钛含量对00Cr13Co9Ni5Mo5马氏体时效不锈钢冲击韧性的影响

通过具有不同钛含量的3炉试验钢,研究了钛含量对00Cr13Co9Ni5Mo5马氏体时效不锈钢的力学性能、金相组织和奥氏体含量的影响。研究结果表明:添加较多的Ti可显著降低基体组织中的有效C、N含量,大幅降低固溶、时效处理后残余/逆转变奥氏体含量,最终使冷脆转化温度显著上升,在提高强度的同时降低了钢的韧性。     

La对微合金高强钢组织及析出相的影响

借助场发射扫描电镜、X-射线衍射仪及电感耦合等离子发射光谱仪等检测手段,研究了La对微合金高强钢组织和析出相的影响。结果表明,实验钢显微组织均为粒状贝氏体、准多边形铁素体、少量板条贝氏体及残余奥氏体,析出相主要为Ti N、Ti C、Nb C、Nb Ti C2、Ti VC2。随La含量的增加,准多边形铁素体相比例降低,尺寸减小,贝氏体相增多且晶粒变小,残留奥氏体和细小析出相增多。     

1Cr21Ni5Ti双相不锈钢脆化现象及韧化措施

研究了1Cr21Ni5Ti双相不锈钢的脆化本质及相应的韧化措施。生产和应用跟踪分析表明：只要经过脆化处理，所有1Cr21Ni5Ti钢都会发生程度不同的脆化，铁素体的准解理断裂是其脆化的本质。高的Ti／C比、尤其是高的残铝使奥氏体相比例明显减少、降低了阻止准解理裂纹扩展的能力，因此高钛、铝含量的钢具有显著的脆化倾向。实验证实，增加锻造比可明显改善奥氏体相的分布和形态，显著改善含高钛、铝钢的冲击韧性。     

Ti含量对耐磨钢相变行为及强韧性的影响

采用全自动相变仪、扫描电子显微镜、电子万能试验机、宏观硬度计等设备和Thermo-Calc热力学计算软件对比研究了Ti质量分数分别为0.018%和0.55%的2种耐磨钢的相变行为和强韧性，分析了相同轧制工艺、回火工艺下实验钢的显微组织和力学性能的差异。结果表明，0.55Ti钢中由于生成了大量微米级的TiC和少量Ti(C,N)粒子，降低了基体中的固溶C含量，提高了奥氏体化温度，同时致使其淬透性相对于0.018Ti钢有所降低；在930℃温度下淬火时，由于淬透性的下降，组织中出现了部分贝氏体组织。在0.55Ti钢中，由于微米级的TiC和少量Ti(C,N)粒子的存在，降低了实验钢的强度。此外，微米级的粒子作为冲击断裂时微裂纹形核点，促进了微裂纹的形核，降低了钢的韧性。     

轻质钢的研究进展(二)——铁素体—奥氏体双相轻质钢和奥氏体轻质钢

首先主要阐述了富Al铁素体—奥氏体双相轻质钢和奥氏体轻质钢的微观组织特征、力学性能和强韧化机制。尽管添加Al可以降低钢的密度和提高比强度,但是它会使钢的弹性模量显著降低。针对这一不利属性,介绍了一种切实可行的提高轻质钢(以及碳钢)弹性模量的措施,即利用凝固过程中原位自生高弹性模量的硬质颗粒(如Ti C和Ti B2等)来增强钢的基体。所形成的颗粒增强钢基复合材料可以具有较常规碳钢和富Al轻质钢更高的弹性模量和比弹性模量。     

马氏体时效钢的动向

马氏体时效钢最早出现于50年代末,当时InCo的Bieber将不含碳的25％Ni1.5％Ti钢,在奥氏体状态下进行时效处理,冷却至室温后转变为马氏体组织从而硬化,即所谓奥氏体时效。为提高马氏体时效后强度,将镍含量降低到20％以下,即使不     

