By studying the domestic and foreign product standards of copper tubes for refrigeration, this paper compares and analyzes the core technical indicators of domestic and foreign copper tubes for refrigeration products, so as to provide reference for the improvement of the product standards of China's refrigeration copper tubes and boost the high-quality development of China's nonferrous metal processing industry.

    Key words: copper tube for refrigeration; standard; comparative study

Source: CNKI

     Author: Chen Zhuli, Jinze, Li Minghua, Qiu Shaojun

    China is the largest copper producer and consumer in the world. In 2018, China's output reached 17.81 million tons, accounting for 67% of the world's total, including 1.69 million tons of copper plate, 1.85 million tons of copper strip, 2.78 million tons of copper tube materials, 2.44 million tons of copper bars, 430000 tons of copper foil, 7.95 million tons of copper wire, and other 670 thousand tons. The copper tube for refrigeration is a large variety in the copper tube industry, which is mainly used in household air conditioning, central air conditioning, refrigerator, industrial refrigerator and other products. Therefore, we take the refrigeration copper tube as an example, through the comparison and analysis of domestic and foreign advanced product standards, find the differences of similar product standards and quality, and put forward countermeasures and suggestions to boost the high-quality development of China's nonferrous metal processing industry.

    1. Analysis of domestic and foreign standard system of copper tubes for refrigeration

    Compared with foreign standards, China's national standards have some differences in standard system, standard level, standard nature and formulation subject, as shown in the table

    Table 1 Comparison of domestic and foreign standards for smooth copper tubes for refrigeration

Tab．1Domesticandforeignstandardcomparisontableofsmoothcopperpipeforrefrigeration

    2. Comparison of standard technical indexes of domestic and foreign copper tubes for refrigeration

    Copper tubes for refrigeration are mainly divided into two categories: smooth copper tubes for refrigeration (representative products are seamless copper and copper alloy tubes for air conditioning and refrigeration equipment) and copper tubes with high heat transfer characteristics (representative products are seamless internal thread copper tubes).

    2.1 smooth copper tubes for refrigeration

    For plain copper tubes for general refrigeration, domestic enterprises mainly implement GB / T 17791-2017 seamless copper and copper alloy tubes for air conditioning and refrigeration equipment. The international standards include ASTM standard of American Society for testing and materials, EU en standard, Japanese Industrial JIS standard, etc. (Table 1). In terms of environmental protection, there are GB / T 26572-2011 "limit requirements for restricted substances in electronic and electrical products" and "management measures for the use of hazardous substances in electrical and electronic products" in China, but they are not required to be enforced at present; the European Union has issued rohs2.0 "directive on the use of certain harmful ingredients in electronic and electrical equipment" and requires compulsory implementation.

In terms of specific standards and indicators, China's national standards and foreign standards have their own strengths (Table 2).

    Table 2 Comparison of national standard GB with EU en, American ASTM and Japanese JIS standards

    (1) The coverage of indicators is more comprehensive. In addition to the lack of hardness index related to tensile strength, the national standard covers conventional indexes such as chemical composition, mechanical properties and overall dimension, and adds two items of flattening test and hydrogen embrittlement test, which enriches the evaluation method of pipe process performance and is more comprehensive than EU en standard and American ASTM standard.

    (2) Some mechanical properties are more stringent. According to the national standard, the mechanical properties of copper tubes for refrigeration are more stringent, and the specified plastic elongation strength Rp0.2 is added. The tensile strength RM can be divided into five grades according to different metal states. The corresponding H80 tensile strength RM * * is 315n / m2, and the specified plastic elongation strength Rp0.2 * * is 250N / mm2. American ASTM standard and Japanese JIS standard RM are grade 2 and grade 4 respectively, and there is no requirement for specified plastic elongation strength Rp0.2.

    (3) The requirement of cleanliness index is higher and finer. In order to prevent "dirty blockage" in the use of refrigeration equipment, the cleanliness of the inner wall of copper tubes for air conditioning and refrigerator refrigeration is specified in the national standard. It is stipulated that the total amount of residue on the inner surface of smooth copper pipe with small diameter (outer diameter ≤ 15mm) for air conditioning shall not exceed 2

    (4) The number of harmful substances limit index is small and it is not required to be enforced. The domestic standard system only limits the six indicators of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers, and does not require compulsory implementation. The rohs2.0 directive adds four phthalate plasticizer indexes compared with the domestic standard and requires compulsory implementation. When the copper pipe for refrigeration is matched with the plastic insulation sleeve, there is still a risk that it does not meet the rohs2.0 requirements, although there is a warranty provided by the insulation sleeve manufacturer. 2.2 seamless internal thread copper pipe seamless internal thread copper pipe is the copper pipe with spiral groove on the inner surface. Compared with the smooth tube with the same wall thickness and outer diameter, the inner surface area of copper tube can be increased by 65% ~ 100% and the heat exchange efficiency can be increased by 2 ~ 3 times. Because of its high efficiency of heat exchange, internally grooved copper tubes are used in air conditioners and refrigerators with high energy efficiency, low power consumption and small volume. When the national standard GB / t20928-2007 "seamless internal thread copper pipe" is formulated, its size and deviation mainly refer to the accuracy requirements of Japan Kobe, Sumitomo, Hitachi and other companies

    3. Summary and Prospect

    China's national standard GB / t17791-2017 has a wide range of application and comprehensive coverage indicators, which is applicable to the requirements of most seamless copper tubes for air conditioning and refrigeration. Some indicators such as cleanliness and mechanics are stricter. In terms of product standards, it is a relatively strict standard and has reached the international advanced level. However, China's standard system in the number of harmful substances limit index is small and does not require mandatory implementation, there is rohs2.0 risk, the risk of technical barriers to trade can not be ignored.

    Standardization is the basic work of quality. In order to further deepen China's copper processing industry, we should strengthen the standard upgrading, integrate with the international market, formulate (revise) the product standards with advanced level in time, so that the products can be popularized and used in the market, and boost the high-quality development of China's nonferrous metal processing industry.

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