根據結構的重要性、載荷特性、焊縫形式、工作環境和受力狀态，應按以下原則選擇不同的質量等級。

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.

• 在需要進行疲勞計算的部件中，所有對接焊縫應全焊，其質量等級如下：

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

垂直于焊縫長度方向，對接焊縫或T型對接角焊縫和焊縫，受壓等級為二級，受拉等級為一級；

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;

如果縱向受力平行于焊縫的長度方向，對接焊縫應為二級。

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

• 要求與母材強度相等的對接焊縫應全焊透，在不需要計算疲勞的構件中，其質量等級受拉時不低于二級，受壓時不低于一級。

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.

• 工作系統重量大、起重量Q≥50t的吊車梁腹闆與L翼緣之間以及吊車支腿上弦杆與節點闆之間的T型焊縫要求全焊。焊縫一般為角接接頭和對接接頭的組合焊縫，其質量不能低于二級。

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”字形接頭的角焊縫或部分熔透的對接接頭和角焊縫的組合焊縫，以及搭接接頭的角焊縫的質量等級如下：

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:

直接承受動荷載的結構和吊車起重量等于或大于50t的吊車梁，這樣的焊縫質量标準應達到二級。

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.

外觀檢查一般采用目測，裂紋檢查應在合适的光照條件下用5倍放大鏡進行。必要時可采用磁粉探傷或滲透探傷，尺寸測量應使用量具和卡尺。

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.

焊縫外觀質量應符合下列要求

The appearance quality of welds shall meet the following requirements

不得有未焊透、根部收縮、咬邊、接頭不良等缺陷，一級和二級焊縫不得有表面夾渣、氣孔、電弧擦傷和裂紋等缺陷。

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.

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