Copper Granule Testing

Copper granule inspection mainly conducts scientific testing and analysis on the chemical composition analysis, metallic copper content determination, apparent quality and particle size distribution, non-metallic impurity content, metallic impurity element analysis, and moisture and oil content determination, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Chemical composition analysis: This is the core item of the copper granule inspection, mainly determining the contents of the elements such as the copper, iron, zinc, nickel, lead, tin and arsenic. The precise chemical compositions are the direct basis of judging the copper granule grades, estimating the recovery values and evaluating their applicability in the subsequent smelting. It is usually required that the copper contents are not lower than 96%.

Metallic copper content determination: Through the chemical titration method or instrumental analysis method, the absolute or relative contents of the copper element in the samples are precisely determined. This indicator is the basis of the copper granule transaction pricing, directly related to their economic values. The testing precision is usually required to reach more than one thousandth.

Apparent quality and particle size distribution: Testing the particle sizes, shapes and particle size distributions of the copper granules. The standard sieves are used for the classification, analysing the mass proportions of the different particle size ranges. The uniform particle sizes are conducive to the stability of the smelting processes, while the excessive fine powders or oversized particles may affect the subsequent processes.

Non-metallic impurity content: Mainly referring to the insulating sheath residues and other non-metallic inclusions such as the plastics, rubbers, fibers and dust. Determined through the ignition loss method or manual sorting and weighing method. The excessively high non-metallic impurities will affect the smelting efficiencies and metal recovery rates, and may generate the harmful fumes.

Metallic impurity element analysis: Emphatically testing the impurity elements harmful to the copper conductivity, ductility and subsequent processing, such as the lead, arsenic, antimony and bismuth. Even if the contents are very low, these elements may form the brittle phases, seriously affecting the properties of the recycled copper materials. The spectrometers need to be used for the precise analysis.

Moisture and oil content determination: The surface moisture contents of the copper granules are determined through the drying and weighing method, and the contents of the oily substances are determined using the solvent extraction method. The excessively high moisture and oil contents may cause the splashing or generate a large amount of smoke when charged into the furnaces, with the safety and environmental protection hazards.

Radioactivity testing: As an important safety screening item, the radioactivity detectors are used to carry out the fast scanning of the copper granules, ensuring that they are not contaminated by the radioactive substances. This is the mandatory inspection link of ensuring the production safety and preventing the nuclear proliferation.

Testing Scope

Crushing and sorting products of the waste wires and cables: This is the main source of the copper granules. Through the testing of the copper particles after the stripping or crushing and sorting, their separation purity, metal recovery rates and residual insulating layer contents are evaluated, determining whether they meet the furnace charging requirements of the recycled smelting.

Processing scraps of the various copper products: Including the chips and particles generated during the machining processes of the copper plates, copper strips, copper rods and copper tubes. The testing of this type of copper granules focuses on the chemical composition consistency, oxidation degrees and whether they are mixed with the other alloys or cutting fluid contaminants.

Recovery materials of the waste electrical and electronic products: The copper particles recovered through the physical methods from the electronic wastes such as the waste circuit boards, motors and transformers. The testing emphases are the trace contents of the precious metals (such as the gold and silver), residues of the harmful substances (such as the halogens), as well as the proportions of the non-metallic impurities such as the plastics and ceramics.

Ore dressing products of the copper smelting slags: The copper concentrate particles enriched from the copper smelting slags through the ore dressing processes. The testing items mainly include the copper grades, sulfur contents, slag inclusions and the possibly existing rare metal contents, used to guide the further smelting or sales pricing.

Import and export trade commodity inspection: In the international trade of the copper granules, the statutory inspection before shipment or after arrival must be carried out according to the contract agreements and the relevant national standards (such as GB/T) or international standards. The contents cover all the items of the qualities, weights, safety and environmental protection, and are the important basis of the settlement and customs clearance.

Incoming acceptance of the recycled copper raw materials: The incoming inspection carried out by the recycled copper smelting or processing enterprises when purchasing the copper granule raw materials. According to the enterprise internal control standards, the key indicators (such as the copper contents, impurities and moisture) are quickly tested, determining whether to accept, how to price and determining the subsequent production process ratios.

Testing Methods

Inductively coupled plasma atomic emission spectrometry (ICP-OES/AES): This is currently the mainstream method of determining the contents of the multiple metallic impurity elements in the copper granules. After the samples are dissolved with the acids, the ICP excites them to generate the characteristic spectra, and the quantitative analysis is carried out through the spectral intensities. It has the advantages of the low detection limits, high precision and simultaneous determination of the multiple elements.

