JB/T 51118-1999

Manufacturers and quality inspection departments of internal combustion engine full round main bearings use this standard to classify products into qualified and first-grade levels. It sets specific requirements for materials, dimensions, surface roughness, and sampling inspection plans to ensure consistent product quality. This standard provides a unified grading basis for the industry, helping to improve the reliability and interchangeability of main bearings.

内燃机整圆主轴承的制造企业和质量检验部门使用本标准，对产品进行合格品和一等品的分级评定。它通过规定材料、尺寸、表面粗糙度等具体指标和抽样检验方案，确保轴承产品的质量一致性。该标准为行业提供了统一的质量分等依据，有助于提升内燃机主轴承的可靠性和互换性。

This standard specifies quality indicators, inspection methods and inspection rules for qualified and first-grade full round main bearings for internal combustion engines, applicable to reciprocating engines with cylinder diameters up to 200 mm. It sets requirements for material hardness, chemical composition, and metallographic structure of steel layers, babbitt, copper-based and aluminum-based alloys, as well as wall thickness tolerance, alloy layer thickness, dimensional tolerances, roundness, and surface roughness. Inspection methods include hardness testing, chemical analysis, metallographic examination, and dimensional measurement. Sampling follows GB/T 2828 with classification into four nonconformity categories A, B, C, and D. This standard replaces JB/T 51118.1~51118.3—94 with only editorial changes.

本标准规定了内燃机整圆主轴承合格品和一等品的质量指标、检验方法和检验规则，适用于气缸直径200mm以内的往复式内燃机。标准对材料（钢层、巴氏合金、铜基合金、铝基合金）的硬度、化学成分、金相组织提出要求，并规定了壁厚公差、合金层厚度、尺寸公差、圆度、表面粗糙度等参数。检验方法包括硬度测试、化学分析、金相检验、尺寸测量等。抽样方案采用GB/T 2828，按A、B、C、D四类不合格进行判定。标准代替了JB/T 51118.1~51118.3—94，仅作编辑性修改。