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Electric arc-welding of repair craft of the casting iron bearing stand


28th February 2010 Bearing Technology 0 Comments

Through to its material technical feature, that iron can welding,etc. the analyses of performances, have introduced the fracture situation of the pinion stand baseplate. Have confirmed the construction scheme of electric arc cold welding of the craft, and put forward the concrete welding craft, have finished the repair of this work piece smoothly.

A defective situation and failure analysis

Fracture situation of the pinion stand

Position and crack beginning, there are two to rupture pinion seat and a baseplate rupture and have two four foundation screw holes of pinion stand baseplate. Give up a size 270mm 250mm 70mm, the fracture size 270mm 100mm 130mm

Have already split completely. The baseplate ruptures in a place .

Failure analysis

Stress is centralized in the place that strengthens the edge of rib and connects with baseplate. Run, pinion flat itself it receives constrained degree to be relatively loud in not using. In charge of the mill and run and bear the loaded function of reversal in the course. Work piece makes defects . Because big constrained degree and loaded function of reversal, prestressing force concentrates the place on destroying, form the crackle, expand to the rib board progressively, rupture.

2 repairs the scheme to choose

Select the electric arc-welding method of the craft for use to repair.

Repair craft to the casting iron bearing stand of electric arc-welding of the craft

The iron can the welding is analyzed

Having brought great difficulty to electric arc-welding, because inherent property and metallurgical characteristic of the casting iron. The details are as follows :

A hot affected zone is apt to organize white mouth, the cooling of casting iron is quick in speed after melting. Fracture and is inclined to bigger while welding.

The content of 2 carbon is high, the casting iron makes up in the composition. Weld easy carbon angry to take in the course, it is apt to take place in the air vent.

3 plasticity is bad, the casting iron is tall in intensity. The residual stress is great, apt to produce and weld the hot crackle while welding.

4 combines and melts to the welding seam in the course of welding, element content such as C S P are high in the casting iron. Will increase the metal hardness, will reduce plasticity and toughness, apt to produce the crackle, and reduce machinability.

5 is apt to present the graphite to melt loudly, the casting iron is in smelting the course. The graphite and matrice produce the interval, make the casting oil, water in the course of using permeate through and form and oxidize things, melting and is shut while hindering welding seriously, meanwhile, increase possibility to weld crackle and air vent.

6 liquid state metal flowability is very bad, the casting iron is being welded while melting. Serious the intersection of hindrance and melting, shutting weld, slag and harmful gas difficult to produce with the ease in the molten bath, will produce the major defect in the welding seam.

Must be from welding the craft, working technique, welding the order, welding several respects of materials to solve. To the above favorable factor .

Weld the choice of the method

It is not low at 400 ℃ to weld the working temperature in the course, weld and can adopt two kinds of methods of heat welding and cold welding by hand with casting iron. Electric arc heat of craft is welded to heat to the work piece wholly 600 ℃- over 650 ℃ begins to be constructed and welded. Will heat to 650 ℃ at once after welding, in order to dispel the stress annealedly.

And oxidize a subsidiary factory of aluminium and have no appropriate heating to equip, the weight of the pinion stand is 1.74t. So adopt the electric arc cold welding law of the craft to repair. The law of cold welding means the temperature, flyer energy welding method are welded between controlling layer by not preheating, strictly.

Weld the choice of the materials

For guarantee, weld quality and lay superficial machinability, should adopt pure the intersection of nickel and base weld pairs of Z308, weld. Noble in but Z308 welding rod price,HT15233 can welding getting worse and the surfaces lowers of base, for lasting surfacing. In order to save the expenses, can adopt, weld, isolate layer, J507 with the intersection of Z308 and welding rod welding rod with Z308 welding rod pack each other and Z308 welding rod stamp the Taxi method to go on and repair, in this way can both reduce the interest and guarantee, weld quality and lay a superficial one but processing characteristics.

Repair craft to the casting iron bearing stand of electric arc-welding of the craft

Weld the order

1 the intersection of crackle and the intersection of and constructing, welding one after another according to reprocess process.

2 guarantees to weld it completely, weld the board side of rib first in the disconnected places. And then from the clear root of the other side, constructs and welds. And then weld the rib board.

3 is welded

Remove defective factors such as all forming a scab, greasy dirt,etc., should totally clear up all welding positions before welding. Then begin to weld and prepare.

The crackle is welded and prepared

Use the angle to major in and waste the crackle place to the polishing machine to waste out the required pairs of Model U slope port. Demand to dispel all crackle inclination while repairing and rubing, after appearance is cleaned out. The smooth transition of edge of slope mouth, blunt, the interval is subject to that it can be welded completely that unilateral.

Broken one gets along with and welds preparing

Appearance uses the angle to major in and wear into the slope port of a pair of Model U the fracture to the polishing machine according to slope port requirement shape, size after clearing up, two basic rule of shape of a place that broken one ruptures . Blunt side, interval with can weld completely while being unilateral and the other side subject to clear root, then the intersection of flat and noumenonn group right ordering broken piece and pinion at scribing platform according to size

Welding

In order to reduce and weld the stress and weld out of shape, the pinion Tower welds and melts the applying amount bigger. Guarantee to weld quality, adopt the job systems of class two, the fixed high-level welder constructs and welds. The ambient temperature guarantees at over 20 ℃, the night shift if hypothermia stops welding while welding. In order to prevent the draught, construct and set up and enclose the covering while welding in case the wind keeps warm. Weld the crackle first while welding, then weld and rupture one. Weld the crackle among two screw holes first while welding the crackle, finish welding, weld the outer crackle.

1 Z308 welding rod wants 150 ℃ to dry 1h, before welding. J507 wants 250 ℃ to dry 2h, dry, put and keep warm the barrel China Insurance Company, Ltd. warmly, uses and fetches at the same time at the same time.

2, in order to do benefit to operating. Will weld one to put on the horizontal level at the time of each welding .

Each section length 3 does not exceed 30mm, adopt the short way, put one, intermittent and dispersing and welding the law fast, while welding. Fill-up the arc hole while accepting arcly.

4 hammer hit speed, take quick, weld line hit, weld line in order to release, weld in conformity with force entirely with blunt the intersection of head and little hammer at once. Strength is duplicated each other lighter and lighter.

5 is finished welding and must cool to under 50 ℃ and can continue constructing and welding together each time. Temperature while controlling layer strictly .

6 pack, weld and build surface, can enlarge, alloy than while being appropriate weld. Adopt light to alloy, weld going on feel secure, .

7 is observed with the fivefold magnifying glass, after removing the slag. Without crackle, continue welding next again.










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