JPS63188493A - Method for regenerating flux for submerged arc welding - Google Patents

Abstract

PURPOSE:To manufacture the flux with the satisfactory quality which is not different form the flux using new raw material by melting a combined batch of the flux added with 10-80% slag disposed of separating into an oxidation period and a deoxidation period to reduce and eliminate harmful components such as FeO, S, P, etc. CONSTITUTION:The flux which is used for the submerged arc welding and slagged is collected and pulverized and the 10-80% slag disposed of whose iron and iron oxide are reduced by the magnetic separation, etc., is added to the raw material for melting whose components are combined in advance. This material added with the slag is molten in an oxidized atmosphere at first while being supplied to a melting furnace and sulfer of impurities is exhausted as an oxide, mainly SO2 gas. Next, a reducing agent such as carbon powder or Al, Mg, Si powder, etc., is charged and the atmosphere in the furnace is made in a deoxidized state and the impurities in which the iron, the iron oxide, etc., are increased are deoxidized and metalized and deposited and separated at the bottom of the melting furnace. In this way, the flux with the satisfactory quality which is not different from the flux using the new material can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for regenerating molten flux that is used in submerged arc welding and turned into slag.

[Conventional technology]

Conventionally, flux for submerged arc welding, regardless of whether it is a molten type or a fired type, turns into slag once it is used for submerged arc welding, so it is either disposed of as waste, or the slag is collected and then pulverized. Attempts have been made to remove a certain amount of iron by magnetic separation, etc., then regenerate the particles by adding and mixing deoxidizers, CaF, etc.; Moreover, it is said that there is a problem in quality assurance when using it for welding high-grade steel structures because it is inevitable that the quality will deteriorate each time it is recycled. In other words, welding flux not only isolates the arc from the atmosphere, but also has an important effect on welding workability and the properties of weld metal. That is, it melts into slag, and then undergoes metallurgical deterioration due to mixing and stirring of the molten slag and molten metal, and a slag-metal reaction to produce weld metal. For example, the PeO in the slag increases compared to the content of the flux before use. This increase is due to the chemical composition of the material to be welded, especially Si+Mn+ (Ti)
The increase in FeO may cause blowholes to occur in the weld metal, or the impact value of the weld metal may decrease, depending on the content of the flux itself or the composition of the flux itself.

For this reason, slag that has been used once cannot be used as it is simply by pulverizing and grading it, and as a way to reuse it, after pulverizing and grading it, Ca is added to the slag recycled flux in proportion to the increased amount of FeO, S, and P. -Method of adding and mixing 5i (
For example, see Japanese Patent Application Laid-Open No. 49-123947), a sufficient amount of metal oxide, Ca, etc. to compensate for the components consumed by welding.
F, etc. and at least one kind of deoxidizing agent in an amount sufficient to reduce the iron oxide generated by welding, and these are completely melted and mixed, cooled and solidified, and then pulverized and sized, and as necessary. There is a rehousing method (Japanese Unexamined Patent Publication No. 106647/1983) in which a recycling additive obtained by removing iron produced by a deoxidizing reaction by magnetic separation or the like is mixed with pulverized slag.

[Problem that the invention seeks to solve]

However, these reproduction methods have various problems, such as the quality gradually deteriorating with repeated reproduction.
For example, the reproduction method is complicated.

Measures for Solving Problems] Therefore, the inventors of the present invention have proposed the above-mentioned conventional methods for regenerating the slag-formed recovered flux of the molten type flux (hereinafter referred to as flux) used in submerged arc welding. We developed and researched a method to eliminate these drawbacks, and completed a method to reduce and remove harmful components in slag such as Fed, S, and P during the flux melting process.

That is, the present invention recovers the slag-formed flux used in submerged arc welding, crushes it, and mechanically removes iron oxides by magnetic separation, etc. After preliminary treatment, 1. 10% of the pre-treated slag (hereinafter referred to as treated slag) is added to the blended raw materials (hereinafter referred to as blending batch) that have been weighed and mixed by the same raw material blending as in the flux production of the component.
This is a regeneration method in which fluxes are added and mixed by ~80% and this mixture is used as a raw material to provide a flux of exactly the same quality as a new product by the melting method described below.

