MH-type gantry crane girder deformation Flame straightening

MH-type gantry crane girder deformation Flame straightening

Flame straightening method is based on the local heating of the metal structure, some parts of the metal structure by "plastic compression", after cooling the residual shrinkage stress reaches the local distortion correction purposes.

Camber insufficient heating plate and the lower side of the triangle under the cover of a rectangular area, insufficient heating Camber upper triangular cantilever webs on the cover rectangular areas and areas. Grilled and roasted point size and location of the point number, according to the specific conditions deformation. But must pay attention to the following points:

1) the most suitable heating temperature of 700-800 ℃, the heating temperature is too high or too low should be. Because the metal is heated to temperatures paragraph (low carbon steel) trend into the yield limit of zero, the metal in the "hot steel" state, the best correction.

2) the same location can not be repeated heating. Otherwise, not only ineffective, the microstructure of the metal also has damage.

3) plus interest should be placed at the bulkhead, the web can be reduced waviness.

4) plus hot should avoid dangerous section. Grilled point corrected by heating parts stress increase, so dangerous section also increased stress load, easy to make correction Deformation.

5)  overhead gantry crane  girder beam deformation emperor should be reinforced. Because stress beam correction emperor, with the massive use for many years, metal materials gradually fatigue, lack of rigidity. Without reinforcement, correction effect not only keep her, but distortion will be more serious. General approach is reinforced girder span both sides of the lower cover to do with the web channel, plus a layer of lower cover, in order to increase the main beam sections.

Flame straightening advantages are: correction better, especially with hard bend also play a role; construction process is also relatively simple. Therefore, the flame straightening method is widely used. However, this correction method has the following disadvantages: the flame straightening, in order to have a "compression molding" effect, required corrective parts of the main beam from the top (the grilled area compressive stress), or no effect, thus increasing the construction difficulty; despite the separator at flame heating, causing the web and the cover can still larger waviness; flame girder reinforcement after correction required, otherwise, will have a more serious distortion.

Given the above analysis, under normal circumstances (except for partial correction of hard curved outer), does not advocate the use of flame straightening method. However, large beams, channels, etc. as well as anti-deformation straightening, use Flame straightening ideal. Neither have large presses, but do not be too spacious grounds. According to the degree of bending steel, suitable to choose a few roasted points, baked triangular facade, flat baked rectangle. Grilled girder bridge gantry crane  point size, the number of decisions based on the degree of deformation can be immediately adjusted, both effort and fast.