Mode Selection of Laser Thermal Treatment of Chipping Machine Knifes for Deadwood Processing

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UDС

674.093

DOI:

10.17238/issn0536-1036.2015.3.84

Abstract

Deadwood shows high durability and hardness. It leads to considerable abrasive wear of chipper knife's edge during deadwood chip processing. In this case material requirements are the following: higher hardness of cutting edge (HRC 62…65 compared with traditional HRC 56…58) on retention of adequate dynamic strength. These characteristics are unachievable by selection of exclusive steel alloying or adjustment of traditional thermal treatment modes. Demanded characteristics can be obtained during laser thermal treatment of chipper knife's edge, by building up a special structural condition of steel. Laser thermal treatment adoption for chipper knife's alloy steel introduces many problems. Deficiency of scientific grounded laser thermal treatment modes is the major problem. Our investigation was focused on working out such modes. Conventional chipper knifes made of 60Cr7WSiMoV steel were used for laser thermal treatment on laser beam machine “Kvant- 15” during scientific investigation. Influence of radiation power on surface coating hardness and quantity of retained austenite in laser impingement point with internal radiation diameter was studied during scientific experiments. Radiation power was regulated by pumping condensers' charge voltage variation. Laser impingement points were arranged without overlapping during condensers' charge voltage variation in the range from 400 to 850 W at a pitch of 50 W, along with overlap ratio 0,5 and 0,75. Three factors were used for optimization: maximum hardness of steel in laser impingement point, minimum percentage (no more 5 %) of retained austenite in laser impingement point and minimum degree of reflowing. Optimal laser processing mode is the following: laser treatment with 3,0 mm diameter shots, 2 Hz pulse repetition frequency and 3 mm/s beam stroking speed. These characteristics provided overlap ratio equal 0,5, with pumping condensers' charge voltage U = 750-800 W relevant to 5…6 J shot power. Optimal edge's structure with hardness HRC 63...64 and high dynamic strength is achieved thereby.

Authors

A.E. Alekseev, Doctor of Engineering, Professor A.I. Dumanskiy, Head of Laboratory I.О. Dumanskiy, Candidate of Engineering, Associate Professor

Affiliation

Northern (Arctic) Federal University named after M.V. Lomonosov, Naberezhnaya Severnoy Dviny, 17,  Arkhangelsk, 163002, Russia; e-mail: i.dumanskij@agtu.ru

Keywords

deadwood, chipping machine, alloy steel, laser thermal treatment.

References

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