JPH10235492A - Welding material for cast iron reinforcing build up welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cast iron reinforcing build-up welding material stable in quality which prevents weld crack without preheating or after-heating, improves tensile strength of a deposited metal and suppresses deterioration in strength under a high temperature. SOLUTION: By weight, 0.1-0.3% Mg and/or 0.01-0.3% Ca, is added to a welding material consisting of, by weight, 60-90% Ni, 0-50% Fe, 0.3-1.5% Si, 4-10% Al. Here, the components are preferably, be weight, 15.0% Fe, 0.3% Si, 4.0% Al, 0.5% C, 0.15% Mg, 0.04% Ca and the balance Ni. Further, Ni band sheet is used as an outer shell, in which rapidly solidified powder of Fe-C and Al powder and the like are mixed and filled in a form of welding wire. This is used in built-up MIG welding without preheating or after-heating of the base metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding material used for overlay welding for locally modifying cast iron parts in automobile parts and the like.

[0002]

2. Description of the Related Art There are the following main methods for welding cast iron and welding rods (welding wires). Covered arc welding method The base metal is subjected to cold or low-temperature preheating (100 to 300 ° C) or high-temperature preheating (500 to 600 ° C), and is electric arc welding using a welding rod of pure Ni, Ni alloy, mild steel or cast iron. Then, welding is performed while covering the arc with an inert gas such as argon or nitrogen. Gas welding method The base material is preheated to 400 to 600 ° C., and a welding rod in which elements such as Al, Ni, Cu, and Si are added to a cast iron rod is heated and melted with an oxygen / acetylene gas flame, and welding is performed.
Heat treatment is generally performed after reheating to 0-600 ° C. and then furnace cooling to about 250 ° C. Carbon arc welding method The base material is preheated to 700 ° C. or higher, and a welding rod is put in an arc formed by a carbon electrode to melt and perform welding. However, it is not generally used because the arc operation is difficult.

Japanese Patent Application Laid-Open No. 4-28497 discloses that the amount of C is 0.01 to 0.5% by weight, the amount of Mn is 1.6 to 6.0% by weight, the amount of Co is 0.3 to 10.0% by weight, and the balance is A Mf temperature (martensite transformation end temperature) of a first-layer deposited metal weld-welded to a cast iron base material, the steel wire being used for overlay welding to a cast iron base material to be Fe; There is described a steel wire for overlay welding in which the content of each of the above components is determined in consideration of the diffusion of C from the material.

Japanese Patent Application Laid-Open No. 4-66293 discloses that Fe-
A welding wire made of a Ni-based alloy, wherein Ni: 40 to
70 wt%, Mn: 1.0 to 3.0 wt%, Si: 0.
A welding wire for cast iron containing 2 to 1.0 wt% and V: 0.2 to 10.0 wt% is described.

[0005]

In the prior art described above, if welding is performed without preheating, generally, the weld metal cracks at the welded portion (strength is reduced due to structural defects in the weld metal or formation of compounds). Cracking caused by tensile stress generated during welding) and boundary cracking (abrupt temperature change during welding causes a structural transformation at the boundary between the deposited metal and the base metal, turning it into white iron (chilling). The hardness increases, and consequently, the ductility decreases, thereby generating cracks caused by the generated stress.

[0006] The above-mentioned welding methods are all unsuitable for continuous welding because they use a welding rod, and generally require preheating, so that the working efficiency is poor. The ones described in the above publications take a form of a wire that can be continuously welded without requiring heat treatment such as preheating.
No. 97 discloses a method for determining the content of each component so that the Mf temperature of the first layer deposited metal welded to the cast iron base material is a predetermined temperature. It is necessary to consider the amount of C in the welding base metal and the amount of C diffusion due to welding conditions at the time of implementation. In addition, V is added to the welding wire described in JP-A-4-66293 in order to improve the strength of the matrix in order to prevent welding cracks, but V is expensive.

[0007] The present applicant has found that in overlay welding MIG welding,
Ni: 60 to 90 wt%, Fe: 0 to 50 wt%, S
A patent application (Japanese Patent Application No. Hei 7-305042) has been filed for the invention of a welding material for strengthening cast iron build-up containing i: 0.3 to 1.5 wt% and Al: 4 to 10 wt%. The welding material of this prior invention can be used in the form of a welding wire to prevent welding cracks without preheating and post-heating, and to stabilize the strength of the deposited metal, but the strength of the deposited metal at a high temperature is greatly reduced. .

According to the present invention, there is provided a welding material for strengthening cast iron cladding which has a stable quality by suppressing a decrease in strength of a deposited metal at a high temperature by adding a predetermined amount of an inexpensive element to the welding material of the prior application. The purpose is to provide.

[0009]

According to the present invention, Ni: 60 to
90 wt%, Fe: 0 to 50 wt%, Si: 0.3 to
In a welding material consisting of 1.5 wt% and Al: 4 to 10 wt%, Mg: 0.1 to 0.3 wt% or / and Ca: 0.1 to 0.3 wt%.
A weld material for reinforcing hardened cast iron to which 01 to 0.3 wt% is added, which is used in the form of a wire in which a Ni strip is used as an outer skin and powder of another element is mixed and filled therein.

