Beyaz Dökme Demir Mikroyapı

... konulu sunumlar: "DÖKME DEMİRLER TEMPER DÖKME DEMİR."— Sunum transkripti:

1 DÖKME DEMİRLERTEMPER DÖKME DEMİR

2 TEMPER DÖKME DEMİR

3 TEMPER DÖKME DEMİR

4 TEMPER DÖKME DEMİRTemper dökme demir, tamamen grafitsiz sert ve kırılgan beyaz dökme demirin, temperleme denilen ısıl işlem ile karbürlerinin parçalanması sonucu oluşan, yüksek mukavemetli, sünek, iyi işlenebilme özelliğine sahip ve mikroyapısı ferrit ve temper karbonundan meydana gelen dökme demir tipidir.

5 TEMPER DÖKME DEMİRBeyaz dökme demir ↓ Isıl İşlem Dekarbürize ortam Nötr ortam (Yavaş soğuma Hızı soğuma) Beyaz Siyah Perlitik siyah T.D.D T.D.D T.D.D

6 TEMPER DÖKME DEMİRBeyaz temper döküm, beyaz dökme demirin, okstileyici bir ortamda tavlanmasıyla elde edilir. Dekarbürizayon esasına dayanan bu yöntemde, karbonun tümü Fe3C halinde bulunan beyaz dökme demirden parçalar, demir oksitle kaplanarak uzun süre yüksek sıcaklıkta tutulur.

7 TEMPER DÖKME DEMİRParça yüzeyinin devamlı dekarbürize olması, bünyedeki Fe3C’nin giderek parçalanmasına ve karbonun difüzyon yoluyla, yüzeye doğru yayılmasına neden olur.

8 TEMPER DÖKME DEMİRSiyah temper döküm ise, beyaz dökme demirin nötr bir atmosfer ortamında tavlanmasıyla (temperlenmesiyle )elde edilir.

9 PERLİTİK TEMPER DÖKME DEMİR

10 TEMPER DÖKME DEMİRTemper Dökme Demir, Beyaz dökme demirin oC’ye ısıtılması ve yavaş soğutulması ile elde edilmiştir

11 TEMPER DÖKME DEMİRİN ISIL İŞLEMİ

12 TEMPER DÖKME DEMİR ENDÜSTRİYEL ÖRNEKLER

13 TEMPER DÖKME DEMİR ENDÜSTRİYEL ÖRNEKLER

Thesis Type: Doctorate

Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey

Approval Date: 2012

Student: ŞÜKRAN MUTLU

Supervisor: KADİR KOCATEPE

High chromium white cast irons are one of the most common foundry alloys due to their excellent wear and corrosion resisatance. Applications of these alloys have included breaker bars, impact crushers impact blocks, raw material crusher parts, rolling mill parts, liners, agricultural machinery parts, pistons and gears, conveyors, bulldozers teeth, pump parts, discs, bracket moulds, segments and bars, several types of mine drilling equipment, parts for the mining and mineral industry parts. Microstructures of high chromium white cast irons contain a significant proportion of a hard M7C3 type carbides provides excellent wear resistance. However, hard and coarse M7C3 type carbides with sharp corners and tips in the microstructure decreases toughness which must also be a consideration for longer service life. It has been reported that the addition of some elements such as titanium, niobium, tungsten, vanadium and magnesium improves the mechanical properties of high cromium white cast irons. Those addition elements plays an important role in the size, morphology and distribution of (Cr,Fe)7C3 carbides and forming of hard phases such as TiC, NbC and VC in in the microstructure of high cromium white cast irons. In this study, the influence of 0,5, 1,0, 1,5 and 2 wt.% of Ti, Nb and V, and 0,05 and 0,1 wt.% Mg on the microstructural characteristics, hardness, wear resistance and impact thoughness of high cromium white cast iron containing 3,26wt.%C and 28wt.%Cr was examined in both as cast condition and after heat treatment at 1080oC temperature for 14 hours and 540oC temperature for 4 hours. Metallographic, quantitative and X-ray diffraction techniques were carried out for microstructural examination. The effect of these elements on the wear resistance, hardness and fracture thoughness of high cromium white cast iron were also evaluated individually. The results obtained show the following; 1- By increasing the content of Ti, Nb, V and Mg in the alloy, the size of M7C3 primary and eutectic carbides was considerably reduced. The content of 0.1wt.%Mg and 2wt.% Ti, Nb and V in the alloy decreased average carbide diameters approximately 230%. 2- The content of 0.05 and 0.1 wt.% Mg in the alloy produced spheoridal shape carbides. 3- By increasing the content of Ti, Nb and V in the alloy, increases hardness while addition of Mg decreases slightly. 4- Additions of Ti, Nb, V and Mg in the alloy increased impact resistance as increases their content. 5- By increasing the content of Ti, Nb, V and Mg in the alloy, increases abrasive wear resistance under 20N load. However, only 1.5 and 2 wt% of Ti, Nb and V are effective in increasing of abrasive wear resistance under 40N load.