固溶温度对马氏体时效钢00Ni14Cr3Mo3Ti组织和力学性能的影响

研究了马氏体时效钢00Ni14Cr3Mo3Ti(%:0.002C、14.06Ni、3.19Cr、3.06Mo、1.32Ti)750～1 050℃固溶处理的组织和力学性能。结果表明,≤900℃固溶处理,该钢奥氏体晶粒和强度无明显变化,固溶温度超过900℃时钢的奥氏体晶粒显著增大,钢的强度呈下降趋势。当固溶温度由750℃增加至900℃时,随固溶处理温度提高,钢中Fe2Mo相量降低,810℃时完全溶解,钢的冲击功由32 J提高至61 J,当固溶温度由900℃增至1 050℃,随奥氏体晶粒增大,钢的冲击功由61 J 降至26 J。     

微合金元素Ti对20CrMnTi齿轮钢质量的影响

研究了钢中Ti回收率的影响因素、Ti含量对钢中Ti夹杂物含量和奥氏体晶粒长大倾向的影响,以及C-Ti对20CrMnTi钢淬透性和力学性能的影响。结果表明,当Ti含量超过0.03%时,20CrMnTi钢中Ti夹杂物含量明显增加;当Ti含量从0.01%增至0.04%,980℃1h处理后钢中晶粒度从5级提高到8级;当控制C-Ti= 0.12%时,钢的淬透性带的宽度为HRC 4～6。     

Ti-Zr复合微合金钢多道次热变形行为有限元模拟及实验研究

为了研究Ti-Zr微合金钢轧制变形过程中变形温度和Zr含量对内部应力应变的分布及奥氏体组织演变的影响，通过热模拟实验和金相分析获得3种不同Zr含量的Ti微合金钢应力应变曲线及奥氏体的晶粒尺寸及分布情况。研究结果表明：变形温度的升高会降低3种实验钢的内部应力，促进应力均匀分布，其中0.12Ti-0.02Zr钢应力下降的最明显，Zr的加入会促进Ti微合金钢再结晶奥氏体的形核和形变诱导析出相的析出，形变储能消耗量增大，不容易在变形过程中积累应力和应变；但过多的Zr会因为大量析出相而使实验钢的变形抗力增大，导致应力和应变累积。综合考虑，使用Ti-Zr复合微合金化技术实现奥氏体组织的超细化均匀时，Zr元素的添加量应控制在0.02%左右。     

热轧低氮18CrMnB钢奥氏体晶粒粗化行为

本文研究了热轧工艺及含Ti量对低N的18CrMnB钢奥氏体晶粒长大倾向的影响。结果表明,热轧压下率及终轧温度对18CrMnB钢奥氏体晶粒长大倾向的影响不太显著,且不呈简单的变化规律,含Ti量对奥氏体晶粒长大倾向影响很大,当含Ti量超过0.053%时,奥氏体晶粒长大倾向明显减少。     

再加热温度对含Nb，Ti钢第二相粒子固溶及晶粒长大的影响

 通过热力学计算和萃取复型分析技术,对高Ti含Nb钢中第二相粒子在不同加热温度下的固溶情况和奥氏体晶粒的长大规律进行了研究。结果表明：再加热温度低于1 180 ℃时,钢中Nb、Ti含量随温度升高显著增加。Nb、Ti固溶量分别在1 210 ℃和1 180 ℃以上趋于稳定;再加热温度在800~1 100 ℃时,以尺寸小于30 nm、分布较均匀的小粒子为主,呈球形,奥氏体晶粒尺寸在30 μm以下。再加热温度在1 180~1 210 ℃时,第二相粒子数量减少,尺寸多在100~200 nm之间,形态多为立方形和球形,奥氏体晶粒尺寸略微增加。随着再加热温度的进一步升高,析出粒子数量迅速下降,尺寸多为大于200 nm的方形粒子,此时奥氏体晶粒迅速长大至100 μm以上;析出粒子组成均为Nb、Ti复合的碳氮化物,其Nb/Ti原子比随温度升高而降低;试验钢的晶粒粗化温度为1 210 ℃,确定实际加热温度为1 180~1 210 ℃。     

Investigation on Metallurgical Factors Controlling Charpy Impact Toughness in 1Cr21Ni5Ti Duplex Stainless Steel

