针对 G20Mn5QT 低合金铸钢在轨道交通制动夹钳座等关键部件中出现的铸造缺陷，系统研究其高质量焊补修复工艺，以提升缺陷修复质量与构件服役可靠性。G20Mn5QT 作为一种广泛应用于转向架、制动系统等关键承载部件的低合金铸钢，其铸造过程中常因工艺波动产生气孔、夹渣、裂纹等缺陷，严重影响构件使用寿命与行车安全。 焊补是修复此类缺陷、降低生产成本、提高材料利用率的关键技术手段，但由于 G20Mn5QT 碳当量较高(0.48~0.64)，组织以马氏体为主，焊接过程中易出现热影响区脆化、冷裂纹及残余应力集中等问题，对焊接工艺提出了严格要求。 基于此，采用焊 条 电 弧 焊 方 法，选用低氢高韧性焊材 ESAB OK48.04，系统研究预热温度、层 间 温 度、热输入等关键参数对焊接接头组织与性能的影响。 通过力学性能测试、硬度分析及金相观察，综合评价焊补接头的综合性能。 研究表明，在预热(200±10) ℃、层间温度 210~300 ℃、热输入 1.0~1.8 kJ/mm 的工艺条件下，焊补接头抗拉强度达 571 MPa 以上，断后伸长率不低于 27%，-40 ℃冲击功最高达 130 J，焊缝与热影响区硬度分布合理，组织过渡连续，无裂纹、气孔等缺陷。 通过优化的焊补工艺，可实现 G20Mn5QT 铸钢缺陷的高质量修复，接头强度与母材相当，低温韧性显著提升。

A systematic investigation was conducted on an advanced weld repair methodology aimed at rectifying castingdefects in critical components, specifically brake calliper brackets manufactured from G20Mn5QT low-alloy cast steel,which are employed in rail transit systems. The primary goal is to improve the quality of defect remediation and enhancethe operational reliability of these components. G20Mn5QT, a low-alloy cast steel widely used in vital load-bearingstructures such as bogies and braking mechanisms, is prone to casting imperfections, including porosity, slag inclusions, andcracking, largely attributable to process variability. These defects substantially undermine the service life and safetyperformance of the components. Welding repair constitutes a pivotal approach to address these flaws, thereby loweringproduction expenses and optimizing material usage. However, the relatively elevated carbon equivalent of G20Mn5QT(ranging from 0.48~0.64), coupled with its predominantly martensitic microstructure, predisposes the welding process tochallenges such as embrittlement within the heat-affected zone, cold cracking, and residual stress accumulation,necessitating stringent control over the welding parameters. On this basis, shielded metal arc welding (SMAW) utilizing thelow-hydrogen, high-toughness electrode ESAB OK48.04 was employed to systematically evaluate the effects of criticalwelding parameters, including preheating temperature, interpass temperature, and heat input, on the microstructural characteristics and mechanical performance of the welded joints. Comprehensive assessments were conducted throughmechanical testing, hardness profiling, and metallographic examination. The findings reveal that under optimized conditions,specifically, preheating at (200±10) ℃, interpassing temperatures between 210 and 300 ℃, and heat inputs ranging from1.0 to 1.8 kJ/mm, the weld repairs achieve tensile strengths exceeding 571 MPa, fracture elongations of no less than27% , and Charpy impact energies at -40 ℃ reaching up to 130 J. The hardness distribution across the weld metal andheat-affected zone is uniform, with continuous microstructural transitions and an absence of defects such as cracks orporosity. The optimization of the weld repair process facilitates the high-quality restoration of casting defects in G20Mn5QTcast steel, yielding joint strengths comparable to those of the base material and significantly improving the low-temperaturetoughness.