BİR LEVHA HADDEHANESİNDEKİ ÜST EĞME SİLİNDİRİ KOVANINDA OLUŞAN HASARIN ANALİZİ

Bu çalışmada bir levha haddehanesinde eğme silindiri kovanında meydana gelen erken hasar incelenmiştir. Oluşan bu hasarın sebeplerini tespit etmek için görsel, kimyasal ve mikroskobik analizler yapılmış ve gelecekte bu tip hasarlarla karşılaşmamak için alınması gereken tedbirlerden bahsedilmiştir. Gerçekleştirilen çalışmalarda herhangi bir kaynak izine rastlanılmamıştır. Yapılan mikroskobik incelemelerde, şiddetli bir şekilde uzamış MnS inklüzyonları, yorulma adımları ve tane sınırlarından ayrılmalar belirlenmiştir. Ayrıca kovan tabanının pah kırılmadan işlendiği de tespit edilmiştir. Krom kaplama prosesinden sonra oluşabilecek hidrojen gevrekliği riskini azaltmak için tavlama ile yapıdan hidrojenin uzaklaştırılmasının ve çatlak hassasiyetini azaltmak için kovan tabanında pah kırmanın önemi vurgulanmıştır.

FAILURE ANALYSIS OF AN UPPER BENDING CYLINDER BUSHING IN A PLATE MILL

Premature failure of a bending cylinder bushing in a plate mill was investigated in this study. Visual, chemical and microscopic analyses were performed to detect the possible reasons of this failure and possible measures to be taken were mentioned not to be encountered for this type of failures in the future. No traces of welding were observed in the performed studies. Intensive elongated MnS inclusions, fatigue striations and splits from the grain boundaries were detected in the microstructural investigations. It was also proved that the base of the bushing was worked without chamfering. The importance of the removing hydrogen from the structure by annealing to decrease the hydrogen brittleness risk which would occur after the chromium coating process, and the chamfering of the bushing base to decrease the crack susceptibility was stressed.

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