In other words, F
Impurities such as ED, S, and P are increasing, and as a result, the ratio of the necessary components of the flux appears to be relatively lower, and the components are different from the flux, but after removing these impurities, They found that the component ratio was almost the same as that of the flux. There are some differences depending on the chemical composition of the flux and the composition of the combination wire and the steel to be welded, and the ratio of MnO, CaF, etc. in the flux may be slightly lower depending on the case, but in that case, the influence will be less. After determining the added ratio of treated slag, or after determining the added ratio of treated slag, the decreasing components are adjusted in advance by calculation from the blending batch,
All you have to do is make sure that the mixed raw materials become the target components.

Next is the removal of impurities, but regarding iron oxidation,
It is known that the collected slag can be removed to some extent by passing it through a magnetic separator after pulverization. It is possible to reduce the amount to around 3%.

However, further iron removal is almost impossible mechanically. In other words, the flux contains Mn as a component.
Those containing O + TiO
, TiO, etc. are fused in some parts, and even MnO and Ti1t, which are useful if the magnetic force is increased beyond a certain level, are removed.
Because they will leave. For these reasons, the present inventors focused on the melting process of molten flux, and considered removing impurities such as Feo, p, and s by utilizing chemical reactions during the process, and This is a completely inverse method that is different from the molten flux method. That is, in normal melting, carbon powder is added to a blended batch for the purposes of improving zero conductivity, (2) making a reducing flux, and (2) making a pumice-like flux.

In other words, in the usual melting method, the desired flux is designed in the form of a blended batch, and it is simply melted under predetermined melting conditions (current, voltage, blended batch supply interval, melting time cycle, etc.). quality can be obtained.

On the other hand, in the melting according to the present invention, carbon powder is not actively added to the blended batch, but 10 to 80% of the treated slag is added or mixed into the blended batch of the flux. Initially, the melting furnace is operated in an oxidizing atmosphere while supplying the blended batch for melting (hereinafter referred to as melting batch) to the melting furnace. During this oxidation melting stage, the impurity sulfur (hereinafter referred to as S) that has increased in the slag-formed flux used is oxidized and converted into sulfur oxides, mainly SO2, along with the exhaust gas from the melting furnace and the dust collection exhaust gas attached to the furnace. It is dispersed and removed into the atmosphere through a device. Needless to say, the sulfur oxides are passed through a desulfurization device installed midway through the process, and are released into the atmosphere in a purified state. The next step was to remove impurities with increased levels of Fed and P. Focusing on the fact that these impurities are easily reduced and turned into metals, the supply of melt batches was completed, and after the melt had fallen off, carbon was removed. Powder or Aj, Mg,
A so-called reducing agent such as Si powder is put in the front of the furnace to bring the atmosphere inside the furnace into a reducing state, and these impurities are turned into metal and separated by sedimentation at the bottom of the furnace. The specific gravity of molten flux in the furnace (hereinafter referred to as melt) is around 3, whereas metal is mainly composed of iron and contains small amounts of Mn, Si, etc., as well as P, which is to be removed. Since its specific gravity is 7 or more, which is heavier than melt, it can be easily deposited at the bottom of the furnace. In addition, flux melting furnaces generally use a tilting top pouring type tapping method, so when tapping, Fed, P
It is quite easy to extract only the so-called supernatant melt, which does not contain impurities such as , S, etc., and in this way, the present invention has developed a method for producing flux with the same good quality as that using new raw materials. It can be provided. Melting type fluxes include so-called reduced type fluxes and those manufactured in the form of pumice, so a process to impart such characteristics is necessary.In the present invention, this process is carried out using It can be performed in parallel with the impurity removal operation, and since the slag has been melted once, it is easy to remelt it, and in electric furnace melting, etc., it has an energy-saving effect of reducing the power required for melting, that is, the power unit consumption. It is possible. In addition, some fluxes have Mn components maintained in a highly oxidized state, but when manufacturing such products, it is sufficient to further perform an oxidation reaction step after the reduction period. Oxygen is oxidized by blowing oxygen into the melt using an oxygen blowing lance etc. ■MnO component in the blending batch is kept low in advance,
By adding manganese dioxide, it is possible to adjust the final target value and oxidize the melt to the expected level. The scale of the oxidation level can be determined by the color tone of the melt. For example, in the case of Mn components, the black side is more oxidized, and as the degree of oxidation decreases, the color changes to brown, yellow, and green. By controlling the color tone, it is possible to adjust the degree of oxidation.

Examples of the present invention will be described below.

Table 1 shows the target components of the flux in the application example.

Naturally, FeO was not added as a target component.

Table 1 Table 2 shows the chemical components of the untreated recovered slag corresponding to these.

