Q550D高强度钢板组织及焊接性能分析

包钢通过成分优化和轧制工艺的优化研制了工程机械用高强度钢Q550D。通过热影响区最高硬度、插销试验、斜Y坡口焊接裂纹试验对Q550D高强度钢的焊接性能进行分析,研究结果表明:Q550D钢板热影响区最高硬度(HV10)为297。插销试验结果表明,在中等拘束条件下,采用HS-70焊丝焊接20 mm厚Q550D钢板,不预热没有裂纹的产生。同时斜Y坡口焊接裂纹试验表明对于20 mm厚Q550D钢板,在不预热条件下焊接,两组试样表面裂纹率和断面裂纹率均为零。     

含硼低成本低碳贝氏体钢焊接性能研究

通过对安阳钢铁公司生产的含硼低成本低碳贝氏体钢AH70DB进行焊接性能研究,分别进行了焊接CCT曲线测定,焊接冷裂纹敏感性研究,以及对焊接热影响区组织性能、焊热热输入量、焊后热处理及焊接接头综合力学性能评定等内容进行了试验研究。研究表明,AH70DB钢淬硬倾向较小,对氢致开裂敏感性较低。在中等拘束条件下焊接,室温10℃以上不需预热;在苛刻拘束条件下,可实现低预热温度,预热温度50℃以上。采用推荐的焊接工艺焊接25 mm厚AH70DB钢板对接接头,焊接接头综合性能良好,能够满足工矿产品的使用要求。     

700MPa级高强度调质钢板焊接性能研究

从低成本700 MPa级调质中厚钢板的焊接性能着手,分析了母材的成分、组织及性能特点,研究了其焊接冷裂纹敏感性、焊接过程中的热输入量以及焊后热处理过程对试验钢焊接接头组织和性能的影响。结果表明,针对50 mm厚的700 MPa级高强度调质钢板,在中等拘束条件下,采用BHG-4M焊丝富氩混合气体保护焊、预热100℃的工艺进行焊接可以防止冷裂纹产生;在苛刻拘束条件下,最低预热温度在120℃以上才能防止裂纹产生;试验钢对焊接工艺规范有较强的适应性,焊接热输入量在8.85~24.17 kJ/cm范围内变化时,试验钢焊接接头的综合力学性能保持在较高水平。     

包钢Q690D钢板斜Y坡口焊接裂纹试验研究

高强钢广泛应用于煤机行业。斜Y坡口焊接裂纹试验是一种拘束程度较苛刻的冷裂纹试验方法,考核对接接头焊接热影响区的根部裂纹情况。通过焊接裂纹试验,确定该钢的基本焊接性,为合理制定焊接工艺提供依据。     

桥梁钢Q345qDNH冷裂纹敏感性研究

通过对包钢生产的桥梁钢Q345 qDNH进行斜Y型坡口焊接裂纹试验、热影响区最高硬度试验及刚性对接试验,试验结果表明:20 mm厚的Q345qDNH桥梁钢冷裂纹敏感性不大,在实际焊接过程中采用不预热或者50℃的预热温度制度,可以避免Q345 qDNH桥梁钢冷裂纹的产生.     

08MnNiVR(B610E)高强度调质钢板的焊接性能

时32mm厚08MnNiVR(B610E)高强度调质钢进行了全面的焊接试验研究.测定了模拟焊接热影响区连续冷却转变(CCT)图,分析了不同冷却速度下的模拟焊接热影响区组织变化;钢板在不预热条件下,焊接热影响区最高硬度为HV327;钢板在焊前预热75℃时,斜Y坡口试验未发现焊接冷裂纹;在平板对接反面拘束裂纹试验和斜Y型坡口焊接裂纹试样sR(Residual-stress relief)处理模拟再热裂纹试验中,没有发现再热裂纹发生.试验结果表明:08MnNiVR(B610E)高强度调质钢具有良好的抗冷裂纹和抗再热裂纹的能力.     

超细化低碳贝氏体钢焊接性能的研究

针对超细化低碳贝氏体钢,采用裂纹敏感性指数Pcm、斜Y坡口接头裂纹率和模拟粗晶热影响区(CGHAZ)的硬度等参数评价了焊接冷裂纹倾向,研究了不同线能量下模拟CGHAZ和气体保护焊(MIG)接头的组织结构和力学性能.实验结果表明:钢的焊接淬硬倾向低,预热温度50℃以上可完全避免焊接冷裂纹产生;采用14～25 kJ/cm的小线能量焊接时,CGHAZ由原奥氏体晶内不同位向的贝氏体铁素体板条束和少量粒状组织构成,具有较高的抗冲击脆断性;与YS800焊丝配套的气体保护焊接头力学性能优异.     