 Based on the fact that toughness degradation occurred in 1Cr21Ni5Ti duplex stainless steel during slow cooling in a temperature interval of 400-600 ℃ following brazed welding, a simulated embrittlement treatment was utilized to evaluate its embrittlement tendency. Accumulated experiences have shown that high Ti and Al contents led frequently to severe toughness deterioration. To elucidate this phenomenon, four heats with various Ti and Al contents were prepared in laboratory scale melts, which were used to investigate the inherent embrittlement nature. The results have shown that 550 ℃ aging led only to a modest toughness reduction, whereas, aging around 475 ℃ resulted in ferrite embrittlement, regardless of Ti, Al levels. However, high Ti, Al levels reduced the austenite phase, which, in the case of its inferior shape and distribution due to insufficient hot deformation, failed to resist cleavage type cracks initiated in the ferrite phase. Increasing hot forged areas reduction could modify the shape and distribution of austenite, resulting in the enhanced resistance of the austenite to the cleavage type cracks, which have been confirmed to be beneficial for brittlement suppression of 1Cr21Ni5Ti duplex stainless steel.     

Austenitization Behaviors of X80 Pipeline Steels With High Nb and Micro-Ti Treatment

 The austenitization behaviors of two high Nb-containing X80 pipeline steels with different Ti contents, including the dissolution of microalloying precipitates and the austenite grain growth behaviors, were investigated by using physical-chemical phase analysis method and optimal microstructure observation. The results illustrate that most Nb can be dissolved into austenite during the soaking at 1180℃, but very little amount of Ti can be dissolved. It is found that during soaking, the austenite grain growth rate is initially high, and then it decreases after 1h soaking; moreover, the austenite grains grow up more rapidly at temperatures above 1180℃ than at temperatures below 1180℃. It is shown that the steel with 0.016%Ti content has a larger austenite grain size than the steel with 0.012%Ti under the same soaking conditions, which has been explained by considering the particle size distribution.     

Ti/Al Interaction and Austenite Grain Control in Crankshaft Manufacturing with 38MnSiVS5 Steel

38MnSiVS5 steel is similar to 38MnVS6 steel (EN), the difference being the addition of a small Ti content. Typical Ti and Al contents in the chemical composition of 38MnSiVS5 steel are Ti=0.020 and Al=0.035 mass%. Both elements combine easily with nitrogen, especially Ti, and it has been observed that relatively high Al levels are harmful for austenite grain size control at reheating temperatures. In this work 38MnSiVS5 steel is used to manufacture a large number of castings, varying only the Ti and Al contents and obtaining ingots with a different Ti/Al ratio in each case. The results show that abnormal growth of the austenitic grain occurs irrespective of the Ti and Al contents, due fundamentally to the partial dissolution and coarsening of TiN precipitates. However, the steels with high Al contents present worse behaviour due to the formation of a second type of precipitates, namely AIN, which quickly dissolve between 1000 and 1100°C, causing a drastic decline in local pinning forces that gives rise to more pronounced abnormal growth of the affected grains.     

Nb(C,N)溶解对高铌奥氏体晶粒长大行为的影响

为了定量研究铌对高铌钢加热过程奥氏体晶粒长大的影响,采用化学溶解过滤分离及电感耦合等离子光谱测定不同加热温度两种试验钢固溶铌质量分数,并对比研究了奥氏体晶粒长大行为。结果表明,在低温条件下,低铌钢固溶铌质量分数高于高铌钢;随加热温度升高,高铌钢固溶铌质量分数快速增加,但即使在1 300 ℃时,铌也不能完成固溶,少量铌存在于(Ti,Nb)(N,C)析出相中;奥氏体晶粒快速长大的温度与固溶铌质量分数快速增加的温度有关。随铌质量分数由0.082%增加到0.120%,奥氏体晶粒快速长大的临界温度由1 050升高到1 150 ℃。高铌钢在1 150～1 250 ℃加热温度范围内,奥氏体晶粒尺寸小于100 μm。     

Investigation on the Effect of Sulfur and Titanium on the Microstructure of Lamellar Graphite Iron

