Effect of annealing parameters on mechanical properties of cold-rolled martensitic steel sheets

Cold-rolled martensitic steel sheets produced on continuous annealing lines with water quenching facility,have advantages of high strength and low alloying element contents.These are in good accordance with the trend of light-weighting and fuel saving for automotive steel.In this article,a cold-rolled martensitic steel is studied to investigate the effect of annealing parameters on its mechanical properties.It is found that the quenching temperature and the slow cooling speed as well as the overageing temperature have significant influence on the strength of the experimental steel.The temperature zone at which the austenite decomposition is slow or has not started may be chosen as the quenching temperature to ensure the steel’s strength stability.The slow cooling speed also influences the steel’s strength greatly.A high cooling rate will lead to significantly higher strength.Tempering would decrease the steel’s tensile strength but would increase its yield strength.     

退火工艺对高耐蚀Galvalume钢板镀层表面结构的影响

采用连续退火、镀锌和合金化模拟机制取了不同退火温度和退火时间条件下Galvalume钢板的退火试样,通过SEM、EDS、XRD等试验方法,进行了退火工艺对于Galvalume钢板镀层表面结构影响研究,阐明了表面相结构和w（Fe）的变化规律。结果表明,随着退火温度和退火时间的增加,Galvalume镀层表面α相和α＋β共...     

Influence of the tempering temperature on the mechanical properties and the phase composition of thin sheet TRIP steel

The strength and the plasticity properties of sheet high-strength austenitic–martensitic VNS9-Sh TRIP steel (23Kh15N5AM3-Sh) are studied as functions of the tempering temperature in the range 125–600°C. A nonmonotonic decease in the strength and the plasticity properties of the steel has been detected when the tempering temperature increases, and they increase in the range 300–450°C. The influence of aging processes, the precipitation of carbide, and the phase transformations in tempering on the mechanical properties of austenitic–martensitic corrosion-resistant steel is discussed.     

退火工艺对超高强冷轧马氏体钢板力学性能的影响

以C-Mn-Si系冷轧马氏体钢为研究对象,分析了退火工艺对超高强马氏体钢强度和冷弯性能的影响。由于碳含量高,试验用钢淬透性良好,当水淬入口温度在710℃及以上时,都能获得极高的抗拉强度和稳定的马氏体组织。随过时效温度升高,马氏体钢抗拉强度降低、延伸率升高;而屈服强度和冷弯性能则先升后降,在180℃过时效时具有最高的屈服强度和最优的冷弯性能。经扫描电镜和显微硬度分析发现,过时效温度的变化会直接影响马氏体钢中的碳化物析出及粗化,当过时效温度大于200℃时,试验用钢碳化物开始粗化,降低了马氏体钢的宏观冷弯性能。     

Effect of processing parameters on the mechanical characteristics of isotropic electrical steel

Novolipetsk Metallurgical Combine. Lipetsk Polytechnic Institute. Translated from Metallurg, No. 4, pp. 44–46, April, 1988.     

Influence of heat treatment parameters on structure and mechanical properties of an HSLA‐100 steel

An HSLA‐100 steel received from the US Naval Research Laboratory has been characterised. The effects of heat treatment parameters such as austenitisation time and temperature, tempering time and temperature on mechanical properties have been studied. The microstructures resulting from different heat treatment conditions have been correlated with mechanical properties through SEM and TEM studies. Quantitative relationships have been developed between mechanical properties and the operational variables within a narrow range of variation of the variables by statistical design of experiments. A quantitative relationship has also been developed for the same for a wider experimental region through curve fitting technique. The best combination of strength and low‐temperature toughness was obtained in the region of 700 °C tempering temperature and 0.3 ‐ 0.4 h tempering time.     

Influence of scale removal on the mechanical properties of low-carbon steel

The influence of heat treatment and of the acidic and mechanical removal of rolling scale on the variation in mechanical properties of 1kp low-carbon steel wire rod is investigated.     

