JP2515701B2 - Flux for end surface treatment used for gas pressure welding of steel materials - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sol-like flux having a surface activating effect (an effect of improving the pressure contact property) and an anticorrosive effect when joining steel materials by a gas pressure welding method.

[0002]

2. Description of the Related Art In general, when joining steel materials by a gas pressure welding method, after the surface to be joined is made as smooth and clean as possible by grinder grinding so that the end faces to be joined are as perpendicular to the axis as possible, no foreign matter is left on the joined surfaces. Without intervening
Clamp the steel material whose end faces are butted against each other with a supporter. Next, while applying pressure (about 30 to 50 MPa) in the axial direction,
The outer periphery of the butt portion (seam) is heated by oxygen-acetylene (generally reducing flame) using a porous ring burner. When the periphery of the abutting portion is red-heated with the passage of time, plastic deformation occurs and a slight compression bulge occurs. In other words, at this time, the gap between the steel material abutting surfaces is closed and they are in close contact with each other. Therefore, since there is no concern about internal oxidation after this time, use a heating flame as a neutral flame (standard flame).
Alternatively, a weak reducing flame is used, and the heating width is expanded in the axial direction around the seam (oscillating heating) sequentially from the concentrated heating on the joining line (seam), and the pressurization is continued until the specified compression amount ( In the case of round steel, in Japan, it is twice the original cross section of steel (D) [about 1, 4
D] When the above pressure is reached, the pressure is released, the pressure of the burner is extinguished, and the pressure welding is terminated. The suitable temperature for pressure contact at this time is about 1,100 to 1,200 ° C.
In this case, the higher the carbon content in the steel or the smaller the gap between the butt faces, the flatter the fracture surface (the flat fractured surface is the joint in the "tensile" or "bending" test of the pressure-welded steel materials. It is clarified that there are few smooth and non-crystalline fracture surfaces exhibiting white gray to black gray which are sometimes observed on fracture surfaces fractured. The cause of such a defective welded portion is that when the welding condition, steel composition, or construction is improper, an oxide film is generated at the welding interface (joined surface), and atomic diffusion hardly occurs or is insufficient. It is also revealed that it will happen because of it.

Here, in the case of gas pressure welding of railroad rails, the joint end face is cut at a right angle to the axis and supplied, but before the pressure welding, a special right-angle grinder is used to carefully perform grinding finishing. Next, it is stipulated that the surfaces to be joined should be cleaned with a gauze containing a cleaning solution, and then pressed immediately, which is practiced. This strict construction management ensures the homogeneity of joint quality and ensures safety.

Next, in steel bars for reinforced concrete, about 95% of steel bars to be joined in Japan are gas pressure welded (1993).
According to a March 2013 survey of the Japan Pressure Welding Association, the number of joints reached about 72 million. These rebars are shear-cut to a predetermined size at a steel mill and supplied to a civil engineering / construction site. At the site, a smaller shear cutting machine is used to cut the rebars to a desired size for processing. In this case, the cut surface of the reinforcing bar is "crushed" by shearing and "drawing", resulting in "end bending (about 1.5D), cross-section deformation, cross-section defect, perpendicularity to rebar axis", etc. Occurs.

When performing pressure welding using the end face of the reinforcing bar in such a supplied state, the baby grinder is used on the day of the pressure contact so that the end face of the reinforcing bar having the above-described shape is as perpendicular as possible according to the standard specifications. Grind and finish with, etc., and use for pressure welding. Therefore, compared with the above-mentioned rail, the joining surface satisfies the JIS standard value of the reinforcing bar even though the various conditions are worse (the [Company] Japan Pressure Welding Association edition, reinforcing bar gas pressure welding work standard It is said that the base material part must be cut after satisfying the standard strength) (edited by [Company] Public Building Association, common specification for construction work).

