Slab cracking after continuous casting of API 5L X-70 grade steel for pipeline sour gas application

Abstract

An API 5L X-70 grade steel for large diameter pipeline application with sour gas resistance was developed. The resulting Fe–C–Mn–Nb slabs were controlled rolled and accelerated cooled. In most of the slabs, mechanical properties equivalent to the above grade were broadly achieved. However, despite achieving excellent mechanical properties, during the test period, several slabs exhibited cracks in the cooling yard, causing their rejection. To elucidate the nature of the crack, several specimens were analysed by employing optical, scanning electron, and transmission electron microscopy. Microstructural characterisation together with microanalysis and thermal analysis carried out on as cast specimens showed the presence of rodlike and/or dendritelike precipitates of the Fe₂ Nb type associated with the cracks. The elimination of the cracks was achieved by increasing the niobium content in the Nb ferroalloy to ensure its dissolution in the liquid bath after its addition during the alloying stage.     

Effect of heat input on microstructure and mechanical properties of dissimilar joints of AISI 316L steel and API X70 high-strength low-alloy steel

The microstructure and mechanical properties of dissimilar joints of AISI 316L austenitic stainless steel and API X70 high-strength low-alloy steel were investigated.For this purpose,gas tungsten arc welding(GTAW)was used in three different heat inputs,including 0.73,0.84,and 0.97 kJ/mm.The microstructural investigations of different zones including base metals,weld metal,heat-affected zones and interfaces were performed by optical microscopy and scanning electron microscopy.The mechanical properties were measured by microhardness,tensile and impact tests.It was found that with increasing heat input,the dendrite size and inter-dendritic spacing in the weld metal increased.Also,the amount of delta ferrite in the weld metal was reduced.Therefore,tensile strength and hardness were reduced and impact test energy was increased.The investigation of the interface between AISI 316L base metal and ER316L filler metal showed that increasing the heat input increases the size of austenite grains in the fusion boundary.A transition region was formed at the interface between API X70 steel and filler metals.     

铈对5CrNiMo模具钢力学性能的影响

通过研究在5CrNiMo模具钢中添加不同量稀土Ce后的强度、塑性和弹性模量的变化,对5CrNiMo模具钢的低周疲劳寿命进行了估算.结果表明:稀土Ce添加量在适当的范围内可显著提高强度和塑性,并且当稀土Ce添加量为0.20%(质量分数)时,5CrNiMo钢的强度、塑性达到最好,比不添加稀土Ce的5CrNiMo钢在相同断裂循环数N′f=100时,总应变范围ΔεT提高61.2%.     

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.     

Influence of dynamic austenite decomposition on the microstructure and mechanical properties of pipe steel

The influence of deformation-induced ferrite transformation on the microstructure of microalloyed pipe steel is investigated by means of a Gleeble 3800 test system. The results show that such dynamic transformation permits considerable reduction in ferrite grain size and improves the mechanical properties of the steel.     

Effect of structural anisotropy of ferrite-bainite pipe steel on mechanical properties in tensile and impact bending tests

Metallurgist - The mechanical properties of thick rolled plate for main pipelines with a ferrite-bainite microstructure in different directions over the plate plane are determined, mechanical...     

稀土La对5CrNiMo模具钢力学性能的影响

研究了加入稀土La后5CrNiMo钢的强度、硬度、冲击韧性变化;并在相同热处理工艺条件下,与不添加稀土La的5CrNiMo钢进行对比.结果表明:稀土La加入量在适当的范围内可显著提高钢的强度、硬度和冲击韧性;当稀土La质量分数为0.033%时,5CrNiMo钢可获得最好的综合力学性能.     

冷却工艺对汽车大梁钢510L组织性能的影响

对汽车大梁钢510L进行了实验室热轧试验,研究了轧后冷却工艺变化对试验钢组织和力学性能的影响.结果表明,在轧后4种不同的冷却模式中,超快冷-层流冷却模式所获得的组织最为细小,强度最高.在层流冷却-空冷-层流冷却模式下,随着卷取温度的降低,抗拉强度显著提高,屈强比降低,可实现510L的升级轧制.     

