硼对冷轧IF钢板疲劳性能的影响

对比研究了Ｂ对添加Ｔｉ和复合添加Ｔｉ、Ｎｂ的冷轧ＩＦ钢板的显微组织和疲劳性能的影响。研究结果表明,Ｂ可以细化这两种ＩＦ钢的退火组织,改善晶界结合强度,提高疲劳强度。疲劳断口分析结果表明,不加Ｂ的ＩＦ钢表现出沿晶断裂特征,加Ｂ后可使ＩＦ 钢断裂性能得以改善,表现出穿晶断裂特征。     

Boron fade

At high temperatures of 900°C or more boron contained in steel escapes readily into an inert atmosphere as many scientists have already observed. The authors have investigated by theoretical analysis of the possible reasons for boron losses of unalloyed and low alloyed steels in an CH₄/H₂-atmosphere at 1000°C and 1 bar, i.e. boron volatilizes in elemental form, in form of boron oxide (B₂O₃) or as diborane (B₂H₆). It was proved that boron escapes from steel primarily as boron oxide, even if the atmosphere does not contain oxygen. Traces of oxygen in an annealing atmosphere seem to be sufficient to combine with the total boron content of the steel when being in the order of up to 100 ppm. A boron containing source such as boron oxide in sufficient amount in the annealing atmosphere can compensate boron losses of steels.     

304不锈钢精密钢带表面“炉灰”缺陷分析

 在304不锈钢精密带光亮退火生产环节，钢带表面易出现金属粉的现象，导致产品表面质量存在不稳定性。针对304不锈钢精密钢带表面出现的“炉灰”缺陷，利用扫描电子显微镜观察其形貌，并用能谱仪对缺陷处局部成分进行了点扫描和面扫描检测。结果表明，304精密钢带“炉灰”缺陷微观形貌为白色微颗粒。结合能谱微区分析结果和相关研究分析，推测“炉灰”缺陷主要是由于304不锈钢基体组织中硼元素质量分数过高，钢带在光亮退火过程中硼原子易与保护气氛中分解的活性较高的氮原子结合，生成氮化硼析出而形成的。通过控制不锈钢基体中硼元素质量分数不大于0.001 5%，从而达到有效降低304不锈钢精密钢带“炉灰”缺陷的目的。     

提高连续退火生产的铝镇静钢性能均匀性的措施的探讨

重点从一贯制工艺着手对如何提高连续退火生产的铝镇静钢性能均匀性的措施进行了探讨，提出了加B、控制Mn的含量、采用U形卷取温度控制、边部加热等措施，通过大生产的实验证实确实有效，可大幅度地提高材料机械性能的均匀性。     

Dislocation sources in silicon

Oxidation induced stacking faults have been observed to function as dislocation generating sources in silicon single crystals when the crystals are annealed at high temperatures. The presence of diffused boron in the silicon results in a large increase in the size of the dislocation colonies generated from the faults. The dislocations generated form three dimensional star shaped colonies with the colonies being decorated by a second phase in the form of fine precipitates or dislocation loops. Depending upon the initial oxidation temperature and the postoxidation annealing treatments both partial and whole dislocations are generated in the samples containing diffused boron. The partial dislocations are 1/3 «111» Frank dislocations and the whole dislocations have Burgers vectors 1/2 «110» and «100». The dislocation loops generated are interstitial and the stacking faults extrinsic in nature. A model is proposed to account for the growth of the colonies. The initial nucleation of the stacking fault is suggested to occur by the formation of an oxide of silicon. Diffusion of boron is postulated to result in a preferential accumulation of boron in the fault with the subsequent growth of the fault occurring when annealing forces in-diffusion of the boron concentrated in the faults.     