HQ 100钢焊接性研究

本文研究了HQ 100钢模拟及实际焊接热影响区各部位的韧性及组织变化,并用插销试验、纵向可调拘束裂纹试验和T型坡口再热裂纹试验对HQ 100钢的裂纹敏感性进行了评定。试验结果表明,模拟热循环峰值温度对HQ 100热影响区韧性有明显影响。随峰值温度升高,冲击韧性下降。Δt 8/5对韧性也有一定影响,当Δt 8/5为10 s时,过热区韧性最佳。实际热影响区峰值温度对韧性的影响也具有同样的规律性,但其韧性比模拟热影响区高一倍左右。组织和晶粒度的不同是造成上述变化的重要原因。抗裂性试验结果表明,HQ 100钢具有良好的抗热裂纹,再热裂纹性能。冷裂敏感性也较低,只要严格控制焊条烘干条件,预热和层温不低于130℃,便不会产生冷裂纹。     

500MPa级高性能桥梁钢板的焊接性研究

结合焊接性理论分析,对500 MPa级高性能桥梁钢板开展了焊接热影响区最高硬度、斜Y坡口焊接裂纹和对接接头系列温度冲击试验研究。试验结果表明,试验钢的碳当量CEV为0.44%,Pcm为18%,在室温下焊接热影响区最高硬度为274 HV10,淬硬倾向小;采用焊条电弧焊和气体保护焊时,板厚≤32 mm时不需要预热;板厚32~60 mm时需要预热80℃;焊接热影响区的ETT50达到-60℃,具有良好的低温冲击韧性。试验钢板焊接性良好,可应用于高性能桥梁的建设。     

80 kg级低温不预热焊接高强钢的开发

根据各合金元素对材料性能、微观组织及焊接冷裂纹等的影响,结合现有设备和工艺技术条件,设计岀80 kg级低温不预热焊接高强钢的化学成分。用该开发钢板做低温不预热焊接Y-形坡口铁研(焊接裂纹)试验发现,空冷48 h后没有出现焊接开裂。同时,在5 ℃、15 ℃及常温下,热输入为20 kJ/cm时,釆用CO₂气体保护焊及手工电 弧焊对试验钢板分别进行了'不预热焊接试验,结果表明,该80 kg级髙强钢板在5℃,15℃及常温下不预热焊接接头 的抗拉强度832～857 MPa, -20 ℃焊缝冲击功55~127J,满足标准要求。     

A study on cold cracking susceptibility in high strength steel fillet weld joints

Controlled thermal severity (CTS) test which simulates the conditions in a single-pass fillet welding was carried out to determine the suitable minimum preheating temperature for the cold-crack-free welding of high strength steel ASTM A 516-70. The dependence of this minimum preheating temperature on diffusible hydrogen contents in weld metal was clarified. Then, the effect of climatic conditions on cold cracking susceptibility as a function of diffusible hydrogen contents in weld metal was studied. It is found that the cold cracking susceptibility of high strength steel is primarily related to the microsturcture of the HAZ which, in turn, is related to the preheating temperature. A lower preheating level, which resulted in harder microstructure, led to increased susceptibility. Suitable minimum preheating temperature required to prevent cold cracking increased with the increase in diffusible hydrogen contents of weld metal as a function of climatic conditions.     

Effect of heat input and preheating on hydrogen assisted weld joint cracking of a 0.13% C, 1.5% Mn, 0.032% Nb high strength steel of 50 mm plate thickness in the IRC test

The effects of preheating and heat input on hydrogen assisted weld joint cracking are investigated at a restraint intensity of 32 kN mm^?2 of a 0.13% C, 1.5% Mn, 0.032% Nb high strength steel of 50 mm thickness in the IRC test, using a high hydrogen experimental electrode of 530 N mm^?2 yield strength. For a heat input ranging from 0.6 to 1.05 kJ mm^?1 a critical preheating temperature of 140°C for almost complete crack prevention, for a range from 1.5 to 2.05 kJ mm^?1, 120°C were found respectively. Nominal stresses at the ends of the 70-80 mm long welds at the start of extensive cracking increase with heat input and preheat, the crack propagating from the HAZ into the weld metal quickly. Under conditions without or close to cracking, however, final stresses after 18 h are reduced with heat inputs. Consequently, crack critical combinations of preheating and heat input are linked to stresses decreasing with heat input but increasing with preheat. From the established IRC-test diagram required combinations of local preheat and heat input for either avoiding hydrogen cracking or overstressing of the weld metal can be determined. Currently used cracking prediction procedures do not consider the effect of heat input and preheat on stress sufficiently and, therefore, may provide unsafe conclusions.     

