The box type structure, cavity cannot antirust paint corrosion, in order to prevent moisture intrusion corrosion beam cavity, sealing the inner cavity of the main girder must keep.
箱型结构的主梁，内腔无法涂漆防锈蚀，为了防止水汽侵入腐蚀主梁内腔，必须保住主梁内腔的密封性。
To install the crane span before installation, camber, level of metal structure of main girder bending, trolley rail height difference, gauge deviation, diagonal bridge survey.
安装前要对起重机安装跨度，金属结构主梁的拱度、水平旁弯，小车轨道高低差、轨距偏差，桥架对角线等进行测量。
LC4 alloy have been used on aerospace industry and others widely, and it is used on main load-carrying structure of airplane, for example girder and bulkhead and junction etc.
LC4铝合金在航空航天等工业中得到了广泛应用，在航空工业中主要用于飞机大梁、隔框、接头等重要承力件。
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