Multi-pass hot caliber rolling technology has significant advantages in producing continuous bars, which can be used as structural and connecting parts with essential applications. Simulation is an important tool for reproducing production processes. The simulation model must show the thermal state, microstructure, and hot workability during the bar’s high-temperature deformation process. However, such a multifunctional simulation model has not yet been reported. Here, a finite element simulation system for hot bar rolling is presented. It is based on the DEFORM-3D software and has been further developed. The most distinctive feature of the proposed simulation system is the integration of a material model that combines constitutive prediction with hot workability prediction. The constitutive model is formulated within an internal state variable framework, enabling the coupled prediction of microstructural evolution and stress response during multi-pass hot deformation. The hot workability prediction model is established based on a backpropagation neural network. By incorporating the microstructural state and deformation conditions as input variables, the model enables dynamic evaluation of hot workability throughout the deformation process. Based on the embedding of the material model, the simulation model can realize the coupled simulation of temperature, deformation, microstructure, and hot workability. Subsequently, the model is validated and applied based on an actual hot bar rolling production line. The simulation successfully predicts the surface cracks in rolled bars and provides insights into the underlying mechanisms of crack formation. The analysis indicates that the primary cause of cracking is the mismatch between the groove geometry and the workpiece geometry, which leads to localized deformation of the corner metal and a sharp temperature drop. Based on this understanding, a matching relationship between the groove geometry and the workpiece geometry is proposed, and the groove structure is optimized accordingly. After optimization, the surface quality pass rate of the rolled bars improved significantly, increasing from approximately 50.7% to about 95.3%. The simulation system can be applied to the hot bar rolling process and other multi-pass hot forming technologies. This is important for optimizing the production process and improving product quality.

As a critical intermediate stage in the continuous casting and rolling process for bar production, the heating quality of a walking beam reheating furnace significantly affects billet shaping and the performance of the finished bars. To address issues such as uneven billet temperature distribution during heating, which leads to non-uniform deformation resistance in the rolling process, causing bending deformation, excessive thermal stress, and the initiation of microcracks and propagation of inherited casting cracks, this study uses 20CrNiMoA steel billets as the research object. The temperature field distribution inside the walking beam reheating furnace was simulated with ABAQUS finite element software. The accuracy of the simulation results was verified through ‘black box’ experiments, which demonstrated that the simulation precision meets the standards required for industrial applications. On this basis, the study systematically investigated the effects of temperature and time parameter settings in different heating zones of the furnace on billet temperature distribution and stress evolution. The results show that increasing the charging temperature improves temperature distribution and peak stress during the preheating stage, while lower furnace temperatures during the preheating phase reduce excessive thermal stress, and optimal furnace settings in heating zone I and II enhance heating efficiency and uniformity. The findings provide theoretical foundations and data support for optimizing on-site production heating process parameters and improving billet heating quality.

The hydrogen embrittlement (HE) susceptibility of ultra-high strength fastener steels is a critical factor for their practical applications. To explore the influence of microstructure on HE for 1400 MPa grade fastener steel, two heat treatment processes, austempering and quenching and tempering (QT), were carried out for 42CrMoVNb steel. The microstructures were observed and analyzed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Slow strain rate test (SSRT) revealed that the austempered 42CrMoVNb steel exhibited significantly superior resistance to HE compared with the tempered condition. The microstructure of the austempered steel consisted of lower bainite and martensite, with carbides distributed within the bainite laths and absent at the original austenite grain boundaries. Additionally, the lower dislocation density in this microstructure further enhances its resistance to HE. These findings suggest that austempering treatment can effectively reduce the HE susceptibility of ultra-high strength fastener steels while maintaining the required strength level of fasteners.

