Influence of silicon and phosphorous on the mechanical properties of both ferrite and dual-phase steels

A study has been made of the influence of up to 2 pct Si and 0.42 pct P upon the strength and ductility of ferrites over a wide grain size range; the grain size was varied fromd ^−1/2 mm^−1/2 = 4 to 14. Although the ductility decreased with increasing strength for all the alloys, the 2 pct Si alloy had the best combination of strength and ductility. The ferrites containing 2 pct Si and 0.2 pct P had greater uniform elongations than conventional HSLA steels at the same tensile strength; it is thought that the ductility of the ferrites is enhanced by the presence of Si while the ductility of conventional HSLA steels is reduced by the presence of carbide precipitates. With the theory for a composite of two ductile phases and the results for the fine-grained alloyed ferrites, the change in uniform elongation as a function of tensile strength was predicted for dual-phase (martensite plus ferrite) steels. Good agreement was found between the prediction and experimental results for dual-phase steels containing up to 0.2 pct P or 2 pct Si; the 2 pct Si alloy had the best combination of strength and ductility of all dual-phase steels so far reported. This study again emphasizes the importance of the high strength, high ductility ferrite in controlling the properties of dual-phase steels.     

Aspects of Orientation-Dependent grain growth in extra-low carbon and interstitial-free steels during continuous annealing

The present work concentrates on the application of orientation imaging microscopy (OIM) based on the electron backscattered diffraction (EBSD) technique to the investigation of the microstructural evolution of an extra-low carbon (ELC) steel and a Ti-Nb-bearing interstitial-free (IF) steel, during continuous annealing. Aspects like the nucleation, the evolution of the recrystallized volume fraction and grain size of grains with different orientations, the interface area limiting recrystallized {111} regions, and the apparent growth rates have been considered. Different criteria have been applied in order to identify crystallites produced during annealing. During the first stages of annealing, a network of grain boundaries with misorientations higher than 10 deg is produced, mainly inside the deformed γ-fiber grains. The crystallites formed within this network, free from cells or subgrains at their interiors, can be considered as potential nuclei. However, among all, only some of them become effective due to an improtant selection. The {111} recrystallized grains have a significant size and number advantage as compared with other texture components, and a hard impingement between clusters of {111} grians is produced during grain growth. The effect of grain growth behind the recrystallization front seems to be negligible as compared with the grain coarsening produced by the migration of this front, driven by the cold-work stored energy. J.L. Bocos, formerly Researcher with CEIT     

Aspects of orientation-dependent grain growth in extra-low carbon and interstitial-free steels during continuous annealing

The present work concentrates on the application of orientation imaging microscopy (OIM) based on the electron backscattered diffraction (EBSD) technique to the investigation of the microstructural evolution of an extra-low carbon (ELC) steel and a Ti-Nb-bearing interstitial-free (IF) steel, during continuous annealing. Aspects like the nucleation, the evolution of the recrystallized volume fraction and grain size of grains with different orientations, the interface area limiting recrystallized {111} regions, and the apparent growth rates have been considered. Different criteria have been applied in order to identify crystallites produced during annealing. During the first stages of annealing, a network of grain boundaries with misorientations higher than 10 deg is produced, mainly inside the deformed γ-fiber grains. The crystallites formed within this network, free from cells or subgrains at their interiors, can be considered as potential nuclei. However, among all, only some of them become effective due to an important selection. The {111} recrystallized grains have a significant size and number advantage as compared with other texture components, and a hard impingement between clusters of {111} grains is produced during grain growth. The effect of grain growth behind the recrystallization front seems to be negligible as compared with the grain coarsening produced by the migration of this front, driven by the cold-work stored energy.     

