船体结构焊缝进行无损检测（Non-destructive testing of ship hull steel welds）中国船舶工业无损检测标准（CB/T）与IACS Rec. 20标准的比较说明Brief introduction for comparing Chinese shipbuilding NDT standards (CB/T)with IACS REC 20几乎所有的中国船厂采用以下无损检测标准对船体结构焊缝进行无损检测：CB/T3177-94（船舶钢焊缝射线照相和超声波检查规则）、CB/T3558-94（船舶钢焊缝射线照相工艺和质量分级）、CB/T3559-94（船舶钢焊缝手工超声波探伤工艺和质量分级）、CB/T3958-2004（船舶钢焊缝磁粉、渗透检测工艺和质量分级）Almost all Chinese shipyards adopt following recognized NDT standards for non-destructive testing of ship hull steel welds：CB/T3177-94（Ship steel weld radiographic testing and UT testing standard，CB/T3558-94（Ship steel weld radiographic testing technology and quality classification），CB/T3559-94（Ship steel weld UT testing technology and quality classification）and CB/T3958-2004 （Ship steel weld magnetic particle & penetration testing technology and quality classification）在IACS URZ23 和IACS Rec. 47中提及使用IACS Rec. 20对船体结构焊缝进行无损检测，为了便于验船师检查无损检测结果，现将上述标准与IACS Rec. 20标准的比较结果具体如下：In IACS URZ23 and IACS Rec. 47, IACS.20 is referred to be applied for non-destructive testing of ship hull steel welds. In order to convenience for surveyor checking NDT results, full comparison between above mentioned national NDT standards with IACS.20 are done, see the contrast tables and conclusions as follows:一、射线照相检测radiographic testing:表1 / Table 1：表1/Table 1：1. 比较CB普通级绿色数据与IACS REC 20的相应数据要求，在相同的透照范围内，透照灵敏度（发现金属丝指数）即像质计要求，CB/T3558-94标准的普通级严于IACS Rec. 20的要求；Regarding wire number visible on the film (nominal diameter) i.e. IQI, comparing green figures between CB/T3558-94 (normal class) and IACS REC 20, within the same nominal thickness range, found that IQI (normal class stipulated on CB/T3558-94) is much more stringent than that of REC 20.2. 比较CB普通级红色IQI数据与IACS REC 20的IQI数据要求，在相同的透照范围内，透照灵敏度（发现金属丝指数）即像质计要求CB/T3558-94标准的普通级小于IACS Rec. 20的要求；Regarding wire number visible on the film (nominal diameter) i.e. IQI, comparing red figures between CB/T3558-94 (normal class) and IACS REC 20, within the same nominal thickness range, found that IQI (normal class stipulated on CB/T3558-94) is less stringent than that of REC 20.3. 所以船厂或无损检测公司在射线照相透照灵敏度（发现金属丝指数）上，可以使用CB/T3558-94标准的普通级要求，并注意在此情况下与IACS Rec. 20要求相一致，即在X 射线片子上看到相应要求的金属丝指数。

Hence, shipyard or NDT company may adopts CB/T3558-94 standard’s wire number visible on the film (nominal diameter), but shipyard has to pay attention to be in line with required IQI stipulated on IACS REC 20, i.e. required wire number visible on the film (nominal diameter), then it can meet IACS REC 20.表2 / Table 2：表2 / Table 2：比较CB/T3558-94标准中，γ射线照相底片密度能够满足IACS Rec. 20标准；如船厂或无损检测公司在实际使用X射线照相时，操作人员应通过使用适当设备或增加曝光量等，使底片密度达到IACS REC 20的要求，这样就可以满足IACS Rec. 20标准对底片密度的要求。

Comparing CB/T3558-94, γ-ray can meet requirement of film density stipulated on IACS REC 20; in case shipyard or NDT company, are using of X-ray in normal practices, NDT operator should choose suitable X-ray equipment or increase exposal etc. to meet IACS Rec. 20 requirement on film density.*注：根据IACS REC 20所述，黑度由船厂或无损检测公司根据ISO17636的表5进行选择：*Note：Acc. to requirement stipulated on IACS REC 20 (6.5.8), the optical density of the radiographs should be selected by the shipyard in accordance with table 5 of ISO17636 :ISO17636表5 / ISO17636 table 5Optical density of the radiographs 等级Class 黑度a / Density aA（普通级）/（Normal class）≥2.0bB（较高级）/（Upper class ≥2.3ca：测量允许误差为±0.1 / Measuring tolerance of ±0.1 is permittedb：经合同各方商定，可将为1.5 / May be reduced to 1.5 if specified, e.g. in an application standard. c：经合同各方商定，可将为2.0 / May be reduced to 2.0 if specified, e.g. in an application standard.表3 / Table 3：IACS Rec. 20标准射线照相质量分级Acceptance criteria for radiographic testing - IACS REC 20缺陷种类Discontinuity 接受标准Acceptance criteria for radiographic testing¹)裂纹Crack 不接受Not accepted未熔合Lack of fusion 单个缺陷最大接受长度t/2或25mm，两者取小者；间断缺陷总计最大接受长度t或50mm，两者取小Continuous²)maximum length t/2 or 25 mm whichever is the less intermittent cumulative³) length maximum t or 50 mm未焊透Incomplete root penetration 位于十字接头的单面对接接头焊缝不接受Not accepted in butt joint welded from one side单个缺陷最大接受长度t/2或25mm，两者取小者；间断缺陷总计最大接受长度t或50mm，两者取小Continuous²)maximum length t/2 or 25 mm whichever is the less intermittent cumulative³)length maximum t or 50 mm夹渣Slag inclusion 单个缺陷最大接受长度t或50mm，两者取小者；间断缺陷总计最大接受长度2t或100mm，两者取小Continuous²)maximum length t or 50 mm whichever is the less intermittent cumulative³)’)length maximum 2t or 100 mm注Note:¹): “t”取焊接板材的最小厚度。