JPH07276067A - Protective agent for gas press welding end face of steel bar - Google Patents

Abstract

PURPOSE:To protect the press welding end faces of steel bars by the rust preventive effect of a protective agent in a period before the start of a press welding operation and to maintain high joint strength at the time of press welding so as to obtain a press welded joint having high reliability by applying this protective agent on the press welding end faces of the steel bars. CONSTITUTION:This protective agent is compounded with a combustion accelerating component consisting of org. matter and inorg. matter having oxidability or combustibility. The combustion accelerating components thereof include chlorates, perchlorates, inorg. peroxides, nitrates, iodates, permanganates, sulfur, iron powder, magnesium powder, org. peroxides, ester nitrates, nitro compds., nitroso compds. and azo compds. The compounding ratio of the combustion accelerating components is generally preferably 0.01 to 1 pt.wt. and more particularly 0.02 to 0.5 pt.wt. per 1 pt.wt. resin component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective agent which forms a coating on the gas pressure contact end surface of a steel bar and exhibits a rust preventive effect.

[0002]

[Prior art and its problems] Conventionally, when joining reinforcing bars to each other, the reinforcing bars are abutted against each other, and the joint is heated by an oxygen / acetylene flame, and when a semi-molten state is reached, pressure is applied in the axial direction for joining. The so-called gas pressure welding method is adopted. In this gas pressure welding method, in order to obtain a good pressure welding joint, by shaping the end face of the reinforcing bar with a grinder etc. immediately before the pressure welding, it is possible to prevent the generation of rust and oxide which are harmful to the pressure welding. , It was necessary to completely remove the deposits such as fats and oils and cement paste.

However, since the working environment at a construction site is not always ideal, it is difficult to make a good press contact end face by grinding, and therefore the joint surface of the reinforcing bar is flat due to poor fusion. May result in defective joints.

In order to improve such a point, there is also known a method in which the end face of the reinforcing bar is ground in advance in a factory or the like, and a rust preventive agent is applied thereto, for example, as disclosed in JP-A-57-47589. Is an oil-based paint, bitumen paint, synthetic resin-based paint, fatty acid-based paint, etc., applied to the joint end surface of the steel bar to produce a highly reliable pressure-welded joint without causing flatness. Stated.

Further, Japanese Patent Laid-Open No. 58-38685 discloses a flux material obtained by adding borax, silica sand, carbon, etc. to a coating material using an alkyd resin as a color-developing material. It is described that by applying the material to the pressure contact surface of the reinforcing bar in advance and performing gas pressure contact, a good pressure contact joint can be obtained even if the work of shaping the cut surface of the reinforcing bar at the site is omitted.

Further, according to Japanese Patent Application Laid-Open No. 58-173092, there is also known a joining accelerator for gas pressure welding of rebar, which is obtained by adding methyl alcohol and kneaded miso to pulverized coal and pine resin derived from pine charcoal or charcoal. Is.

However, in any of the above-mentioned rust preventive agents, there is a possibility that paint components constituting the rust preventive agent may remain in the joint portion. As a result, the joint strength between the reinforcing bars is reduced, and the reliability of the pressure welding joint is reduced. It turned out that there was a problem that it decreased.

[0008]

OBJECTS OF THE INVENTION Accordingly, an object of the present invention is to provide a protective agent for a gas pressure welding end surface of a steel bar, which can obtain a pressure welding joint having high joining strength and high reliability.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The protective agent for gas pressure welding end surface of steel bar according to the present invention is characterized by containing 0.01 to 1 part by weight of a combustion promoting component with respect to 1 part by weight of a resin component. is there.

The burning extinction temperature of the protective agent is preferably 550 ° C. or lower. Further, the combustion promoting component,
It is preferable to use any one kind or two or more kinds of organic peroxides, nitrates, nitro compounds, nitroso compounds and azo compounds.

Further, the protective agent is an oxygen scavenger and / or
Alternatively, it is desirable that a dehydrogenating agent is blended.

[0012]

In the gas pressure welding work, when the ends of the steel bars butted against each other are heated, the protective agent applied to the end faces gradually evaporates and evaporates, and burns until the temperature reaches about 550 to 600 ° C. Disappear. When the steel bars are pressed together in the axial direction to be joined, the resin component and the solvent constituting the protective agent have already vaporized and burned due to the action of the combustion promoting component and do not remain at the joint.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The resin component constituting the protective agent of the present invention forms a coating film having an anticorrosive function, has good adhesion to the joining end surface of a steel bar, and is of a pressure welding machine. What can be burned by a flame is preferable. Examples of such a resin component include alkyd resin, acrylic resin, urethane resin, epoxy resin, phenol resin, urea resin, melamine resin, and the like, and the protective agent of the present invention uses these resins alone, or , Mixed and used.