Effect of boron on the microstructure and tensile properties of dual-phase steel

The effect of boron on the hardenability of austenite during the production of dual-phase steel and on tensile properties has been studied. Increasing boron content from 0. 0005 to 0. 0029 wt pct decreased the volume fraction of austenite present at constant intercritical annealing temperature but increased the fraction of the austenite which transformed to martensite on cooling. Increasing boron also decreased the sensitivity of martensite content to cooling rate and, therefore, of tensile properties to cooling rate. The lower volume fraction of austenite present at constant intercritical annealing temperature, and the consequentially higher carbon content of the austenite, was in agreement with the known effect of boron on the phase diagram. The previously determined effect of carbon concentration in austenite on the austenite’s martensitic hardenability was sufficient to explain the observed effects of increasing boron content. The absence of a direct effect of boron was investigated using particle-tracking autoradiography (PTA) to follow changes in boron segregation. The pattern of segregation to prior austenite grain boundaries in the initial, normalized condition dispersed slightly on holding in the (α + γ ) phase field, but no evidence was found of resegregation to α/γ interfaces. X. P. SHEN, on leave from the Central Iron and Steel Research Institute, Beijing, People’s Republic of China.     

The use of a boron addition to prevent intergranular embrittlement in Fe-12Mn

Fe-12 Mn alloys undergo failure by catastrophic intergranular fracture when tested at low temperature in the as-austenitized condition, a consideration which prevents their use for structural applications at cryogenic temperatures. The present research was undertaken to identify modifications in alloy composition or heat treatment which would suppress this embrittlement. Chemical and microstructural analyses were made on the prior austenite grain boundaries within the alloy in its embrittled state. These studies failed to reveal a chemical or microstructural source for the brittleness, suggesting that intergranular brittleness is inherent to the alloy in the as-austenitized condition. The addition of 0.002 to 0.01 wt pct boron successfully prevented intergranular fracture, leading to a spectacular improvement in the low temperature impact toughness of the alloy. Autoradiographic studies suggest that boron segregates to the austenite grain boundaries during annealing at temperatures near 1000 °C. The cryogenic toughness of a Fe-12Mn-0.002B alloy could be further improved by suitable tempering treatments. However, the alloy embrittled if inappropriate tempering temperatures were used. This temper embrittlement was concom-itant with the dissolution of boron from the prior austenite grain boundaries, which reestablishes the intergranular fracture mode.     

Simulation of the Soaking and Gas Jet Cooling in a Continuous Annealing Line using Dilatometry

The present study concerns the simulation of a continuous annealing line (CAL), using dilatometry. Simulations of CAL have been performed on four commercial steel grades with different chemical compositions in order to investigate how the alloying elements C, Mn, Si and B affect the microstructure and hardness of dual phase (DP) and martensitic steels. Three annealing cycles corresponding to those used in a CAL have been applied. When annealing intercritically, as is the case in DP‐steel production, the materials do not reach equilibrium during soaking. Mn and C increase the austenite content and consequently the hardness of the materials. Higher levels of Si (0.4 wt %) are required to retard the formation of new ferrite during cooling in the gas jet section, prior to quenching. B increases hardenability effectively when annealing in the austenite region but is not as efficient during intercritical annealing, which implies that boron restrains ferrite nucleation rather than impeding ferrite growth. Results from DICTRA calculations show that it is possible to simulate the phase transformations during soaking, gasjet cooling and quenching.     

Grain boundary segregation of boron in INCONEL 718

The segregation behavior of boron at grain boundaries in two INCONEL 718⁺ based alloys with different B concentrations was studied. The alloys, one containing 11 ppm of B and the other 43 ppm, were homogenized at 1200 °C for 2 hours followed by water quenching and air cooling. A strong segregation of boron at grain boundaries was observed using secondary ion mass spectrometry after the heat treatment in both the alloys. The segregation was found mainly to be of nonequilibrium type. The homogenized samples were also annealed at 1050 °C for various lengths of time. During annealing, boride particles were observed to first form at grain boundaries and then to dissolve on continued annealing at 1050 °C. The mechanisms of segregation and desegregation of B are discussed.     

Solidus Surface of the Mo–Fe–B System

Powder Metallurgy and Metal Ceramics - The arc-melted Mo–Fe–B alloys with boron content up to ~41 at.% were studied after annealing at subsolidus temperatures by X-ray diffraction,...     

