Precipitation-hardening stainless steel flux

Abstract

To provide a precipitation hardening stainless steel flux for solving a problem with poor aspect ratio of weld beads formed between two precipitation hardening stainless steel work-pieces.SOLUTION: A precipitation hardening stainless steel flux contains: silicon dioxide of 20 to 25%; molybdenum trioxide of 20 to 25%; chrome oxide of 20 to 25%; nickel trioxide of 15 to 20%; aluminum oxide of 4 to 8%; aluminum nitride of 4 to 8%; nickel oxide of 4 to 8%; and copper oxide of 4 to 6%.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a flux, and particularly to a flux for precipitation hardening stainless steel.

Background Art

[0002] Generally, iron-chromium-nickel stainless steel (Fe-Cr-Ni stainless steel) is separately added with elements such as copper (Cu), aluminum (Al), titanium (Ti), niobium (Nb), and molybdenum (Mo), and further subjected to solution treatment and aging treatment, then a precipitation hardening (PH) stainless steel with excellent mechanical strength, wear resistance, and good atmospheric corrosion resistance can be formed. Precipitation hardening stainless steel is widely applied to golf club heads, gas turbine blades, valves of oil pipelines, components for nuclear power generation, and the like.

[0003] Tungsten inert gas welding (TIG welding) is a high-quality arc welding process and is often applied to welding operations of metal materials such as aluminum alloys, titanium alloys, stainless steels, and nickel-based alloys. Tungsten inert welding involves using an inert gas (argon, helium, or argon-helium mixture) to protect the tungsten electrode, which generates an arc as the welding heat source. A conventional welding rod is melted at the point where two precipitation-hardening stainless steel workpieces meet, forming a molten pool. After the molten pool cools and solidifies, a weld bead is formed that tightly joins the two precipitation-hardening stainless steel workpieces. As a result, after welding, the two precipitation-hardening stainless steel workpieces become a precipitation-hardening stainless steel weld, and the welding process is complete. However, due to the low energy density heat source characteristics of tungsten inert welding, the resulting weld bead is wide and shallow, which posed a problem when welding thicker workpieces (for example, workpieces with a thickness of 3 mm or more) as the penetration depth was insufficient.

[0004] To solve the above problem, the operator can perform a conventional beveling process on the workpiece before welding. As shown in Figure 6, in a conventional beveling process, the side edge 92 of the precipitation-hardening stainless steel workpiece 9 is milled with a milling cutter M to form a bevel 91, and similarly a bevel 92' is formed on the side edge 91' of another precipitation-hardening stainless steel workpiece 9'. Next, as shown in Figures 7 and 8, when welding, the operator brings the side edges 91 and 91' of the two precipitation-hardening stainless steel workpieces 9 and 9' into contact, so that the bevels 92 and 92' form an open structure with an angle. Furthermore, using a tungsten electrode E and a conventional welding rod S, multiple welding steps can be performed in this structure to form a weld bead 93. However, while the groove preparation process can increase the penetration depth of the weld bead 93, it resulted in the weld bead 93 being too wide. Furthermore, during the welding process, the welding heat source forms a heat-affected zone near the weld site, and the conventional groove preparation process and subsequent multiple welding processes excessively enlarge this heat-affected zone. This not only reduces the mechanical strength of the resulting precipitation-hardening stainless steel weld, but also causes serious thermal deformation and residual stress in the precipitation-hardening stainless steel weld, and can significantly worsen the corrosion resistance of the weld bead. In addition to the above, the conventional beveling process and the subsequent multiple welding processes increase production time and manufacturing costs.

[0005] In view of the above, if a flux applicable to welding precipitation-hardening stainless steel can be provided, the conventional beveling process and the subsequent multiple welding processes can be eliminated, thereby solving the above-mentioned problems. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Taiwan Publication No. I773514 [Overview of the project] [Problems that the invention aims to solve]

[0007] To solve the above problems, the object of the present invention is to provide a precipitation-hardening stainless steel flux that can form deep and narrow weld beads and eliminate the conventional beveling process and subsequent multiple welding processes. [Means for solving the problem]

[0008] The terms of directionality or similar terms used throughout the specification of this invention, such as "front," "back," "left," "right," "top (summit)," "bottom (bottom)," "inside," "outside," and "side," are based on the directions shown in the accompanying drawings. Each of these directions or similar terms is merely for the purpose of assisting in the explanation and understanding of each embodiment of the invention and does not limit the invention. Throughout the specification of this invention, the counter words "one" or "one" used with respect to parts or components are used for convenience and to give a common meaning to the scope included in this invention, and should be interpreted as one or at least one in this invention, and unless explicitly stated otherwise, the concept of one also includes cases of multiple.