[0010]

In the past, Mg has been used as a spheroidizing element of graphite when casting spheroidal graphite cast iron. Regarding the mechanism of the spheroidization, the Mg-Si compound serves as a nucleus to grow graphite round. Impurities such as S and O are removed, and the interfacial energy in the molten metal increases, resulting in a sphere having a minimum surface area. The graphite is activated by being adsorbed on the graphite surface and becomes spherical by the pressure of the molten metal. There is a theory such as that, the effect is not necessarily clear. As a result of the test, when Mg is added to the welding material, graphite in the deposited metal becomes spherical, and the strength of the deposited metal increases. However, the addition of a large amount of Mg deteriorates the weldability and causes F in the deposited metal.
An e-Mg compound is formed, which causes a reduction in strength. Ca
Has been used as an inoculant to increase the number of eutectic cells (the number of co-extruded graphite) during casting of cast iron. As a result of the test, it was confirmed that the addition of Ca to the welding material dispersed fine graphite in the deposited metal. However, the addition of a large amount of Ca lowers the conductivity of the welding wire in the case of MIG welding, and significantly deteriorates the weldability.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The composition of a general welding wire for cast iron is as follows: Ni: 60 to 90 wt%, Fe: 0 to 50 wt%,
Si: 0.3 to 1.5 wt%, but in the invention of the prior application, Al: 4 to 10 wt% is added thereto, and the basic composition is Ni: 60 to 90 wt%, Fe: 0 ~ 50
wt%, Si: 0.3 to 1.5 wt%, Al: 4 to 10
Al in the welding wire suppresses the combination of Fe and C in the cast iron to form chill (white iron), and is based on the increase in hardness due to chill that easily occurs at the welding boundary. Prevents boundary cracking.

[0012] The present invention relates to a welding material of the prior application,
g is 0.1-0.3 wt% or Ca is 0.01-0.3
wt%, and Mg: 0.1 to
It is preferable to add 0.3 wt% and Ca: 0.01 to 0.3 wt%. The addition of Mg to the welding material causes the graphite in the deposited metal to become spherical and increases the strength of the deposited metal, and the addition of Ca to the welding material disperses fine graphite in the deposited metal. It was confirmed by the test described below.

[0013]

EXAMPLE A powder composite wire was used in which a Ni strip was used as an outer jacket, and a rapidly solidified powder of Fe-C and an Al powder were mixed and filled therein. The composition was as follows: Fe: 12.0 wt%, Al :
4.0 wt%, C: 0.4 wt%, Si: 1.1 wt
%, Mg: 0.1 to 1.6 wt% (four types), the balance being Ni, and MIG welding was performed on the base material cast iron of FC250. Table 1 shows the welding conditions. The state of spheroidization of graphite in the weld metal of the welded sample was visually observed in a microphotograph, and the appearance and cracking state of the bead were visually observed in three stages (そ れ ぞ れ).
Table 2 shows the results of the evaluations (△ to ×).

[0014]

[0015] Note: The composition of the welding wire of Comparative Example 2 is Fe: 15.0 wt%, Al: 4.0 wt%, C: 0.6 wt%, Si: 1.3 wt%, the balance is Ni, and Mg is not added. It is what it was.

FIG. 2 shows a micrograph of the structure of the weld metal of Comparative Example 2 and the appearance of the bead. FIG. 2A shows the upper part of the weld metal, FIG. 2B shows the lower part, and FIG. 2C shows the appearance of the bead. FIG. 2 clearly shows that the graphite in the deposited metal is not spheroidized. FIG. 3 is a diagram showing the configuration of FIG.
As shown in the photograph, graphite in the deposited metal was spherical due to the addition of Mg, and the beads were good. FIG. 4 is a photograph of Example 3 similar to FIG. 2, in which the amount of C in the welding wire is smaller than that of Comparative Example 2, so that the amount of graphite in the deposited metal is smaller. It is close to a sphere and has good beads. FIG. 4D shows that the thickness of the base material is 1
Although the thickness was reduced to 0 mm, the beads were smooth and good in this case as well. FIG. 5 is a micrograph of the structure of the deposited metal of Comparative Example 1, and FIGS. 5A to 5C show each cross section of the sample, and FIGS. 5D to 5F are enlarged photographs of each cross section. In Comparative Example 1, the addition of a large amount of Mg produces an Fe-Mg compound at the grain boundary, and as shown in Table 4 below, the strength of the deposited metal decreases. From the above, it is appropriate that the amount of Mg added to the welding material of the prior application is in the range of 0.1 to 0.3 wt%.

Next, the results of a test in which the addition of Ca was made 0.01 to 2.8 wt% (seven levels) in place of the addition of Mg in the welding wire and the welding conditions and evaluation method were the same as described above were as follows. It is shown in Table 3.

