三级焊缝是否要求无损检测（焊缝无损检测和等级分类有哪些要求）

根据结构的重要性、载荷特性、焊缝形式、工作环境和受力状态，应按以下原则选择不同的质量等级。

According to the importance of the structure, load characteristics, weld form, working environment and stress state, different quality grades shall be selected according to the following principles.

• 在需要进行疲劳计算的部件中，所有对接焊缝应全焊，其质量等级如下：

1. In the components requiring fatigue calculation, all butt welds shall be fully welded, and their quality grades are as follows

垂直于焊缝长度方向，对接焊缝或T型对接角焊缝和焊缝，受压等级为二级，受拉等级为一级；

The compression grade of butt weld or T-butt fillet weld and weld perpendicular to the weld length is grade II and the tensile grade is grade I;

如果纵向受力平行于焊缝的长度方向，对接焊缝应为二级。

If the longitudinal force is parallel to the length of the weld, the butt weld shall be class II.

• 要求与母材强度相等的对接焊缝应全焊透，在不需要计算疲劳的构件中，其质量等级受拉时不低于二级，受压时不低于一级。

2. The butt weld with the same strength as the base metal shall be fully welded. In the components that do not need to calculate fatigue, its quality grade shall not be lower than grade in tension and grade in compression.

• 工作系统重量大、起重量Q≥50t的吊车梁腹板与L翼缘之间以及吊车支腿上弦杆与节点板之间的T型焊缝要求全焊。焊缝一般为角接接头和对接接头的组合焊缝，其质量不能低于二级。

3. The T-shaped weld between the web and l flange of the crane beam with large working system weight and lifting capacity Q ≥ 50t and between the upper chord of the crane leg and the gusset plate shall be fully welded. The weld is generally a combination of fillet joint and butt joint, and its quality shall not be lower than grade II.

4.不要求完全熔透的“工”字形接头的角焊缝或部分熔透的对接接头和角焊缝的组合焊缝，以及搭接接头的角焊缝的质量等级如下：

4. The quality grades of fillet welds of "I" joints that do not require full penetration or combined welds of butt joints and fillet welds with partial penetration, as well as fillet welds of lap joints are as follows:

直接承受动荷载的结构和吊车起重量等于或大于50t的吊车梁，这样的焊缝质量标准应达到二级。

For structures directly bearing dynamic load and crane beams with crane lifting capacity equal to or greater than 50t, such weld quality standard shall reach grade II.

外观检查一般采用目测，裂纹检查应在合适的光照条件下用5倍放大镜进行。必要时可采用磁粉探伤或渗透探伤，尺寸测量应使用量具和卡尺。

Visual inspection is generally adopted for appearance inspection, and crack inspection shall be carried out with 5x magnifying glass under appropriate lighting conditions. Magnetic particle flaw detection or penetrant flaw detection can be used when necessary, and measuring tools and calipers shall be used for dimension measurement.

焊缝外观质量应符合下列要求

The appearance quality of welds shall meet the following requirements

不得有未焊透、根部收缩、咬边、接头不良等缺陷，一级和二级焊缝不得有表面夹渣、气孔、电弧擦伤和裂纹等缺陷。

There shall be no defects such as incomplete penetration, root shrinkage, undercut and poor joint. The primary and secondary welds shall be free of defects such as slag inclusion, air hole, arc scratch and crack on the surface.