[0009] The precipitation-hardening stainless steel flux of the present invention may contain 20-25% silicon dioxide, 20-25% molybdenum trioxide, 20-25% chromium oxide, 15-20% nickel trioxide, 4-8% aluminum oxide, 4-8% aluminum nitride, 4-8% nickel oxide, and 4-6% copper oxide.

[0010] As a result, the precipitation-hardening stainless steel flux of the present invention, with its specific composition ratio of silicon dioxide, molybdenum trioxide, chromium(III) oxide, nickel(II) trioxide, aluminum oxide, aluminum nitride, nickel(II) oxide, and copper oxide, can effectively improve the aspect ratio of the weld bead formed when used for welding precipitation-hardening stainless steel workpieces. This not only reduces thermal deformation and residual stress caused by welding, but also eliminates the need for beveling and subsequent multiple welding processes when welding precipitation-hardening stainless steel workpieces with a thickness of 3 mm or more. Furthermore, it avoids the problems of reduced strength and excessively large heat-affected zone in precipitation-hardening stainless steel welds caused by the beveling process, thereby reducing the increased working time and manufacturing costs associated with the beveling process.

[0011] Furthermore, the precipitation-hardening stainless steel flux of the present invention may have an average particle size of 50 to 90 μm. This improves the uniformity of the mixing of each powder particle of the precipitation-hardening stainless steel flux, making it easier to uniformly apply the precipitation-hardening stainless steel flux to the surfaces of two precipitation-hardening stainless steel workpieces. In addition, during TIG welding, the precipitation-hardening stainless steel flux can be completely melted by the welding heat source, effectively increasing the aspect ratio of the weld bead. [Brief explanation of the drawing]

[0012] [Figure 1] A diagram showing the application of the precipitation-hardening stainless steel flux according to the present invention to the contact points of two precipitation-hardening stainless steel workpieces. [Figure 2] This diagram illustrates the process of welding two precipitation-hardening stainless steel workpieces using tungsten inert welding to form a welded product. [Figure 3] This figure shows the cross-sectional shape of the weld bead of precipitation-hardening stainless steel (B00 group) formed by single-pass TIG welding without using precipitation-hardening stainless steel flux. The area enclosed by the dashed line is the extent of the weld bead, D is the depth of the weld bead, and W is the width of the weld bead. [Figure 4] This figure shows the cross-sectional shape of the weld bead of precipitation-hardening stainless steel (B04 type) formed by single-pass TIG welding using precipitation-hardening stainless steel flux (A04 type). The area enclosed by the dashed line is the extent of the weld bead, D is the depth of the weld bead, and W is the width of the weld bead. [Figure 5] This figure shows the cross-sectional shape of a weld bead of precipitation-hardening stainless steel (B07 type) formed by single-pass TIG welding using precipitation-hardening stainless steel flux (A07 type). The area enclosed by the dashed line is the extent of the weld bead, D is the depth of the weld bead, and W is the width of the weld bead. [Figure 6] A diagram showing the process of pre-grooving in a conventional groove-grooving process. [Figure 7] A diagram showing a multi-pass welding process in a conventional groove machining process. [Figure 8] A cross-sectional view of a weld bead formed through a multi-pass welding process in a conventional groove machining process.

Embodiments for Carrying out the Invention

[0013] To make it easier to understand the above objects, other objects, and advantages of the present invention, embodiments of the present invention are given as follows and will be described in detail with reference to the drawings. Also, in different drawings, those denoted by the same reference numerals are regarded as the same and their descriptions are omitted.

[0014] The precipitation hardening stainless steel of the present invention may be of types of precipitation hardening stainless steel such as UNS S17400, UNS S17700, and UNS S66286, which are matters understandable by those skilled in the art, but are not limited thereto.

[0015] The precipitation hardening stainless steel according to one embodiment of the present invention Flux may contain components such as silicon dioxide (SiO2), molybdenum trioxide (MoO3), chromium(III) oxide (Cr2O3), nickel(III) oxide (Ni2O3), aluminum oxide (Al2O3), aluminum nitride (AlN), nickel(II) oxide (NiO), and copper(II) oxide (CuO), and can be used for welding a precipitation hardening stainless steel workpiece with a thickness of 3 mm or more in combination with a TIG welding process.

