CN1739908A

CN1739908A - Weld flux for plasma arc welding of stainless steel

Info

Publication number: CN1739908A
Application number: CN 200510105423
Authority: CN
Inventors: 柴国明; 董春林; 朱轶峰; 张慧
Original assignee: Beijing Air Manufacturing Engineering Inst Chinese Aviation Industry No1 Grou
Current assignee: Beijing Air Manufacturing Engineering Inst Chinese Aviation Industry No1 Grou
Priority date: 2005-09-28
Filing date: 2005-09-28
Publication date: 2006-03-01
Anticipated expiration: 2025-09-28
Also published as: CN100357059C

Abstract

The active weld flux for plasma arc welding of stainless steel features that the flux consists of chromium oxide 35-45 wt% and zirconium dioxide 45-55 wt%, except calcium fluoride. Using the active weld flux in plasma arc welding of stainless steel makes the welding process simple, with great melding depth, low power consumption, high efficiency, low cost and good forming performance.

Description

Welding flux for stainless steel plasma arc welding

Technical Field

The invention relates to an activated welding flux for stainless steel plasma arc welding, which is a mixture formed by mixing chromic oxide, zirconium dioxide and calcium fluoride through physical action.

Background

Plasma Arc Welding (PAW) is an advanced process for welding by using a plasma gun to compress a free arc between a cathode (e.g., a tungsten electrode) and an anode into an arc of high temperature, high ionization, high energy density, and high flame flow velocity. It can weld stainless steel, titanium alloy, nickel base alloy and other metals and alloys in horizontal and vertical positions. The material which can be welded by the electric arc welding can be almost completely used by the plasma arc welding, and has concentrated energy and strong penetrating power; the welding speed is high, and the welding deformation is small; the joint strength is high; the double surfaces can be formed by one-time welding without beveling; low sensitivity to cracks and the like. Meanwhile, the plasma welding equipment has low investment, low welding cost, less preparation before welding, excellent joint quality and small weldment deformation, and can weld high-strength steel without preheating, so that full-automatic welding can be realized, and a vacuum technology is not needed, therefore, the plasma welding equipment is an advanced manufacturing technology which is particularly suitable for modernization of national defense weapons in China. The disadvantages of conventional plasma arc welding are also apparent. The welding of medium-thickness welding parts needs to increase current, so that the fusion width is increased, the fusion depth is increased little, and the conventional plasma arc welding has poor stability and small process margin in the welding process, has high sensitivity to the change of material components and is easy to have undercut phenomenon.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide an activated flux for plasma arc welding of stainless steel, which realizes the excellent use effects of low energy consumption, high efficiency, low cost, good forming and the like in the process of welding stainless steel by plasma arc welding.

At present, many scientific and technical personnel at home and abroad use the activated flux to play an obvious effect in TIG welding. Research on active plasma arc welding is also relatively weak. The invention applies the activated welding flux to the welding process of plasma arc welding and provides a new technical proposal.

The aim of the invention is achieved by the following measures:

the welding flux for the stainless steel plasma arc welding is characterized in that: the welding flux comprises the following components in percentage by mass: 35-45% of chromium sesquioxide, 45-55% of zirconium dioxide and the balance of calcium fluoride.

The active agent is prepared by uniformly mixing the active agent raw materials according to a specified proportion and grinding the mixture. Before welding the workpiece, a certain amount of active agent is put into a container, and a proper amount of acetone is added to make the active agent into paste. The pasty active agent is coated on the surface of a workpiece to be welded by a flat brush, and the workpiece can be welded after acetone is volatilized.

During welding, the arc temperature is high and, since the dissociation energy of a substance is generally lower than the ionization energy of a substance, the active agent species in the arc atmosphere will first dissociate to a large extent into an atomic state. Wherein the fluoride and the oxide respectively generate fluorine gas molecules or fluorine atoms and oxygen gas molecules or oxygen atoms in the dissociation process, and the dissociation process is respectively shown in the formula:

because the dissociation process requires additional energy, it is an endothermic reaction. The dissociation of polyatomic active agent species absorbs a large amount of dissociation energy, forcing the arc to contract in order to reach a new energy balance, the greater the dissociation energy of the active agent, the greater the energy absorbed during dissociation, and the greater the extent of arc contraction.

At the same time, oxygen enters the molten bath again, so that the surface tension of the molten bath is reduced. An inward flow is formed at the surface, the central region of the weld pool has a higher surface tension due to the higher temperature, and the liquid metal will also flow from the periphery to the center and further down at the surface, which effectively transfers heat to the bottom of the weld pool, resulting in a deep and narrow weld pool.

Drawings

Fig. 1 and 2 are illustrations of the drawings of example 1, wherein fig. 1 shows the weld penetration without using an active agent, and fig. 2 shows the weld penetration with using an active agent.

Fig. 3 and 4 are illustrations of drawings of example 2, wherein fig. 3 shows a weld undercut shape without an active agent, and fig. 4 shows a weld undercut shape with an active agent.

Detailed Description

Example 1

Weighing 45 g of chromium oxide, 45 g of zirconium dioxide and 10 g of calcium fluoride, uniformly mixing, and grinding to prepare the activator. Before welding the workpiece, a certain amount of active agent is put into a container, and a proper amount of acetone is added to make the active agent into paste. The pasty active agent is coated on the surface of a workpiece to be welded by a flat brush, and the workpiece can be welded after acetone is volatilized. The welding current of plasma arc welding is 150A, the welding speed is 250mm/min, the plasma gas flow is 0.3LPM, the protective gas flow is 15LPM, the arc length is 5mm, and the melting depth is doubled after the activator is used, as shown in attached figures 1 and 2. In FIG. 1, the weld penetration was 1.58mm without using the activator, and in FIG. 2, the weld penetration was 3.94mm with using the activator.

Example 2

Weighing 35 g of chromium oxide, 55 g of zirconium dioxide and 10 g of calcium fluoride, uniformly mixing, and grinding to prepare the activator. Before welding the workpiece, a certain amount of active agent is put into a container, and a proper amount of acetone is added to make the active agent into paste. The pasty active agent is coated on the surface of a workpiece to be welded by a flat brush, and the workpiece can be welded after acetone is volatilized. The plasma arc welding has the welding current of 160A, the welding speed of 400mm/min, the plasma gas flow of 2.7LPM, the protective gas flow of 15LPM and the arc length of 4mm, and the undercut can be eliminated by using the activator shown in the attached figures 3 and 4. In fig. 3, the undercut without active agent is shown, while in fig. 4, the undercut with active agent is greatly improved.

By adopting the invention

When the active welding flux is used for the plasma arc welding of stainless steel, the existing welding process is simplified, the defect of shallow fusion depth is overcome, the problem of undercut of a welding seam is well solved, and the aims of low energy consumption, high efficiency, low cost and good forming are fulfilled.

Claims

1. A fluxfor plasma arc welding of stainless steel characterized by: the welding flux comprises the following components in percentage by mass: 35-45% of chromium sesquioxide, 45-55% of zirconium dioxide and the balance of calcium fluoride.

2. The flux for stainless steel plasma arc welding of claim 1 wherein: the welding flux comprises the following components in percentage by mass: 35-40% of chromium sesquioxide, 50-55% of zirconium dioxide and the balance of calcium fluoride.

3. The flux for stainless steel plasma arc welding of claim 1 wherein: the welding flux comprises the following components in percentage by mass: 40-45% of chromic oxide, 45-50% of zirconium dioxide and the balance of calcium fluoride.