硫化物形态对超高强度钢冲击韧性的影响

本文对比分析了"真空感应+真空自耗重熔"和"电弧炉+VOD+真空自耗重熔"两种工艺冶炼的超高强度G50钢力学性能.利用扫描电镜和能谱分析等检测手段研究了不同冶炼工艺生产的G50钢中夹杂物类型和尺寸分布.研究结果表明:电弧炉+VOD+真空自耗重熔工艺冶炼的G50钢横向和纵向冲击韧性分别相对"VIM+VAR"工艺得到很大的改善,各向均匀性得到改善.电弧炉+VOD+真空自耗重熔工艺冶炼的G50钢中夹杂物颗粒状和椭圆形弥散均匀分布,阻碍空洞合并,导致冲击性能尤其是横向冲击性能得到极大的改善.     

真空感应炉脱硫工艺试验

在真空感应炉中冶炼超洁净钢种,硫含量的控制是一个难点。本文设计了四种不同的冶炼方案,研究了脱硫渣成分配比、脱硫渣量、精炼参数、钢液中的碳含量、脱硫渣的加入时间等因素对钢液中硫含量的影响。结果表明,将1000 g含Ca O、Ca F2各50%的脱硫渣随炉加入坩埚内,选择合适的精炼参数,在允许的范围内提高钢液中的碳含量,钢液的脱硫率可达80%以上。     

真空感应炉冶炼GH3030氧、氮含量控制工艺

试验研究了80kg真空感应炉冶炼GH3030氧、氮含量控制工艺。本文设计了三种不同的冶炼方案,研究了精炼参数、脱氧剂碳、返回料的种类及其添加比例等因素对GH3030液中氧、氮含量的影响。结果表明,将0.08%(质量分数)脱氧剂碳和3kg返回料随原料加入炉内,熔化后在精炼真空度为30Pa、精炼温度为1510℃下精炼15分钟,GH3030液中氧可控制到16ppm,氮可控制到7ppm;锯屑对GH3030液中氧、氮含量的不利影响要大于刨屑及冒口。     

真空感应炉冶炼焊丝钢Mn含量控制工艺

实验研究了150 kg真空感应炉冶炼焊丝钢Mn含量控制工艺。本文设计了四种不同的冶炼方案,研究了Mn合金加入前炉内压力及钢液温度、随炉C量、返回料的使用对Mn收得率的影响情况。结果表明,随炉C量为0.08%(质量分数)且Mn在炉内压力为20000 Pa、钢液温度为1570℃的条件下加入收得率可达98.3%;纯返回料冶炼,返回料中Mn的收得率可达96%。     

浅析低合金低硅钢Si的控制

简要分析了低合金低硅钢生产过程钢水增硅的原因；较为深入的研究．论述了减少和防止低硅钢生产过程增硅的原理，从转炉冶炼、挡渣出钢、顶渣改质、脱氧合金化方式、LF精炼工艺及连铸中包排渣等方面，详细制定了防止钢水增硅的措施，形成了一套较为完整的低硅钢硅含量控制的工艺。结合了工厂的实际，满足了钢种的要求，取得了满意的效果。     

RH精炼开发冷轧用超低碳钢的技术革新

对于精炼能力不足的炼钢厂，采用RH真空单重精炼工艺替代双重精炼工艺，具有积极意义。但是和RH＋LF或LF＋RH双重精炼工艺不同，采用RH真空单重精炼工艺开发冶炼冷轧超低碳钢，主要难点在于钢中夹杂物控制，控制不恰当会严重影响浇铸性能。使用适量铝渣作为顶渣改质剂和优化RH真空炉的过程控制．取得较好效果。     