高强钢焊接氢致裂纹断口微观形貌的研究及模式化

采用插销实验和扫描电镜观察方法详细研究了焊缝扩散氢含量和非金属夹杂物对10Ni5CrMoV低碳中合金高强钢焊接热影响区氢致裂纹断口微观形貌的影响。结果得出,扩散氢含量是影响氢致裂纹断口微观形貌的主要因素,在插销净截面应力300～800MPa的范围内,加载应力对延迟扩展区断口形貌无明显影响。钢中硫化物夹杂的增加使扩展区形貌从IG_(HE)向MVC_(HE)转变,而含氧化物夹杂钢则转为QC_(HE)。作者提出了一个新的适于解释氢致裂纹扩展第Ⅱ阶段断口微观形貌的竞争开裂模式,从而从氢致裂纹本质机制上圆满说明了上述实验结果。     

Evaluation of Cracking Resistance of Copper-Bearing Age Hardening Steel Weldment

The weldability of a low-carbon copper-bearing age hardening steel was evaluated using cracking suscepti- bility calculation, HAZ maximum hardness measurement, and Y-groove cracking evaluation test. The results show that the hardenability characteristics and cold cracking susceptibility of the steel are very low. The results also indicate that a crack-free weldment can be obtained during the welding of this type of steel even at an ambient temperature as low as -5 ℃ as well as in an absolute humidity lower than 4 000 Pa without any preheat treatment. A slight preheat treatment can prevent the joint from cracking when welding is carried out at lower ambient temperature or higher absolute humidity.     

挤压工艺参数对挤压过程影响规律的仿真模拟研究

研究对象是某6063工业铝型材,将建立好的三维模型导入到有限元Altair Hyperxtrude分析软件进行仿真模拟,通过改变型材挤压工艺参数（挤压比、棒料预热温度、模具预热温度、挤压筒预热温度、挤压速度）,研究其对金属流动的规律,基于直交表Taguchi方法分析各挤压工艺参数对型材截面速度分布和挤压力的影响规律.结果表明:对于型材截面流动均匀程度指标参数,最佳挤压参数为挤压棒料外径205 mm、挤压垫速度3.2 mm/s、棒料预先加热温度480 ℃、挤压模具预先加热温度470 ℃、挤压筒预先加热温度440 ℃;对于挤压力指标参数,棒料外径200 mm、挤压垫速度1.4 mm/s、棒料预先加热温度490 ℃,挤压模具预先加热温度480 ℃、挤压筒预先加热温度460 ℃.      

Weldability of Low Carbon Transformation Induced Plasticity Steel

Transformation induced plasticity （TRIP） steel exhibited high or rather high carbon equivalent （CE） because of its chemical composition, which was a particularly detrimental factor affecting weldability of steels. Thus the weldability of a TRIP steel （grade 600） containing （in mass percent, %） 0.11C-1. 19Si-1.67Mn was extensively studied. The mechanical properties and impact toughness of butt joint, the welding crack susceptibility of weld and heat affected zone （HAZ） for tee joint, control thermal severity （CTS） of the welded joint, and Y shape 60° butt joint were measured after the gas metal arc welding （GMAW） test. The tensile strength of the weld was higher than 700 MPa. Both in the fusion zone （FZ） and HAZ for butt joint, the impact toughness was much higher than 27 J, either at room temperature or at -20 ℃, indicating good low temperature impact ductility of the weld of TRIP 600 steel. In addition, welding crack susceptibility tests revealed that weldments were free of surface crack and other imperfection. All experimental results of this steel showed fairly good weldability. For application, the crossmember in automobile made of this steel exhibited excellent weldability, and fatigue and durability tests were also accomplished for crossmember assembly.     

Investigation of the conditions for weld metal hydrogen cracking of low carbon offshore steels by the IRC weldability test

Three low carbon structural steels of different plate thickness have been investigated for hydrogen assisted cold cracking by the IRC weldability test at different restraint intensities. At diffusible hydrogen levels of 10–15 N ml/100 g Fe (ISO 3690), cracking decreases at increasing heat inputs due to a drop in restraint stress and hardness as well as an increase in hydrogen diffusion times. Critical heat inputs for crack prevention range from 0.95 to 1.4 kJmm^?1. Higher restraints enforce higher cracking stresses as well as final stresses of uncracked test welds. Higher restraints and lower heat inputs also induce faster stress increase during cooling which, for the steels containing Ni and Cu, shift the location of cracking from the HAZ to the weld metal. The steel without Ni and lower maximum HAZ hardness reveals weld metal cracking only, regardless of welding conditions. It can be concluded that for weld metal cracking, the relation between stress increase- and hydrogen effusion rates but also the relation between weld metal and HAZ microstructure and mechanical properties are responsible.     

Weldability of 1 000 MPa Grade Ultra-low Carbon Bainitic Steel

Maximum hardness test in weld heat-affected zone(HAZ),oblique Y-groove cracking test and mechanical property test of welding joint of 1 000 MPa grade ultra-low carbon bainitic steel were carried out,so as to research the weldability of the steel.The results show that the steel has lower cold cracking sensitivity,and preheating temperature of 100 ℃ can help completely eliminate cold cracks,generating good process weldability.The increase of preheating temperature can reduce the hardening degree of heat-affected zone.The strength of welding joint decreases and hardness reduces when heat inputs increase,and excellent mechanical properties can be obtained when low welding heat inputs are used.Fine lath bainites of different orientations combined with a few granular bainites that effectively split the original coarse austenite grains are the foundation of good properties.