The goal of this work was to identify the inclusions in lamellar graphite cast iron in an effort to explain the nucleation of the phases of interest. Four samples of approximately the same carbon equivalent but different levels of sulfur and titanium were studied. The Ti/S ratios were from 0.15 to 29.2 and the Mn/S ratios from 4.2 to 48.3. Light and electron microscopy were used to examine the unetched, color-etched, and deep-etched samples. It was confirmed that in irons with high sulfur content (0.12 wt pct) nucleation of type-A and type-D graphite occurs on Mn sulfides that have a core of complex Al, Ca, Mg oxide. An increased titanium level of 0.35 pct produced superfine interdendritic graphite (~10 μm) at low (0.012 wt pct) as well as at high-S contents. Ti also caused increased segregation in the microstructure of the analyzed irons and larger eutectic grains (cells). TiC did not appear to be a nucleation site for the primary austenite as it was found mostly at the periphery of the secondary arms of the austenite, in the last region to solidify. The effect of titanium in refining the graphite and increasing the austenite fraction can be explained through the widening of the liquidus-eutectic temperature interval (more time for austenite growth) and the decrease in the growth rate of the graphite because of Ti absorption on the graphite. The fact that Ti addition produced larger eutectic cells supports the theory that Ti is not producing finer graphite because of a change in the nucleation potential, but because of lower growth rate of the graphite in between the dendrite arms of a larger fraction of austenite. In the presence of high-Ti and S, (MnTi)S star-like and rib-like inclusions precipitate and act as nuclei for the austenite.     

�Ѻ������������ְ����徧���������������Ե�Ӱ��

The influence of heating temperature and holding time of different Ti content of microalloy high strength steel on austenite grain size and the influence of the precipitation characteristics on mechanical properties were quantificationally investigated through the methods of metallography, phase analysis and X-ray diffraction. The results show that, under the heating temperature of 1000-1150?? and the same soaking time,the steel B has small size of austenite grain. However when the temperature rises to 1150?? and above, austenite grain size in steel B increases fast, bulky containing Ti precipitates almost have no side effect on austenitic grain growth. With Ti content in steel increasing, MC precipitated phase in steel A and B respectively is 7. 5%, 159. 0% of the total M3C precipitated phase. When the ratio of MC/M3C increases, the corresponding strength of steel also increases. The mass fraction of less than 10nm precipitation phase in steel A and B is 2. 2% and 21. 7%.     

Effects of Ti and Nb on the Grain Refinement and Mechanical Properties of AISI 4145 Steel

In this study, we investigated the effects of Ti and Nb additions on the grain size of prior austenite and mechanical properties such as yield strength, yield ratio, and impact toughness in quenched and tempered AISI 4145 steel. It was found that the grain size of prior austenite directly influenced the mechanical properties. Thermodynamic calculations were carried out to find the characteristics of the precipitates such as dissolution temperature of precipitates, the average size of precipitate particles, precipitate fraction, and mean distance among precipitate particles, quantitatively. A specimen with low Ti content had a smaller Ti/N ratio than the stoichiometric ratio of 3.42 and showed an effective inhibition of grain growth of prior austenite, whereas a specimen with high Ti content showed a little effect to prevent the austenite grain growth compared with a Ti-free sample. Based on the thermodynamic simulation, the (Nb, Ti) (C, N) complex was precipitated and contributed to the inhibition of austenite grain growth, resulting in not only higher yield strength and yield strength/tensile strength ratio but also improved toughness.     

Mechanical Properties of TRIP Steel Microalloyed with Ti

The precipitation state, microstructure, retained austenite stability, and mechanical properties of cold-rolled Ti-microalloyed CMnAlSiP TRIP steel were investigated. The precipitation state was analyzed in each processing step by means of transmission electron microscopy, chemical analysis using the anodic dissolution method, and by model calculations. Ti additions refined the microstructure mainly by the pinning of austenite and ferrite grain boundaries by various Ti-containing precipitates. Ti additions also resulted in a refinement of the size of the retained austenite islands and caused a slight decrease of the volume fraction and carbon content of the retained austenite. The morphology of the retained austenite was also changed and the stability of the retained austenite decreased, but Ti addition still resulted in an adequate strength-ductility balance and a tensile strength close to 1 GPa.