低碳铝镇静钢中AlN的沉淀析出

 利用热处理和化学相分析对薄板坯连铸连轧低碳铝镇静钢中AlN的沉淀析出行为进行了试验研究。结果显示,在薄板坯连铸连轧的低碳铝镇静钢中仅有很少量的氮被固定为AlN,大部分氮仍为自由氮,其原因是在薄板坯连铸连轧流程中的连铸出坯、均热、连轧和层流冷却等阶段,AlN在钢中很少沉淀析出。在热轧钢板卷取后的缓慢空冷过程中可以沉淀析出少量的AlN,这些AlN不能起到细化晶粒的作用。     

薄板坯连铸连轧低碳铝镇静钢中酸溶铝的作用研究

对薄板坯连铸连轧低碳铝镇静钢中酸溶铝的作用进行了研究.研究结果显示,对于薄板坯连铸连轧流程生产的低碳铝镇静钢,当钢中酸溶铝的质量分数在0.005%～0.043%时,酸溶铝对热轧板材的晶粒度及力学性能没有明显影响,但是对热轧板材再加热时的晶粒长大却有明显影响,随钢中酸溶铝含量的增加,钢的晶粒粗化温度不断提高.因此对于那些不需要强调焊接性能的普通热轧钢板,w(Als)可以控制在0.01%左右;对于那些需要强调焊接性能和某些特殊性能的钢板将w(Als)控制在0.02%～0.04%比较合适.     

薄板坯连铸连轧流程低碳Al镇静钢组织细化原因探讨

研究了薄板坯连铸连轧流程生产的低碳Al镇静钢普遍存在的组织偏细,强度偏高的问题。研究结果表明,薄板坯连铸出坯后已有AlN沉淀析出,经均热1 423 K×30 min后仍有约30×10-6AlN未溶解。这些AlN微细沉淀对抑制奥氏体再结晶晶粒长大、抑制相变铁素体晶粒长大起到一定作用,使钢带组织细化;另外,薄板坯连铸连轧流程轧后冷却段长度偏短,冷却强度偏高也是造成组织细化,强度偏高的主要原因。     

硼对低碳铝镇静钢中AlN、MnS析出的影响

通过实验室模拟薄板坯连铸连轧(TSCR)流程实验,研究了向低碳铝镇静钢中加入质量分数为3.0×10-3%的微合金元素B对AlN、MnS在连铸连轧过程中析出的影响.结果表明:微合金元素B可以在高温奥氏体中优先与自由N结合形成粗大BN颗粒,且常与MnS复合析出,抑制了细小AlN的析出,减少了钢中细小AlN的含量.     

薄板坯连铸连轧流程低碳铝镇静钢组织细化的原因

薄板坯连铸连轧流程生产的低碳Al镇静钢普遍存在组织偏细，强度偏高的现象，这为高强度带钢生产提供了有利条件，但也为冷轧基料生产带来了一定的困难。国内外已对薄板坯连铸连轧流程生产的低碳Al镇静钢组织细化原因进行了大量的分析和研究，得到了一些认识。本研究表明，薄板坯连铸出坯后已有AIN沉淀析出，经均热后仍有约0．0030％的AIN未溶解。这些AIN微细沉淀对抑制奥氏体再结晶晶粒长大、抑制相变铁素体晶粒长大起到一定作用，使钢带组织细化；另外，薄板坯连铸连轧流程轧后冷却段长度偏短，冷却强度偏高也是造成组织细化，强度偏高的主要原因。     

薄板坯流程连铸连轧过程中的细晶化现象分析

研究了薄板坯连铸连轧工艺的铸坯凝固组织特征和钢带的组织演变规律。通过化学相分析、微观组织分析研究发现，微细AIN粒子在薄板坯连铸过程中可沉淀析出，铸坯经20～30min均热后AIN仅部分溶解。对AIN析出的热力学和动力学分析也证实了AIN在铸坯上沉淀析出的合理性。这些在连轧开始前原始奥氏体中析出的AIN沉淀是抑制变形奥氏体再结晶晶粒长大，细化奥氏体组织，并最终使钢带组织细化的主要原因；同时，薄板坯连铸连轧流程冷却辊道短、冷却强度大等因素也是导致薄板坯连铸连轧过程中Al镇静钢组织细化的主要原因。     

低碳铝镇静钢热轧板表面夹渣的原因分析与控制

通过低碳铝镇静钢热轧板表面夹渣的调查,分析了经LF精炼、中薄板坯连铸生产的低碳铝镇静钢热轧板表面夹渣形成原因。通过炼钢和LF精炼生产工艺优化,降低钢中T.O含量;通过提高连铸中包耐材品质、减少二次氧化、稳定钙处理效果;通过浸入式水口结构改进和保护渣性能的优化,解决了稳态浇铸时结晶器卷渣及其导致的热轧板表面夹渣问题。     