Therefore, for the purpose of improving the gas pressure contact property, it is generally practiced to use an acetylene excess flame for heating at the initial stage of pressure contact. That is, the acetylene excess flame is an incomplete combustion flame, and complete combustion can be performed only by taking in oxygen in the heating atmosphere in the vicinity of the pressure contact portion, so that the heating atmosphere becomes reductive and helps prevent oxidation of the surfaces to be joined. The use of this reducing flame improves the pressure contact property, that is, as a means to suppress the flat fracture surface that is incomplete pressure contact to the minimum,
In recent years, it has been commonly used by the crimping industry. In this case, however, the effect can be expected if the pressure is applied by using a proper burner or equipment after understanding the theory, but other imitations are not limited to this.

Thus, although efforts have been made to provide a good joint, factors such as weather and snow that worsen the joining conditions are further added in the actual construction work. The reality is that it is "poor in sex." In addition, if the heating method as described above is used, the usage rate of acetylene will inevitably increase, which may cause a cost increase, but there is no simple means for improving the pressure contact property other than this method, and this is the only method. The current situation is that it must be used as a weapon.

By the way, according to the literature, "the element for improving the gas pressure contact property of steel is V or C". This is because carbon in the steel material combines with oxygen in the heating atmosphere to generate CO gas and forms a reducing atmosphere together with the heating flame, which helps prevent oxidation between the surfaces to be joined,
Naturally, the pressure contact property is improved. Therefore, in the pressure welding of low carbon steel such as reinforcing steel, if a heating flame is used as the acetylene-rich reducing flame to heat the pressure welding, the carbon in acetylene (C ₂ H ₂ ) will function and during the welding of high carbon steel. As described above, it is the whole picture of these theories that the heating atmosphere can be made reducible and "the press contact property can be improved".

On the other hand, by further developing this theory, it is expected that the above-mentioned effect can be expected by abutting the members coated with a certain kind of special flux on the joint surface and pressing them together. No. 25314 is the essence of the invention.

In the present invention, a mixture containing three elements of (a) a resin mainly composed of carbon, oxygen and hydrogen, (b) an organic solvent, (c) carbon black or graphite is suitable as a flux for pressure welding of steel materials. I verified that for the first time.

The main composition of the flux is C, O and H.
As a result, without using a strong reducing flame as described above, the heating atmosphere during pressure welding is kept reducing, and due to the synergistic effect of preventing oxidation of the surfaces to be joined and slightly carburizing,
Theoretically prevent the generation of flat fracture surface, dramatically and easily improve the reliability of joint strength,
It is also possible to reduce the unit price of bonding.

The inventors further conducted various studies to put it into practice as a standard product in the field, and as a result, it was possible to minimize the influence of the skill level of the worker and the working conditions, and the most stable and uniform pressure contact improvement. The present invention has been obtained as a highly reliable flux having both an effect and an anticorrosive effect, and a flux which is superior from the viewpoint of environmental protection.

The present invention is a flux for end surface treatment in steel material gas pressure welding, which comprises a mixture of a resin mainly composed of carbon, hydrogen and oxygen, an organic solvent and carbon black or graphite, wherein the resin is an epoxy resin. Is a flux for end face treatment used for gas pressure welding of steel.

[0014]

[Examples] The superiority of the flux performance of the present application will be experimentally proved below. The steel material used in the experiment is JIS G2112.
"Steel for reinforced concrete", which is D32 and D38 of the most used SD345 materials in Japan.

As the pressure welding device, an automatic pressure welding machine ([company] Japan Pressure Welding Association officially approved, Autowell bar) was used in order to enhance the reproducibility of data. The test rebar D32 was used in the preliminary experiment. The number of repetitions was 5 to 10, but these data are omitted. Reinforcing bar D38 was used in this experiment, and 15 were pressed with the symbol "Z" among these, and 10 with each other. The setting conditions with the automatic pressure welding machine are the pressure welding time:
2'30 to 35 ", compression amount: 23 mm on average, and oxygen: acetylene mixing cost is 1.0: 1.1 to 1.2.

