Temper dökme demirlerde bileşimin mekanik özelliklere etkisi

Abstract

Bu çalışmada siyah temper dökme demirlerde bileşime bağlı alarak mekanik özellikler ile temper grafitin şekli ve boyutlarının değişimi incelenmiştir. Bileşim ile ilgili alarak değişimi incelenen ana alaşım elementleri C, Si ve Mn dır. Değişimi incelenen bu üç alaşım elementi için üç seri döküm yapılmıştır. Bu dökümlerde değişimi incele nen her bir element belirli bir bileşim aralığında değiştirilerek diğer alaşım elementleri sabit tutulmuştur. Örneğin C serisinde C miktarı, belirli bir bileşim aralığında kademeli bir artış gösterirken diğer alaşım elementleri sabit tutulmaya çalışılmıştır. Böylelikle üç seri döküm tamamlanmıştır. Temper dökme demirler beyaz dökme demirin ısıl işle mi ile üretildikleri için elde edilen dökümler temperleme ısıl işlemine tabi tutulmuştur. Yaklaşık otuz saatlik bir ısıl işlemden sonra elde edilen temper dökme demirlerin mekanik özelliklerini belirlemek amacıyla çekme, eğme ve darbe deneyleri yapılmıştır. Bu deney sonuçlarından faydalanılarak optimum özellikleri veren bileşim; % 2.25 C, % 1.10 Si ve % 0.6k Mn olarak belirlenmiştir. Elde edilen temper dökme demirlerin metalagrafik yapıları incelenmiş, aynı zamanda görüntü analiz cihazı ile grafit şekli, boyutu ve alanı kantitatif olarak belirlenmiştir. Mekanik deneylerden her seri döküm için optimum özelliği veren alaşımlarda mekanik deney sonuçları ile görüntü analiz sonuçları karşılaştırılarak irdelenmiştir,

The term "Cast Iran" like the term: "Steel", identifes a large family of ferrous alloys. Cast irons primarily are alloys of iron that contain more than %2 carbon and from 1 to % 3 silicon. Wide variations in properties can be achieved by varying the balance between carbon and silicon by allaying with various metallic or nonmetallic elements and by varying melting, casting and heat treating practices. Cast irons as the name implies are intended to be cast to shape rather then formed in the solid state. Cast irons have law melting temperatures, are very fluid when molten, do not form undesirable surface films when poured, and undergo slight to moderate shrinkage during solidification and cooling. However cast irons have relatively law impact resistance and ductility, which may limit their use. Mechanical properties of cast irons especially strength, ductility, and modulus elasticity depend strongly on structure and distribution of micro structural ;. constituents. Physical properties such as conductivity and damping capacity also are strongly infuenced by micrastructure. In any cast iron, the microstructural feature that has the most significant effect on properties is free graphite. Shape and distribution of free graphite are more useful than composition for classifying cast irons; the compositions ranges for different types of cast iron overlap, and in many instances, iron of given compositions can be made into any of the four basic types by varying casting or heat treating practice. The structure of the matrix surrounding the free graphite particles also influences mechanical properties. vxi The four basic types cast iron are white iron, gray iron ductile iron and malleable iron. White iron and gray iron derive their names from the apperances of their respestive fracture surfaces: White iron exhibits a white, crystalline fracture surface and gray iron exhibits a gray fracture surface with exceedingly thiny facets. Ductile iron derives its name from the fact that, in the as cast form, it exhibits measurable ductility. By contrast, neither uhite nor gray iron exhibits significant ductility in a standart tensile test. Malleable iron is cast as uhite iron, then, malleablized that is, heat treated to impact ductility an otherwise exceedingly brittle material. Besides that four basic types, there are other specific forms of cast iron to uhich special names have been applied. For example chilled iron, mottled iron, compacted grapite iron. Carbon equivalence (CE) is a method that often is used to simplify evaluation of the effect of composition in unalloyed cast iron. CE equals total carbon content (TC) plus about one third of the sume "of the silicon and phosphorus contents: CE = TC + (% Si + % P)/3 Comparison of CE uith the eutectic composition in the Fe-C system (4.3 % C) uill indicate whether a cast iron will behave as a hypoeutectic or hypereutectic alloy during the solidification. Uhen CE is near the eutectic value, the liquid state persist to a relatively lou temperature and solidification takes place over a small temperature range. The latter characteristic can be important in promoting uniformity of propereties uithin a given cast. In hypereutectic irons (CE grather than about k.3%), there is a tendency for kish graphite Proeutectic graphite that, forms and floats free in the molten iron to precipitate on solidif icaiton under normal cooling conditions. In hypereutectic irons, the lower CE the greater tendency for white or mottled iron to form solidification. Vlll Malleable iron is a cast ferrous metal that is initially produced as white cast iron, then is heat treated to convert the carbon containing phase from iron carbide to a noduler form of graphite called temper carbon. There are two types of ferritic malleable iron, "blackheart" and "whiteheart" only the blackheart type is produced in the United