Present situation and countermeasure of low-alloy spring steel wire rod for domestic automobile

The variety,inner quality and surface quality of low-alloy spring steel wire rod for domestic automobile is summarized in detail.And according to commercial low-alloy spring steel wire rod variety, product quality level and its actual application situation on automobile supplied by present industrially developed country metallurgy enterprises,it is pointed that the variety of low-alloy spring steel wire rod for domestic automobile can't satisfy the requirements of automobile industry development,compare with overseas advanced technology,product quality has the following gaps:the first is that steel purity is low,the control level of non-metallic inclusions is not steady,there is often large grain difficult deforming non-deformation inclusions existing,the control level of steel purity has big difference,the level of large steel factory is high,but its steady has a large gap compare with foreign advanced level,not to mention small steel factory which research and development powder is low.The second is surface complete decarburization can' t be avoided completely.The third is that surface defects are more.The fourth is that composition segregation and structure segregation are not steady,steel wire can't be drawn normally when the segregation is serious. In all,the segregation of 55SiCrA is superior to 60Si2MnA obviously.The industrialization of domestic high level low-alloy spring steel wire rod can't seek quick success and instant benefits,independent innovation perseveringly must be adopted,the success may be reached after master core technologies and adopt the science way of step by step.

Study on rolling process optimization of high carbon steel wire

The existing problems in the manufacture of SWRH82B high carbon steel wire were discussed by sampling and testing the microstructure and properties of the steel from the workshop. To solve the problems, the experimental parameters for thermal simulation were optimized, and the thermal simulating experiments were carded out on a Gleeblel500 thermal simulator. The process parameters for the manufacture were optimized after analysis of the data, and the productive experiments were performed after the water box in front of the no-twist blocks was reconstructed, to control the temperature of the loop layer. The results from the productive experiments showed that the cooling rate of 10-15℃/s was reasonable before phase transformation, about 5℃/s during phase transformation, and 600-620℃ was the suitable starting temperature for phase transformation. The ultimate strength of the Ф11.0 mm wire was increased to 1150-1170 MPa with an increase of 20-30 MPa, the percentage reduction of section was to 34%-36% with an increase of 1%-3% by testing the finished products after reconstruction.

BWR4耐候钢热轧盘条的研制开发

主要介绍了首钢长钢公司采用转炉、LF精炼炉、小方坯连铸机和55万t棒线复合产线工艺路线生产BWR4耐候钢热轧盘条的关键工艺技术。轧制盘条力学性能稳定,1/3冷顶锻合格率为100%,耐大气腐蚀指数在6.54以上,轧制盘条质量指标符合《耐候钢结构紧固件用热轧盘条及圆钢》标准要求,可满足用户加工5.8级螺栓使用要求。

Si对缆索钢丝绳用热轧盘条组织和力学性能的影响

利用扫描电镜和能谱(EBSD)仪器对两种不同Si含量的热轧盘条的横截面和纵截面的组织形貌进行观测,并用万能试验机测试热轧盘条的拉伸性能,结果表明:随着Si含量的增加,珠光体转变的过冷度增加,热轧盘条的珠光体团尺寸和珠光体片间距减小。Si元素使Mn元素在渗碳体中偏聚,增加了渗碳体的稳定性,减小了渗碳体片层的球化倾向。Si元素使盘条横、纵截面珠光体的织构强度减弱,珠光体组织更加均匀,取向更加随机。Si元素能大幅度提升热轧盘条和成品钢丝的强度,小幅度提升塑性。低Si盘条的抗拉强度为1134 MPa,均匀伸长率为7.1%;高Si盘条的抗拉强度为1263 MPa,均匀伸长率为7.3%。低Si钢丝的抗拉强度为1937 MPa,均匀伸长率为2.2%;高Si钢丝的抗拉强度为2106 MPa,均匀伸长率为2.3%。

埋弧焊丝用H08Mn钢盘条氧化铁皮研究及其轧制工艺

H08Mn钢盘条多用于制作埋弧焊丝,其表面的氧化铁皮对拉拔前机械除鳞效果有明显影响。介绍了盘条氧化铁皮的形成机制、氧化铁皮的种类和构成;采用不同的工艺参数,包括始轧温度、精轧温度、吐丝温度和首道辊速度,轧制了H08Mn钢盘条,随后检测了盘条氧化铁皮的厚度、盘条的晶粒度和抗拉强度。结果表明:采用这样的工艺参数即880℃的精轧温度、900℃的吐丝温度和18 m/min(按5%递增)的首段辊道速度轧制的H08Mn钢盘条,其氧化铁皮厚度小于20μm且易剥落,晶粒度和抗拉强度均有利于后续拉拔加工。