[0016] Specifically, the precipitation hardening stainless steel flux can contain 20 - 25% silicon dioxide, 20 - 25% molybdenum trioxide, 20 - 25% chromium oxide, 15 - 20% nickel sesquioxide, 4 - 8% aluminum oxide, 4 - 8% aluminum nitride, 4 - 8% nickel oxide, and 4 - 6% copper oxide. Thereby, when used in the TIG welding process, the weld bead formed between two precipitation hardening stainless steel workpieces can have an aspect ratio of 0.8 or more, the heat affected zone formed between the two precipitation hardening stainless steel workpieces can be reduced, and thus, the thermal deformation and residual stress of the precipitation hardening stainless steel weldment can be reduced.

[0017] Also, the average particle size of the powder of the precipitation hardening stainless steel flux may be 50 - 90 μm. Thereby, the mixing uniformity of the powder particles of the precipitation hardening stainless steel flux can be improved, so that not only can the precipitation hardening stainless steel flux be easily and uniformly applied to the surfaces of the two precipitation hardening stainless steel workpieces, but also during TIG welding, the precipitation hardening stainless steel flux can be completely melted by the welding heat source, and thus, the aspect ratio of the weld bead can be effectively improved.

[0018] As shown in FIG. 1, before the operator performs the TIG welding process, the side edges 11, 11' of the two precipitation hardening stainless steel workpieces 1, 1' are abutted, and the precipitation hardening stainless steel flux 2 is applied to the abutting portion of the two precipitation hardening stainless steel workpieces with a wire brush B, and the subsequent welding operation can be performed after the application is completed. As shown in FIG. 2, by using the welding heat source H and the tungsten electrode E together, the precipitation hardening stainless steel flux 2 is melted between the side edges 11, 11' of the two precipitation hardening stainless steel workpieces to form a molten pool, and after the molten pool cools and solidifies, a weld bead 12 is formed. At this time, due to the use of the precipitation hardening stainless steel flux 2, the formed weld bead 12 has a form with a deep penetration depth, a narrow width, and a large aspect ratio.

[0019] To prove that the above-mentioned precipitation-hardening stainless steel flux, when used in a TIG welding process, allows two precipitation-hardening stainless steel workpieces to be welded together and improves the aspect ratio of the formed weld bead, the following tests were conducted.

[0020] (A) Preparation of precipitation-hardening stainless steel flux

[0021] Powders such as 15% silicon dioxide, 30% molybdenum trioxide, 20% chromium oxide, 12% nickel trioxide, 6% aluminum oxide, 6% aluminum nitride, 6% nickel oxide, and 5% copper oxide were mixed and then dissolved in methanol as a solvent to produce the A01 precipitation-hardening stainless steel flux. The preparation method for the A02 to A12 precipitation-hardening stainless steel fluxes was the same as above, but the composition ratios of the powders such as silicon dioxide, molybdenum trioxide, chromium(III) oxide, nickel trioxide, aluminum oxide, aluminum nitride, nickel(II) oxide, and copper oxide are as shown in Table 1.

[0022] Table 1, Composition ratio of precipitation-hardening stainless steel fluxes for groups A01 to A12. [Table 1]

[0023] (B) Properties of precipitation-hardening stainless steel welds

[0024] In this test, two steel plates made of precipitation-hardening stainless steel (UNS S17400), both with a thickness of 7 mm, were designated as precipitation-hardening stainless steel workpieces 1 and 1'. After removing dirt from both workpieces 1 and 1' using silicon carbide sandpaper with a grit size of #240, both workpieces 1 and 1' were wiped with acetone.

[0025] Then, as shown in Figure 1, the side edges 11, 11' of the two precipitation-hardening stainless steel workpieces 1, 1' were brought into contact, and slurry-like sets of precipitation-hardening stainless steel flux 2 A01-A12 were applied to the surfaces of the precipitation-hardening stainless steel workpieces 1, 1' with a bristle brush B. After the methanol had completely evaporated, TIG welding was performed.

