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Welding method for centrifugal casting ductile iron pipe

A welding method and centrifugal casting technology, which are applied in welding equipment, manufacturing tools, arc welding equipment, etc., can solve the problems of complicated welding process of ductile iron pipes, rising engineering cost, white mouth, etc., and improve the microstructure of weld seam and mechanical properties, improve the toughness of weld deposited metal, and reduce the effect of welding crack tendency

Active Publication Date: 2016-11-09
STATE GRID SHANDONG ELECTRIC POWER +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, steel pipe poles for power transmission are all made of carbon steel structure and hot-dip galvanized anti-corrosion treatment. The following problems exist in the production and application of hot-dip galvanized steel structure pole towers: (1) The structural defects of the structure itself lead to heavy weight and increased project cost; (2) ) poor corrosion resistance, complex anti-corrosion treatment process, high cost and environmental pollution, especially in coastal areas and industrial pollution areas; (3) high daily operation and maintenance costs
However, in the welding process of ductile cast iron pipes, the efficiency of traditional electrode arc welding is low, the weld shape is poor, and special electrodes for cast iron are required, the cost of welding materials is high, and the post-weld effect is not ideal; the carbon content in cast iron is high , S, P and other impurities are high, and defects such as white holes, cracks, and pores are prone to appear in the traditional electrode arc welding process. Usually, preheating at 400-700 ° C is required during the welding process, and post-weld annealing or post-welding is required if necessary. Normalizing
Therefore, the welding process of ductile iron pipes is complicated and the welding cost is high, which seriously restricts the application of ductile iron pipes in wind power generation

Method used

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  • Welding method for centrifugal casting ductile iron pipe
  • Welding method for centrifugal casting ductile iron pipe
  • Welding method for centrifugal casting ductile iron pipe

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Experimental program
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Effect test

Embodiment 1

[0033] Material to be welded: arc-shaped plate of ferrite-based nodular cast iron pipe fittings produced by centrifugal casting process, specifications: plate thickness 8mm, arc length 25cm, width 15cm. The chemical composition (mass percentage) of the ductile iron is: C 3.5-3.7%, Si 2.1-2.3%, Mn 0.27%, P 0.061%, S 0.008-0.010%, Mg 0.050%, Fe balance. The mechanical properties are: tensile strength 460MPa, elongation 16%.

[0034] The welding process is as follows:

[0035] (1) Butt joints are used for welding, and a straight Y-shaped bevel is opened along the inner side of the 25cm×6mm arc-shaped plate section, with a single-sided bevel angle of 30° and a blunt edge of 2mm. Butt joints in the form of figure 1 shown.

[0036] (2) Preheat with oxygen-acetylene flame before welding, and preheat the groove of the ball iron arc plate to 100°C.

[0037] (3) Using CO 2 For gas shielded welding, the chemical composition of the welding wire is as follows (mass percentage): C 0.08...

Embodiment 2

[0044] Two pairs of ductile iron plates, the specifications are as follows: plate thickness 6mm, width 20cm, arc length 10cm. Open a straight Y-shaped groove along the inner side of the 20cm×6mm section, the groove angle is 30 degrees on one side, and the blunt side is 2mm. CO with diameter φ1.2mm solid welding wire 2 Gas shielded welding.

[0045] The mass percentage of the chemical composition of the welding wire used is as follows: C 0.08%, Mn 1.80%, Si 2.00%, P≤0.025%, S≤0.025%, Ni 3.20%, Cr≤0.015%, Mo≤0.015%, V≤0.03%, Cu ≤0.50%, Fe balance.

[0046] (1) Preheat with oxygen-acetylene flame before welding, and preheat the groove of the ball-milled cast iron plate to 100°C.

[0047] (2) The inner weld uses CO 2 Gas shielded welding is used for continuous welding, and the welding parameters are as follows: welding voltage 20V, welding current 110A, welding wire dry elongation 10mm, welding speed 16cm / min, CO 2 The gas purity is 99.9%, and the gas flow rate is 16L / min.

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Abstract

The invention discloses a welding method for a centrifugal casting ductile iron pipe. The welding method for the centrifugal casting ductile iron pipe comprises the following steps of (1) using the arc-shaped plate of the ductile iron pipe as a base material, carrying out welding by adopting a butt joint, and forming a straight-Y-shaped groove in the inner side or the outer side of the arc-shaped plate; (2) preheating a welding joint to the temperature from 100 DEG C to 150 DEG C before welding; (3) carrying out welding by adopting CO2 gas shielded welding, continuously welding a first weld joint at the groove of the arc-shaped plate, and welding a weld joint on the back by adopting a backstep welding method; and (4) carrying out heat insulation after welding, and carrying out slow cooling to the room temperature. According to the welding method for the centrifugal casting ductile iron pipe, a novel centrifugal casting ductile iron pipe plate is welded by adopting a CO2 gas shielded welding method under the condition of low temperature preheating, and compared with a traditional shielded metal arc welding method, the welding method provided by the invention has the advantages that the welding technology is simplified, the production cost is reduced, and the welding efficiency is obviously improved.

Description

technical field [0001] The invention relates to the field of welding technology, in particular to a welding method for centrifugally cast ductile iron pipe fittings. Background technique [0002] With the popularization of wind power generation technology, the domestic installed capacity of wind power has been increasing continuously, and my country has become a large-scale wind power market and a big wind energy equipment manufacturing country in the world. Wind turbines are generally composed of blades, generator cabins, towers, control systems and other parts. There are mainly two types of towers: truss type and tube tower type. The truss tower is cheap to manufacture, but it is inconvenient to maintain. The tube tower tower can be rolled and welded by steel plates, forming a conical tube structure with a small upper part and a larger lower part, and an escalator is installed inside to lead directly to the engine room. The tube tower tower has the characteristics of com...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23K9/16B23K9/235B23K9/23
CPCB23K9/16B23K9/23B23K9/235
Inventor 金丽勇李亚江徐子军刘洪亮
Owner STATE GRID SHANDONG ELECTRIC POWER
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