真空冶炼提高马氏体时效钢的韧性

马氏体时效钢的韧性随其强度的提高而下降。本文着重研究影响马氏体时效钢韧性与塑性下降的因素,也研究了真空感应冶炼、真空电弧重熔与电子束精炼工艺对排除马氏体时效钢中杂质的影响。研究结果表明,间隙元素C、S、N、O与其它杂质元素对马氏体时效钢的韧性与塑性的影响很大。马氏体时效钢中Ti(C、N)含量的增加会降低其断裂韧性与面缩率。真空感应冶炼加真空电弧重熔不仅能准确地控制马氏体时效钢中的化学成分,还能有效地排除其中有害杂质元素。电子束重熔工艺能更有效地排除马氏体时效钢中锑、铅、锡及其它杂质元素,也能进一步脱除马氏体时效钢中的碳与氧含量,因此能提高马氏体时效钢的断裂韧性与塑性。     

上钢五厂开发桶式真空钢包炉精炼不锈钢技术

为了适应钢材市场变化的需要和探索生产超低碳不锈钢的新工艺，我厂经过多年的努力，在桶式结构的40t真空钢包炉上加装了拉瓦尔水冷氧枪，摸索出一套真空精炼工艺，开发了桶式真空钢包炉精炼不锈钢的技术，生产了200多炉低碳和超低碳不锈钢（包括超纯工业纯铁），取得了明显的效益。在保证冶炼效果和经济效益的前提下，冶炼不锈钢时，对初钢液条件、真空降碳保铬等工艺制度进行了合理的选择和控制，并采取了相应的辅助措施，使真空吹氧脱碳时的钢液喷溅得到有效控制。在不具备真空测温和真空取样装置的条件下，采用氧浓差电势仪、炉气温度变…     

标准化纵横谈

标准先进性刍议人们一般认为 ,一个标准是否先进 ,主要看技术指标的高低 ,这话似乎很有道理 ,很少有人怀疑过它还有什么不足之处。如钢中硫磷含量 ,按钢类或用途不同 ,大致分为四类 :普通钢 ,硫磷上限约为 0 0 4～ 0 0 5 % ;优质钢 ,约 0 0 3 5～0 0 4% ;高级优质钢 ,约 0 0 2 5～ 0 0 3 5 % ;超高级优质钢 ,通常采取炉外精炼 ,使硫磷减少到双零几以下。从此例中得出一条启示 ,指标高低首先决定于钢的用途 ,而要达到各等级硫磷含量水准 ,必须采取不同的工艺或工艺手段 ,甚至采用不同的原材料和燃料。每吨钢的成本随着硫磷含量的减少而…     

H08A焊接用钢圆盘条生产与实践

重钢采用转炉冶炼,150mm×150mm小方坯连铸,高速线材轧机轧制工艺试制了H08A焊接用钢圆盘条.通过4000多吨H08A焊接用钢圆盘条的生产实践,成品焊条质量符合标准及用户要求.     

A medium-Mn steel processed by novel twin-roll strip casting route

A medium-Mn steel (Fe–0.3C–4Mn–1.82Al–0.6Si wt-%) was produced by a novel processing route involving twin-roll strip casting, hot rolling and intercritical annealing (IA). Macrosegregation was absent in the as-cast strip. The microstructure of the as-cast strip consisted of martensite and austenite (～10 vol.-%), and the solidification structure was characterised by dendritic structure. With an increase in IA temperature from 680 to 725 and to 755°C, austenite fraction in intercritically annealed steels was increased from 22 to 45% and then decreased to 27%. The 710°C intercritically annealed steel yielded excellent mechanical properties with a tensile strength of ～1007?MPa and total elongation of ～48%, achieved by a high volume fraction of austenite (～42%) with appropriate mechanical stability.     

Mikrostruktur und mechanische Eigenschaften der reibgeschweißten γ‐TiAl‐Feingusslegierung Ti‐47Al‐3.5(Mn+Cr+Nb)‐0.8(B+Si)

Microstructure and mechanical properties of friction welded γ‐TiAl based alloy Ti‐47Al‐3.5(Mn+Cr+Nb)‐0.8(B+Si) in investment cast condition. This paper describes properties of joints produced by friction welding of the intermetallic γ‐TiAl based alloy Ti‐47Al‐3.5(Mn+Cr+Nb)‐0.8(B+Si) in investment cast and hot‐isostatically pressed condition. The effect of friction welding parameters on microstructure and local properties are examined and discussed. It is found that the properties of the joint are essentially affected by properties of as‐cast Ti‐47Al‐3.5(Mn+Cr+Nb)‐0.8(B+Si) base material, both at room temperature and 700 °C.     

