Due to the low hardness, poor wear resistance and insufficient toughness of the front bucket teeth and main knife plate of the loader and excavator, brittle fracture is easy to occur under the dual action of abrasive impact force and sliding friction force.According to incomplete statistics, the national annual consumption of bucket teeth and the main knife plate up to hundreds of tons.
Wear - resistant surfacing welding is a layer of wear - resistant alloy on the surface of carbon steel or low alloy steel parts.In this way, it can not only improve the wear resistance of the parts, meet the use requirements of the main knife plate and bucket teeth, but also maintain the strength and toughness of the original and reduce the cost of the original matrix material.
I. surfacing welding process
1.Surfacing welding method
When selecting the surfacing welding method, the following requirements should be met: that is, the dilution rate is low;High deposition speed and efficiency;Workpiece size, shape complexity and batch size;Low overall cost.
The concrete structure of the bucket and the above factors can be considered comprehensively.
The choice principle of surfacing metal: one is to meet the performance requirements of the parts.Second, it has good weldability. It should be easy to weld and obtain the surfacing layer with good bonding and no defects with the substrate.It is necessary to pay attention to the compatibility between the surfacing metal and the matrix, and fully estimate the influence of the matrix dilution on the properties of the surfacing layer.When the carbon equivalent of matrix is high, in order to prevent cracking, preheating and buffer technology can be considered.If not, consider using the transition layer.Third, considering the economy of surfacing welding, the selected surfacing alloy should be the one with the lowest price among various alloys with the same performance, and the one with the simplest welding process and the least processing cost.
Due to the strong impact of the bucket main knife plate and bucket teeth caused by chisel type abrasive wear, should be selected to withstand the impact wear of the surfacing alloy electrode.According to the requirements, through consulting materials, through the test, finally selected the cost-effective heap 4102 and heap 1102 electrode.
3.Surfacing welding technology of main knife plate
(1) process parameters
From the characteristics of the main knife plate, production efficiency and reduce dilution rate, the choice should be: surfacing electrode 4102, electrode diameter?Must have 4 mm;Arc stable ax5-500 dc welder, dc reverse welding, welding current 160A.
(2) matters needing attention
(1) before welding will be surfacing welding parts of the scale, rust, water and oil removal clean.
(2) if the main plate surfacing selected in the bucket after the completion of welding, the surfacing caused by the main plate distortion is difficult to correct, for this reason, the surfacing welding should be carried out before the main plate group welding to the bucket.
(3) because the main knife plate is long and thin, easy to cause distortion when surfacing, correction is very troublesome.In order to prevent welding deformation, it should be fixed on the metal frame with higher constraint degree before surfacing, and the middle and section back welding method should be adopted.
(4) to improve productivity and reduce dilution rate, the appropriate use of downhill welding operation.
If surfacing causes deformation of the main knife plate, the application of oil press, such as leveling.
6. The hardness of the surfacing layer after surfacing welding should be greater than HRC50.
4.Bucket tooth surfacing welding process
(1) due to the hardness requirements of bucket teeth higher than the main knife plate, and poor weldability, if the use of electrode 1102 direct surfacing, although the hardness can meet the requirements, but because of the difference between the two materials linear expansion coefficient, surfacing layer easy to peel off.For this, need to add a layer of transition layer, choose?A 4mm electrode 4102 is used to surfacing the transition layer first, and then the electrode 1102 is used as the cover layer. The total thickness of the two layers is 5~6mm, accounting for about 1/2 each. The hardness of the surface layer is greater than HRC60.
(2) heat concentration during bucket tooth surfacing welding, in order to prevent its deformation, generally 4 bucket teeth should be surfacing welding at the same time, adopt short pass welding, and rotate in turn to reduce the heat accumulation to the minimum.
(3) wear resistance surfacing welding can be carried out on the new bucket tooth (protection), also can be used for the repair of the old bucket tooth.When repairing the old bucket tooth, it is necessary to fill out the badly worn part with ordinary welding materials first, and then use the above surfacing technology to surfacing a layer of wear-resistant materials.