Effect of manganese on annealing texture,plastic anisotropy,and mechanical properties of low-carbon steels containing 0.067 Pct phosphorus

To establish the range of manganese content in phosphorus-containing low-carbon steels that will provide superiorr _m andAr values in cold-rolled sheets, the effects of manganese on annealing texture, plastic anisotropy, and mechanical properties of steels containing 0.067 pct P were studied. Both vacuum and air-melted laboratory heats were investigated. Results show that highr _m and low Ar values, a desirable combination for deepdrawing applications, can be obtained with manganese contents up to 0.25 pct, when the hot-rolled band is cold-rolled 80 pct, and annealed at 710 or 780° (1310 or 1435∮F) for 20 h. Annealing at the higher temperature developed better plastic anisotropy than did annealing at the lower temperature. Ther _m values of the air-melted steels were superior to those of the vacuum-melted steels. It is believed that complex interactions of manganese with other elements in the steel, such as sulfur and oxygen, and possibly carbon, influenced the annealing behavior of the steels.     

Structure and properties of powder metallurgy phosphorous steels

The effect of structure on the properties of powder metallurgy steels alloyed with phosphorus was investigated. Initial mixtures were prepared by the traditional method and by mechanical alloying. Mechanical alloying decreased the sintering temperature, increased the density, and improved the properties thanks to the formation of dispersed phases, a high-density cellular dislocation distribution, and the trapping of phosphorus atoms by the dislocation atmosphere, which prevented coagulation of the phosphides. It was established that when closed porosity is formed, the changes in mechanical properties and fracture resistance do not agree. National Research Institute for Powder Metallurgy and Coatings Technology, Perm'. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(406), pp. 59–64, March–April, 1999.     

退火温度对冷轧中锰钢力学性能的影响

在不同温度下对冷轧中锰钢(Fe-0.1C-5Mn)进行退火试验,研究了其力学性能的变化,通过单轴拉伸试验获得了不同热处理条件下的力学性能。研究结果表明:退火温度从550℃升高至800℃,冷轧中锰钢的抗拉强度和屈服强度先降低后升高;断后伸长率和均匀伸长率以及强塑积则先升高后降低,在650℃时达到最大值。在650℃退火后产生较多的逆转变奥氏体,在形变过程中产生持续TRIP效应,冷轧中锰钢获得了较高的强度以及良好的塑性,强塑积可以达到31 GPa%。     

Effect of manganese on the annealing texture and strain ratio of low-carbon steels

A correlation between the plastic strain ratio, or γ value, and the manganese content of laboratory-prepared, low-carbon steels has been established. The \(\bar r\) value decreases consistently when manganese is increased from 0.05 to 0.56 pct. Excellent \(\bar r\) values are associated with manganese contents of 0.1 pct or less. The desirable (111) fiber texture in the low-manganese steels is obtained through recrystallization without appreciable grain growth. It is believed that a very low content of manganese in the steel, or its consequential effects in connection with nonmetallic impurities, may have influenced significantly the characteristics of recovery, hence the nucleation of recrystallized grains, of the various deformation texture components. X-ray line sharpening of several reflections during the early stages of annealing appears to be consistent with this interpretation.     

Effects of silicon content and intercritical annealing on the manganese partitioning in dual phase steels

 Steels of constant manganese and carbon contents with 0.34-2.26 wt. % silicon content were cast. The as-cast steels were then hot rolled at 1100°C in five passes to reduce the cast ingot thickness from 80 to 4 mm, air cooled to room temperature and cold rolled to 2 mm thickness. Dual-phase microstructures with different the volume fraction of martensite were obtained through the intercritical annealing of the steels at different temperatures for 15 min followed by water quenching. In addition of intercritical annealing temperature, silicon content also altered the volume fraction of martensite in dual-phase steels. The partitioning of manganese in dual-phase silicon steels were investigated using energy-dispersive X-ray spectrometry (EDS). The partitioning coefficient, defined as the ratio of the amounts of alloying element in the austenite to that in the adjacent ferrite, for manganese increased with increasing intercritical annealing temperature and silicon content of steels. It was also shown that the solubility of manganese in ferrite and austenite decreased with increasing intercritical temperature. The results were discussed by the diffusivity and the solubility of manganese in ferrite and austenite present in dual-phase silicon steels.     