The 16MnCrS5 gear steel, known for its exceptional machinability and hardenability, is commonly utilized in the production of gears and worms in the automotive industry. However, the quenching process of this steel tends to provoke deformation, leading to increased wear and an inability of gear teeth to mesh. This issue seriously restricts the broader use of 16MnCrS5 gear steel. This study explores the quenching deformation of 16MnCrS5 gear steel through a combination of experimental research and numerical simulation to provide theoretical insight to mitigate this deformation in industrial production. The quenching deformations of C-notch samples derived from 16MnCrS5 gear steel, varying in grain size, banded structures, and hardenabilities were first measured. Subsequently, employing the deform finite element analysis software, the temperature field, stress field, and phase field during the quenching of these samples were simulated, thereby visually portraying the corresponding quenching deformation processes. The results indicate that the quenching deformation of 16MnCrS5 gear steel escalates with an increase in grain size and the proportion of banded structures. For instance, the sample with a grain size of 75 mu m demonstrated nearly double the quenching deformation of the sample with a grain size of 22 mu m. Moreover, when the grade of the banded structure surpasses 3, the quenching deformation of the sample markedly increases. Concurrently, the results revealed a positive correlation between quenching deformation and hardenability of 16MnCrS5 gear steel. Specifically, when the hardness at 9 mm from the quenching end (J9) > 32.2 HRC, the sample.. s core is largely martensitic, showing a stronger correlation with hardenability. Conversely, when J9 <= 32.2 HRC, there is noticeable bainitic transformation in the sample.. s core, resulting in a weaker correlation between the quenching deformation and hardenability. The experimental research and numerical simulations suggest that the intrinsic mechanism of quenching deformation in 16MnCrS5 gear steel is mainly attributable to thermal stress and martensitic transformation-induced stress. Notably, the temporal and spatial inhomogeneity of the martensite transformation in time and spatial distribution is the predominant factor affecting the quenching deformation of 16MnCrS5 gear steel.

According to the abnormal fracture phenomenon of 87MnSi steel wire rod for bridge cable， the evolution of microstructure and mechanical properties during production processing were systematically analyzed. The results show that the microstructure of the rod is composed of pearlite and a small amount of proeutectoid ferrite， and the cementite lamellae are randomly distributed. After cold drawing， the cementite lamellae are rotated or fibrotic， and some cementite are broken and dissolved， the dissolution amount is 1.40wt.%（9.69%）. After ho-dip galvanizing， the dissolved cementite is spheroidized. In the process of cold drawing， hot-dip galvanizing and stabilization treatment， the microhardness of wire rod （329.8HV） increases （450.2HV） firstly， then decreases （447.9HV） and increases （474.8HV） finally. The cementite dissolved in the cold drawing process increases the hardness of the steel wire to 468.3HV， while the spheroidized cementite in the hot galvanizing process decreases the hardness to 439.8HV， and deteriorates tensile property. When the degree of spheroidization of cementite on the edge is obvious， the microstructure and mechanical properties of the steel wire inside and outside are greatly different， and the fracture is eventually caused by uneven force during stabilizing treatment.

Dynamic ferrite transformation is a vital microstructure evolution mechanism for carbon alloy steels and an essential technology for manufacturing high-performance steel materials. In practice, carbon steel hot working processes are usually carried out at various temperatures, involving the evolutionary behavior of the single-phase austenite and the ferrite dynamic transformation process. Few models can simultaneously predict the microstructural state and deformation resistance in the single-phase austenitic interval and the dynamic ferrite transformation interval. The deformation mechanisms involve work-hardening, dynamic recovery, and dynamic recrystallization of austenite and ferrite phases, as well as the dynamic transformation of austenite to ferrite and coordinated deformation between the two phases. Therefore, this paper extends the application range of the model based on the viscoplastic unified constitutive model by considering the above deformation mechanisms. The constitutive model proposed in this paper applies to both the single-phase austenite interval and the dynamic ferrite transformation interval. Moreover, it can accurately predict carbon alloy steel's microstructure state and deformation resistance in different intervals. This paper can help to construct a hot deformation constitutive model in a wide range of deformation temperature intervals of steel materials.