The protective agent of the present invention is blended with a combustion promoting component made of an organic or inorganic substance having an oxidizing property or a flammability property. These combustion promoting components include chlorates such as potassium chlorate and sodium chlorate, perchlorates such as sodium perchlorate and ammonium perchlorate, inorganic peroxides such as potassium peroxide and sodium peroxide. ,
Potassium nitrate, ammonium nitrate and other nitrates, potassium iodate and other iodates, sodium permanganate and other permanganates, sulfur, iron powder, magnesium powder, benzoyl peroxide and other organic peroxides, such as ethyl nitrate Examples thereof include nitrates, nitro compounds such as nitrocellulose, nitroso compounds such as ammonium N-nitrosophenylhydroxylamine, and azo compounds such as azobismethylbutyronitrile.

Since the combustion promoting component has a function of accelerating vaporization, evaporation and combustion of the protective agent during pressure contact, it is necessary to add a sufficient amount for burning the protective agent. The blending amount of the combustion promoting component is generally the resin component 1
0.01 to 1 parts by weight, especially 0.02 to parts by weight
0.5 parts by weight is preferred. Even if blended in an amount of more than 1 part by weight, the combustion promoting action remains unchanged.

In actual gas pressure welding, heating is performed with a reducing flame to prevent oxidation based on the standard rebar gas pressure welding method, and after the pressure welding end surface is completely closed, heating is performed with a neutral flame. And, as a standard, the pressure welding work start 30 to 4
After 0 seconds, the end faces of the reinforcing bars are completely welded at 600 to 800 ° C., so that the reducing flame is switched to the neutral flame. Therefore, in the present invention, the combustion extinction temperature of the protective agent is set to 600 ° C. or lower, preferably 550 ° C. or lower by adding the above combustion promoting component. Here, the combustion extinction temperature is the temperature at which the protective agent burns and vaporizes, and refers to the temperature at which no weight reduction is observed even if heating is continued beyond that.

These combustion promoting components may be used alone or
It can be mixed and used, and particularly when the combustion promoting component is the above-mentioned organic substance, the component is also completely combusted and decomposed at the time of pressure welding and does not remain in the pressure welding portion, which may adversely affect the bonding strength of the pressure welding joint. Absent.

A deoxidizing agent and / or a dehydrogenating agent may optionally be added to the protective agent of the present invention. The oxygen scavenger acts as a filler for the protective agent, and also has an action of promoting the reducing atmosphere in the pressure contact atmosphere during pressure contact. As the oxygen scavenger, fine powder of ferrosilicon, ferromanganese, carbon black or the like can be used.

Further, the dehydrogenating agent acts as a filler for the protective agent, and has an action of adsorbing and removing hydrogen in the pressure-welding atmosphere during pressure-welding to prevent the invasion of hydrogen into the molten steel. Examples of the dehydrogenating agent include chlorinated polyethylene, chlorinated polypropylene, polytetrafluoroethylene, and tetrafluoroethylene-hexafluoropropylene copolymer (commonly known as 4-6).
Fluorinated resin), tetrafluorinated ethylene-perfluoroalkyl vinyl ether copolymer (abbreviated as PFA), organic halides such as trifluorinated ethylene resin (halogenated polyalkylene) or inorganic halides such as fluorite and cryolite Is used. The appropriate amount of the oxygen scavenger and / or the hydrogen scavenger to be added is 0.05 to 2 parts by weight per 1 part by weight of the resin component.

If desired, waxes, rust preventives, and slag forming agents can be added to the protective agent of the present invention. The waxes adjust the viscosity of the protective agent and promote the rust preventive action, and as these waxes, beeswax, wax, palm wax, carnauba wax, paraffin wax and the like can be used.

As the rust preventive, an amine compound such as diethylamine or a carboxylic acid salt such as benzoic acid can be used. The slag forming agent is a filler extender, and it does not adversely affect the pressure contact surface at the time of pressure contact, limestone,
Fine powders of clay, fluorspar, cryolite, asbestos and the like can be used. The amount of each of the waxes, the rust preventives, and the slag forming agents is appropriately about 0.05 to 0.5 parts by weight with respect to 1 part by weight of the resin component.

The protective agent of the present invention contains the above-mentioned resin component and combustion promoting component, and further, if necessary, an oxygen scavenger and / or a dehydrogenating agent, waxes, a rust preventive and a slag forming agent. It is prepared by adding a solvent to and kneading. The solvent to be added is not particularly limited as long as it has compatibility with the resin component, and for example, toluene, xylene, methyl ethyl ketone, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, carbon tetrachloride, etc. Can be illustrated. The solvent may be blended so as to have a viscosity suitable for forming a film, and generally, about 3 to 10 parts by weight is preferable with respect to 1 part by weight of the resin component.