Slurry Preparation and Rolling of Semi-solid 60Si2Mn Spring Steel

The nondendritic semi-solid slurry preparation of 60Si2Mn spring steel has been studied in this paper. The experiments have shown that when stirred for 2 min on the test condition, the semi-solid slurry with 50%～60% fraction solid and spherical primary austenitic grains in the size of 100～300μm can be obtained and is easy to be discharged from the bottom little hole of the stirring chamber. The nondendritic slurry of 60Si2Mn spring steel can be rolled into given plate form successfully, but the solid phase and liquid phase is easy to be separated in rolling process so that the solid primary austenite is concentrated in the center and the liquid is near the edge of the rolled plate. The rupture strength and elongation of the plate rolled only once with semi-solid slurry are lower than that of the traditionally repeated hot-rolled plate of 60Si2Mn spring steel.     

Removal of low-volatile impurities from magnesium by sublimation

The sublimation refining of magnesium with initial Fe, Ni, Cu, Si, and Al contents from ～10^?3 to 10^?2% at temperatures from 700 to 800 K with a 80% degree of distillation reduces the impurity concentrations by one to two orders of magnitude in the first process and by an additional order of magnitude in a second cycle. The effective separation factor α found using the main distillation equation is on the order of 10 for the impurities and processes in question.     

ZG 1Mn19Ni3Al 铸焊结构低温性能研究

通过化学成分设计和金相组织设计，开发了一种适用于与１６Ｍｎ钢组成铸焊结构的新铸钢ＺＧ１Ｍｎ１９Ｎｉ３Ａｌ。研究了这两种材料组成的焊板在常温、低温（－１９６℃）下的力学性能和冲击断口形貌。试验结果表明，夹杂物和焊接线能量对其低温冲击韧性有着显著的影响。具有γ＋ε双相组织的ＺＧ１Ｍｎ１９Ｎｉ３Ａｌ钢用于低温（－１９６℃）铸焊结构中时要注意钢水精炼和采用适当的焊接线能量     

Characterization of steel mill electric-arc furnace dust

In order to make a complete characterization of electric-arc furnace (EAF) dust, as hazardous industrial waste, and to solve its permanent disposal and/or recovery, bearing in mind both the volumes formed in the Croatian steel industry and experiences of developed industrial countries, a study of its properties was undertaken. For this purpose, samples of EAF dust, taken from the regular production process in the Zeljezara Sisak Steel Mill between December 2000 and December 2001, were subjected to a series of tests. The chemical composition of EAF dust samples was investigated by means of a several different analytical methods. The results from the chemical analysis show that the approximate order of abundance of major elements in EAF dusts is as follows: Fe, Zn, Mn, Ca, Mg, Si, Pb, S, Cr, Cu, Al, C, Ni, Cd, As and Hg. Granular-metric composition of single samples was determined by applying sieve separation. Scanning electron micro-structural examination of EAF dust microstructure was performed and results indicated that all twelve EAF dusts were composed of solid spherical agglomerates with Fe, Zn, Pb, O, Si and Ca as the principal element. The investigation of grain morphology and the mineralogical composition of EAF dust were taken by combination of high resolution Auger electron spectroscopy (HR AES), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction analysis. The analysis of XPS-spectra determined the presence of zinc in the form of ZnO phase and the presence of lead in the form of PbO phase, i.e. PbSO3/PbSO4 forms. The results of the X-ray diffraction phase analysis show that the basis of the examined EAF dust samples is made of a mixture of metal oxides, silicates and sulphates. The metal concentration, anions, pH value and conductivity in water eluates was determined in order to define the influence of EAF dust on the environment.     

