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冬季镀锌方管焊接出现断裂是怎么回事?

来源:http://www.jnxxjm.com

【 发布于:2019-05-22 16:18:56 】


立冬过后,环境温度较低镀锌方管焊接过程中焊件产生的内应力和焊接热过程惹起的焊件的外形和尺寸变化。焊接过程的不平均温度场以及由它惹起的部分塑性变形和比容不同的组织是产生焊接应力和变形的基本缘由。当焊接惹起的不平均温度场尚未消逝时,焊件中的这种应力和变形称为瞬态焊接应力和变形;焊接温度场消逝后的应力和变形称为剩余焊接应力和变形。

After the beginning of winter, the internal stress of the galvanized square pipe welded at lower ambient temperature and the shape and size change of the welded parts caused by the welding heat process. The uneven temperature field in the welding process and the different plastic deformation and specific volume caused by it are the basic reasons for the welding stress and deformation. When the uneven temperature field caused by welding has not disappeared, the stress and deformation in the weldment are called transient welding stress and deformation; the stress and deformation after the disappearance of welding temperature field are called residual welding stress and deformation.

1、设置防护棚

1. Setting up protective shed

在室外施工,当环境温度低于-5℃时,必需在焊接区域设置防护棚,以进步焊接环境温度、并防风防雨。

In outdoor construction, when the ambient temperature is below - 5 C, it is necessary to install protective shed in the welding area to improve the welding ambient temperature, and to prevent wind and rain.

2、焊前预热

2. Preheating before welding

焊前应对焊缝停止预热,预热区域应在焊接坡口两侧,必要时采用随同预热的办法,确保预热温度和层间温度。加热温度为80~150℃,预热范围为焊缝各侧面的1.5t(t为板厚),且不小于100mm。测温采用远红外测温仪,测温点在距坡口边缘75mm处,平行于焊缝中心的两条直线上。

The preheating zone should be on both sides of the weld groove. If necessary, the method of accompanying preheating should be adopted to ensure the preheating temperature and interlayer temperature. The heating temperature ranges from 80 150 C, and the preheating range is 1.5T (t is plate thickness) on each side of the weld, and not less than 100mm. The temperature is measured by far infrared thermometer. The temperature measuring point is 75 mm away from the edge of groove, parallel to two straight lines in the center of weld.

2.1、焊缝预热温度

2.1. Weld preheating temperature

20171219787446.jpg

注:Q345GJ预热温度参照Q345执行;Q390、420预热温度参照Q460;当板厚t=100~110mm时,Q420、Q460和铸钢件的最低预热温度为180℃。

Note: Q345GJ preheating temperature refers to Q345; Q390, 420 preheating temperature refers to Q460; when plate thickness t = 100 ~ 110mm, the minimum preheating temperature of Q420, Q460 and steel castings is 180 C.

2.2、定位焊预热温度比正式焊缝高30~50℃。

2.2. The preheating temperature of positioning welding is 30-50 C higher than that of the formal weld.

3、焊缝层间温度

3. Interlayer temperature of weld

焊缝层间温度应严厉按下表执行

The interlayer temperature of weld seam should be strictly executed according to the following table

4、焊速与焊道布置

4. Welding speed and bead arrangement

手工电弧焊平、横、仰焊焊接速度以规则每根焊条焊接的焊缝长度;

The welding speed of manual arc welding is flat, transverse and up-ward, and the welding seam length of each electrode is regulated.

气体维护焊以单道焊缝不允许摆动,焊层厚度控制在5~6mm,焊条(炬)与工件夹角不小于30°。立焊时允许最大摆动宽度:15mm~20mm。

Single weld is not allowed to swing in gas maintenance welding. The thickness of welding layer is controlled at 5-6 mm, and the angle between welding rod (torch) and workpiece is not less than 30 degrees. The maximum allowable swing width for vertical welding is 15 mm to 20 mm.

5、焊后缓冷

5. Slow cooling after welding

在零度以下厚方管焊接完成后,在焊缝两侧板厚的2~3倍范围内,应采取保暖和冷措施,并使焊缝迟缓冷却,冷却速度应

After the welding of thick square pipes below zero degree is completed, in the range of 2-3 times the thickness of the plates on both sides of the weld, the measures of keeping warm and cooling should be taken, and the weld should be cooled slowly, and the cooling speed should be increased.

立冬过后,环境温度较低镀锌方管焊接过程中焊件产生的内应力和焊接热过程惹起的焊件的外形和尺寸变化。焊接过程的不平均温度场以及由它惹起的部分塑性变形和比容不同的组织是产生焊接应力和变形的基本缘由。当焊接惹起的不平均温度场尚未消逝时,焊件中的这种应力和变形称为瞬态焊接应力和变形;焊接温度场消逝后的应力和变形称为剩余焊接应力和变形。

After the beginning of winter, the internal stress of the galvanized square pipe welded at lower ambient temperature and the shape and size change of the welded parts caused by the welding heat process. The uneven temperature field in the welding process and the different plastic deformation and specific volume caused by it are the basic reasons for the welding stress and deformation. When the uneven temperature field caused by welding has not disappeared, the stress and deformation in the weldment are called transient welding stress and deformation; the stress and deformation after the disappearance of welding temperature field are called residual welding stress and deformation.



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