Effect of annealing on structure and properties of a dispersion strengthened superalloy,IN-853

Dispersion strengthened nickel-base superalloy bar has been produced by hot extrusion of mechanically alloyed powders. The fabrication methods produce an ultra-fine grained material which resists grain growth up to a critical temperature around 1506K (2250°F). Above this temperature, a discontinuous grain growth process leads to the formation of coarse elongated macrograins. The material becomes completely coarse grained in short times. Annealing below this temperature produces only slight grain coarsening, and relieves stored strain energy. Changes in properties are related to the grain growth and strain annealing processes.     

Corrosion properties of austenitic Cr-Mn-Ni-N steels with various manganese concentrations

The structure and corrosion properties of two high-nitrogen 05Kh20AN8MF steels additionally alloyed with 9 and 17% Mn have been studied. Metallographic, X-ray diffraction, and fractographic studies show that both steels have an austenitic structure and high plasticity properties after quenching from 1100 and 1100°C and subsequent aging at 500°C for 2 h. The steel alloyed with 9% Mn and 0.58% V exhibit a higher strength. Both steels have a higher corrosion resistance in a 3.5% NaCl aqueous solution than 12Kh18N9T steel. After aging at 400–600°C, the corrosion rate and the sensitivity to stress corrosion cracking increase.     

Structure formation during the sintering of powder steels alloyed with copper,chromium, and phosphorous

The process of structure formation during the sintering of powder steels alloyed with copper, chromium, and phosphorous was investigated. The microstructure of the materials, and distribution of alloying elements in the iron grains, were studied by the methods of electron and scanning electron microscopy. The effect of dispersion of the ferrochromium powder on its solubility in iron was examined.Kirov Factory for the Manufacture of Articles from Metal Powder. Translated from Poroshkovaya Metallurgiya, Nos. 5/6, pp. 56–62, May–June, 1995.     

基于退火路径的中锰钢组织转变与力学性能

为了更好地指导中锰钢工业试制,利用扫描电镜、电子背散射衍射、透射电镜和拉伸试验机等研究了不同退火路径下低碳中锰钢的组织转变及合金元素配分行为,并评价了其对力学性能的影响.结果表明,热轧中锰钢的显微组织主要由铁素体、板条马氏体、粒状贝氏体和残余奥氏体构成.经冷轧变形后,原组织中的铁素体和马氏体晶粒破碎,残余奥氏体和M/A...     

The effect of coiling temperature and continuous annealing on the properties of bake hardenable IF steels

Five bake hardenable IF steels were investigated. The transformation and recrystallization behaviour, the precipitation and the mechanical properties were studied. The coiling temperature was varied between 580 and 720°C. Soaking was carried out in a temperature range from 700 to 900°C and the soaking time ranged from 60 to 240 s. It was found that boron significantly retards transformation and recrystallization. The bake hardening is increased but deep drawability is lowered by boron additions. In the Ti-containing steels, TiS, Ti₄C₂S₂ and MnS precipitate competitively during the hot rolling process after reheating to 1250°C. To obtain a reasonable bake hardening effect, the amount of carbide forming elements should be substoichiometrical related to C.     

The effect of manganese and sulfur contents on the magnetic properties of cold rolled lamination steels

The effect of Mn and S contents on the magnetic properties of cold rolled lamination steel was investigated in eleven low C steels. The results indicated that Mn content was a major factor influencing the magnetic quality of the lamination steels. An optimum range of Mn was a prerequisite for optimum permeability and exciting power. For Mn contents up to 1.25 Pct, the core loss improved nonlinearly with increasing Mn content. At higher Mn contents, the magnetic properties deteriorated for the experimental conditions used as a consequence of poor grain size development after the final decarburizing anneal. Decreasing the S content from 0.018 Pct to 0.010 Pct improved the core loss at all induction levels. The permeability and exciting power were improved at 1 T, but a very slight deterioration in permeability and exciting power was seen at 1.5 and 1.7 T. Estimations of core loss improvement based on regression equations indicated that lowering the S content from 0.018 Pct to 0.010 Pct improved the core loss in w/lb-mil as follows: 0.0041 at 1 T, 0.0079 at 1.5 T, and 0.0093 at 1.7 T (1 w/lb-mil = 86.8 w/kg-mm). The response surface analyses indicated that Mn content in the range of 0.7 Pct to 1 Pct, depending on the S content, should develop optimum magnetic properties. However, Mn content at the low end of this range is preferred for practical applications. This paper is based on a presentation made at the symposium “Physical Metallurgy of Electrical Steels” held at the {dy1985} annual AIME meeting in New York on February 24–28, {dy1985}, under the auspices of the TMS Ferrous Metallurgy Committee.     