收集不同钢厂70 kg级高强焊丝盘条、粗拉半成品钢丝及成品焊丝样品,利用显微镜、扫描电镜等检测设备对免退火拉拔后的材料金相组织、力学性能、显微硬度等指标进行研究.盘条的贝-马复合相组织经拉拔后,仍有部分难变形的组织以"颗粒"状存留在材料内部,并形成显微孔隙缺陷,而贝-马复合相控制越细、分布越弥散,材料的强韧性越高,拉拔性能越好.

Dynamic recrystallization (DRX) is of great significance for refining grains, improving mechanical properties, and obtaining high‐quality products during thermomechanical deformation. This article studies the DRX behavior of low‐carbon steel within the temperature range of and the strain rate of 0.01–1 s −1 based on the Gleeble‐3800 thermal‐simulation experimental machine and establishes a DRX kinetic model suitable for different strain rates. The established model is embedded in the DEFORM‐3D simulation software to simulate the DRX behavior of high‐temperature plastic deformation of the material and to study the influence of the deformation amount, deformation temperature, and strain rate on the deformation inhomogeneity of the material. The results show that under the strain rate of 0.01–1 s −1 , the 2/5 position from center to surface corresponds to the preset strain, and under the strain rate of 0.1–1 s −1 , the 1/2 position from center to surface corresponds to the preset strain, and the importance of the sampling position is proved in combination with the DRX behavior. This article establishes a sampling theory that describes the position corresponding to the preset deformation amount, and it is important for guiding subsequent microstructural characterization experiments to reveal the DRX behavior of materials during thermomechanical deformation.

The structure and mechenical properties of Φ52 mm 45MnVTi steel finished rolling at 917～922 ℃ and water-cooling-self-tempering with 680～830 ℃have been tested and researched.Results show that the microstructure of asprepared steel consists of ferrite and pearlite,with the decrease of self-tempering temperature,the yield strength and tensile strength of steel gradually increase,and toughness increases at first and then decreases. When the range of self-tempering temperature is 750 to 770 ℃,the microstructure of steel products is fine ferrite and pealite, and the test steel average value of tensile Strength 841 MPa,yield Strength 547.5 MPa,impact energy 50.5 J with an optimal match between the strength and toughness of steel and pearite lamellar spacing 2.39 μm,to meet the use requirements.

ER70S-6盘条生产焊丝出现拉拔断裂,通过对断裂样品进行电镜扫描以及金相分析,发现贝氏体和马氏体复合相组织是造成断裂的直接原因.根据该组织形成机制从元素偏析和轧后控冷两个方面分析,提出并实施延长盘条出罩时间、强化盘条保温效果等措施,改善盘条基体组织,解决了断丝问题.

In the process of copper alloy hot continuous rolling, the problem of copper sticking to the roller seriously affects the surface quality, performance, and service life of the copper products. Roll sticking occurs as the adhesion energy of Cu is lower than that of Fe and the Fe-Cu interface, and the severe surface deformation which forces the copper into direct contact with the roll during the process of profile rolling. Based on the copper deformation law and adhesion phenomenon in the hot continuous rolling process, a rolling deformation model and roll copper adhesion model or copper alloy hot continuous rolling were established, and their simulation was realized using finite element software. Through finite element modeling of the hot rolling deformation zone, the distribution of the temperature, contact normal stress, and exposure rate in the hot rolling deformation zone were obtained, which were consistent with the actual roll adhesion phenomenon and copper adhesion position. To address the copper sticking behavior of the rolls, the process optimization method of matching the motor speed with the elongation coefficient (the 1# and 2# motor speeds were adjusted to 1549 r/min and 1586 r/min, respectively), adjusting the roll gap to 7.9 mm, and increasing the number and pressure of roll spray nozzles were put forward, which effectively solved the problem of copper sticking to the roll, significantly improved the surface quality of the copper and the service life of the roll, and can be used in production.