The protective agent of the present invention is used by applying it to the end surface of a steel bar to form an anticorrosive film. The coating method may be either brush coating or spraying, and aerosol spraying is also possible except for two-component type epoxy resin-based ones. The work of forming the coating may be performed at the time of factory work for cutting the steel bar into a predetermined length by shirring or the like, or may be performed after the end face grinding treatment work by a grinder at the construction site.

In the pressure welding work, when the ends of the steel bars butted against each other are heated by the flame of the pressure welding machine, the protective agent applied to the end faces gradually vaporizes and evaporates until the temperature reaches about 550 to 600 ° C. Burns and disappears. After the ends of the steel bars are sufficiently heated to be in a semi-molten state, the steel bars are axially pressed and joined together. At this time, the resin component and the solvent constituting the protective agent have already vaporized and burned due to the action of the combustion promoting component, so that there is no obstacle during the pressure welding work, and a good pressure welding joint can be obtained.

Further, in the case of the protective agent containing the oxygen scavenger and / or the hydrogen scavenger, an oxygen absorption atmosphere is formed, or hydrogen around the ends of the steel bar is adsorbed and removed to remove the hydrogen in the molten steel. Prevent intrusion.

[0026]

Next, preferred embodiments of the present invention will be described.
First, the protective agents 1 to 14 and the protective agent A having the following composition were prepared.
~ D were prepared. For each protective agent, an equal mixed solvent of toluene, isopropyl alcohol, ethyl acetate and methyl ethyl ketone was used. The epoxy resin system is a two-component type, and only the curing agent is prepared separately, and it is used by adding it to the resin component and other compounded products immediately before coating.

Protective agent 1 Acrylic resin 20 parts by weight Potassium chlorate 1 part by weight Ferromanganese 1 part by weight Solvent 80 parts by weight

Protective agent 2 Alkyd resin 20 parts by weight Sodium perchlorate 1 part by weight Carnauba wax 3 parts by weight Solvent 80 parts by weight

Protective agent 3 Acrylic resin 20 parts by weight Potassium peroxide 1 part by weight Chlorinated polyethylene (chlorination rate 70%) 2 parts by weight Solvent 80 parts by weight

Protective agent 4 Alkyd resin 20 parts by weight Ammonium nitrate 1 part by weight Carbon black 5 parts by weight Paraffin wax 3 parts by weight Solvent 80 parts by weight

Protective agent 5 Alkyd resin 20 parts by weight Potassium iodate 1 part by weight Cryolite 2 parts by weight Paraffin wax 3 parts by weight Solvent 80 parts by weight

Protective agent 6 Alkyd resin 20 parts by weight Sodium permanganate 2 parts by weight Chlorinated polypropylene (chlorination rate 80%) 2 parts by weight Solvent 80 parts by weight

Protective agent 7 Phenolic resin 20 parts by weight Sulfur 10 parts by weight Solvent 70 parts by weight

Protective agent 8 Phenolic resin 20 parts by weight Magnesium powder 1 part by weight Fluorite 5 parts by weight Solvent 80 parts by weight

Protective agent 9 Epoxy resin 20 parts by weight Iron powder 1 part by weight Carbon black 5 parts by weight Solvent 80 parts by weight (Curing agent 27 parts by weight)

Protective agent 10 Acrylic resin 15 parts by weight Benzoyl peroxide 10 parts by weight Solvent 70 parts by weight

Protective agent 11 Urea resin 20 parts by weight Ethyl nitrate 1 part by weight Beeswax 1 part by weight Solvent 80 parts by weight

Protective agent 12 Epoxy resin 20 parts by weight Nitrocellulose (nitrification degree 11.5%) 5 parts by weight Polytetrafluoroethylene 2 parts by weight Solvent 70 parts by weight (Curing agent 24 parts by weight)

[0039]

Protective agent 14 Acrylic resin 15 parts by weight Azobismethylbutyronitrile 10 parts by weight Diethylamine 3 parts by weight Solvent 70 parts by weight

Protective agent A Acrylic resin 20 parts by weight Aluminum powder 10 parts by weight Solvent 80 parts by weight

Protective agent B Epoxy resin 10 parts by weight Solvent 80 parts by weight (Curing agent 45 parts by weight)

Protective agent C Alkyd resin 20 parts by weight Borax 5 parts by weight Solvent 80 parts by weight

Protective agent D Coarse pine resin 30 parts by weight Pulverized coal 10 parts by weight Kneading paste 10 parts by weight Solvent 70 parts by weight

[Combustion Extinction Test] An experiment for measuring the combustion extinction temperature of each of the above protective agents was conducted. A certain amount of protective agent was applied to the differential thermal balance, and the maximum temperature during pressure welding was 120.
By heating up to 0 ° C. at a rate of 20 ° C./min, the temperature change and the weight change were recorded, and the combustion extinction temperature of the protective agent was measured. The combustion extinction temperature of each protective agent is shown in Table 1.

