A TIG welding flux for dissimilar steels is used to solve the problem that the conventional friction stir welding procedure for butt-joint welding a stainless steel workpiece and a carbon steel workpiece cannot be used on site, as well as the problem that the increased operating time and manufacturing cost due to forming bevel faces on both the stainless steel workpiece and the carbon steel workpiece. The TIG welding flux for dissimilar steels includes 25-35 wt % of silicon dioxide (SiO.sub.2), 20-30 wt % of cobalt (II, III) oxide (Co.sub.3O.sub.4), 15-20 wt % of manganese (II, III) oxide (Mn.sub.3O.sub.4), 10-15 wt % of nickel (III) oxide (Ni.sub.2O.sub.3), 7-12 wt % of molybdenum trioxide (MoO.sub.3), 6-11 wt % of manganese (II) carbonate (MnCO.sub.3), 5-10 wt % of nickel (II) carbonate (NiCO.sub.3), and 2-4 wt % of aluminum fluoride (AlF.sub.3).

A TIG welding flux for dissimilar steels is used to solve the problem that the conventional friction stir welding procedure for butt-joint welding a stainless steel workpiece and a carbon steel workpiece cannot be used on site, as well as the problem that the increased operating time and manufacturing cost due to forming bevel faces on both the stainless steel workpiece and the carbon steel workpiece. The TIG welding flux for dissimilar steels includes 25-35 wt % of silicon dioxide (SiO.sub.2), 20-30 wt % of cobalt (II, III) oxide (Co.sub.3O.sub.4), 15-20 wt % of manganese (II, III) oxide (Mn.sub.3O.sub.4), 10-15 wt % of nickel (III) oxide (Ni.sub.2O.sub.3), 7-12 wt % of molybdenum trioxide (MoO.sub.3), 6-11 wt % of manganese (II) carbonate (MnCO.sub.3), 5-10 wt % of nickel (II) carbonate (NiCO.sub.3), and 2-4 wt % of aluminum fluoride (AlF.sub.3).

An objective of the present invention is to provide a flux that suppresses occurrence of flux drying up during soldering and occurrence of precipitation during storing.

The flux comprising, based on the whole flux, 3.5 to 11% by mass of a rosin ester, more than 0% by mass and 18% by mass or less of a rosin resin other than a rosin ester, and 70% by mass or more and less than 96.5% by mass of a solvent.

An objective of the present invention is to provide a flux that suppresses occurrence of flux drying up during soldering and occurrence of precipitation during storing.

The flux comprising, based on the whole flux, 3.5 to 11% by mass of a rosin ester, more than 0% by mass and 18% by mass or less of a rosin resin other than a rosin ester, and 70% by mass or more and less than 96.5% by mass of a solvent.

A flux containing an organic acid, a water-soluble base agent, and a solvent, but not containing water is adopted. In this flux, the organic acid includes 1,2,3-propanetricarboxylic acid. The water-soluble base agent is one or more selected from the group consisting of a nonionic surfactant and a weak cationic surfactant. The content of the 1,2,3-propanetricarboxylic acid is 1% by mass or more and 15% by mass or less with respect to the total amount of the entire flux, the total content of the water-soluble base agent is 30% by mass or more and 65% by mass or less with respect to the total amount of the entire flux, and the total content of the solvent is 30% by mass or more and 65% by mass or less with respect to the total amount of the entire flux. According to this flux, the wettability of solder can be enhanced and ball missing after reflow and flux residue washing is suppressed.

A flux containing an organic acid, a water-soluble base agent, and a solvent, but not containing water is adopted. In this flux, the organic acid includes 1,2,3-propanetricarboxylic acid. The water-soluble base agent is one or more selected from the group consisting of a nonionic surfactant and a weak cationic surfactant. The content of the 1,2,3-propanetricarboxylic acid is 1% by mass or more and 15% by mass or less with respect to the total amount of the entire flux, the total content of the water-soluble base agent is 30% by mass or more and 65% by mass or less with respect to the total amount of the entire flux, and the total content of the solvent is 30% by mass or more and 65% by mass or less with respect to the total amount of the entire flux. According to this flux, the wettability of solder can be enhanced and ball missing after reflow and flux residue washing is suppressed.

A flux for electroslag welding used for electroslag welding may include a basic oxide, an amphoteric oxide, an acidic oxide, and a fluoride. With respect to a total mass of the flux, the basic oxide may include 5.1 mass % or more and 30.0 mass % or less of CaO, the acidic oxide includes 17 mass % or less of SiO.sub.2, and the fluoride includes 35 mass % or more and 73 mass % or less of CaF2. A content of the CaO is 30 mass % or more with respect to a total mass of the basic oxide, a content of the SiO.sub.2 is 80 mass % or more with respect to a total mass of the acidic oxide, a content of the CaF.sub.2 is 80 mass % or more with respect to a total mass of the fluoride, and a value of (2×[CaF.sub.2]+[CaO])/[SiO.sub.2] is 5 or more and 56 or less.

A flux for electroslag welding used for electroslag welding may include a basic oxide, an amphoteric oxide, an acidic oxide, and a fluoride. With respect to a total mass of the flux, the basic oxide may include 5.1 mass % or more and 30.0 mass % or less of CaO, the acidic oxide includes 17 mass % or less of SiO.sub.2, and the fluoride includes 35 mass % or more and 73 mass % or less of CaF2. A content of the CaO is 30 mass % or more with respect to a total mass of the basic oxide, a content of the SiO.sub.2 is 80 mass % or more with respect to a total mass of the acidic oxide, a content of the CaF.sub.2 is 80 mass % or more with respect to a total mass of the fluoride, and a value of (2×[CaF.sub.2]+[CaO])/[SiO.sub.2] is 5 or more and 56 or less.

A coating composition for a heat exchanger tube including vanadium (V), a flux, and a binder, wherein the vanadium is included in an amount of 28 to 38 parts by weight with respect to 100 parts by weight of the composition, and a coating method of a heat exchanger tube using the same are provided.

A resin flux solder paste includes a solder powder, and a flux, in which the flux contains at least an epoxy resin, a curing agent, a curing accelerator, and an activator, the epoxy resin contains 10% to 90% by weight of one or more of a biphenyl aralkyl type epoxy resin, a naphthalene type epoxy resin, and a dicyclopentadiene type epoxy resin, having an epoxy equivalent of 200 to 400, with respect to a total amount of the epoxy resin, and the curing agent contains 30% to 95% by weight of a biphenyl aralkyl phenol resin having a hydroxyl group equivalent of 150 to 350 with respect to a total amount of the curing agent, and 5% to 70% by weight of a phenol novolac resin having an allyl group having a hydroxyl group equivalent of 100 to 200 with respect to the total amount of the curing agent.