Effect of prestrain on the mechanical properties of eutectoid steel

This investigation was designed to study the effect of prior compressive deformation and temperature on the subsequent dynamic fracture toughness, K,_Id, of fully pearlitic 1080 rail steel. Charpy instrumented impact tests on precracked specimens were performed at room temperature at a variety of prior strain levels from 0 to 20 pct. In addition, transition temperature tests were performed on specimens of zero, low (5 to 10 pct), and high (15 to 20 pct) prior strains. Dynamic fracture toughness (K,_Id) and energy absorbed per fractured area (W/A) were obtained from instrumented impact data. It was found that, at room temperature, compressive strain had no effect on either K_Id or W/A. In the transition temperature range, W/A decreased with increasing prior strain, while there was no effect on K_Id. At temperatures in the upper shelf region, prior strain decreased both K,_Id and W/A. There was no effect on the transition temperature as the amount of prior strain was increased. Thus, while both dynamic fracture toughness and impact properties can be significantly changed by varying temperature, cold working the material has at best a modest effect on impact energy and then primarily only in the upper shelf region.     

Influence of ladle-treatment temperature on melt properties and the mechanical characteristics of steel in hot-deformed pipe

The influence of the treatment temperature for 20XMΦA and 20A steel in a ladle-furnace unit on the kinematic viscosity of the melt and the mechanical properties of the pipe metal is investigated.     

Effect of silicon additions on the mechanical properties of eutectoid steel

Tensile, impact and fatigue strengths of 0%, 2% and 4% silicon steels of eutectoid compositions have been determined using standard testing methods. Tensile and impact strengths tests show an increase in brittleness (loss in elongation) and an increase in yield point, tensile strength and fatigue strength due to Si additions.     

配分时间对低碳热轧F-Q&P钢组织性能的影响

摘要：基于合金减量化原则,热轧后采用以超快冷技术为核心的两相区弛豫 淬火配分（F-Q&P）工艺技术,借助OM、SEM、TEM、XRD和室温拉伸等试验手段,研究了配分时间对试验钢组织性能的影响。研究表明：随着配分时间延长,铁素体体积分数逐渐增加,残余奥氏体含量先增加后降低,马氏体的体积分数逐渐减小;抗拉强度降低,伸长率增加,强塑积增加,屈强比较低为0.55～0.60,n值较高为0.14～0.18。配分时间对各相的体积分数、形貌、分布和析出行为有影响。30s配分的试验钢,组织中较多的细长条马氏体、细小铁素体和薄片状残余奥氏体提高了材料的位错密度和均匀变形能力,表现出最优的综合性能。     

Ti对高强耐候钢力学性能的影响

通过光学显微镜、透射电镜（TEM）以及力学性能测试等手段分析了薄板坯连铸连轧（TSCR）工艺生产Ti微合金化高强耐候钢的成分及工艺对显微组织和力学性能的影响．研究结果表明：钢中加入Ti,屈服强度有明显的提高;钛质量分数为0．05%～0．08%时,高强耐候钢的晶粒尺寸随着钛含量的增加基本不变;高强耐候钢强度的提高主要取决于钢中有效钛的含量,有效钛不仅与钛的含量有关。而且还与S,N的含量有关;在有效钛含量一定的条件下,析出强化的大小主要取决于轧后的卷取温度．     

热处理工艺对27SiMn钢力学性能的影响

27SiMn液压支架管经过调质热处理来实现其良好的综合力学性能.采用四因素三水平的热处理正交试验,研究了不同热处理工艺参数（淬火温度、淬火保温时间、回火温度和回火保温时间）对力学性能的影响,并确定了最优热处理工艺制度为930℃,40 min淬火和480℃,50 min回火.经最优热处理工艺处理后,其力学性能为：屈服强度895 MPa,抗拉强度1030MPa,伸长率15%,断面收缩率54%,冲击功53.3 J,满足了GB/T 17396—1998标准中对27SiMn钢的性能要求.     

热处理对TRIP 590钢微观组织及力学性能的影响

采用Gleeble3800热模拟机对TRIP钢拉伸试样进行不同工艺条件的快速热处理模拟实验,并采用金相分析、显微硬度测试等方法对试样进行组织观察和性能测试,目的是通过适宜的热处理工艺促使材料微观组织中出现适量的残余奥氏体组织,增强该材料在变形过程的相变诱导塑性(TRIP)效应,强化材料结果表明:在两相区内,TRIP钢中的残余奥氏体含量随着退火温度和退火时间的增加而增大,以25℃/s缓慢加热到700℃,再以150℃/s的速率快速加热到820℃保温120s后淬火处理,处理后的试样,残余奥氏体体积分数达到13％,显微硬度最高,达到262HV.