[0018]

FIG. 6 is a photograph similar to FIG. 2 for Example 4, showing that graphite in the deposited metal is refined by addition of Ca, and the bead is good. FIG. 7 is a photograph similar to FIG. 2 for Example 7, in which graphite in the deposited metal is further refined by addition of Ca, and the bead is good. FIG. 8 is a photograph similar to FIG. 2 for Example 8, in which the graphite in the deposited metal is finer due to the addition of Ca, but the distribution is non-uniform. Further, although the bead has no blowhole, the weldability is deteriorated, so that the wire is hardly melted, and the bead makes waves. FIG. 9 is a photograph similar to FIG. 2 of Comparative Example 3, in which graphite in the deposited metal is finer due to the addition of a large amount of Ca, but the weldability is poor and many blow holes are generated on the bead surface. By changing the welding conditions, Fig. 9C
9A and FIG.
Although 0 A and 20 V were set, it was difficult to obtain a good bead. From the above, it is appropriate that the amount of Ca added to the welding material of the prior application is in the range of 0.01 to 0.3 wt%.

Next, Mg: Mg:
0.1-0.3 wt% and Ca: 0.01-0.3 wt%
Examples of the present invention in which% is added will be described. Example 10 Fe: 12.0 wt%, Si: 1.5 wt%, Al:
4.0 wt%, C: 0.4 wt%, Mg: 0.15 wt
%, Ca: 0.04 wt% Welding wire with the balance of Ni.

FIG. 1 shows the results of a test conducted under the same welding conditions as in Table 1 above. FIG. 1A is an enlarged micrograph of a cross section of a welded metal sample, and FIGS. It is clearly shown that the graphite is spherical and finely dispersed. The beads were good, and the results of the tensile strength test of this sample are shown in Table 4 below together with the test results of the base material and the comparative example.

[0022]

As is clear from Table 4, Comparative Example 2 in which Mg and Ca were not added had a large strength at room temperature, but a large decrease in strength at a high temperature of about 23%. In Comparative Example 1, the additive amount of Mg was too large, and an Fe—Mg compound was generated at the grain boundaries as shown in FIG. 5, and thus the strength of the deposited metal was lower than that in Comparative Example 2. On the other hand, Embodiment 1
In the case of No. 0, the tensile strength at room temperature is maximum, and the decrease in strength at high temperature is as small as about 8%, so that the quality of the deposited weld metal is stable.

Each of the above embodiments is effective as a weld material for strengthening the cast iron build-up, as a countermeasure against cracks between ports in the cast iron cylinder head of the engine. It can also be applied to joining with dissimilar materials.

[0025]

Industrial Applicability The present invention is directed to a welding material which can be formed into a welding wire which can be continuously welded without heat treatment such as preheating and post-heating of a base material in overlay welding for local modification of cast iron parts. In addition, by adding a predetermined amount of inexpensive Mg or Ca, it is possible to improve the tensile strength of the deposited metal in addition to the characteristics of the above-mentioned welding material, and to suppress the strength reduction at high temperatures to stabilize the quality.

[Brief description of the drawings]

FIG. 1 is a micrograph showing a welded metal structure of Example 10.

FIG. 2 is a micrograph showing a deposited metal structure of Comparative Example 2.

FIG. 3 is a micrograph showing a welded metal structure of Example 1.

FIG. 4 is a micrograph showing a weld metal structure of Example 3.

FIG. 5 is a micrograph showing a deposited metal structure of Comparative Example 1.

FIG. 6 is a micrograph showing a weld metal structure of Example 4.

FIG. 7 is a micrograph showing a welded metal structure of Example 7.

FIG. 8 is a micrograph showing a weld metal structure of Example 8.

FIG. 9 is a micrograph showing a welded metal structure of Comparative Example 3.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B23K 9/23 B23K 9/23 D (72) Inventor Asao Koike No. 8 Tozawa, Fujisawa-shi, Kanagawa Isuzu Central Research Co., Ltd. In-house (72) Inventor Masato Motoyoshi 8 Tsurana, Fujisawa City, Kanagawa Prefecture Isuzu Central Research Institute Co., Ltd.

Claims (3)

[Claims] 1. Ni: 60 to 90 wt%, Fe: 0 to 5
0 wt%, Si: 0.3-1.5 wt%, Al: 4-1
Mg: 0.1-0.3 wt% in welding material consisting of 0 wt%
% Or / and Ca: 0.01 to 0.3 wt% is added. 2. Fe: 12.0 wt%, Si: 1.5 w
t%, Al: 4.0 wt%, C: 0.4 wt%, Mg:
The weld material for reinforcing hardened cast iron according to claim 1, wherein the composition is 0.15 wt%, Ca: 0.04 wt%, and the balance is Ni. 3. A Ni strip as an outer skin, in which Fe—C
The MIG welding wire according to claim 1, wherein the rapidly solidified powder, the Al powder, and the Fe-based alloy powder are mixed and filled.