Influence of hot-rolling conditions on texture development in deep-drawing steels

As the textures of deep-drawing sheet steels are important for certain material properties the purpose of this paper was to take a closer look at the hot-rolling, cold-rolling and annealing textures of different deep-drawing steel grades. Several Al-killed mild steels and vacuum-degassed Ti-IF steels have been hot rolled in the mill varying the finishing temperature (FT). After coiling, cold rolling and short-time annealing the textures at different thickness levels have been measured by means of (110)-pole figures and orientation distribution functions (ODFs). For both steel groups the textures at the surface of the hot strip exhibit a more or less pronounced shear type character. Towards the mid-thickness level (with lower FT more clearly) typical (cold-) rolling textures exist characterized by a strong {001}<110> orientation and in the Ti-IF steels additionally by a significant {112}<110> orientation density. In the case of high FT cold rolling and annealing lead to favourable {111}-textures where deep-drawing application is concerned. For the Al-killed steels lowering FT results in diffuse recrystallization textures whereas in the Ti-IF steels a sharp texture with near {223}<582> orientations can be observed which have not been known for these steels before. The results prove that the hot strip textures can be of great importance for the resulting annealing textures and the according material properties.     

机械合金化对ODS铁素体钢粉末的微观形貌和结构的影响

研究了不同转速和球磨时间对氧化物弥散强化合金粉末的微观形貌和结构的影响.XRD和SEM结果表明:当转速为380r·min^-1时,既能提高球磨效率,又可避免粉末在球磨过程中发生团聚.机械合金化中晶粒尺寸和平均颗粒尺寸的减小导致XRD衍射峰的宽化.当球磨时间为30h时,粉末平均粒径随着球磨时间的增加而迅速减小至13.4μm,粉末多呈球形,粒度分布较窄.SEM-EDS结果表明,各合金元素在粉末内部分布均匀.     

The effects of composition and annealing conditions on the stability of columbium (niobium)-treated low-carbon steels

The effects of composition and annealing conditions on the yielding behavior of vacuum melted, columbium(niobium) -treated, low-carbon steels were investigated. Additions of columbium were found to result in stabilization,i.e. freedom from inhomogeneous yielding or Lüder’s strain in the as-recrystallized condition. Stabilization is accounted for by considering the role of columbium as a carbide former, thereby reducing the carbon content in solution to a very low level. The nitrogen present is preferentially removed from solid solution by the formation of A1N. The results were used to estimate the solubility product of columbium carbide in ferrite. The amount of columbium required to provide stability is a function of total carbon content and annealing temperature.     

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Effect of cooling conditions on the evolution of non- metallic inclusions in high manganese TWIP steels was investigated based on experiments and thermodynamic calculations. The inclusions formed in the high manganese TWIP steels are classified into nine types: (??) AlN??(??) MgO??(??) CaS?? (??) MgAl2O4?? (??) AlN+MgO?? (??) MgO+MgS?? (??) MgO+MgS+CaS?? (??) MgO+CaS?? (??) MgAl2O4+MgS. When the cooling rate decreases from 4. 83 ??/s to 0. 75 ??/s, the inclusion types change from (??), (??), (??)(??) to ????(??), (??) and (??). With the increase of the cooling rate, the volume fraction and area fraction of inclusions are almost constant; the size of inclusions decreases and the number density of inclusions increases in the steels. With increase of cooling rate, the variation of the size, number, and area fraction of AlN is the same with the variation of those of total inclusions in the steels. The thermodynamic results of inclusion types calculated with FactSage are consistent with the observed results.