Karakterizacija čelika nepoznatog sastava

undergraduate thesis

• Title (english): Characterisation of unknown steel
• Author: Ivan Trupina
• Mentor: Vera Rede (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2016-03-03, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Cilj ovog rada je napraviti karakterizaciju vruće valjane, okrugle čelične šipke nepoznatog sastava kako bi se ocijenila kvaliteta materijala i njegova moguća primjena. Rad se sastoji od teorijskog i eksperimentalnog dijela. U teorijskom dijelu opisana je analiza kemijskog sastava, kvalitativna i kvantitativna analiza mikrostrukture te opis metode za određivanje mehaničkih svojstava materijala. U eksperimentalnom dijelu prikazani su rezultati ispitivanja dobiveni analizom kemijskog sastava, kvalitativnom i kvantitativnom analizom mikrostrukture, statičkim vlačnim ispitivanjem, mjerenjem udarne radnje loma na Charpy-jevom batu i mjerenjem tvrdoće po Vickersu. Rezultati analize kemijskog sastava pokazali su da je analizirani materijal po sastavu najbliži čeliku oznake 42CrMo4, odnosno niskolegiranom Cr–Mo čeliku za poboljšavanje. Mikrostruktura analiziranog čelika je potpuno martenzitna, a veličina kristalnih zrna je oko 7. Izmjerene vrijednosti za vlačnu čvrstoću i istezljivost su u granicama koje za čelik 42CrMo4 u popuštenom stanju propisuje norma EN 10083-3:2006. Vrijednosti ostalih mehaničkih svojstava ne zadovoljavaju propise norme. Navedena norma propisuje tehničke uvjete isporuke za niskolegirane čelike za kaljenje i popuštanje. S obzirom da je kemijski sastav u propisanim granicama, pretpostavlja se da su loša mehanička svojstava posljedica neodgovarajuće toplinske obrade čelika.

Abstract (english)

The aim of this paper is to make a characterization of hot rolled, round steel bar of unknown composition that we could rate the quality of material and possibly its possible application. The work consists of theoretical and experimental part. In the theoretical part, the analysis of chemical composition, qualitative and quantitative analysis of the microstructure and the methods for determining the mechanical properties of materials, are described. The experimental part presents the results of tests obtained by analyzing the chemical composition, qualitative and quantitative analysis of the microstructure, static tensile testing, measuring fracture tendency to Charpy-ement piston and measuring the hardness by Vickers. Results of the analysis of the chemical composition showed that analyzed material in its composition is closest to 42CrMo4 steel or to low alloyed Cr-Mo steel for quenching and tempering. The microstructure of analyzed steel is fully martensitic, and the size of crystal grains is about seven. The measured values for tensile strength and elongation are within the limits for the 42CrMo4 steel in tempered condition which is provided by the standard EN 10083-3: 2006. The values of other mechanical properties do not satisfy the regulations of the standard. The specified standard prescribes the technical conditions of delivery for low alloyed steels for quenching and tempering. Considering that the chemical composition is within the prescribed limits, it is assumed that the poor mechanical properties are results of improper heat treatment of steel.

• Keywords: karakterizacija materijala; kemijski sastav; mikrostruktura; svojstva
• Keywords (english): characterization of materials; chemical composition; microstructure; properties
• Language: croatian
• URN:NBN: urn:nbn:hr:235:966199
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka strojarstva (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-22 15:41:11