45Mn17Al3低磁钢焊接特性及工艺研究

针对45Mn17Al3低磁钢与其焊接材料合金系性能差异较大的特点,对手工电弧焊、脉冲MIG焊、陶瓷衬垫焊焊接特性进行分析,改进了焊接工艺,为低磁钢焊接材料的工程应用提供了试验依据.     

Enhancement of mechanical properties of Al–Mg–Si alloys by means of manganese dispersoids

Abstract

The effects of Mn dispersoids on the enhancement of mechanical properties in Al–Mg–Si(–Mn) alloys have been studied to develop a new high Mn alloy which does not need an aging heat treatment after a shaping process (i.e. extrusion process). By adding Mn to Al–Mg–Si alloys, sphere- or rod shaped Mn dispersoids of a size ranging from 0·05 to 0·5 μm are formed by the use of proper heat treatments. The as extruded alloys containing 1·0 wt-%Mn are measured to have higher tensile properties with good ductility, as compared with those of the commercial Al alloy 6N01 (Al–0·69Mg–0·79Si–0·48Cu–0·27Zn–0·37Mn–0·3Cr– 0·11Ti, wt-%). These phenomena are obtained from the dispersion hardening effect and homogeneous deformation by Mn dispersoid particles acting as obstacles to dislocation movement. Comparing the fatigue crack growth behaviour between the high Mn alloys and the commercial 6N01 alloy in the as forged condition, high Mn alloys are shown to have higher fatigue crack growth resistance and show a more tortuous crack path. This result can be explained by the increasing energy absorption through crack deflections and tortuous crack paths by the Mn dispersoids.     

Influences of Nb-microalloying on microstructure and mechanical properties of Fe–25Mn–3Si–3Al TWIP steel

The Fe–25Mn–3Si–3Al TWIP steel was microalloyed by niobium in this paper, and the appropriate heat treatment and cold rolling processes were drafted in order to improve the poor yield strength of the steel. The results show that the yield strength of the steel increases from 320 MPa to 445 MPa, and the tensile strength increases from 680 MPa to 795 MPa, but the uniform elongation decreases from 65% to 55%. Nb addition can strongly hinder the growth of recrystallized grains, moreover Nb atoms react with C atoms to form nanoscale NbC precipitations, and these precipitations can block the dislocation motion, and then the yield strength and initial work hardening ability of Fe–25Mn–3Si–3Al steel is clearly improved. Furthermore, the strain-induced twinning is still a major deformation mechanism for the Nb-microalloying TWIP steel, and the twinning induced plasticity (TWIP) effect ensures a satisfactory ductility for the steel. Finally, the modified TWIP steel obtains a better match between the strength and plasticity by the joint action of precipitation strengthening and TWIP effect.     

Continuous cooling transformation behaviour of Si–Mn and Al–Mn transformation induced plasticity steels

Abstract

The continuous cooling transformation (CCT) behaviour of two transformation induced plasticity (TRIP) steels was investigated using quench dilatometry. One was an established steel grade with a composition (wt-%) of Fe–0·2C–2Si–1·5Mn while the other steel was a novel composition where 2 wt-% Al replaced the silicon in the former grade. Characteristics of the α→γ transformation during reheating and the subsequent decomposition of austenite during continuous cooling were studied by dilatometry, and CCT diagrams were constructed for both steels. The effects of accelerated cooling and steel composition on γ transformation start temperature Ar ₃, phase transformation kinetics, and microhardness were investigated. The results showed that the Al–Mn steel had a much wider α→γ transformation range during reheating, compared with the Si–Mn steel. Furthermore, the Al–Mn steel exhibited no significant change in the rate of expansion during α→γ transformation. On the other hand, during continuous cooling, the Al–Mn steel exhibited higher Ar ₃, faster transformation kinetics, a higher volume fraction of polygonal ferrite in the microstructure, and lower hardness, compared with the Si–Mn steel. The addition of aluminium was found to have a significant effect on the products of phase transformation, kinetics, and form of the CCT diagram. For both steels, an increase in cooling rate lowered the Ar ₃ temperature, decreased the time of transformation, and increased the hardness.