Influence of annealing conditions on selective oxidation of boron in BH steel sheets

Annealing experiments were conducted on BH steel to which 10 × 10- 6boron was added. The annealing temperature,holding time,H2 content,and dew point were varied in the experiments in order to investigate their influences on the selective oxidation of boron. A higher annealing temperature and longer holding time is found to lead to a higher concentration of boron at the extreme surface,which reaches saturation after the steel sheet is held for a critical period of time that depends on the annealing temperature. The effect of H2 content on the selective oxidation of boron depends on the annealing temperature and dew point. It has almost no influence on the external oxidation of boron when the sheet is annealed at 820 ℃ in an atmosphere with a dew point of- 40 ℃. At a dew point of- 10 ℃,a lower H2 content results in a lower peak value of boron in the subsurface area but deeper internal oxidation of boron. An increase in the dew point from- 40 ℃ to- 10 ℃ can significantly promote internal oxidation of boron at depths of 50- 200 nm from the surface. With the suppression of external oxidation of boron as well as manganese and silicon,a relatively clean surface with reduced and refined oxides can be achieved by increasing the dew point.     

Investigation of the mechanical performance of Al-coated DI steel sheets prepared by DC magnetron sputtering

Aluminum films coated on DI steel sheets were prepared by direct current(DC)magnetron sputtering. The influence of the deposition conditions and film thickness on the formability of coated steel sheets was studied. The results of the cupping test and drawing test show that the substrate temperature and thickness of Al films are the key factors that affect Al adhesion and formability of coated steel sheets.Adhesion became worse when the thickness of Al sheets was more than 2μm.And formability was improved remarkably when the substrate temperature was increased to 200℃.     

Influence of elastic and plastic anisotropy on the flow behavior in a duplex stainless steel

The load partitioning between two phases in a cold-rolled duplex stainless steel has been experimentally studied in situ by X-ray diffraction, for different loading directions. It was found that the load partitioning between the two phases is dependent on the loading direction. For loading in the rolling direction, both phases deform plastically to the same degree, while more plastic deformation occurs in the austenitic phase during loading in the transverse direction. For loading in the 45-deg direction, more plastic deformation occurs in the ferritic phase. The strong crystallographic texture in the ferritic phase makes the material anisotropic, with a higher stiffness and yield strength in the transverse direction compared to the rolling direction. The measured texture was used as input to theoretical predictions of both elastic and plastic anisotropy. The plastic anisotropy was predicted by assuming intragranular slip as the main deformation mechanism. The predicted anisotropic material properties were then used in finite-element simulations to study the flow behavior of the material in different directions. The predicted flow behavior was found to be in good agreement with the experimentally observed load partitioning between the phases for loading in the rolling and transverse directions. However, the yield strength of the ferritic phase during loading in the 45-deg direction was found to be lower than what was predicted. The reason for this is the difference in slip characteristics in different sample directions, because of the morphological texture.     

Influence of on-line tempering parameters on microstructure of medium-carbon steel

A new process involving ultra-fast cooling(UFC)and on-line tempering(OLT)was proposed to displace austempering process,which usually implements in a salt/lead bath and brings out serious pollution in the industrial application.The optimization of the new process,involving the evolution of the microstructure of medium-carbon steel during various cooling paths,was studied.The results show that the cooling path affected the final microstructure in terms of the fraction of pearlite,grain size and distribution of cementite in pearlite.Increasing the cooling rate or decreasing the OLT temperature contributes to restraining the transformation from austenite to ferrite,and simultaneously retains more austenite for the transformation of pearlite.It is also noted that bainite was observed in the microstructure at the cooling rate of 45°C/s and the OLT temperature of 500°C.Through either increasing the cooling rate or decreasing the OLT temperature,the distribution of cementite in pearlite is more dispersed and grain is refined.Taking the possibility of industrial applications into account,the optimal process of cooling at 45°C/s followed by OLT at 600°C after hot rolling was determined,which achieves a microstructure containing nearly full pearlite with an average grain size of approximately 7μm and a homogeneously dispersed distribution of cementite in pearlite.     

The effect of thermal-cycle treatment parameters on the mechanical properties of hot-stamped powdered steel

In order to improve the properties of powdered carbon steels and grain refinement, thermal-cycle treatment was performed with the use of both induction and furnace heating. This resulted in an extra-fine-grain structure and it increased the values of strength, plasticity, and impact strength. The optimum number of cycles is 3–10.     