低温高磁感取向硅钢连铸与均热过程AlN与MnS析出的热力学

针对薄板坯连铸连轧流程结合"获得抑制剂法"所制备的低温高磁感取向硅钢,通过热力学计算研究了AlN与MnS在连铸与均热过程中的析出规律与行为。计算结果表明,连铸过程中AlN在凝固后的高温α相中便可能析出,而MnS仅可能在凝固后的α+γ两相区内析出。钢中AlN与MnS在均热过程中均处于部分固溶与部分析出的状态。后续高温渗氮处理后初次晶粒的异常长大并不明显,表明渗氮处理前钢中固有抑制剂的数量相对充足。     

硼对低碳铝镇静钢中AIN、MnS析出的影响

通过实验室模拟薄板坯连铸连轧(TSCR)流程实验,研究了向低碳铝镇静钢中加入质量分数为3.0×10-3%的微合金元素B对A lN、MnS在连铸连轧过程中析出的影响.结果表明:微合金元素B可以在高温奥氏体中优先与自由N结合形成粗大BN颗粒,且常与MnS复合析出,抑制了细小A lN的析出,减少了钢中细小A lN的含量.     

硼对薄板坯连铸连轧低碳深冲钢板织构的影响

以薄板坯连铸连轧(CSP)工艺下生产的含B和无B低碳热轧、罩式退火板为实验材料,研究了B对低碳深冲钢板织构的影响.利用电解化学相分析、内耗和拉曼实验等方法和结果,从化学成分、析出物两个方面对热轧、退火板中织构的形成与发展进行了系统分析.结果表明:无B热轧板的AlN含量比含B热轧板中的高,后者的织构优于前者;退火板中含B钢和无B钢中AlN含量几乎相等,然而无B退火板织构优于含B退火板的.AlN不是影响织构发展的唯一决定因素,B、BN也会影响织构的发展.     

酸溶铝对罩退IF钢组织和性能的影响

作为重要的脱氧元素,铝质量分数对低碳铝镇静钢中的夹杂物数量和产品性能有重要影响。对工业生产中的罩退Ti- IF钢中酸溶铝(自由铝)质量分数变化(范围为0.0050%~0.0550%)对成品性能的影响进行了研究,对最终产品进行单轴拉伸和光学显微组织观察,发现与低碳铝镇静钢不同,除了屈服强度微小波动外,酸溶铝质量分数对罩式退火的Ti- IF钢的其他力学性能没有显著影响,退火后的组织呈现等轴状,晶粒度级别在9.0~9.5之间,成品均表现出良好的力学性能和成形性能。     

Low carbon manganese steels microalloyed with vanadium and nitrogen

With the objective of studying the effect of vanadium and nitrogen microalloying on microstructure and strength of low carbon steels with different manganese contents, three series of low carbon steels (0.1% C) with manganese content (between 0.8 and 3.5%), vanadium content (up to 0.17%) and nitrogen content (up to 0.025%) have been designed and investigated in the hot forging condition using a preheating and finish forging temperatures of 1200 and 950°C, respectively. Steels with a manganese content up to 2.3% revealed ferrite-pearlite structures, whereas higher manganese contents from 2.7 to 3.5% resulted in the formation of bainitic structures. A pronounced effect of manganese on the mechanical properties of steels was detected at lower manganese contents < 1.5%, due to solid solution and grain refining effects, and higher manganese contents > 2.3, due to bainite formation. Manganese content in the range of 1.5-2.3% had less pronounced effect due to solely solid solution hardening. Vanadium microalloying effectively increased the strength of steels through solely precipitation strengthening or both precipitation strengthening and grain refining effect. The effectiveness of vanadium was greatly enhanced by increasing the nitrogen content. The grain refinement of vanadium-nitrogen microalloying seems to be due to inhibition of austenite grain growth as a result of precipitation of vanadium nitride in austenite during forging. Precipitation strengthening of these steels is achieved by precipitation of vanadium carbide and nitride in ferrite or bainite. Nitrogen enhanced the precipitation strengthening of vanadium microalloyed steels which could be attributed to the finer vanadium nitride dispersion precipitates compared with vanadium carbide. Up to 70% of the total nitrogen content of steel precipitates as vanadium nitride which could be achieved with V/N ratio of about 6-7. Microalloying of low carbon-manganese steels (0.1% C and 1.8% Mn) with 0.15% vanadium and 0.025% nitrogen was found to be effective in attaining high levels of yield and ultimate tensile strengths of 835 and 940 N/mm², respectively in the forging condition.     

Metallurgical Interpretation on Grain Refinement and Synergistic Effect of Mn and Ti in Ti-microalloyed Strip Produced by TSCR

The grain refinement mechanism and synergistic effect of Mn and Ti involved in the Ti-microalloying technology of thin slab casting and direct rolling （TSCR） were elucidated. Because the inevitable precipitation of TiN in high Ti-containing liquid steel decreases the volume fraction of TiN precipitated from austenite and the rapid coarse- ning rate leads to a large size of TiN particles, a relatively weak inhibition effect on the recrystallized grain growth was obtained compared with that in the low Ti-containing steel. However, the ferrite grain size in high Ti-containing steel can be refined by the so-called non-recrystallization rolling. The complex addition of Mn and Ti can improve the strength and toughness of strip remarkably, and the mechanisms are that Mn decreases the transformation tempera- ture, refines the ferrite grains, and enhances the formation of bainite and TiC precipitation in ferrite.     

