The impact properties of hot rolled carbon steel （used for the manufacture of reinforcement steel bars） and the quenched ＆ tempered （Q＆T） low alloy steel （used in the pressure vessel industry） were determined....The impact properties of hot rolled carbon steel （used for the manufacture of reinforcement steel bars） and the quenched ＆ tempered （Q＆T） low alloy steel （used in the pressure vessel industry） were determined. The microstructure of the hot rolled carbon steel contained ferrite/pearlite phases, while that of the quenched and tempered low alloy steel contained bainite structure. Impact properties were determined for both steels by instrumented impact testing at temperatures between -150 and 200℃. The impact properties comprised total impact energy, ductile to brittle transition temperature, crack initiation and propagation energy, brittleness transition temperature and cleavage fracture stress. The Q＆T low alloy steel displayed much higher resistance to ductile fracture at high test temperatures, while its resistance to brittle fracture at low test temperatures was a little higher than that of the hot rolled carbon steel. The results were discussed in relation to the difference in the chemical composition and microstructure for the two steels.展开更多
Consistent mechanical and machining properties are essential in many applications where ductile irons offer the most cost-effective way to produce structural parts.In the production of hydraulic rotators,dimensional t...Consistent mechanical and machining properties are essential in many applications where ductile irons offer the most cost-effective way to produce structural parts.In the production of hydraulic rotators,dimensional tolerances are typically 20μm to obtain designated performance.For castings where intermediate strength and ductility is required,it is common knowledge that conventional ferritic-pearlitic ductile irons such as ISO 1083/500-7 show large hardness variations.These are mainly caused by the notoriously varying pearlite content,both at different locations within a part and between parts in the same or different batches.Cooling rate variations due to different wall thickness and position in the molding box,as well as varying amounts of pearlite-stabilizing elements,all contribute to detrimental hardness variations.The obvious remedy is to avoid pearlite formation,and instead obtain the necessary mechanical properties by solution strengthening of the ferritic matrix by increasing silicon content to 3.7wt%-3.8wt%.The Swedish development in this field 1998 resulted in a national standardization as SS 140725,followed in 2004 by ISO 1083/ JS/500-10.Indexator AB decided 2005 to specify JS/500-10 for all new ductile iron parts and to convert all existing parts.Improvements include reduction by 75%in hardness variations and increase by 30%in cutting tool life,combined with consistently better mechanical properties.展开更多
文摘The impact properties of hot rolled carbon steel （used for the manufacture of reinforcement steel bars） and the quenched ＆ tempered （Q＆T） low alloy steel （used in the pressure vessel industry） were determined. The microstructure of the hot rolled carbon steel contained ferrite/pearlite phases, while that of the quenched and tempered low alloy steel contained bainite structure. Impact properties were determined for both steels by instrumented impact testing at temperatures between -150 and 200℃. The impact properties comprised total impact energy, ductile to brittle transition temperature, crack initiation and propagation energy, brittleness transition temperature and cleavage fracture stress. The Q＆T low alloy steel displayed much higher resistance to ductile fracture at high test temperatures, while its resistance to brittle fracture at low test temperatures was a little higher than that of the hot rolled carbon steel. The results were discussed in relation to the difference in the chemical composition and microstructure for the two steels.
文摘Consistent mechanical and machining properties are essential in many applications where ductile irons offer the most cost-effective way to produce structural parts.In the production of hydraulic rotators,dimensional tolerances are typically 20μm to obtain designated performance.For castings where intermediate strength and ductility is required,it is common knowledge that conventional ferritic-pearlitic ductile irons such as ISO 1083/500-7 show large hardness variations.These are mainly caused by the notoriously varying pearlite content,both at different locations within a part and between parts in the same or different batches.Cooling rate variations due to different wall thickness and position in the molding box,as well as varying amounts of pearlite-stabilizing elements,all contribute to detrimental hardness variations.The obvious remedy is to avoid pearlite formation,and instead obtain the necessary mechanical properties by solution strengthening of the ferritic matrix by increasing silicon content to 3.7wt%-3.8wt%.The Swedish development in this field 1998 resulted in a national standardization as SS 140725,followed in 2004 by ISO 1083/ JS/500-10.Indexator AB decided 2005 to specify JS/500-10 for all new ductile iron parts and to convert all existing parts.Improvements include reduction by 75%in hardness variations and increase by 30%in cutting tool life,combined with consistently better mechanical properties.