States. This materiel has a matrix of f errite with interspersed nodules of temper carbon. "Cupola malleable iron" is a blackheart malleable iron produced by cupola melting and used for pipe fittings and similar thin section castings. Because of its low strength and ductility, cupola malleable iron usually is not specified for structural applications. Pearlitic malleable iron is designed to have combined carbon in the matrix, resulting in higher strength and hardness than available in ferritic malleable iron. Martensitic mallebale iron is produced by quenching and tempering pearlitic malleable iron. Malleable iron like ductile iron, possesses considerable ductility and toughness because of its combination of nodule shape graphite in a low carbon metallic matrix. Because of the way in which graphite is formed in mallebale iron, however, the nodules are not truly spherical as they are in the ductile iron but rather than somewhat irregular aggregates. advantage where low solidification shrinkage is needed to avoid hot tears, or where the section is too thick to permit solidification as white iron. Malleable iron castings are produced in section thickneses ranging from about 1.5 to 100 mm and in weights from less than 30 g to 1 BO Kg or more. In one xx * The structures of all castings were consist of tempered carbon in ferritic matrix. The shape of the tempered carbon nodules mere found in aggregated form, * Although brittle fructure was observed in the impact tests for all series/the impact energy becomes more critical at about below -6G C. * The microstructure implies the mechanical properties strongly. The chemical composition and the heat treatment have a significant effect on the microstructure. * The optimum mechanical properties were obtained at 2.25 % C, 1.10 % Si, 0.64 % Mn composition in which the diameter of temper carbon is about ^20 jnm and the number of temper carbon per square mm is about 11D. * The mechanical properties of the determined composition of malleable iron correspond to (30-06) grade in the B5I 6681 and ISO 5922. sta'ndarts. XVI After the melting and casting processes, the testing materials were heat treated to convert white iron to the blackheart malleable iron in Foundry of Trakya Factory.- Tests samples mere subjected to the heat treatment about 3G hours in a controlled gas atmosphere furnace. Mechanical tests which are tensile, charpy impact and bending tests, were carried out in the laboratory to get the mechanical properties. The microstructural studies were also performed to get structure^property relations in the cast samples. In order to achieve this aim, metallographic studies and feature analyses for graphite in the samples mere made. The results of the experimental study are as follows: * The optimum properties for carbon were obtained from the cast which contains 2.25 % C. (The other elements of these series are ranging from 1.2B-1.34 %Si 0.49-0.60% MnjQ.1D-G.1496 5, 0.03-0.06 % P). The increase in carbon from 2.10 % to 2.25% increased the mechanical properties. It was also observed that the change in carbon over 2.25 % decreased' the mechanical properties. The tensile strength, bending stress, elongation and hardness properties were found to be 3B1 l\l/mm2, 516 N/mmz B % and 126 HB, respectively. * The optimum properties for silicon were obtained from the cast uhich contains 1.10 %5i. (The other elements of these series are ranging from 2. 32-2. 44%C, 0.56-0.60 % Mn, 0.10-0. 25 %S, 0.03-0.06 % P). The increase in silicon from 1.00 % to 1.10 % increased the mechanical properties. It was also observed that an increase in silicon content increased the number of graphite. The tensile strength, bending stress, elongation and hardness properties were found to be 400 N/mm2, 672 N/mm2 11 % and 143 HB, respectively. * The optimum properties for manganese were obtained from the cast which contains 0.64 % Mn. (The other elements of these series are ranging from 2.25- 2.36 % C, 1.00-1.2B % SijO.10-0.14 % 5, 0.03-0.06 % P). Although, the increase of manganese content leads an increase in mechanical properties but also retards the heat treating time. xv * The structures of all castings were consist of tempered carbon in ferritic matrix. The shape of the tempered carbon nodules mere found in aggregated form, * Although brittle fructure was observed in the impact tests for all series/the impact energy becomes more critical at about below -6G C. * The microstructure implies the mechanical properties strongly. The chemical composition and the heat treatment have a significant effect on the microstructure. * The optimum mechanical properties were obtained at 2.25 % C, 1.10 % Si, 0.64 % Mn composition in which the diameter of temper carbon is about ^20 jnm and the number of temper carbon per square mm is about 11D. * The mechanical properties of the determined composition of malleable iron correspond to (30-06) grade in the B5I 6681 and ISO 5922. sta'ndarts. XVI After the melting and casting processes, the testing materials were heat treated to convert white iron to the blackheart malleable iron in Foundry of Trakya Factory.