线棒材和H型钢产品的缺陷组织

选取线棒材HRB400E钢、45钢、Q355B钢中的不合格试样,对其中贝氏体、网状铁素体、魏氏组织、带状组织等缺陷组织产生的原因进行分析。结果表明:采用调整钢材加热温度、出精轧温度、轧后冷却速率等工艺参数的方法,可以避免材料产生缺陷组织。研究结果可为提高钢材产品的合格率提供支持。

发电机定子铁芯局部断齿及绝缘损坏分析及处理

汽轮发电机的定子结构和山西临汾热电有限公司1号汽轮发电机发生的定子铁芯、线圈烧损划伤故障及处理过程进行介绍和分析。山西临汾热电有限公司1号汽轮发电机自2015年大修投产运行中各项参数正常,无温度、振动超标等其他异常现象。2020年计划性大修时,在进行1号发电机解体抽出1号发电机转子后,发现发电机汽侧定子铁芯压指处有一个烧熔的坑洞,且1号发电机转子表面及定子腔内多处存在划伤情况,联系发电机厂家进行了分析处理。

《轴承钢盘条》国家标准研制

介绍轴承钢盘条国家标准制定的任务来源、制定工作程序及重点建议探讨;对标准关键条款进行解释;说明标准技术内容与GB/T18254-2006《高碳铬轴承钢》在技术指标和检测方法上的差异。

车致拱桥短吊杆弯曲效应及疲劳体系可靠性评估方法研究

拱桥短吊杆疲劳脆断是引起桥梁垮塌的主要原因,吊杆中平行钢丝的体系失效机制尚不明确。为解决这一问题,本文采用瞬态分析法分析了车载作用下拱桥短吊杆的“弯拉”作用,研究了吊杆中平行高强钢丝的应力分布特征,讨论了平行钢丝的疲劳失效路径。研究表明:短吊杆疲劳破坏失效时弯曲受拉侧的高强丝应力最大,平行钢丝由受拉侧向受压侧进行疲劳断裂传递。以国内系杆拱桥芙蓉镇大桥为例,计算其短吊杆体系可靠指标,吊杆运营25年后其可靠度指标进入预警区间。

60Si2MnA钢弹簧疲劳断裂原因分析

采用直径为4 mm、经油淬和回火的盘条制作的60Si2MnA钢弹簧,在疲劳试验早期断裂。检测了盘条的化学成分和拉伸性能,并对断裂的弹簧进行了断口分析和金相检验。结果表明:盘条的化学成分和拉伸性能均符合要求,但弹簧表面有细微裂纹、机械损伤和脱碳层等缺陷以及马氏体,导致疲劳性能降低从而在疲劳试验时过早断裂。

《汽车紧固件用冷镦钢盘条》标准浅析

介绍了正在报批的《汽车紧固件用冷镦钢盘条》行业标准研制的背景、必要性、标准的主要内容和遗留的问题等。标准主要包含非热处理型、表面硬化型、调质型(包括含硼钢)、非调质型四类汽车紧固件用冷镦钢盘条,公称直径为5~42 mm。该标准是我国盘条领域的一项专用标准,标准的研制使冷镦钢领域的标准体系更加完善,有利于推进汽车紧固件用钢国产化发展。同时指出GB/T 6478-2015《冷镦和冷挤压用钢》须改进的地方,供该标准修订时参考。

盘条打包质量改进

打包质量是盘条质量的重要组成部分。对钢带打包冷镦钢盘条在运输过程中的倾斜、散卷等问题进行分析,采取强制冷却、降低盘条打包温度、控制卷型、改进打包方式、改进小绕线、提高物流运输质量等措施,提高了盘条打包质量。大规格冷镦钢盘条到货后的散卷率降低了约20%,提高了用户的满意度,减少了卷型异议的产生。

钢帘线用热轧盘条粗拉断裂原因分析与控制措施

钢帘线用热轧盘条在粗拉过程中偶发出现拉拔断裂问题,对拉拔断口进行了扫描电镜微观形貌观察、光学电镜金相组织观察。结果表明,轧制过程中成品产生的颈缩缺陷是导致盘条粗拉断裂的原因。提出了优化减定径孔型、合理控制过钢量、提高温度控制稳定性、加强轧件表面质量控制等改进措施,改进后颈缩缺陷发生率降低了80%。

低碳钢盘条轧后控冷新技术

利用热模拟试验研究了低碳钢盘条在不同控冷工艺条件下奥氏体组织的转变和氧化铁皮的生成规律,分析了开冷温度和冷却速率等参数的变化对低碳钢盘条显微组织、氧化铁皮的相结构、各层氧化铁皮生成厚度及总厚度产生的影响,得出低碳钢盘条轧后控冷增加了组织中针状铁素体含量及合理的氧化铁皮结构厚度。

