Analysis of Copper and Copper Base Alloys, Using Shimadzu PDA-7000

Transcription

1 C M Analysis of Copper and Copper Base Alloys, Using Shimadzu PDA-7000 Copper alloys are designated by their chemical composition with characteristic properties such as high corrosion resistance, mechanical properties, ductility and electrical conductivity, making them suitable for broad fields of application. With the addition of one or more alloying elements, the properties of copper can be considerably modified and optimized to a particular application. Copper alloys are classified as following: Pure Copper and Low Alloy Copper The most important technical characteristic of pure copper is its electrical conductivity. The presence of impurities, such as phosphorus, iron and cobalt, deteriorates the electrical conductivity. Impurities impede the movement of the electrons in the metal. Elements such as silver, arsenic, chromium, zirconium, cadmium, iron or phosphorus, added at low concentrations increase the mechanical properties, particularly strength characteristics. Low alloy coppers is used for special applications such as spring blades contacts, welding electrodes, conductor material, electrical engineering, tubing, and etc. Copper - Zinc Alloys (Brass) Brasses can contain up to 45% zinc. Determinates of the quality and the mechanical properties of brass are the alloying elements where Al, Sn, Si, Fe, Mn, Ni, As, P and Pb are common. Aluminum increases the consistence, and corrosion resistance. The addition of tin and silicon have a good influence on slip properties. Arsenic and phosphorus improves resistance to corrosion. The presence of Phosphorus improves the fluidity of the melt. Iron and manganese are used for grain refinement. Nickel has also positive influences on corrosion resistance and high-temperature strength. Lead, improves the cutting properties and up to 3% may be added to the brass alloys. Brasses are used in a broad field of application such as sew-down nuts, ship propeller, shells, bearings or cartridges. Copper Tin Alloys (Pb/Sn-Bronze) Copper tin alloys are good to cast and mainly used for applications for the manufacture of bearing linings, worm gears and helical gears. Copper tin alloys which contain lead in a range from 5% to 18% with additions of Sb, Zn, Fe and Ni are especially used for sleeve bearings. Such bearings have a long life time, good reliability properties for safety devices and provide for applications of high pressure. Copper Aluminum Alloys (Aluminum Bronze) These alloys also called aluminum bronzes contain up to 14% aluminum. Aluminum is responsible for the good resistivity against corrosion, sulfuric acid and brine. Besides aluminum these alloys can contain iron, manganese, nickel, silicon and arsenic. The mechanical properties of aluminum bronze are similar to those of low alloy steels such as good ductility and resiliency. These alloys have attained great technological importance, in particular for ship propellers, pumps, heat exchangers etc. and are also weldable and good to machine. Copper Zinc Nickel Alloys (Nickel Silver) Copper zinc nickel alloys are similar to brasses but with 11% to 28% nickel content. These materials have high corrosion resistance. Along with nickel, CuNiZn-alloys contain up to 0.4% manganese, 0.1% to 5% iron, 0.5% to 2.0% aluminum and also occasionally up to 3% lead. The addition of lead improves the cutting property of the metal. The typical application for these types of alloys is jewelry products, cutlery, electrical resistors, and etc. Copper Nickel Alloys (Cupro Nickel) Cupro-nickel can contain up to 45% nickel. These alloys are corrosion resistant and provide high temperature strength properties which are similar to those of stainless steels. The addition of about 2% manganese and 1.5% iron increases the corrosion resistance. Cupro-nickel is typically used for tubes, regulating resistance or to manufacture coins. Page 1 of 5

