What is Flame Straightening Method for Crane Main Girder Deformation?
Sometimes ZZHZ will use flame straightening method to correct crane main girder deformation. Flame straightening method refers to that local heating on the metal structure produces plastic compression on some places and remained local shrinkage stress can correct the bend after cooling.
gantry crane
As using the flame straightening method, ZZHZ takes detailed main girder deformation condition into consideration and decides size, numbers and position of heating points, some tips below must be considered:
1)????? the most appropriate heating temperature 700-800?, over-high or over-slow heating temperature should be avoided.
2)????? Repeated heating at the same position should be forbidden, or it will cause a bad result as well as a damage to the metallographic structure.
3)????? Heating point should be located in baffle plate to reduce bending of web plate
4)????? Heating point should be avoided on the dangerous section. Stress at part around heating point increases after heating correction, so load stress in the dangerous section increases and bending correction will not work.
5)????? Strengthen the main girder after distortion. Because main girder stress will be large after correction, metal materials get tired with not enough stiffness after many years using. If strengthening the main girder is neglected, the correction effect will lose and the distortion will be more serious.
Advantages for the flame straightening method:
1. Good correction result, especially on harder crook;
2. Simple construction technology
Disadvantages:
1. As using flame straightening method, to achieve compression molding, main girder correction part must be jacked up, or it has no effect, which increases the work difficulty
2. Even though flame heating is at the position of baffle plate, it can still cause a large shape wave on the web plate and cover plate
3. Main girder strengthening must be done after flame correction, or it will cause a more serious distortion.
ZZHZ CRANES
According to analysis above, ZZHZ does not use flame straightening method in general condition. While the method is most appropriate as aligning and make pre-deformation on the large joint steel, U-bar and other materials. Large press machine or too capacious area is not necessary. Just properly choose size, numbers and position of heating points according to structural steel bending and deformation degree, the correction can be done, convenient and simple.
