JPS58112691A - Fused flux for submerged arc welding and its production - Google Patents

Abstract

PURPOSE:To improve welding workability and the mechanical properties of weld metal by contg. a specific weight ratio of S in the components of SiO2, MnO fluxes and limiting the contents of FeO and P. CONSTITUTION:Main flux components of slag forming agents are, by weight, 20-60% SiO2, 10-50% MnO, <=30% CaO, <=30% MgO, and <=15% CaF2, and 0.02-0.10% S is contained therein. Also, <=3% FeO and <=0.05% P are contained. Content of s and excess content of oxygen are calculated with respect to the raw materials to be compounded in the flux and vulcanizers contg. S such as iron sulfide and calcium sulfide, carbon, 1 or>=2 kinds deoxidizers among Fe-Si; Si-Mn; Al, etc. or coke, etc. contg. relatively much S are added, then these materials are melted in a reducing atmosphere at <=1,700 deg.C, whereby the flux is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a flux for submerged arc welding that has excellent properties in terms of welding workability and mechanical quality of metals to be joined when used for welding mild steel to 60 kg class high tensile strength steel. The present invention relates to a manufacturing method thereof.

As the field of application expands, submerged arc welding is required to be adaptable to various kinds of steel materials, but conventional welding is also being used to increase efficiency and reduce the number of reworks due to defects. Construction conditions are currently being considered.

Regarding welding flux as applied thermal spray,
As a more advanced quality characteristic that can meet the usage conditions,
The weld metal is required not only to have excellent mechanical properties but also to have excellent welding workability.

Factors that impair workability in submerged arc welding are mainly the occurrence of surface defects such as pits and pockmarks, and the problem of slag removability. These are serious problems that even affect the existence of automatic welding, and low susceptibility to the occurrence of defects and easy peeling of welding slag are essential for submerged arc welding fluxes. At the same time, with the trend of the times, weld metals are increasingly required to have excellent low-temperature impact properties, and it has been a concern of those skilled in the art to solve both of these issues at the same time, and many attempts have been made to date. However, the reality is that the results are not satisfactory.

As a result of thorough studies, the inventors of the present invention have discovered a new technical idea that completely defies conventional common sense.The main point is that S (sulfur) is Containing F in the range of 0.02 to 0.1096 and controlling the F.0 component to 3- or less dramatically improves welding workability. In addition, it has been found that the low-temperature toughness of the weld metal can be maintained at a high level by controlling P(#) in the composition to 0, 5% or less. Furthermore, as a result of careful study in obtaining such flux, we have established an extremely rational and innovative manufacturing method.

In other words, up until now, S in the 7 lux for submerged arc welding has been considered harmful as a fixed concept from iron metallurgy, and as a part of causing weld cracking and toughness deterioration, it has been used in the selection of raw materials or in preliminary treatment for the purpose of desulfurization. It was even common knowledge that gas injection during melting was controlled. However, the situation is different in welding, and on the contrary, this No. 8 investigates the prevention of defects such as pits and pockmarks and slag peeling, and the reason for this is thought to be as described below.

The high-temperature arc heat during welding dissociates the air, moisture, and other gasified components of the material, including flux, in the vicinity of the weld, and dissolves them in the form of N, H, Co, etc. in the molten metal. As cooling progresses, the supersaturated dissolved gas is gradually released, which causes bubbles to form and grow at the slag-metal interface. In particular, when metal solidifies, a large amount of gas is released to the solidification interface, and this gas is trapped by the previous bubbles. The amount of bubbles generated and whether they are included in the slag layer and float separately are influenced by the welding conditions and welding material, but it is estimated that the viscosity and surface tension of the slag are directly involved. Ru. In other words, when the slag has a high viscosity and a large surface tension, the generated bubbles are fixed at the interface with the molten metal, and as cooling progresses, the gas generated also concentrates in the bubbles, resulting in an increase in internal pressure. This also puts pressure on the molten metal surface. As a result, an indentation (circular or needle-shaped depression) is formed on the solidified metal surface. In addition, when the amount of gas generated is large, the bubbles become too large and partially detach from this interface due to buoyancy, and escape to the outside through the slag layer.