2 Gun Metal Gun metals contains from 3% to 11% tin and 2% to 7% zinc. Zinc improves the casting properties and reduces the sensitivity of the melt to oxygen. For grain refining, approximately 1% nickel is alloyed. The addition of 1% to 6% lead favors the cutting properties. The typical application for these types of alloys is the use of fittings, instrument accessories, bearing boxes etc. Even if the copper and copper base alloys are used for their physical properties, it is necessary to evaluate their chemical composition. Therefore, besides the testing methods such as tensile strength and hardness, the chemical composition is often an important factor to determine the suitability of the material for a particular application. Spark emission spectrometry is the most popular method to determine chemical composition of a metal. This technique provides very fast and reliable analysis. Instrumentation The metal analyzer PDA-7000 is a high performance optical emission spectrometer. One of the first advantages is the simultaneous determination of many elements. The PDA-7000 with incorporated argon flushed spark stand and high performance spark source, has been designed for accurate quantitative analysis of copper and copper base alloys. The analysis of up to 32 elements including trace and gaseous elements is performed in less then one minute. Equipped with a 600 mm spectrometer, the PDA-7000 analyzes up to 64 elements. Pulse height distribution analysis method (PDA) and the time resolved integration method (TRS) are incorporated in the measuring cycle. The combination of these two methods improves the analytical precision of trace elements. The accuracy, detection capability, reproducibility and higher sample throughput are achieved, which result in higher productivity. Samples And Sample Preparation Samples can be taken from melts, sheets, semi-finished or finished products. The classical method for ladle analysis is to acquire a small amount of the melt. Using a test spoon, remove a sample from the molten metal bath that the operator will quickly pour into the mold. It is required that the samples be homogenous for optimum precision and accuracy when analyzing by optical emission instruments.. Rapid cooling in a special mold prevents the formation of larger precipitates and phase separations. Samples with good homogeneity (fine-grained and homogeneous crystalline structure) provide reproducible and accurate analyses. In order to perform an analysis by spark emission spectrometry the surface should be prepared as follows. The unnecessary parts of a cast sample are cut using a grinder and/or cutter. Copper and copper base material have a relative soft surface. To avoid contamination, the samples should be prepared using a milling or lathe machine. For incoming control, without trace element determination, the sample may be prepared using a disk or belt grinder. However it is recommended to replace the grinding paper often to keep the contamination low. Samples from semifinished or finished products should have a minimum diameter of >12 mm. Argon The argon must have a purity of %, with less than 2 ppm of Oxygen, less than 3 ppm H 2 O (< - 70 C dew point) and less than 10 ppm Nitrogen. In case of oxygen determination, oxygen must be below 1 ppm. Shimadzu can provide argon purifiers if obtaining this purity level is difficult. A pressure of four bars at the entrance is necessary, and the argon flow rate should be approximately 7 l/min. during pre-spark and analysis time. Operating Parameters Counter electrode: Tungsten Argon flush time: 3 seconds Pre spark time: 6 seconds Integration time: 8 seconds Page 2 of 5

3 Analytical Data / Precision The summary of precision data for copper and copper base alloys is given below. The precision data was evaluated by using appropriate test samples of various types. These samples cover a large variety of grades of different copper and copper alloys.. Element Detection Limit Quantitative Working Range Content Precision ppm 3 sigma % % ±% 1 sigma Ag Al As Be Bi C Cd Co Cr Fe Mg Mn Ni O (*) 0.1 Page 3 of 5

4 Element Detection Limit Quantitative Working Range Content Precision ppm 3 sigma % % ±% 1 sigma P Pb Sb Se Si Sn Te Ti (*) 0.05 Zn Zr (*) Reliable data not available Page 4 of 5

5 Calibration Shimadzu spectrometer can be factory calibrated for copper and copper base alloys. For the specific alloy types, please see Hereford the factory calibration summaries. The factory calibration is based on certified reference material (ISO 9000) and provides high accuracy. The factory calibration set up, results in a shorter installation time and the instrument can be used immediately for production control. Detection Limit The Detection limit is defined as three times the standard deviation (σ) of the background, expressed in parts per million unit (ppm). These values are valid for low alloyed steel only. Analysis performed close to the detection limit are semi quantitative, due to poor relative precision (RSD: 33% ). Precision Precision is defined as the determination of the standard deviation of 10 successive measurements. The reproducibility is related to the distribution of the elements in the samples. Page 5 of 5