Tables 1 and 2 show the chemical composition and mechanical properties of the test steel materials, and Table 3 shows the fluxes Y, A to E, and the fluxless Z used for these.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3] First, since this pressure welding experiment is to clarify the superiority or inferiority of the invented flux, the pressure welding was performed under the condition slightly deviated from the optimum pressure welding condition, and the flat fracture surface was easily produced. Further, as shown in FIG. 6, the fluxes of Y, A to E were applied by spraying on the end face of the reinforcing bar 1 by spraying using a spray cylinder, and a coating film 2 was formed and the pressure welding was performed.

Next, a notch 4 for cutting is made on the joining line of the pressure contact bulge 3 of the joint obtained by the pressure contact test by a high speed cutting machine or the like (see FIG. 1), and an external force is applied to these to bend and break (see FIG. 2). Each of the fracture surfaces obtained in step 1) was taken in close-up and enlarged and baked to obtain a fracture surface photograph. When pressure welding was performed without using flux, the pressure contact bulge was broken without notching, and a fracture surface photograph is shown in FIG. Next, the fracture surfaces are inked to distinguish between a healthy fracture surface and a flat fracture surface (so-called incomplete pressure contact fracture surface) (see FIGS. 3 and 4), and the area of each of them is divided into 3 by using a planimeter. Measure each time, and use the average value as the "flat area ratio" for each joint (in the static tensile or bending test (including notch) of the pressure-welded joint, the flat fracture area occupies the entire area of the fracture surface fractured from the pressure-welded surface. The ratio of the surface areas) is calculated and the area ratios are compared to determine "the superiority or inferiority of the pressure contact improvement effect". FIG. 3 is a fracture surface photograph when B is used as a typical example in the fluxes A to E, and shows that there is no flat fracture surface and that it is a healthy fracture surface. FIG. 4 is a photograph of a fractured surface when pressure-welded without flux, showing that the fractured surface is mostly flat.

First, Z in the bottom column of Table 3 is the case of ordinary pressure welding without using flux. As the flux "Y" in the uppermost column, the flux according to Japanese Examined Patent Publication No. 57-253145 is shown as a comparative example. Further, A, B, C, D, and E are fluxes according to the present invention, and the characteristic difference from these fluxes is that "Y" is the basic of the conventional type, and other "A.
"B, C, D, E" is completely different from "Y" in "other components" shown in the right column of Table 3. As described above, this is done by considering various formulations in consideration of "pollution and global environmental protection", and also considering the main effect of forming a coating film and the resulting rust-preventing effect and pressure-contact improving effect. The conclusion. The pressure welding results (flat area ratio) using these fluxes will be described in detail with reference to FIG.

"A" ... The amount of carbon added is exactly the same as that of "Y", except that the other components are based on the newly developed composition. , The degree of carburization was found to be slightly higher than usual,
That is, the flat area ratio is sufficiently smaller than “Y”, and the purpose is sufficiently achieved.

"B" ... From the experimental result of "A" mentioned above,
It was decided to fix the composition of "other components" and to change only the carbon content for the experiment. First, here are the experimental results when the amount of carbon added is 2.75%. With this composition, the press contact property showed an appropriate improvement effect, and of course the flat area ratio was small, and it was found from the results of the microscopic examination that there was no problem. Therefore, the flux B is practically effective.

"C" ... The flux shown here is "B"
It was set to 2.5% by changing only the amount of carbon added. According to the experimental results, the effect of improving the pressure contact property and the result of the microscopic examination are appropriate, and it is considered that there is no problem in practical use. Therefore, the "C" flux is recognized to be practically effective.

"D" ... This flux is made to be "2.0%" by further reducing only the carbon addition amount from the above "C". The experimental results show that the flat area ratio is slightly larger in each flux of "A, B, C, D", and the microscopic results of the joint and its vicinity show that the degree of carburization is also comparatively high. Although it is slightly less, the findings of the microscopic result are good and the flat area ratio is small in comparison with “Z” without flux. In short, this flux clearly shows the effect of improving the pressure contact property as compared with the case where no flux is used.

