Abstract: because of its unique material properties, copper alloy is widely used in the fields of industrial production, aviation and aerospace. Copper alloy is usually a eutectic alloy. In the current copper alloy materials, its performance is mainly determined by the content of Cu element and other impurity elements. Because the contents and properties of Cu and other impurity elements are different, so the quantitative research and material properties are also different. This paper mainly studies and summarizes the detection of the chemical content of copper alloy at this stage. At the same time, the detection methods of Cu content and impurity elements in copper alloy are summarized and analyzed, and the overall introduction is made. The analysis methods of several copper alloys are compared. It can be used as a reference for the production of copper alloys, the analysis and control of copper elements and copper impurities.

    Key words: copper alloy; composition analysis; detection method research

    1. Electrolytic gravimetric method

    This method can be used for the detection of various types of copper alloys with high accuracy and accuracy. There are relevant provisions in international and national standards. The main mechanism of copper detection in this way is based on the acid environment and electrolysis with a certain current. At this time, copper will precipitate from the platinum electrode, and then the cathode electrode before electrolysis can be determined+ The copper content can be determined by analyzing the mass difference between the sample and the cathode electrode after electrolysis.

    1.1 main electrode reaction process of cathode

    Cu2++2e-→、Cu 2H++2e-→H2

    1.2 main electrode reaction process of anode

    N4OH-+4e-→O2+2H2O

    For the sample with copper content more than 99.90%, it is necessary to consider whether the sample is oxidized before testing. Therefore, it is necessary to soak the sample in CH3COOH (1 + 4) solution for a period of time, and then wash and dry it with pure water and alcohol for detection.

    For materials with large copper content, nitric acid / sulfuric acid liquid is usually used to completely dissolve the sample. If only sulfuric acid is used for dissolution, more hydrogen will appear in the cathode in the subsequent electrolysis process. At this time, the copper produced by electrolysis has a large space and is easy to be oxidized. However, when only dissolved by nitric acid, a large amount of hydrogen will be produced during the reaction process NO2 - will make copper dissolve again, which makes the precipitation of copper incomplete. Therefore, generally speaking, there are 2 ~ 5ml nitric acid solution (ρ = 1.4g/ml) and 5ml sulfuric acid (ρ = 1.84g/ml) per 150ml electrolyte.

    Other alloys of copper may contain various elements, and the acids used in dissolution are also different. In general, the sample is dissolved by nitric acid, then H2SO4 is added, and then the electrolysis operation is carried out after dilution. If there is more Sn in the sample, there will be more Metastannic Acid insolubles when the sample is dissolved with nitric acid. At this time, a certain amount of HCl O7 and H2SO4 must be added for further dissolution, and then the solution is dissolved with dilute nitric acid and added to the electrolyte for electrolysis. However, if the content of Pb in the sample is more than 1%, it is not necessary to add H2SO4 after the sample is completely dissolved with nitric acid. A small amount of HCl solution (0.1g / ml) can be added, because less chloride ions do not corrode the electrode. When there is more Si in the sample, HF / HNO3 can be used to dissolve the sample, and then PTFE container is used to replace the glass cup. A certain amount of Pb (NO3) 2 solution can be added to protect the platinum anode, and then 0.002% NH4Cl buffer solution is added to carry out the electrolysis process.

    The dissolution temperature of the sample has a great influence on the detection accuracy, so it is necessary to dissolve at low temperature and remove nitrogen oxides in micro boiling state. Excessive boiling will cause loss of element analysis and lower detection results. Nitrogen oxides must also be removed, which will hinder the subsequent electrolysis process, usually in the micro boiling state

    After 1.5 ~ 3 h, the reaction was almost complete. If the PTFE container is used for electrolytic reaction, some hydrogen peroxide solution can be added to reduce the original solution to remove nitrogen oxides.

    When the current density is small, the concentration of copper in the cathode will increase, and the mutual interference between metals will be small. The Au, Ag, Se, te concentrations in copper alloy are small, and they need to be removed in advance when the SN concentration is high; when the content of Sn, as, Sb and Bi are low, the precipitation of these substances can be avoided by electrolysis with low current and static state. Therefore, if it is pure copper material, the low current and static electrolysis method is usually used for Electrolytic detection, and the alloy with copper content less than 99.9% also needs to be electrolyzed by small current when testing and analyzing samples. In the detection of quality control, enterprises usually use high current density and electrolysis by stirring. Usually, it can reach 4 ~ 6A. When the blue of electrolyte turns clear, the current drops by * * 2A ~ 5A. In such electrolysis process, Bi element is basically in the cathode. No matter the current, Ag will precipitate in the cathode. The copper content in the residual liquid after electrolysis must also be detected for accurate detection.

    Generally speaking, the current of 2a is applied after the blue color of electrolyte is faded. When the residual copper content is less than 0.05mg, and the copper and copper alloy content is less than one thousandth of the sensitivity of the balance, copper has been completely precipitated.

    2. Iodometry

    Compared with the electrolytic method, the accuracy of iodometric method is worse than that of electrolytic method