the reactivation ratio Ra (%) in a cyclic voltammetry curve, and the smaller the corrosion current is, the better the corrosion resistance is, and the smaller the reactivation ratio is, the lower the intergranular corrosion tendency of the material is.

Example 1

And (3) putting the sample into a heat treatment furnace with the temperature of 750 ℃ for heat preservation for 15min, taking out the sample, and quenching the sample by using an ice-water mixture to obtain a homogenized material. The compression temperature used for compression deformation was 25 ℃ and the compression rate was 0.08 mm/s. The compression deformation is respectively set to be 5 percent, 10 percent and 15 percent, the deformed materials are respectively annealed for 15min at 400-600 ℃, the annealing is carried out in a heat treatment furnace with preset temperature, and then the materials are quenched by an ice-water mixture. The proportion of the special low-energy Sigma CSL grain boundary in the processed sample changes along with the change of the deformation amount, and specific test results are shown in Table 1.

One end of the treated sample was connected to a wire and sealed with epoxy resin, and only one side was exposed. Electrochemical experiments were then performed. Initial corrosion potential of-0.3V, the end scanning potential is 0.1V, the scanning speed is 5mV/s, the corrosion temperature is 25 ℃, and the electrolytic corrosion solution comprises HCl and CH₃COOH:H₂O ═ 1:3: 80. The total low sigma CSL grain boundary proportion inside the sample after the thermomechanical treatment, the corrosion current and the reactivation ratio were varied with the variation of the deformation, and the specific test results are shown in table 1.

Test results of samples with different deformation amounts at 1400 DEG C

Example 2

The industrial pure copper is subjected to heat treatment at different annealing temperatures, wherein the annealing temperatures are respectively 500 ℃ and 600 ℃, and the deformation is 5 percent, 10 percent and 15 percent. The total low sigma CSL grain boundary proportion in the sample after the thermomechanical treatment and the corrosion current and the reactivation ratio are changed along with the change of the annealing temperature, and the specific test results are shown in Table 2

TABLE 2 test results for samples at different annealing temperatures

Comparative example

In order to compare the difference in structure and performance between the treated material and the experimental base material, an electrochemical corrosion test was performed on the homogenized material without the above-described thermomechanical treatment. And then, adopting a more visual immersion corrosion test, selecting dilute hydrochloric acid with 1mol/L corrosive liquid, immersing for 10 x 24h in a water bath kettle at the constant temperature of 50 ℃, and comparing with a sample with 10% deformation and heat preservation for 15min at 600 ℃ by taking the corrosion weight loss rate as an index of corrosion resistance. The test results are shown in Table 3. Compared with the material after homogenization treatment, the low sigma CSL crystal boundary proportion of the thermomechanical treatment material subjected to crystal boundary engineering is improved, and the corrosion resistance is stronger.

TABLE 3 test results of grain boundary engineering work materials and raw materials

The material processed by the method is made into a standard metallographic specimen, the grain boundary characteristic distribution of the material is tested by utilizing a back scattering electron diffraction technology after grinding, mechanical polishing and electrolytic polishing, and the proportion of low-energy sigma CSL grain boundaries in the structure reaches 81%; under the same homogenization treatment, the corrosion current of the sample is obviously reduced, the reactivation rate is reduced, and the corrosion resistance is greatly improved compared with that of the original material.

FIG. 1(a) shows the distribution of grain boundary characteristics in the raw material structure, wherein the proportion of special grain boundaries (∑ 29) is 67.66%, FIG. 1(b) shows the distribution of grain boundary characteristics in the material structure treated by the above method, wherein the proportion of special grain boundaries is 81.70% (see Table 2), the black lines in the figure represent high-energy free grain boundaries, the gray lines represent low-energy Sigma CSL grain boundaries, FIG. 1(c) shows the Tafel curves of the original sample and the sample treated by grain boundary engineering, 1 represents the original sample, and the corrosion current is 4.25 × 10^-4mA, 2 represents the sample after the grain boundary engineering treatment, and the corrosion current of the sample is 3.53 multiplied by 10^-5mA。

Claims

1. The method for improving the corrosion resistance of the industrial pure copper is characterized by comprising the following steps of:

(2) rapidly putting the homogenized sample into an ice-water mixture for quenching;

(3) carrying out compression deformation on the quenched sample;

(4) repeating the operation of the step (3) until the deformation reaches 10 percent;

(5) annealing the deformed sample at 600 ℃ for 15 min;

(6) the annealed samples were cooled in an ice-water mixture.

2. The method according to claim 1, wherein in the step (3), the compression deformation is performed at room temperature and the compression speed is 0.08 mm/s.