The upper row shows the values as they are, and the lower row shows the component ratios assuming that impurities are removed. In this way, the component ratio when impurities are removed from the apparent component value of recovered slag is close to the target component of the product, and it is possible to add and dissolve the slag up to the addition rate without correction. It shows that there is.

Next, Table 3 shows an example of the chemical composition of the treated slag in an application example in which the slag was actually coarsely crushed and then magnetically separated.

Tables 4a and 4b show the composite component values of compounded punches containing 10 to 85% of the treated slag in Table 3. In this way, if we look only at the target component values, it is possible to regenerate the flux to be obtained, but in order to separate and remove impurities by appropriately combining the oxidation and reduction reactions that are the method of the present invention,
Since it is difficult to actively carry out the chemical reaction using slag alone and it takes a long time, from a practical standpoint, the appropriate mixing ratio of 9-treated slag to a new blending batch is ~80%. In addition, MnO and C, which are easily worn out during welding,
The slag addition/mixing ratio was set to a maximum of 80% in order to facilitate the replenishment and adjustment of aF3, etc. Furthermore, since the purpose of the present invention is to industrially regenerate used slag, the lower limit of the addition rate was set at 10% for economical reasons, but there is no problem in terms of quality with addition of less than 10%. Of course.

The conditions for melting these slag-added batches in an electric furnace are as follows:
It is almost the same as the production of normal melting type flux, but in order to promote the oxidizing atmosphere during raw material melting, which is the basis of the present invention, the melting voltage of the electric furnace is set slightly lower and the melting current is set slightly higher. The input power should be approximately the same. - As an example, compared to the normal conditions of voltage 300V and current 6000A, the present invention uses 260 to 280V and 6400A to 6
On the contrary, the melting voltage is set a little higher at the stage of melting at 600A, finishing feeding the raw materials, reducing Fe0, etc., metalizing, trapping impurities such as P in the metal, and co-precipitating it at the bottom of the furnace. , the dissolution current is set slightly low to promote a reducing atmosphere. - In the example, the voltage is 300 to 320 V and the current is 6000 A, and 0.5 to 1
．． 0χ was added and electricity was forcibly applied to create a reducing atmosphere, and 5~
With a holding time of 10 minutes, Fe0min is reduced to a metal whose main component is iron, and the specific gravity of the generated metal is 7 or more compared to the specific gravity of the melt of about 3, so this metal can be reduced to about 10min. It sinks towards the bottom of the hearth. Since the tilting method of melting furnaces is generally used, it is possible to tap only the melt that has become the target component of the so-called supernatant, and use the normal processing method in the subsequent process to obtain the same flux as new.

Tables 5 and 6 show quality comparison examples between a new product and a product recycled according to the present invention regarding the applied flux. Table 5 shows examples of chemical components of recycled products.

As can be seen from the table, Fe0 content, etc. decreased, and as a result, other components were relatively adjusted and became almost the same regardless of the slag addition rate.

However, when the slag addition is 85%, the removal effect of T and Fe0 decreases, the T and FeO in the recycled product rises rapidly, the impact value level of all weld metal decreases, and an effective regeneration effect is not achieved. Not yet. For these reasons, the upper limit of the slag addition rate in the present invention was set to 80%.

Table 6 shows an example of mechanical test results for all deposited metals welded using a combination of these recycled products and the submerged arc welding wires shown in Table 7. As can be seen from the table, these values show almost no difference from new products and demonstrate the superiority of the molten flux regeneration method according to the present invention.

Furthermore, although not shown here, the basic unit of melting power decreases with the addition of slag, and the rate of decrease decreases as the amount added increases, but it is 100 to 30 kWh/t per 10% addition rate.
A secondary effect was also obtained in that it was possible to save energy to the extent that it was possible to turn it on.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the groove shape for weld metal from which the results of Tables 6a and 6b were obtained. Figure 1

Claims (1)

[Claims] The slag of the molten submerged arc flux used in submerged arc welding is collected, pulverized, and subjected to magnetic separation to reduce iron and iron oxides.
Adding 0 to 80%, the melting method is divided into an oxidation period and a reduction period. During the oxidation period, impurities such as sulfur are oxidized with oxygen from higher oxides, and iron and iron are dissolved in the exhaust gas during the reduction period. Regeneration of flux for submerged arc welding, characterized by metalizing oxides with a reducing agent, trapping phosphorus etc. in the metal, separating and removing it at the bottom of a melting furnace, and regenerating it as a melting type submerged arc flux. Method.