As shown in Table 1, all of the protective agents 1 to 14 are burnt out at 550 ° C. or lower, so that the protective agent does not remain in the pressure-welded portion during welding of the end face of the reinforcing bar. On the other hand, the combustion extinction temperatures of the protective agents A to D exactly overlap with this welding temperature range, so that unburned matter of the protective agent remains on the pressure contact end face, which may affect the pressure contact strength.

[Gas Pressure Contact Test] Each protective agent 1 to 14 and protective agents A to D were applied to a small opening to form a film 25 mm
After preparing the rebar, leaving it for 3, 7, 14 and 28 days, using a gas pressure welding machine (D25 type, manufactured by Sakae Industry Co., Ltd.),
A gas pressure welding test was conducted without removing the coating.

For each test piece obtained by the above gas pressure welding, a tensile test, a bending test, a breaking test and an X-ray transmission test were carried out according to JIS Z 3120 (inspection method for steel bar gas pressure welding joint for reinforced concrete). The results of these tests are shown in Table 1.
Shown in. In the column of the bending test in Table 1, the mark ○ indicates that the product passed, and the mark × indicates that the product failed. In the column of the X-ray transmission test, the ∘ mark indicates that the product passed, and the X mark indicates that the product failed.

[0049]

TABLE 1 combustion disappearance allowed tensile bending test fracture X-ray transmission temperature (℃) days (N / mm ²⁾ Test Test over test protectant 1 510 3 540 ○ ○ ○ protectant 2 490 7 559 ○ ○ ○ protectant 3 535 14 556 ○ ○ ○ Protective agent 4 460 28 581 ○ ○ ○ Protective agent 5 505 3 552 ○ ○ ○ Protective agent 6 510 7 546 ○ ○ ○ Protective agent 7 480 14 576 ○ ○ ○ Protective agent 8 520 28 543 ○ ○ ○ Protective agent 9 525 3 557 ○ ○ ○ Protective agent 10 490 7 579 ○ ○ ○ Protective agent 11 470 14 581 ○ ○ ○ Protective agent 12 460 28 578 ○ ○ ○ Protective agent 13 485 3 579 ○ ○ ○ Protective agent 14 490 7 576 ○ ○ ○ Protective agent A 600 3 141 × × × Protective agent B 650 28 97 × × × Protective agent C -14 106 × × × Protective agent D -7 257 × × ×

As a result of the tensile test, all the test pieces coated with the protective agents 1 to 14 were base material fractures, and no abnormality was observed in other tests. On the other hand, the test pieces to which the protective agents A to D were applied had fractures on the pressure contact surface, and in the results of the fracture test, foreign matter considered to be combustion residues was recognized on the pressure contact surface.

[0051]

The protective agent of the present invention is applied to the pressure contact end surface of a steel bar to protect the pressure contact surface due to its rust-preventive effect during the period until the start of the pressure contact work, while causing a joint failure during the pressure contact. In other words, it is possible to obtain a pressure-bonded joint having high joint strength and high reliability.

Further, the function of the blended combustion promoting component increases the temperature rising rate of the steel bar end surface during heating,
Since the pressure welding work time can be shortened, there is also an effect that workability at the site can be improved.

Further, in the case of a protective agent containing a deoxidant and / or a dehydrogenating agent, the deoxidizing agent acts to prevent end surface oxidation, and the dehydrogenating agent acts to prevent hydrogen from flowing into molten steel. It is possible to prevent intrusion.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kosho Isogai 2-1, Tsukudo-cho, Shinjuku-ku, Tokyo Kumagai Gumi Co., Ltd. Tokyo Head Office (72) Inventor Hiroshi Sakamoto 2-1, Tsukudo-cho, Shinjuku-ku, Tokyo Stocks Company Kumagai Gumi Tokyo Head Office

Claims (4)

[Claims] 1. 0.01 to 1 relative to 1 part by weight of a resin component.
A protective agent for gas pressure welded end faces of steel bars, which is prepared by blending parts by weight of a combustion promoting component. 2. The protective agent according to claim 1, which has a combustion extinction temperature of 550 ° C. or lower. 3. The combustion promoting component is any one or more of organic peroxides, nitrates, nitro compounds, nitroso compounds and azo compounds.
Protective agent described. 4. The protective agent according to claim 1, further comprising a deoxidizing agent and / or a dehydrogenating agent added to the protective agent.