JPH01181993A - Mixed type flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To manufacture the mixed type flux for submerged arc welding obtaining an excellent bead shape and good pockmark resistance by specifying the grain size composition in case of manufacturing a flux by mechanically mixing a granular raw material. CONSTITUTION:In the flux manufacturing a granular raw material by mixing mechanically the grain size structure that those which are coarser than 850mu at its grain diameter are taken at <=30%, those which are smaller than 210mu at <=10% and those which are 500mu min. 800mu max. at <=30% is taken. The welding metal equipped with both an excellent bead shape and good pockmark resistance is obtd. by using the mixed flux for submerged arc welding thus prepd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) By specifying the grain size composition of a mixed flux, the present invention provides a submerged flux that provides excellent bead shape and good potmark resistance in welding steel structures. This relates to flux for arc welding.

(Prior Art) Fluxes used in submerged arc welding are broadly classified into molten fluxes, sintered fluxes (including sintered fluxes, the same applies hereinafter), and raw material mixed fluxes, depending on the manufacturing method. Melting type flux is made by melting the raw material in a melting furnace such as an electric furnace, cooling it and pulverizing it to the appropriate particle size, and baking type flux is made by granulating the raw material powder to the appropriate particle size with a fixing agent such as water glass. After that, the flux is heated and dehydrated at a predetermined temperature, and the raw material mixed type flux is manufactured by mechanically mixing the raw materials of appropriate particle size as they are.

Among the above-mentioned fluxes, the particle size structure of the molten type flux is described in Japanese Patent Publication No. 60-36875, for example, by creating a particle size structure in which the gaps between coarse particles are filled with fine particles, high quality weld metal can be obtained. However, in the case of a mixed type flux, unlike in the case of a molten type or a sintered type, it is manufactured by mechanically mixing raw materials with different particle shapes and specific gravities as they are, so there is no problem in the molten pool. Particle size must be adjusted to ensure uniform flux distribution.

However, with respect to mixed fluxes, there has been no study on the influence of the grain size composition on welding quality, and only the influence of the chemical composition of the flux has been studied, for example, as in Japanese Patent Application No. 62-33197.

(Problems to be Solved by the Invention) The present invention aims to improve welding quality, especially pits, by specifying the particle size structure based on the findings obtained as a result of investigating the influence of the particle size structure of mixed flux on welding quality.
The object of the present invention is to provide a mixed flux for submerged arc welding that is free from welding defects such as pockmarks.

(Means for Solving the Problems) The gist of the present invention is to provide a flux manufactured by mechanically mixing powdery raw materials, the particle size of which is 850.
A mixed type flux for submerged arc welding characterized by having a particle size composition of 30% or less of particles coarser than μm, 10% or less of particles finer than 210 μm, and 30% or more of particles of more than 500 μm and 800 μm or less.

The structure and function of the flux of the present invention will be explained below.

(Function) First, the flux of the present invention must be manufactured by mechanically mixing raw materials.

This is because, in the case of mixed flux, there is no need to select raw materials with a composition that can be melted in normal manufacturing equipment, unlike when manufacturing raw materials by melting, and it is possible to design the flux relatively freely. This is because there is no problem of moisture absorption or powdering due to welding, unlike sintered fluxes that are granulated with a fixing agent such as.

Another major feature is that if the particle size of the raw materials is well controlled, the manufacturing process only requires a mixing process and can be manufactured at low cost.

Here, it is of course within the scope of the present invention to melt and crush only easily processed raw materials as part of the raw materials for the mixed type flux to form a molten type flux and then mix it.

Next, the reason for limiting the particle size structure of the flux of the present invention is as follows.
If the proportion of coarse particles with a particle diameter of more than 850 μm exceeds 30%, the gas pressure applied to the molten pool becomes unstable, resulting in the inconvenience that a single bead shape cannot be obtained if the bead undulations are rough.

On the other hand, if the content of fine particles with a particle size of 210 μm or less exceeds 10%, the slag layer above the molten pool becomes too large, resulting in poor gas release from the molten pool, causing pock marks, arc instability, and poor bead shape. The cause of

Furthermore, as the specific surface area of the flux increases, the amount of moisture attached to the flux increases, causing gas defects such as pits and pockmarks.

Furthermore, in order to obtain good flux fluidity and degassing properties other than the above-mentioned coarse particles and fine particles, it is necessary to have a particle size of more than 500 μm and 850 μm or less. 30% or more is required. Of course, a flux having 100% particle diameters of 500 μm to 850 μm may also be used, and good welding workability can be obtained by having uniform particle diameters.

The raw materials used in the present invention may be any raw materials as long as they have an appropriate particle size (e.g., Cab, Mg, etc.).
o, A R2031 Metal oxides such as MnO and TlO2, CaCO5+ Mgco3. Metal carbonates such as NazCCIs, CaFz+Na5A 1. Minerals, composites, or slags containing inorganic substances such as metal fluorides such as Fb, singly or in combination, Ca, Mg, A
1. It is possible to mix deoxidizing agents such as St and Mn and alloys thereof, alloying agents such as Ni, Cr, Mo, and alloys thereof.

(Example) Seven types of fluxes from Fl to Fl as shown in Table 1 were experimentally produced by simply mechanically mixing raw materials having various particle sizes. Fl to F4 are fluxes of the present invention, which have been adjusted to have particle size configurations as shown by symbols A to D in Table 2.

Further, F5 to Fl in Table 1 are comparative examples for clarifying the effects of the present invention, and the particle size structure was adjusted to be as shown by symbols E to G in Table 2, respectively.

Among the raw materials used here, nickel slag is slag generated by ferronickel smelting.

Next, downward V-groove welding and horizontal corner welding were performed using this flux, and the welding workability was investigated. The results are shown in Table 3. The chemical composition of the test wire used in this welding is shown in Table 4, the chemical composition of the test steel plate is shown in Table 5, and the welding conditions are shown in Table 6. Incidentally, FIG. 1 is a diagram showing the groove shapes of Wl and W2 in Table 6.

Good results were obtained in terms of arc stability, beat appearance, and anti-pockmark properties for the fluxes No. 1 to No. 15 in Table 3, which are examples of the present invention. The arc became unstable and the bead shape became rough.

In addition, N17 with a large coarse particle content and particle size of 500 μm to 850 μm
Regarding No. 8, in which there were few grains in the m range, many pockmarks occurred and good welding results could not be obtained.

(Effects of the Invention) As described above, in the flux of the present invention, by specifying the particle size structure of the mixed flux,
Table *5 iOz: 45%, MnO: 2S%, MgO:
10%, Aj! zOs: 5%, CaFz: 10%
Table 2 Table 4 Table 5 Table 1 Also, it is possible to obtain a weld metal that has both a good bead shape and good pock mark resistance.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are diagrams of groove shapes used in examples of the present invention. 1.1a...Base material. Patent applicant Nippon Steel Corporation

Claims (1)

[Claims] 30wt% of flux manufactured by mechanically mixing powdery raw materials with a particle size coarser than 850μm
(hereinafter referred to as %) Below, those finer than 210 μm are 1
0% or less, 30% over 500 μm and 850 μm or less
A mixed flux for submerged arc welding characterized by having the above particle size structure.