含硼钢试验开发

本次试验开发含硼钢,相继试验了含硼烧结矿、含硼铁水和铁块、含硼钢坯、含硼钢材中硼元素的变化规律,并结合我公司的工装条件,确认了各环节的工艺可行性,为同行业的工艺实现提供参考,以及合理利用硼资源。     

汽车紧固件用钢的发展动向

简要介绍了汽车紧固件用钢的性能要求,冶炼及轧制的特点;对相关的洁净螺栓钢、微合金非调质钢、免退火钢、硼钢、耐延迟断裂高强钢的现状和发展动向进行阐述;指明了实施汽车紧固件用钢国产化的努力方向。     

Effects of boron doping on the grain-growth kinetics and mechanical properties of γ/γ′ nickel-aluminum alloys

The effects of 0.5 at. pct of boron doping on the microstructures and mechanical properties of γ/γ′ nickel-aluminum alloys have been investigated in the present study. A nickel-rich grain-boundary zone was observed in the boron-doped alloy after homogenization at 1100 °C and prolonged annealing at 1200 °C. Boron doping also caused remarkable improvements in toughness and tensile elongation and caused the fracture mode to change from completely intergranular to completely transgranular. The grain growth following recrystallization at 1200 °C was found to be retarded upon boron doping. A sudden increase in tensile elongation and a sudden drop in hardness were also observed upon prolonged heating during isothermal annealing at 1200 °C. The results are interpreted with reference to boron-nickel cosegregation at the grain boundaries.     

Effect of boron on high-temperature creep behavior of austenitic stainless steel DIN 1.4970

Samples of austenitic stainless steel DIN 1.4970 containing about 40 ppm of boron and a boron-free version of this steel were creep tested at 700 °C in both the solution-annealed and aged conditions to determine their creep ductility and strength. The microstructure before creep tests was determined using transmission electron microscopy. The distribution of boron in both the steels after solution annealing (SA) and aging was mapped by means of α-autoradiography. It has been observed that in the solution-annealed condition, the creep strength of 1.4970 steel is higher than that of the boron-free version; whereas after aging, the strength of 1.4970 steel is lower than that of the boron-free version. The creep ductilities were hardly influenced by the presence of boron. The results are discussed in terms of microstructure and boron distribution in the matrix. Formerly with the Indira Gandhi Centre for Atomic Research, Kalpakkam, India.     

The microstructural response of mill-annealed and solution-annealed INCONEL 600 to heat treatment

Samples of INCONEL* 600 were examined in the mill-annealed and solution-annealed states, and after isothermal annealing at 400 °C and 650 °C. The corrosion behavior of the samples was examined, analytical electron microscopy was used to determine the microstructures present and the chemistry of grain boundaries, and Auger electron spectroscopy was used to measure grain boundary segregation. Samples of different alloys in the mill-annealed state were found to have quite different microstructures, with Cr-rich M₇C₃ carbides occurring either along grain boundaries or in intragranular sheets. The corrosion behavior of the samples correlated well with the occurrence of grain boundary chromium depletion. Solution annealing at 1190 °C caused dissolution of all carbides, whereas at 1100 °C the carbides either dissolved or the grain boundaries moved away from the carbides, depending upon alloy carbon content. Low-temperature annealing at 400 °C had little effect on millannealed or fully solutionized samples, but in samples with intragranular carbides present, the grain boundaries moved until intersecting or adjacent to the carbides. Isothermal annealing at 650 °C caused carbide nucleation and growth at grain boundaries in fully solutionized samples. Chromium depletion at grain boundaries accompanied carbide precipitation, with a minimum chromium level of 6 wt pct achieved after 5 hours. Healing was found to occur after 100 hours. Solution-annealed samples with intragranular carbides present had more rapid corrosion kinetics since the grain boundaries moved back to the existing carbides. Thermodynamic analysis of the chromium-depletion process showed good agreement with experimental measurements. The Auger results found only boron present at grain boundaries in the mill-annealed state. Aged samples had boron, nitrogen, and phosphorus present, with phosphorus and nitrogen segregating to the greatest extent. The kinetics of phosphorus segregation are much slower at 400 °C compared with 650 °C.     