"E" ... This flux uses a one-pack type epoxy resin and has completely different components from A to D. When this flux is applied to the surface to be pressure-bonded and pressure-bonded, A to D
The flat area ratio is a little higher than that, but of course it is 1% or less. Similar to the other A to D, this flux also has a flat fracture surface of 0% when it is joined under standard pressure welding conditions.

"Y" ... This flux has already been invented and put into practical use, but the experiment was conducted under the same conditions as the others because the test rebar was different from that at that time and for the purpose of comparison with the flux of the present invention. It was Although the results were generally good, it was confirmed that the fluxes A to E were superior from the findings of the microscopic result and the observation result of the flat fractured surface.

The pressure welding experiments for "no flux" and "Z" are as follows.
This is a very important experiment for comparison with others. However, the pressure welding conditions were exactly the same as those of the other experiments, and the standard pressure welding conditions were slightly shifted. The experimental results have a problem that the flat area ratio is larger than that when flux is used and the homogeneity is lacking depending on working conditions.

The inventors conducted similar experiments on graphite 1 to
5%, epoxy ester resin and high polymer one-pack type epoxy resin 10 to 50% were used, but the amount of carbon after the formation of the flux coating film on the end face of the pressure welded bar (graphite amount ... Organic solvent volatilizes in the air) Is more than 11%, the area ratio of the flat fracture surface is reduced, but the degree of carburization is too high, the joint is embrittled and the fracture load is also reduced.

Although the amount of carbon in the coating film is about 1 to 4%, it is more effective than the case where no flux is used, but the lower limit value is taken into consideration in consideration of the range in which a remarkable and stable effect is obtained in practical use. Is suitably 5%.

Further, if the epoxy resin represented by the epoxy ester resin or the polymer one-pack type epoxy resin exceeds 30%, the spray effect is deteriorated and a uniform coating film 2 cannot be formed. And the like, it is difficult to form a uniform coating film 2, and the carbon content is relatively increased, which is harmful.

Based on the above experimental results, in the flux of the present invention, the carbon content of A to E shown in Table 3 is 2% to 3%.
It was found that the optimum range is 20% to 30% for the resin content.

Among the above epoxy resins, the epoxy ester resin has a good effect of forming a coating film by spraying and an excellent rust preventive effect. It is also highly compatible with liquid propane gas and can be sprayed with a spray cylinder without using CFC gas, which is effective for environmental protection.

Among the epoxy resins, the polymer one-pack type epoxy resin has poor compatibility with liquid propane gas, but has excellent rust-preventing effect and coating film forming effect. This invention relates to the gas pressure welding of the reinforcing bar, as the end surface treatment flux in this gas pressure welding, paying attention to the characteristics of the epoxy ester resin and the polymer one-pack type epoxy resin as the resin component, and selecting this as the optimum component, It is an experimental proof of its suitability.

Particularly, the gas pressure welding of the reinforcing bar depends on the technique of the pressure welding process and depends on the environment. For example, it is assumed that the work will be performed under wind, rain, and snow, and the skill of pressure welding will vary. Also, after the flux is applied to the end surface of the reinforcing bar, pressure welding may be performed over time.

As described above, the epoxy ester resin and the polymer one-pack type epoxy resin are excellent in the rust preventive effect, and the pressure welding can be performed soundly by well suppressing the generation of rust due to rain and snow or the passage of time after the coating film formation. It is suitable because it quickly responds to the conditions of the pressure welding site.
Further, both resins can cover the difference in the skill of the operator and provide a uniform pressure welding joint. Further, the epoxy ester resin can be satisfactorily sprayed by using liquid propane gas, for example, without using CFCs which are harmful to the environment.

The practical results using the fluxes A to E according to the present application are shown below. Here, pressure welding was performed with a standard flame without using an acetylene excess flame. This practical experiment is 199
It was carried out at the actual construction site during the period from December 2 to October 1993. First, examples of construction sites are as shown in Table 4 below.

