Features of the microstructure of 20GL steel

Conclusion Manganese has a significant influence on the structure formation and properties of 20GL steel. With a content of more than 0.6% manganese promotes the formation of a lamellar bainitic structure consisting of ferrite and microzones of residual austenite or products of its decomposition. In individual cases these microzones may be competely isolated from one another but more frequently, apparently, they form a branched skeleton of ferrite grains. Such a microstructure of heterogenized ferrite grains provides a marked effect of microcomposition strengthening of steel.With a higher manganese content in the steel the residual austenite may remain in the form of edges on the ferritic grain boundaries. This causes significant embrittlement of the steel, especially at low temperatures. In 20GL, 20TL, and 20GFL steels with a content of up to 1.4% Mn areas with austenite edges are rarely observed and do not cause significant embrittlement of the steel.In describing and standardization of the microstructures and evaluation of the mechanical and service properties of parts of 20GL steel it is necessary to take into consideration the nonuniformity of the structure and properties across the section of heat treated castings.Deceased.Bryansk Technological Institute, Bezhetsk Steel Casting Plant. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 27–31, November, 1986.     

20钢花键冷滚打成形表层物理力学性能优化

为了实现对20钢花键冷滚打成形表层物理力学性能的合理控制,以冷滚打转速、进给量和滚打轮圆角半径为试验参数,进行了冷滚打成形正交试验,分别测量花键分度圆处的表层加工硬化程度和残余应力,采用田口理论信噪比权衡各加工参数对花键表层物理力学性能的影响程度;运用熵权理论与田口过程能力指数设置各评价指标的权重,建立花键表层物理力学性能的改进田口过程能力指数优化模型,使用广义简约梯度法对模型进行优化,将得到的最优加工工艺参数组合通过冷滚打成形试验进行验证,并对其表层微观组织形貌进行观察和分析。结果表明:进给量对冷滚打花键表层物理力学性能影响程度最大,滚打轮圆角半径次之,冷滚打转速最小;花键表层物理力学性能最优加工参数组合为冷滚打转速1581 r·mm-1,进给量42 mm·min-1,滚打轮圆角半径2 mm;所对应的花键表层物理力学性能最优值为:表层加工硬化程度148. 92%,表层残余应力-85. 83 MPa。     

新型重载辙叉贝氏体钢的组织与性能

用光学显微镜、扫描电镜、X射线衍射分析仪、冲击试验机和万能试验机等对自行研制的重载辙叉用贝氏体钢进行了组织和力学性能研究。结果表明:该试验钢在正火空冷态下即可得到贝氏体组织,由XRD衍射图谱得出组织为无碳化物贝氏体。材料经正火+300 ℃回火后抗拉强度高达1380 MPa,冲击吸收能量高达63.33 J,具有理想的强韧性配合,硬度高且抗回火稳定性好,低温冲击试验表明材料满足了在低温环境下的使用要求。     

Effect of alloying elements on the structure and properties of cast low-alloy steel for wear-resistant castings

Zaporozh'e Machine-Building Institute, Krivoy Rog Central Mining-Repair Plant for Mining and Concentration Equipment. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 50–52, May, 1990.     

高强韧轨道交通用钢药芯焊丝的力学性能及组织分析

针对轨道交通装备用屈服强度为450 MPa级低合金高强钢研制了一种焊接工艺性能优良、具有高强韧性、良好抗疲劳性能的药芯焊丝,并对研制的药芯焊丝熔敷金属拉伸、低温冲击韧性和疲劳强度等力学性能及组织进行了分析.结果表明,研制的药芯焊丝成分设计合理,焊缝组织以针状铁素体和粒状贝氏体为主,晶粒细小,有效提高了焊缝的强韧性,使焊缝具有优良的低温韧性和疲劳性能.药芯焊丝熔敷金属的抗拉强度达到620 MPa,-40℃低温韧性夏比冲击吸收功为96 J,指定寿命为2×106次循环下的疲劳极限为354 MPa,分别是设计目标值的1.1倍、1.6倍和2.2倍,能够满足轨道交通装备用屈服强度为450 MPa级低合金高强钢的焊接需求.     

Evaluation of high-strength steel castings possessing improved weldability

Naval components fabricated from HY-80 high-strength steels require an expensive preheat during welding to avoid heat-affected zone (HAZ) cracking. Quenched-and-tempered low-C, high-Ni steels were evaluated as potential alternatives to HY-80 steel castings with section sizes of 230 to 300 mm thickness. The investigation examined the feasibility of obtaining mechanical properties equivalent to HY-80 by heat treatment and evaluated weldability. The steel resulted in a crack-free casting, and preliminary tests suggest that it could be welded without preheating. Optimized heat treatment provided reasonably good yield strength (517 to 538 MPa) and Charpy impact toughness (63 to 80 J Charpy V-notch (CVN) energy at −73 °C). The former properties were just below HY-80 casting requirements of 550 MPa. Thus, while this composition might not be a suitable replacement for HY-80, there are other potential casting applications. These include surface ship shaft struts and rudder inserts that have less stringent strength and toughness requirements.     

半椭球体薄壁铸件的差压铸造工艺优化

从半椭球体铸件的结构特点出发,结合差压铸造的特性,对其在铸造过程中可能出现的缩孔、缩松等铸造缺陷进行了分析,制定出合理的差压铸造工艺。针对清铲过程中出现的不足,对铸造工艺进行了优化,既方便了清铲,又提高了工艺出品率,最终生产出合格的铸件。