薄板坯连铸连轧生产冷轧基板的工艺与组织性能分析

比较分析了薄板坯连铸连轧的工艺特征,轧制工艺特点及板坯热历史,第二相粒子的析出行为,传统流程与TSCR流程中低碳钢的组织、析出、位错、性能差异等,结合薄板坯连铸连轧生产低碳钢板力学性能的生产统计结果实例,提出了冷轧冲压板用热轧基板的成分和性能要求及解决的途径,并给出了在CSP线上进行冷轧基板的冶金成分与工艺控制的生产性试验的初步结果.     

微钛固氮降低含铌钢皮下裂纹敏感性的机理

 降低含铌低合金钢铸坯的裂纹敏感性,是实现热装热送工艺的必要条件,采用超高温激光共聚焦显微镜(HT-CLSM)、透射电镜(TEM)等手段研究了钛含量不同的含铌低合金钢(Q390、Q390GJD)高温铸坯的晶粒度及析出物特征,旨在揭示微钛固氮降低含铌钢皮下裂纹敏感性的机理。热力学计算与TEM检测结果表明,增加钢中钛质量分数(由0.010%上升到0.023%)提高了氮化钛粒子的析出温度(大于1 400 ℃),高温析出细小弥散的氮化钛粒子可钉扎奥氏体晶界,细化高温铸坯的晶粒度(由4级变成6.5级),晶粒尺寸降低了约44%,使高温铸坯的裂纹敏感性明显降低;氮化钛粒子优先析出固氮降低了铌碳氮化物、氮化铝的开始析出温度,并作为异质形核核心,抑制了铌、铝析出物在晶界析出概率,降低了析出物脆化晶界的危害。通过微钛固氮调控氮化物的析出温度、析出位置及细化晶粒的作用,有效降低了含铌钢第三脆性温度槽的宽度和深度,同时,高温抗拉强度提高了21.3%~27.5%,铸坯皮下裂纹发生率降低了80%以上。为了避免析出物的晶界链状析出导致含铌钢铸坯热装轧制裂纹,应将其钛质量分数控制在0.015%~0.020%的合理范围。     

Influence of base composition on the strength of vanadium-microalloyed steel bars

In this work, the effect of base composition on the strength of hot-rolled V-microalloyed steel bars was studied. Industrial heats with a wide range of carbon contents from 0.15 to 0.3% and manganese contents from 0.65 to 1.3% in combination with V-microalloying up to 0.1%, were carried out. The grain size of the produced hot rolled steel bars was measured and the different strengthening mechanisms were analysed. Carbon and manganese were found to have pronounced effect on refining the microstructure. Vanadium-micraolloying up to 0.1% has a slight grain refinement. This slight grain refinement effect of vanadium decreases with increasing the carbon content. The strengthening potential of vanadium seems to be due to precipitation strengthening rather than grain refinement effect. Both carbon and manganese in combination with vanadium showed a significant effect on increasing the precipitation strengthening. The vanadiumprecipitation strengthening is correlated with carbon and manganese contents. Two modified equations are derived to predict the yield strength of hot-rolled steel bars, in terms of chemical composition and grain size or only chemical composition.     

CSP流程中B对低碳Al镇静钢组织及力学性能的影响

研究了B元素对CSP流程生产的低碳Al镇静钢热轧钢带的组织及力学性能的影响,探讨了B元素在CSP流程中的析出规律及对AlN和MnS析出行为的影响.试验结果表明:B元素能够起到使钢带组织软化的作用.在连铸过程中B与N结合形成粗大的BN粒子,减少了钢中固溶氮的质量分数,抑制AlN细微颗粒的析出,减少了铁素体组织细晶强化及AlN析出强化的作用,从而降低了材料的强度.     

珠钢电炉-薄板坯连铸连轧流程VN微合金钢组织性能研究

阐述了珠钢电炉-薄板坯连铸连轧流程VN微合金钢钒的析出规律、微观组织特征和强化机理。研究表明：在电炉-薄板坯连铸连轧流程采用VN微合金化,铸坯中析出以钒（C,N）为主,并有少量TiN或（Ti,V）（C,N）复合析出,平均粒度大约为40nm,热连轧开始前铸坯中大量存在的钒（C,N）能够抑制后续热连轧过程中变形奥氏体再结晶晶粒长大,使铁索体组织超细化;强化机制以细晶强化为主、沉淀强化为辅;采用VN微合金化技术开发的550MPa级VN微合金钢组织细化至3．0—4．0μm,产品具有良好的综合性能。