Selection of Material and Heat Treatment Cycle for Wear Reduction in Oil Palm (Elaeis Guineensis) Harvesting Knives

Abstract

Harvesting of oil palm is a tedious and labor intensive work. Nonavailability of proper tool increases the severity of the problem. Knives used for harvesting the oil palm are either imported or made by local artisans using locally available scrap material. In the present study, oil palm harvesting knives imported from Malaysia and locally made by manufactures in Kerala, India were tested for chemical composition and hardness. On the basis of the results, medium carbon steel was selected for fabrication of oil palm harvesting knives. To obtain the various combinations of microstructure, mechanical properties and wear resistance; these knives were subjected to quenching and tempering treatment with varying tempering temperature (from 250 to 550°C at an interval of 50°C). Abrasive wear resistance of this steel before and after heat-treatment was studied in laboratory using dry sand abrasion test rig as per ASTM G 65 standard at different rotational speed of rubber wheel ranging from 50 to 200 min-1 at an interval of 50 min-1. The study revealed that both the factors i.e. tempering temperature and rotational speed of rubber wheel exerted significant influence on abrasive wear resistance. At 250°C tempering temperature, the hardness and abrasive wear resistance is observed to be maximum under the laboratory evaluation. Similar wear resistance behavior was also observed under field condition when the knives were used to cut frond and bunch of oil palm by human laborers.

Berba palmi je naporan i intenzivan postupak. Problem je izraženiji zbog nedostatka odgovarajućih alata. Noževi koji se koriste se uvoze ili ih izrađuju lokalne zanatlije od otpadnog gvožđa. Ovde su ispitivani noževi uvezeni iz Malezije i noževi lokalne proizvodnje, a određivan im je hemijski sastav i tvrdoća. Na osnovu rezultata izabran je srednje ugljenični čelik za izradu noževa. Za dobijanje različitih kombinacija mikrostrukture, mehaničkih osobina i otpora habanju ovi noževi su grejani i naglo hlađeni na različitim temperaturama (od 250 do 550°C u intervalu od 50°C). Otpor ovog čelika na abrazivno habanje pre i posle kaljenja je ispitivano u laboratoriji upotrebom abrazivnog testa sa suvim peskom prema standardu ASTM G 65, sa različitim brzinama rotacije gumenog točka, od 50 do 200 min-1 u intervalu od 50 min-1. Ispitivanjem je utvrđeno da su oba faktora, temperature kaljenja i brzina rotacije gumenog točka, imala značajan uticaj na otpor abrazivnom habanju. Na temperature od 250°C dobijeni su maksimalna tvrdoća i otpor habanju u laboratorijskim uslovima. Sličan otpor habanju uočen je i u poljskim uslovima, kada su noževi korišćeni za ručno sečenje lišća i grana.