- Tests samples mere subjected to the heat treatment about 3G hours in a controlled gas atmosphere furnace. Mechanical tests which are tensile, charpy impact and bending tests, were carried out in the laboratory to get the mechanical properties. The microstructural studies were also performed to get structure^property relations in the cast samples. In order to achieve this aim, metallographic studies and feature analyses for graphite in the samples mere made. The results of the experimental study are as follows: * The optimum properties for carbon were obtained from the cast which contains 2.25 % C. (The other elements of these series are ranging from 1.2B-1.34 %Si 0.49-0.60% MnjQ.1D-G.1496 5, 0.03-0.06 % P). The increase in carbon from 2.10 % to 2.25% increased the mechanical properties. It was also observed that the change in carbon over 2.25 % decreased' the mechanical properties. The tensile strength, bending stress, elongation and hardness properties were found to be 3B1 l\l/mm2, 516 N/mmz B % and 126 HB, respectively. * The optimum properties for silicon were obtained from the cast uhich contains 1.10 %5i. (The other elements of these series are ranging from 2. 32-2. 44%C, 0.56-0.60 % Mn, 0.10-0. 25 %S, 0.03-0.06 % P). The increase in silicon from 1.00 % to 1.10 % increased the mechanical properties. It was also observed that an increase in silicon content increased the number of graphite. The tensile strength, bending stress, elongation and hardness properties were found to be 400 N/mm2, 672 N/mm2 11 % and 143 HB, respectively. * The optimum properties for manganese were obtained from the cast which contains 0.64 % Mn. (The other elements of these series are ranging from 2.25- 2.36 % C, 1.00-1.2B % SijO.10-0.14 % 5, 0.03-0.06 % P). Although, the increase of manganese content leads an increase in mechanical properties but also retards the heat treating time. xv * The structures of all castings were consist of tempered carbon in ferritic matrix. The shape of the tempered carbon nodules mere found in aggregated form, * Although brittle fructure was observed in the impact tests for all series/the impact energy becomes more critical at about below -6G C. * The microstructure implies the mechanical properties strongly. The chemical composition and the heat treatment have a significant effect on the microstructure. * The optimum mechanical properties were obtained at 2.25 % C, 1.10 % Si, 0.64 % Mn composition in which the diameter of temper carbon is about ^20 jnm and the number of temper carbon per square mm is about 11D. * The mechanical properties of the determined composition of malleable iron correspond to (30-06) grade in the B5I 6681 and ISO 5922. sta'ndarts. XVI After the melting and casting processes, the testing materials were heat treated to convert white iron to the blackheart malleable iron in Foundry of Trakya Factory.- Tests samples mere subjected to the heat treatment about 3G hours in a controlled gas atmosphere furnace. Mechanical tests which are tensile, charpy impact and bending tests, were carried out in the laboratory to get the mechanical properties. The microstructural studies were also performed to get structure^property relations in the cast samples. In order to achieve this aim, metallographic studies and feature analyses for graphite in the samples mere made. The results of the experimental study are as follows: * The optimum properties for carbon were obtained from the cast which contains 2.25 % C. (The other elements of these series are ranging from 1.2B-1.34 %Si 0.49-0.60% MnjQ.1D-G.1496 5, 0.03-0.06 % P). The increase in carbon from 2.10 % to 2.25% increased the mechanical properties. It was also observed that the change in carbon over 2.25 % decreased' the mechanical properties. The tensile strength, bending stress, elongation and hardness properties were found to be 3B1 l\l/mm2, 516 N/mmz B % and 126 HB, respectively. * The optimum properties for silicon were obtained from the cast uhich contains 1.10 %5i. (The other elements of these series are ranging from 2. 32-2. 44%C, 0.56-0.60 % Mn, 0.10-0. 25 %S, 0.03-0.06 % P). The increase in silicon from 1.00 % to 1.10 % increased the mechanical properties. It was also observed that an increase in silicon content increased the number of graphite. The tensile strength, bending stress, elongation and hardness properties were found to be 400 N/mm2, 672 N/mm2 11 % and 143 HB, respectively. * The optimum properties for manganese were obtained from the cast which contains 0.64 % Mn. (The other elements of these series are ranging from 2.25- 2.36 % C, 1.00-1.2B % SijO.10-0.14 % 5, 0.03-0.06 % P). Although, the increase of manganese content leads an increase in mechanical properties but also retards the heat treating time. xv * The structures of all castings were consist of tempered carbon in ferritic matrix. The shape of the tempered carbon nodules mere found in aggregated form, * Although brittle fructure was observed in the impact tests for all series/the impact energy becomes more critical at about below -6G C. * The microstructure implies the mechanical properties strongly. The chemical composition and the heat treatment have a significant effect on the microstructure. * The optimum mechanical properties were obtained at 2.25 % C, 1.10 % Si, 0.64 % Mn composition in which the diameter of temper carbon is about ^20 jnm and the number of temper carbon per square mm is about 11D. * The mechanical properties of the determined composition of malleable iron correspond to (30-06) grade in the B5I 6681 and ISO 5922. sta'ndarts.