[0026] As shown in Figure 2, a welding heat source H and a tungsten electrode E were used together to melt precipitation-hardening stainless steel flux between the side edges 11, 11' of two precipitation-hardening stainless steel workpieces 1, 1' to create a molten pool. After the molten pool cooled and solidified, a weld bead 12 was formed, yielding precipitation-hardening stainless steel welds in sets B01 to B12. The precipitation-hardening stainless steel welds in set B00 were formed by TIG welding two precipitation-hardening stainless steel workpieces 1 and 1' under the condition that no flux was applied.

[0027] In the TIG welding process, the welding current is 140A, the welding speed is 50mm / min, the shielding gas flow rate is 10L / min, an EWLa-2 (φ3.2mm) tungsten electrode E is used, the working angle of the tungsten electrode E is 60°, and the distance from the tip of the tungsten electrode E to the surface of the two precipitation-hardening stainless steel workpieces 1 and 1' (i.e., the arc length) is 1mm.

[0028] After TIG welding, cross-sections of the weld beads 12 of the precipitation-hardening stainless steel welds in groups B00 to B12 were taken, and the depth D and width W of each weld bead 12 were recorded. Furthermore, the aspect ratio of the weld bead of each precipitation-hardening stainless steel weld was calculated. The depth D, width W, and calculated aspect ratio of the weld beads 12 for the precipitation-hardening stainless steel welds in groups B00 to B12 are shown in Table 2.

[0029] Table 2, Depth, width, and aspect ratio of weld beads for precipitation-hardening stainless steel welds in groups B00-B12. [Table 2]

[0030] Figures 3-5 show the cross-sectional morphology of the precipitation-hardening stainless steel weld bead 12 in welds of groups B00, B04, and B07, respectively, and it was found that only in the weld of group B07 the weld the weld bead 12 completely penetrated the material. Furthermore, as shown in Table 2, compared to the weld beads 12 of precipitation-hardening stainless steel welds of groups B01-B05 and B10-B12, the weld beads of precipitation-hardening stainless steel welds of groups B06-B09 are deeper and narrower. As a result, the aspect ratio of the weld beads of welds of groups B06-B09 is at least 0.8, and can reach 0.94 (group B07), thus allowing for the formation of a narrower heat-affected zone, and consequently reducing thermal deformation and residual stress of the weld.

[0031] As described above, the precipitation-hardening stainless steel flux of the present invention, when used for welding precipitation-hardening stainless steel workpieces, can effectively improve the aspect ratio of the weld bead formed by silicon dioxide, molybdenum trioxide, chromium(III) oxide, nickel(II) oxide, aluminum oxide, aluminum nitride, nickel(II) oxide, and copper oxide having a specific composition ratio, thereby reducing thermal deformation and residual stress caused by welding. Furthermore, even when welding precipitation-hardening stainless steel workpieces with a thickness of 3 mm or more, it is possible to eliminate the groove preparation process and subsequent multiple welding processes. Moreover, it avoids the problems of reduced strength and excessively large heat-affected zone in precipitation-hardening stainless steel welds caused by the groove preparation process, and has the effect of reducing the increased working time and manufacturing costs associated with the groove preparation process.

[0032] Although the present invention has been disclosed with respect to the above embodiments, these embodiments are not intended to limit the present invention. Those skilled in the art will know that various modifications to the above embodiments will remain within the scope of the invention, as long as they do not deviate from the spirit and scope of the invention. Accordingly, the scope of protection of the present invention includes all modifications within the scope of the language set forth in the claims described below and equivalents. [Explanation of Symbols]

[0033] 1, 1' ···Precipitation-hardening stainless steel workpiece 11, 11'...Side edge 12 ···Weld bead 2. Precipitation-hardening stainless steel flux 9, 9' ···Work 91, 91' ···Slope 92, 92'...Side edge 93 ···Weld bead B...hairbrush D... Depth of the weld bead E ···Tungsten electrode H ···Welding heat source M... Milling machine S ···Welding rod W...Weld bead width

Claims

1. A precipitation-hardening stainless steel flux characterized by containing 20-25% silicon dioxide, 20-25% molybdenum trioxide, 20-25% chromium(III) oxide, 15-20% nickel(II) trioxide, 4-8% aluminum oxide, 4-8% aluminum nitride, 4-8% nickel(II) oxide, and 4-6% copper(II) oxide.

2. The precipitation-hardening stainless steel flux according to claim 1, characterized in that the average particle size of the powder of the precipitation-hardening stainless steel flux is 50 to 90 μm.

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