At this time, since the arc cavity is disturbed, the bead waveform is disturbed, and the slag releasability is significantly deteriorated, and serious defects such as pitting and slug-in are also caused. Here, the addition of S has the effect of significantly lowering the surface tension and viscosity of the bath melt slag, so it is extremely effective in preventing the occurrence of the above-mentioned defects. There is no effect if it is less than 0.02%,
190. If it exceeds 10%, the fluidity of the slag will be too good, resulting in deterioration of the bead shape, which is not preferable.

Furthermore, the amount of FeO in the flux is involved as a component that influences the action and effect of S. In other words, as shown in the following equation, F. and release oxygen.

This reacts with S, gasifies it, and separates it from the slag layer.

This is what causes FeO to dissipate and lose the effect of O8, so it is especially important to keep FeO below a predetermined amount.

F・0→F・+O, S+20→SO□↑Sara KP o,
By setting it to os% or less, the impact toughness as a mechanical property of the weld metal can be dramatically improved.

Next, the inventors conducted further studies on a method for producing flux that can maintain the above-mentioned welding workability and maintain good mechanical properties, and as a result, they discovered an extremely rational and innovative production method. It's been a long time since I've been in the middle of a long time.

The materials used as ordinary flux raw materials are mainly manganese oxide ore, silicic acid, lime, alumina, magnesia clinker, fluorite, etc., which are pretreated with ore and subjected to melting. All of these contain FeO, P*8, etc. as impurity components with some variation, and in preliminary treatment, FeO, P*8, etc. are removed except for S.
P does not fluctuate over time and at the same time cannot be controlled at a constant level only by selecting raw materials. In addition, especially for manganese oxide ore, manganese dioxide is often used as it is, or as Mn0z or F.
! 120. It retains excess oxygen in the form of

This oxygen has a tendency to react with S and dissipate as 5O2f gas when dissolved, but the yield is unstable due to the variation in the amount of S, and the effect of S as described above is unstable. It cannot be provided stably. Also,
The F@O component itself is an oxygen supply source and increases inclusions in the weld metal, thereby deteriorating toughness. For the above purpose, we simultaneously added a reducing agent corresponding to the amount of oxygen in the raw material and supplemented the eight components with a vulcanizing agent, and also performed melting in a reducing atmosphere at a temperature below 1,700°C. >f8 amount t-0.02~0.10 f4F)
It has been discovered that this is essential for controlling the range tSO to a constant value. Furthermore, in the dissolution of raw materials containing a large amount of F・O, P, the reduction reaction effect reduces the F・0 component due to iron removal, and the dephosphorization effect due to the solid solution of P in the iron content is S.
It is essential to maintain a stable yield and effectively demonstrate its workability improvement effect.

Based on the above knowledge, the present invention has been expanded and configured, and will be described in more detail.

The main seven components of the preferred slag forming agent in the present invention are Sly, 20~$Q9G, MmO10 in weight ratio.
~50%, CaO≦30%, MgO≦mouth].

To set CaF2≦15-, add S to this from 0.02 to α1
〇-Containing sasse, KaF@0 <3 S, P <0.
05%.

This 7LAX is a dissolving raw material that contains svt such as iron sulfide, calcium sulfide, etc., by calculating the amount of S and excess oxygen added by 9% compared to the usual FUSIX blended raw materials. vulcanizing agent and carbon,
F・-81, 81-Mm, etc. One or more kinds of OR'rll agents, etc., and coke etc. containing a relatively large amount of 8 are added, and this is heated at a temperature of 1700℃ or less. It is produced by melting under a closed atmosphere.

Hereinafter, preferred ranges of ingredients in the sour cream according to the present invention will be explained.

sio□ is an essential component for vitrifying slag and maintaining appropriate viscosity, and if its content is less than 30% or more than 60%, welding workability will deteriorate overall.

MEIO coexists with 8102 to improve the melting point and viscosity of slag! It has the effect of keeping the IL weld metal sound, but if it is less than 10 inches, it is not sufficient, and if it exceeds SOx, the viscosity will drop too much and the bead shape will become bad, which is not preferable.

CaO is added to adjust the basicity and improve the mechanical properties of the welded part, but if it exceeds 30 -, problems such as hydrogen cracking will occur due to an increase in the amount of hydrogen absorbed, and the amount of generated gas will increase, resulting in bits.