深拉钢丝用70钢盘条的研制与开发

新余钢铁集团有限公司(简称新钢,下同)为满足φ5.5 mm规格深拉钢丝用70钢盘条抗拉强度≥1 050 MPa的要求,优化设计了盘条成分,通过控制C元素含量,适当提高Si、Mn元素含量,降低S、P有害元素含量以增强盘条性能;优化了盘条生产过程中的控冷工艺,对比不同试验方案,得出较优控冷工艺参数为吐丝温度880~900℃,风机风量1#—4#设定为40 Hz,5#—8#设定为15 Hz,其余关闭,保温罩全开。生产的70-SL盘条抗拉强度平均值为1 100.5 MPa,均满足抗拉强度≥1 050 MPa的性能要求。通过盘条成分优化与工艺优化相结合的方法,成功研制出了抗拉强度满足要求的盘条产品,为开发其他系列高碳钢盘条提供参考。

82B高碳钢盘条连续冷却转变曲线的测定及其相变规律

采用GLEEBLE3800型热模拟试验机对82B高碳钢盘条进行连续冷却试验,利用光学显微镜及扫描电子显微镜对不同冷却速率的试样进行显微组织分析,绘制连续冷却转变曲线。结果表明:开始产生马氏体组织的临界冷却速率为5℃/s,冷却速率为0.5~5℃/s时,组织为珠光体和索氏体;通过性能对比发现,冷却速率为3℃/s时,82B高碳钢盘条的综合性能达到最佳。

60Si2Mn钢盘条断裂原因

某60Si2Mn钢盘条在卷簧过程中发生断裂。采用宏观观察、化学成分分析、金相检验、夹杂物分析、扫描电镜分析等方法对该盘条的断裂原因进行分析。结果表明:在卷簧前及卷簧初期的拉拔过程中,盘条表面受到了严重的挤压或擦蹭,使组织变形,并形成了隐晶马氏体;在后续的拉拔过程中,盘条内部应力集中处萌生了微裂纹,裂纹不断扩展,最终导致盘条断裂。

Improvement of Inner Quality of High Carbon Wire Rod Steel Using Combined Electromagnetic Stirring

To improve the quality of high carbon wire rods,combined electromagnetic stirring was introduced in the continuous casting of round billets with a diameter of 250mm at Tianjin Rockcheck Steel Group Co.In this paper,the positioning of final electromagnetic stirring(F-EMS)was determined by nail-shooting method.Furthermore,the effect of mold electromagnetic stirring(M-EMS)on the macrostructure and internal defects in the round billets was investigated to find out the optimal operating parameters for continuous casting of SWRH 82B round billets.The results show the desirable positioning of F-EMS locates 9.7m below the mold level where the molten steel can be effectively driven by electromagnetic force and disperse central composition segregation.The shrinkage cavity is totally eliminated with the rotational M-EMS.The ratio and index of central composition segregation and center porosity can be reduced significantly. Furthermore,the equiaxed crystal ratio is considerably increased to 64%under 480A/3Hz M-EMS and 500A/10Hz F-EMS. Fine microstructure and mechanical property of wire rod are presented after optimization of combined electromagnetic stirring.Accordingly,the probability of occurrence of cup-cone fracture of wire rod is reduced dramatically.

高强度螺栓用35CrMo免退火冷镦钢热轧盘条的研制

通过入减定径温度780℃,入减定径减面率42%(Φ18.4 mm→Φ14 mm),冷却速度0.42℃/s,35CrMo钢热轧材显微组织为F+P,铁素体含量≥40%,实际晶粒度10~11级,抗拉强度≤750 MPa,断面收缩率≥60%,硬度值214~225HV,实现免退火直接进行大减面率拉拔。

高碳线材洁净钢的工艺研究与应用

以河钢SWRH82A高碳线材生产工艺为基础,采用夹杂物电镜扫描方法,研究SWRH82A钢生产过程中各个工序w(O)、w(N)的变化规律及夹杂物的类型、数量、分布,分析该钢种各工序夹杂物的变化情况和改进措施。通过生产检测数据得出:要满足高品质洁净钢要求,需在LF精炼过程中采取微正压操作;开浇前对中间包内部进行氩气吹扫2~4 min,中间包钢水使用覆盖剂、碳化稻壳进行双层覆盖;浇注过程中对大包长水口全程添加氩气保护,同时对中间包上水口与浸入式水口衔接处进行充氩气保护,以有效减少钢水吸气;钢水浇铸时运用结晶器电磁搅拌+末端电磁搅拌技术,以促进夹杂物上浮。