Composite electrolytic nickel-phosphorus-boron coatings

Conclusions The feasibility is demonstrated of obtaining Ni-P-B coatings with a uniform distribution of boron particles in their Ni-P matrices. The presence of boron particles has a marked effect on the phosphorus content of such coatings and on the rate of deposition of nickel. Diffusion annealing of Ni-P-B coatings leads to the formation of a new phase and to an improvement in their physicomechanical properties, in particular hardness and wear resistance.Translated from Poroshkovaya Metallurgiya, No. 10(226), pp. 71–74, October, 1981.     

Recrystallization of a cold-rolled low-carbon steel by cold-plasma-discharge rapid annealing

A new annealing technology has been developed by the authors in order to conduct fast steel annealing. This process consists of steel heating by cold-plasma discharge. It allows the opportunity for new annealing cycles with higher heating rates (up to 300 K/s), shorter soaking times, and controlled cooling rates, so that well-recrystallized samples have been achieved in less than several seconds of total process time. This article reports the influence of various parameters of the annealing cycle (heating rate, maximum annealing temperature, and cooling rate) on the recrystallization and properties of a cold-rolled low-carbon steel. This study shows that the annealing time can be significatively reduced using this new technology, compared to the industrial continuous annealing technology used today, to obtain equivalent metallurgical properties.     

Sintering of boron carbide containing small amounts of free carbon

Conclusions A study was made of the sintering kinetics of grade ch. boron carbide, technical boron carbide cleaned of impurities, and boron carbide synthesized from the elements. An investigation was carried out also into the reactive sintering of a mixture of boron and carbon black. Reactive sintering fails to yield dense parts in boron carbide. The best sinterability is exhibited by a fine technical boron carbide powder cleaned of free carbon and other contaminants. Parts with a porosity of less than 5% can be produced from such a powder by pressing and subsequent sintering. However, it is not the presence of free carbon that controls the sintering behavior of boron carbide, since pure and synthesized boron carbide powders containing no free carbon are characterized by poor sinterability. The high activity of the technical powder is probably linked with the presence of structural defects and stresses generated in the course of its manufacture, during milling and quenching. The annealing spectrum of these defects covers a wide temperature range, and consequently the energy of activation for the densification of boron carbide steadily grows with increase in shrinkage.Translated from Poroshkovaya Metallurgiya, No. 7 (151), pp. 27–31, July, 1975.     

Tension compensation technique based on the roughness attenuation of a furnace roller during continuous annealing

Strip tension fluctuation caused by the attenuation of a furnace roller’s surface roughness leads to strip deviation in continuous annealing. After several field experiments and theoretical studies, this work established a model for the surface roughness attenuation of a furnace roller during continuous annealing. The model is fully integrated with the equipment and process features of a continuous annealing unit. With the stability of strip travelling as the control object and the absence of strip deviation and buckling as constraints, a tension compensation technique of continuous annealing was developed, and a related theory was applied to production and practise. Software was also developed for predicting the roughness attenuation of a furnace roller during continuous annealing and determining tension compensation for a specific process of the unit. Integrated optimisation of tension parameters in all processes of continuous annealing was also achieved.     

Development of a new method to produce melts suitable for the production of amorphous Fe−Si−B materials

Research work was performed on the development of a new reduction process for the melting and refining of boron containing alloys used in the production of amorphous material for transformer cores. Based on fundamental thermodynamics principles, a reduction refining process was developed which employs conventional steelmaking vessels for using steel scrap, ferro alloys, and boron ores to produce an Fe−Si−B alloy. The process can eliminate the need for ferro boron alloy, high purity iron, and remelt stock to produce the Fe−Si−B alloy. Process variables were established which show the effects of mixing time, reductant alloy additions, slag chemistry, and temperature on the reduction kinetics. Final melt chemistries have lower levels of sulfur, nitrogen, and other tramp elements than conventional methods for producing the Fe−Si−B melt.