Repair welding measures and process introduction o

Repair welding measures and process introduction of cycloid needle wheel of reducer of tower crane

qt16 tower crane, after 9 years of use, suddenly appeared the failure that the tower body could not rotate during construction. When disassembling and overhauling the reducer, it was found that there were many cracks, wear and falling blocks on the second stage cycloid needle wheel of the reducer. Because there are no spare parts in stock, it is decided to repair by welding

1. weldability analysis

the cycloid needle wheel is made of GCr15, which has high carbon content, high hardening tendency, easy to crack and s, P segregation, high thermal cracking sensitivity and poor weldability

2. repair welding measures

(L) eliminate cracks

according to the different shape, depth and length of cracks, use a grinder to eliminate shallow and short cracks first, and then deep and long cracks. The grinding sequence is from the end of the crack to the elimination of the crack, so as to prevent the crack from spreading and grind the groove at the same time. For cracks that are not cracked through, make the groove bottom transition smoothly to reduce stress concentration; For the crack through, a single V-shaped groove shall be made

(2) repair welding process

correct the crack so that its surface is in a plane, and fix it by spot welding. The repair welding sequence is to weld the short and shallow crack first, then weld the crack through, and finally weld the damaged part to the original shape

when repairing short and shallow cracks, pay attention to arc from the end of the crack first to prevent cracks during welding. Weld point by point and observe while welding. Through the repair welding observation of the first crack, it is not only revealed the essence of the concept and the realization principle, but also there is no new crack, which proves that the welding process is feasible

when repairing cracks, the back must be thoroughly cleaned with a grinding machine before welding to expose metallic luster. For worn and damaged parts, oil stain and rust shall be removed before repair welding

(3) welding specification parameters

because the part requires good wear resistance and high precision, but poor weldability, it is selected with good crack resistance The stainless steel electrode with wear-resistant and acceptable machinability (the shape of the sample is different) is used as the filling material. Its brand is A307, the specification is ￠ 3.22mm, heated to 350 ℃ and baked for 2h, the welding current is 90-100a, the welding voltage is V, and the welding line energy is kJ/cm. The welding machine is ax-320, reverse connection.

(4) post welding treatment. The whole part is insulated and slowly cooled after welding. After cooling to room temperature, it is processed on the lathe for two planes, and the excess surfacing metal on the edge is trimmed with a file, Until the cycloid needle wheel is restored to its original geometric size

3. Effect

the cycloid needle wheel has been used for more than 5 years since it was repaired. The performance of the machine is widely used in building materials, aerospace, machinery manufacturing, wire and cable, rubber and plastic, textile, household appliances and other occupations. The data inspection and analysis are good, which fully meets the use requirements and saves maintenance costs