DENSITY ANALYSIS OF SAMPLES MADE OF COPPER-CHROMIUM MATERIALS

АBSTRACT

The article considers the pressing pressure applied during sample preparation, which ranged from 100 to 650 MPa. The study examines how changes in chromium content and pressing pressure affect the final density of copper and chromium samples. Experimental results show that the density increases with higher chromium content and sintering temperature. The samples containing 3-4% chromium reached the highest density levels. The article presents a detailed analysis of density measurement methods and explains the influence of pressing parameters and sintering temperature. It was found that the highest densities were obtained under high pressure conditions with optimal chromium content. This research is a significant scientific contribution to improving the quality and productivity of copper and chromium-based materials for industrial applications.

АННОТАЦИЯ

В статье рассмотрены давление прессования, применяемое во время подготовки образцов, варьировалось от 100 до 650 МПа. В исследовании изучается, как изменения содержания хрома и давления прессования влияют на конечную плотность образцов меди и хрома. Экспериментальные результаты показывают, что плотность увеличивается с более высоким содержанием хрома и температурой спекания. Образцы, содержащие 3-4% хрома, достигли самых высоких уровней плотности. В статье представлен подробный анализ методов измерения плотности и объясняется влияние параметров прессования и температуры спекания. Было обнаружено, что самые высокие плотности были получены в условиях высокого давления с оптимальным содержанием хрома. Это исследование является значительным научным вкладом в улучшение качества и производительности материалов на основе меди и хрома для промышленного применения.

Keywords: Copper, chrome, powder, material, sample, density.

Ключевые слова: Медь, хром, порошок, материал, образец, плотность.

Introduction

Due to the widespread use of products obtained by the powder metallurgy method, the demand for the quality of parts made of copper-chromium-based materials increases, and the development of the technology for obtaining quality products based on an efficient method and its implementation is considered important. It is important to improve new technologies through production the electrodes of resistance spot welding machines, which is widely used in the automotive industry, made of copper-chromium-based materials by powder metallurgy and increase the service life of the electrodes [1-5].

Research Methods

Press molds were selected that provide the necessary geometric shape and size for obtaining samples of work piece from copper-chromium materials. We measured the charge powder required for each press mold at an accuracy of 0.01 g and pressed it into the press-mould to obtain sufficient density and initial strength. The pressure required for pressing the samples was carried out at a pressure of 500 MPa according to the regulation on the procedure for pressing copper-chromium materials, developed in cooperation with "Research and manufacturing association for production of rare metals and hard alloy metals" and Scientific and Technological Center under "Almalyk Mining and Metallurgical Combine" JSC. The process of pressing the samples was carried out by a one-way pressing method with a P-250 model hydropress [6-8].

Determination of the density of copper chromium powder based alloy samples was carried out according to the literature requirements in the following order:

• distilled water and samples with a diameter of 20 mm and a height of 25 mm were selected for test;

The density of copper-chromium powder based alloy samples was calculated using the formulas below: [7-8].

,                                                    (1)

Where ρ – Density of copper chromium powder based alloy sample, g/cm³; P₁ – density of distilled water, g/сm³;

m₁ – Mass of copper-chromium powder based alloy sample in air, g;

m₂ – Mass of copper-chromium powder based alloy sample in distilled water, g.

 Masses of samples in air and water were measured on a 0.2 mm diameter stainless steel wire grid with an accuracy of ±0.001 mm. The measurement was carried out under conditions where the air bubbles were removed from the sample and the temperature of the distilled water was the same [7-8].

Table 1.

Chemical composition and technological indicators of preparation of research samples

Research Results

According to the obtained results, the change of the density of the samples after sintering depending on the amount of chromium and the pressing pressure of the work piece is presented graphically in Figure 1.

∆ - Sintering at 900 °С;  × - Sintering at 1000 °С.

Figure 1. Variation of the density of the sample after sintering as a function of the pressing pressure when the chromium content is 3%

∆ - Sintering at 900 °С;  × - Sintering at 1000 °С

Figure 2. Variation of the density of the sample after sintering depending on the pressing pressure when the chromium content is 4%

The results of the experiment showed that the density of the samples with a chromium content of 2% to 4% after sintering increased with the increase of pressing pressure of the work piece and sintering temperature. The sample containing 3% chromium had the highest density of 8.35 g/cm³ (Figure 1), while the density of the sample containing 4% chromium was 8.4 g/cm³ (Figure 2). From the graphs shown above, it can be seen that the density of the copper-chromium powder composite alloy has a direct proportional relationship with the pressing pressure at any sintering temperature range.

The analysis of the graphs shows that the density of the copper-chromium powder alloy has the highest value when the sintering temperature is 1000 °C and the chromium content is 2%. This situation is related to the liquid phase sintering process at the sintering temperature of 1000 °C, at relatively low sintering temperatures, solid-phase sintering occurs in contrast [6-8].

Conclusion

In conclusion, the density of the sample decreased from 8.35 g/cm³ to 8.4 g/cm³ in the range of chromium content from 3% to 4%. Pressing the charge at pressures higher than 500 MPa results in a strong deformational compression of the press mold and copper-chromium powders in it.

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