This tends to cause pockmarked defects and the characteristics of the present invention are lost.

Although MgO has the same effect as CaO, it exhibits particularly good effects in terms of slag peeling.

However, if more than 30% is added, 10aF2, which is not suitable, will cause defects due to hydrogen absorption, similar to CaQ.
is added to adjust the viscosity and melting point of the slag, and
It shows an effective effect on preventing fs suction defects V by maintaining the welding arc length at an appropriate level and lowering the partial pressure of other gases. However, if it is added in excess of 1596, the bead shape deteriorates and slag 0 peelability -bt It is unsuitable because it deteriorates.

Next, the present invention will be explained using examples.

EXAMPLE Table 1 shows the component ratios of the raw materials blended in a conventional manufacturing method for a commercially available fusion type Fluxum D411 for submerged arc welding in comparison with an example of the present invention.

Table 2 shows the analysis values and raw material blending ratios of the raw materials used for 7 luxes of C.

4,0 (surplus oxygen) in Tables 1 and 2 means:
It is calculated as follows for each raw material.

(Note) It's good, and the number in [ ] is the atomic weight, F・0 → F・+
0, Fe12,5→2F・+30, T, M! 1
0! →T, Photo.

It is calculated as the surplus oxygen content due to the reaction of T
0Mno 2 has MI&s04 and kk20B form 1
10 also included excess oxygen in MnO2.

In the manufacturing method of the present invention, 0111 base material is added in an amount exceeding the amount required to reduce excess oxygen according to the quality characteristics, but it is necessary to control the atmosphere of the melting furnace and to reduce the amount of carbon material used for the furnace material. It is also influenced by the contribution of To
Therefore, even if the amount is less than this value, the object and effect of the present invention will not be lost.

In addition, as shown in 81m vulcanization 16, as shown in JgxWIJ, using an oxidation-reduction/machining meter, we primarily take into account the S yield that is increased by potting, and also according to the quality characteristics of the 7tx. The amount required for the formulation was determined and added.

Here, if the deoxidizing agent and the vulcanizing agent as reducing agents are those used in ordinary chemistry, metallurgy, etc., no difference is recognized in their effects.

1. Using the raw materials listed in Table 1 in an electric furnace with a capacity of approximately 1 ton.
40 Q kw (The composition of the flux that was loaded with D power and cooled at the outlet is as shown in Table 3. The average melting temperature at this time was approximately 1,450°C, and the load was 2
．． Increased the power to 200 kW and the melting temperature to about 1.7! S.

The 8 components in the flux when heated to He is unsophisticated.

The flux shown in Table 3 (after water cooling or air cooling treatment I[O,
Table 5 shows the welding workability when welding the I-groove butt and fillet submerged arc welding (dried, crushed and adjusted particle size) under the conditions shown in Table 4, and the impact properties of the entire weld metal due to the V-groove. It was arranged in layers.

Table 4 Welding conditions Table 5 Welding test results (:: Very good O: Good / Δ: Slightly poor ×: Bad As a result, iron removal and dephosphorization were carried out by controlling the amount of S in the sulfur and chlorine. It was found that all of the 7 lacs obtained by the method had excellent ratio properties.The technical idea of the present invention can also be applied to 7 lacs containing TlO2 as a main component.

Such effects cannot be easily imagined from conventional common sense, and in terms of raw material resources, low-grade raw materials can be used, and a flux and its manufacturing method that is inexpensive to produce and has excellent specific properties. It was developed by
The present invention is of great benefit to industry.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the relationship between the redox delta parameters of the raw material compositions shown in Table 1 and the B amount ratio (yield) in the 7 lux composition shown in Table 3, using melting temperatures.

Claims (2)

[Claims] (1) Consisting of ordinary slag forming agent components, in which 8
Contains 0.02 to 0.10-, and F.0≦3. An age-melting type flux for submerged arc welding, characterized in that P≦o, o s s. (2) S amount and excess of normal flux blending raw materials
a! l! Add vulcanizing agent and deoxidizing agent according to the quantity,
A method for producing a molten flux for submerged arc welding, characterized in that this is carried out in a reducing atmosphere at a temperature of 1,700°C or less.