通过采用示波冲击试验机对贝氏体非调质钢YG1401进行系列温度冲击试验,并采用体式显微镜和扫描电镜对断口宏观形貌及微观扩展形貌进行观察,结合示波冲击试验所测的裂纹起裂功及裂纹扩展功研究该材料从24～-80 ℃的冲击断口形貌变化规律.结果 表明:该材料的DBTT为-12℃.试验材料在24～-10℃区间冲击时,材料代表高韧性的裂纹稳定扩展区面积最大.在-30℃冲击时,裂纹稳定扩展区面积急剧下降.随着冲击温度的进一步下降,裂纹稳定扩展区面积不断下降.24～-10℃区间内冲击断口形貌表现为由密集细小韧窝组成的粗大的撕裂棱和塑性变形量较大的二次解理组成的混合断裂形貌,随着温度的进一步降低,断口放射区形貌为细小撕裂棱和一次解理为主的混合断裂形貌.

根据高速线材孔型轧制的特点,采用埃克隆德热连轧公式计算精轧机的轧制力和力矩,并将计算结果与实际的设备运行数据对比,总结得到在不同的轧制速度、规格、温度和钢种等条件下的一般规律,用于指导设备的日常维护,最大限度地避免设备故障.

针对42CrMo连铸圆坯在生产回转支撑用锻件时锻造加工后探伤不合格的问题,对不合格锻件缺陷位置探伤定位后,进行低倍检验、渗透、断口试验、电镜扫描以及金相分析,结果表明,锻件锻造加工后内部出现密集的白点缺陷是导致探伤不合格的原因.进一步分析白点形成机理、锻造加工后冷却过程和原始连铸圆坯生产过程,可知白点是钢中的氢和内应力共同作用而产生的一种裂纹缺陷.提出了延长连铸中包烘烤时间、限定锻件加工尺寸等措施,该问题得到有效解决.

Diameter 26 mm SWRCH35K wire rod is used to produce 8 mm wall thickness nut,the hardness of nut surface and core after quenching is lower than requirement.Through chemical composition analysis,metallographic examination and end quenching test,the quenching property of base metal is determined to meet the requirement of processing performance of nut.The simulated quenching test of 3 schemes were given,it is determined that the influence factors of nut hardness not up to standard are as follows:the quenching temperature is low,the cooling rate of quenching medium is low,surface decarburization occurs during annealing and so on.It is recommended that the nut manufacturer increase the quenching temperature to 880 ℃,the quenching medium is replaced by aqueous sodium acid solution,inspection annealing equipment and revised annealing process to make sure the annealing process is not decarburization,it solves the problem of nut hardness after quenching does not reach the standard.

60Si2MnA spring steel must has good metallurgical quality,surface quality,metallographic structure and so on.The production process of spring steel wire rod is introduced,in the process of converter smelting,average value of tapping carbon content is no less than 0.12%;in the LF refining process,the basicity of slag is controlled from 1.5 to 2.5;in the VD vacuum degassing process,the total vacuum time is no less than 20 min;in the continuous casting process,the superheat degree is controlled to be 20 ～ 30 ℃,the casting speed is controlled 1.6 ～ 1.9 m/min,the stack cooling time is no less than 24 h;the process control parameters of heating furnace are given;reducing sizing temperature control is no more than 880 ℃,wire laying temperature is no more than 860 ℃,the roller speed is 0.16 ～0.30 m/s.The wire rod is analyzed and the result shows:the inclusions mainly belong to B and D type,inclusion leveling no more than 1.5 grade,decarburization depth is no more than 1.0％D,the properties indexes meet the requirements of the users for producing oil quenching and tempering spring wire.

介绍了高线精轧机的运行情况,提出了辊箱错辊的危害性,并对错辊的原因从装配和维护角度进行分析,提出了具体控制错辊的方法.