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铸铁护栏焊接头出现裂纹的原因!

来源:http://www.kpp647.com添加时间:2019-05-14 13:49:25

裂纹是焊接铸铁的一个严重问题,铸铁焊接接头上的裂纹可能出现在焊缝金属中,也可能在基本金属即母材上。母材的裂纹一般出现近缝区,可能是纵向,横向或斜向的。山东铸铁护栏厂家在这里提示大家,由于铸铁塑性极差,几乎不能发生任何塑性变形,而且强度又低,所以在焊接应力及铸件本身应力(组织应力)的共同作用下,当局部应力大于强度极限时,就产生裂纹。严重时,会使焊缝金属和母材分离,即焊缝从基本金属上脱离下来,即所谓剥离。

Cracks are a serious problem in welded cast iron. Cracks in welded joints of cast iron may occur in weld metal or in base metal. The cracks of base metal usually appear near the crack zone, which may be longitudinal, transverse or oblique. Shandong cast iron guardrail manufacturer reminds us here that because of the poor plasticity of cast iron, hardly any plastic deformation can occur and the low strength, cracks will occur when the local stress is greater than the strength limit under the joint action of welding stress and the stress (tissue stress) of the casting itself. In severe cases, the weld metal will be separated from the base metal, that is, the weld will be separated from the base metal, that is, the so-called stripping.

如果焊缝强度较高而母材强度较低,或结合处产生白口时,由于白口铸铁收缩率(1。6%-2。%)比铸铁收缩率(0。9%-1。8%)大,且塑性也差,故均产生剥离。焊缝金属内的裂纹,一般常见的是横向裂缝,有时也有纵向及斜向裂纹,在焊缝断口处没有高温氧化时常见的蓝颜色。裂纹生成时常发出清脆的金属开裂声。通常裂纹发生在热态焊缝金属的暗红色消失后,即600℃以下,直到焊缝与焊件整体温度均匀化之前。最容易发生裂纹的温度在400℃以下,通常这种在热应力和组织应力的共同作用下发生的裂纹称为热应力裂纹。

If the weld strength is higher and the strength of base metal is lower, or the white cast iron shrinkage (1.6% - 2.0%) is larger than that of cast iron (0.9% - 1.8%) and the plasticity is poor, the peeling will occur. Cracks in weld metal are generally transverse cracks, sometimes longitudinal and oblique cracks. There is no common blue color when high temperature oxidation occurs at weld fracture. Cracks often produce crisp cracking sounds of metals. Usually the cracks occur after the dark red of the hot weld metal disappears, that is, below 600 C, until the temperature of the weld and the whole weld is homogenized. The temperature at which cracks are most likely to occur is below 400 C. Usually, the cracks that occur under the combined action of thermal stress and tissue stress are called thermal stress cracks.

山东铸铁护栏

(1) 焊前预热和焊后缓冷的措施:

(1) Preheating before welding and slow cooling after welding:

焊前将焊件整体或局部预热和焊后缓冷不但能减少焊缝的白口倾向,并能减小焊接应力和防止焊件开裂。

Preheating the whole or part of the weld before welding and slow cooling after welding can not only reduce the whiteness tendency of the weld, but also reduce the welding stress and prevent the cracking of the weld.

(2) 采用电弧冷焊减小焊接应力的措施:

(2) Measures to reduce welding stress by arc cold welding:

选用塑性较好的焊接材料,如用 镍,铜,镍 铜,高钒钢等作为填充金属,使焊缝金属可通过塑性变形松弛应力,防止裂纹;用细直准焊条,小电流,断续焊,分散焊的方法可减小焊缝处和基本金属的温度差而减小焊接应力;通过锤击焊缝可以消除应力,防止裂纹。

Welding materials with good plasticity, such as nickel, copper, nickel-copper and high vanadium steel, are selected as filler metals to make the weld metal relax stress and prevent cracks through plastic deformation; the temperature difference between the weld and the base metal can be reduced by fine collimating electrode, small current, intermittent welding and dispersed welding; and the stress can be eliminated by hammering the weld to prevent cracks.

使焊缝冷却时能补受阻碍底自由收缩,从而避免用力过大而导致裂纹。

When the weld is cooled, it can compensate for the free shrinkage of the hindered bottom, thus avoiding excessive force leading to cracks.

(3) 采用热焊法并控制好温度.

(3) Adopt hot welding method and control temperature well.

当温度高于600℃时,由于产生于一定的塑性变形.而使部分内应力得到消除,一般在600℃以上焊接时就不会产生热应力裂纹.

When the temperature is higher than 600 C, some internal stresses are eliminated due to certain plastic deformation. Generally, thermal stress cracks will not occur when welding above 600 C.

以上就是山东铸铁护栏给我们整理提供的精彩内容了,不知道小伙伴们懂了没有,如果大家还有疑问欢迎咨询我们官网的客服人员:http://www.kpp647.com

The above is the wonderful content of Shandong cast iron fence for us. I don't know if our friends understand it. If you have any questions, please consult our customer service staff on our official website: http://www.kpp647.com.



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