engleski

INFLUENCE OF ARTILLERY WEAPON BARREL SUPERHEAT ON ABRASION WEAR RESISTANCE OF MATERIAL

This paper researches the influence of the artillery weapon barrel superheat on the change of abrasion wear resistance of material. A great quantity of the powder gasses evolves by the weapon firing in the weapon barrel. The temperature of these gasses reaches up to 3800 K, and their maximum pressure is up to 6000 bar. The powder gasses have a compound chemical composition, so they make a very aggressive atmosphere in relation to the barrel material. At the same time, the powder gasses contain the solid particles too: the soot particles and the unburned powder grains. These particles are moving by great speed in the strong turbulent streaming of the powder gasses. At the same time, the contact pressure on the rotating band and the barrel bore surfaces appears. It results with normal force effect on the contact surfaces, so a strong sliding friction force is generated on those surfaces. The sliding friction energy transforms to the heat energy too, so the barrel material heating is very intensive in such firing conditions. Therefore, the rate of fire is determined for every artillery weapon to keep the barrel heating on the allowed level. The test samples production was based on the previous analysis of some weapon barrel materials. So, the abrasion test samples are made of heat treated steel 42CrMo4. This steel has the similar chemical, metallographic and mechanical properties as the analysed weapon barrel steel. The test samples were tempered at 600 °C, 700 °C, 800 °C and 900 °C, over a period of one hour, and then air cooled. It’s the similar way of heating and cooling as the superheating and cooling of the barrel by intensive firing. The wear resistance is represented by the sample mass loss after 100, 500 and 1000 rotations of rubber wheel. The test results represent that unheated samples have got the best wear resistance in comparison with the heated samples. The wear resistance increases as many as 5, 6 % if material was previously heated at 600 °C. The heating of material at 700 °C causes 9, 8 % and the heating at 800 °C causes 15, 1 % more intensive material wear. The significant material wear increase is shown in the samples which were heated at the 900 °C. The samples heated in this way represent as many as 58 % bigger material loss than unheated samples. The test results show that adhering to the determined fire rate is very important: the exceeded fire causes the weapon barrel superheat, as well as the significant decrease of the material wear resistance.

weapon barrel; fire rate; superheat; abrasion

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