[0038]

[Table 4] Of the press contact points shown in Table 4 above, 20 to 30% were subjected to a tensile test by cutting, and all of these were base material cutting. Also, 20 to 30% of the remaining pressure contact points
Was subjected to ultrasonic flaw inspection, but all of them passed, and there was no problem at all. These were subjected to end-face treatment with the flux of the present application before the press-contacting day and then press-contacting at a later date, on the day of the wind, rain, and snow or due to the circumstances of the site work process.

Next, practical results in civil engineering related work (viaduct) will be described. In this construction, after the instruction that the end surface grinding work of the pressure welding target reinforcing bar cannot be performed at the pressure welding site, after performing the grinding work collectively at a place about 300 to 500 m away from the pressure welding site, next, each end surface Was coated with the flux of the present application. After that, at the required date and time, the rebar of the edge treatment agent was transported to the pressure welding site and pressure welding was performed. Table 5 shows the construction works that have been recorded.

[0040]

[Table 5] These pressure-welded joints passed all of the same inspections as the above-mentioned construction site.

[0041]

As described above, the flux of the present invention is
It is possible to respond promptly to various demands of the site in terms of the actual construction work, and moreover, such as "pressing construction on windy and snowy days" which has been prohibited in the past and "post-day pressure welding" after end face treatment. It was proved that the problem could be easily cleared and that a higher quality joint than the conventional one could be provided even if the operator's skill level was neglected to some extent.

In recent years, in the field of civil engineering and construction work, various efforts have been made to promote themes such as prefabrication by industrialization and homogenization of products, shortening of construction period, and labor saving. The pressure welding work is no exception. For example, regarding the pressure welding work on rainy and snowy days, which has been banned from the past, in the "Common Specifications for Construction Work" published by the Public Building Association of Japan, "Be careful when working on rainy days, because the reinforcing bars tend to burn." It has said. This corresponds to various plans such as various new ideas and new construction methods at present, so that it can respond to smooth promotion of construction,
It suggests that proper efforts should be focused.

In response to such demands, the flux of the present application can immediately meet the pressure welding work on rainy and snowy days as described above, and it is a high quality joint that can pass all inspections of the joint. Can be provided. In addition, this flux is sealed in a spray cylinder, and by using a spray type, the cleanliness of the flux can be maintained and can be provided for convenience of use, and it can be sprayed by using liquid propane without using CFC gas, thus environmental conservation Is effective for.

Further, the above-mentioned flux has a great anti-corrosion effect, and can deal with rain and snow and the time-dependent pressure contact condition after the coating film formation, and can perform the pressure contact soundly.

[Brief description of drawings]

FIG. 1 is a side view of a main portion of a pressure-welded joint for reinforcing bars with a notch.

FIG. 2 is a side view of the press-fitting joint for explaining breakage of the joint.

FIG. 3 is an enlarged photograph showing a metallographic structure of a sound fracture surface of a reinforcing bar pressure welding joint joined by using the present invention.

FIG. 4 is an enlarged photograph showing the metallographic structure of the flat fracture surface of the pressure-reinforcing bar joint without using a flux, which is contrasted with the present invention.

FIG. 5 is a graph showing an area ratio of a flat fracture surface when a conventional flux and a flux of the present invention are used.

FIG. 6 is an enlarged side view showing a state in which flux is applied to the end faces of the reinforcing bars to be joined.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sanji Koike 1312 Tahikamicho, Takamatsu City (72) Inventor Yasushi Sato 3-15-8 Kasuya, Setagaya-ku, Tokyo (56) Reference JP-A-56-56792 (JP, A) JP-A-56-56793 (JP, A) JP-A-58-38685 (JP, A) JP-A-58-173092 (JP, A)

Claims (2)

(57) [Claims] 1. A flux for end face treatment in steel material gas pressure welding, which comprises a mixture of a resin mainly composed of carbon, hydrogen and oxygen, an organic solvent, and carbon black or graphite, wherein the resin is an epoxy resin. A flux for end face treatment used for gas pressure welding of steel materials, which is characterized in that 2. The end surface treating flux used for gas pressure welding of a steel material according to claim 1, wherein the epoxy resin is an epoxy ester or a polymer one-pack type epoxy resin.