Influence of the deformation mechanism on the anisotropy of the mechanical properties and workability of magnesium alloys

An experimental calculation method for the estimation of anisotropy is developed for semifinished sheet and pressed products made from magnesium alloys. The method makes it possible to calculate the anisotropy parameters from quantitative data on the texture and the relative values of the reduced critical shear stresses for the slip and twinning mechanisms operating in these alloys. The optimal alloying of magnesium alloys is shown to provide two methods for enhancing the deep drawing characteristics, namely, decreasing the intensity of the basal texture due to the formation of dispersed intermetallic compounds and increasing the compressive-strain resistance compared to tension due to a change in the deformation mechanism. Yttrium and neodymium are found to be most efficient in this respect, because they favor such a deformation mechanism that increases the Lankford coefficient by two to four times at the same texture in sheets. In addition, neodymium alloying weakens the intensity of the basal texture, which also favors an increase in the Lankford coefficient.     

Influence of pipe processing on the mechanical properties of K60 steel sheet

The mechanical properties of thick steel sheet (13?C27 mm) produced at PAO MK Azovstal?? and the basic metal in K60 pipe (diameter 1220 mm) for the VSTO pipeline manufactured at PAO Khartsyzskii Trubnyi Zavod are subjected to statistical analysis, so as to establish the variation in the mechanical properties of the steel as a function of the sheet thickness and the wall thickness of the pipe and also under the influence of pipe processing.     

Optimization of the technological conditions of producing thin sheets and strips from corrosion-resistant VNS9-Sh steel

The technological conditions of producing thin sheets and strips from corrosion-resistant VNS9-Sh steel are optimized at the stages of casting, deformation, and heat treatment. The effect of the as-cast phase composition of VNS9-Sh steel on the ductility of the metal during cold rolling and on the mechanical properties of the end products in the form of thin sheets and strips is studied. It is shown that, for the required level of the mechanical properties of sheets and strips to be achieved, the magnetization of as-cast steel samples should be J = 3–10 mV on the scale of an IFSS (MKL) device, which corresponds to 1.5–5% martensite in the as-cast steel. It is also shown that the required level of mechanical properties (σ_u ≥ 1470 MPa, δ ≥ 12%) is achieved after work hardening of 17–35% and that 40–50% deformation martensite and 50–60% cold-worked austenite exist in a ready strip if the magnetization of as-cast steel samples is 3–10 mV and the strip is subjected to work hardening. The effect of tempering temperature in the range 100–450°C is studied to increase the yield strength of the steel in the form of a ready strip at low degrees of cold deformation (17–25%). The increase in the yield strength without a decrease in the ultimate tensile strength is maximal after tempering at 125°C for 1 h due to strain aging processes.     

Influence of phase transformations on the mechanical properties of high-strength austenitic Fe-Mn-Cr steel

The influence of Cr and N additions on the mechanical properties of a Fe-Mn-C steel was investigated. The chemical composition was found to have a pronounced effect on the strain-hardening behavior, due to the strain-induced sequence of the γ → ▓ → α′ martensitic transformations. It was found that Cr and N suppress this transformation sequence. At Cr levels higher than 7.5 mass pct, no α′ martensite was formed, which led to a pronounced improvement of the ductility. The differences in transformation behavior can be attributed to the change in the intrinsic stacking-facult energy (ISFE): in the compositional range studied, Cr and N additions cause an increase of the ISFE.     

薄板坯的铸态高温力学性能研究

为了提高数值模拟精度,针对薄板坯连铸连轧过程中的工艺特点和材料特性,提出采用铸态钢20来进行高温压缩模拟实验的方法,为液芯压下结构提供材料高温流变应力模型.研究选取沿柱状晶方向的铸态钢试样分别在900、1 100、1 200和1 250℃4个温度点下,采用应变速率分别为0.001、0.005、0.010和0.050/s来进行实验与分析,了解铸态钢在高温条件下的流变行为,研究温度和应变率对材料流动应力的影响.并通过试验数据的多元非线性回归建立铸态钢高温流变应力应变关系模型,为后续的铸轧过程模拟提供准确的材料模型.