X-ray fluorescence spectrometry (XRF): A fast and non-destructive screening method. Without destroying the samples, the direct surface analysis can be carried out on the copper granule particles or pressed tablets, quickly obtaining the semi-quantitative or quantitative results of the main components. Often used for the fast on-site identification and classification, but the precision is usually lower than the wet chemical analysis.

Chemical titration method (iodometric method): The classic standard method of determining the copper contents. After the samples are dissolved, the potassium iodide is used to reduce the divalent copper ions to generate the iodine, and then the standard sodium thiosulfate solutions are used to titrate the precipitated iodine. This method has the high accuracy, often used as the arbitration method, but the operation is cumbersome and time-consuming.

Ignition loss method: The common method used to determine the non-metallic impurities (mainly the insulating organic matters). A certain amount of samples is weighed, and the controlled ignition is carried out in the high-temperature furnaces. The organic matter contents are calculated through the mass differences before and after the ignition. The operation needs to strictly control the temperatures and times, preventing the oxidation of the copper.

Sieve analysis method: Used to determine the particle size compositions of the copper granules. A set of test sieves with the standard apertures is used to carry out the mechanical sieving of the representative samples. The masses of the samples on the various sieve layers and in the bottom pans are respectively weighed, calculating the mass percentages, thereby obtaining the particle size distribution curves.

Atomic absorption spectrometry (AAS): Used to determine the specific trace metallic impurities such as the lead and cadmium. This method is based on the absorption of the characteristic light radiation by the ground-state atoms, with the very high sensitivity for the detection of certain elements. It is the important supplement of the ICP method.

Manual sorting and visual inspection method: An auxiliary but indispensable qualitative method. Through the manual sorting, whether the copper granules are obviously mixed with the other metal particles such as the iron and aluminum, large non-metallic sundries, or have the severe oxidation and oil stains is intuitively judged, providing the preliminary judgment for the instrumental analysis.

Testing Standards

Domestic Standards:

1. GB/T 467, Copper cathode

2. GB/T 5121, Methods for chemical analysis of copper and copper alloys

3. GB/T 6005, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of openings

International Standards:

1. ISO 197-1, Copper and copper alloys — Determination of copper content — Part 1: Electrolytic method

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Inductively coupled plasma optical emission spectrometer (ICP-OES): The core equipment of the chemical composition analysis. Consisting of the sampling systems, ICP light sources, spectral systems, detection systems and computer control systems, it can efficiently and accurately simultaneously determine the contents of dozens of elements in the copper granules, with the detection limits reaching the ppm levels.

X-ray fluorescence spectrometer (XRF): Including the handheld and desktop types. The handheld XRF is convenient for the fast on-site screening; the desktop wavelength dispersive or energy dispersive XRF can provide the more precise quantitative analysis results, and is the important tool of the laboratory raw material acceptance and process control.

Electronic analytical balance: The basic equipment of all the quantitative analyses, with the precision required to reach at least one ten-thousandth of a gram (0.1mg). Used to precisely weigh the samples, standards, as well as the mass changes during the processes such as the titration and ignition. Its accuracy is directly related to the reliability of the final testing results.

Standard test sieves and sieve shaker: The dedicated equipment used for the particle size analysis. The sieve mesh aperture sequences of the test sieves need to comply with the standards (such as GB/T 6005), and the sieve shakers provide the standardized sieving power and times, ensuring the repeatability and comparability of the sieving results.

Box-type resistance furnace (muffle furnace): Used for the ignition loss method to determine the organic matter contents. The furnace chamber temperatures need to be able to be stably controlled at the specified temperatures (such as 550±25℃), and be equipped with the temperature controllers and thermocouples, ensuring the condition consistency of the ignition processes.

Microwave digestion instrument: Used for the sample pre-treatment, quickly and completely dissolving the solid copper granule samples in the acids through the microwave heating in the sealed containers. Compared with the traditional hot plate digestion, this method has the less acid consumption, low blank values and high efficiencies, and can prevent the losses of the volatile elements.

Moisture rapid tester: Using the halogen lamp or infrared heating methods, quickly drying the samples and weighing them in real time, automatically calculating the moisture contents. Suitable for the fast moisture acceptance testing of the copper granule raw materials, more convenient and efficient than the traditional oven methods.

Radioactivity detector: Usually the handheld gamma dose rate meters or surface contamination monitors. Used to carry out the radioactivity safety scanning of each batch of the copper granule raw materials, ensuring that their radiation levels are within the normal background ranges. It is the necessary protective equipment of ensuring the production site safety and environmental compliance.