JPH08141783A - Welding material for hard facing and composition determining method therefor - Google Patents

Abstract

PURPOSE: To manufacture the welding material low in hardness after the cladding by welding, and capable of being improved in the hardness by the super cooling by specifying the basic composition of the welding material for hard facing by the parameters of Ni equivalent and Cr equivalent in addition of the Ms temperature. CONSTITUTION: After the welding material is cladded by welding to the cast iron base metal, it is hardened by the super cooling to execute the hard facing by welding of the cast iron base metal. The basic composition of the welding material is determined by the parameters Ni equivalent and Cr equivalent obtained by the approximate triangle surrounded by LH20 where the latitude difference is 20 in terms of HRC of the equi-hardness line LH to indicate the hardness difference before and after the super cooling which is surrounded by LA to indicate the limit where the martensite is not generated in the Schaefller structure and LC which is the limit not to precipitate the carbide, and by the parameter of the martensitic transformation starting temperature (Ms temperature). The basic composition of the welding material can be determined without actually making a test piece and measuring the hardness thereby.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding material such as a coated arc welding rod, a welding wire, and a powder for plasma welding, which is used for hardfacing a cast iron base material, and more specifically, aluminum and a steel sheet. Welding used in fields where the shape is complicated and machinability and hardness after welding are required, such as cold pressing dies including press dies for pressing metal thin plate materials etc. It is about materials.

[0002]

2. Description of the Related Art For example, a trimming die for cutting a blank material of a certain length from a metal thin plate roll material such as aluminum or a steel sheet, or a blank die after drawing the blank material with a draw die, there is no need for a peripheral portion. As a method of manufacturing a trimming die for cutting off a portion, there is a method of welding and overlaying a welding material as a blade material on a die material cast into a predetermined shape, and shaving a blade from this overlay portion. .

Since the welding material for such weld overlay is machined into a predetermined shape and the blade is cut out, it is preferable that the hardness after the overlay is low, and after the blade is cut out by machining, a comparison is made. It is desirable that the hardness becomes high easily.
According to Japanese Unexamined Patent Publication No. 6-15481, the martensite transformation start temperature (hereinafter referred to as Ms temperature) of the welding material is set to 150 ° C. or less, and the hardness of the weld overlay after welding overlay is HRC45 or less. In addition, a welding material is known in which the hardness is HRC45 or more by performing a supercooling treatment at 0 ° C. or less after welding.

[0004]

The composition of the conventional welding material is determined by using only the Ms temperature as a parameter. When the Ms temperature is lowered, a large amount of austenite remains at room temperature to facilitate machining, but it is not clear from the Ms temperature alone whether or not the material hardens to the required hardness after the supercooling treatment. Therefore, conventionally, a large number of samples are prepared, and the composition is actually determined by overlaying and supercooling treatment, and it takes a lot of time and cost to determine the composition.

As a result of earnest efforts, the inventor of the present invention has discovered that there is a close relationship between each region in the Schaeffler structure chart and the hardness difference before and after the supercooling treatment.
That is, the Schaeffler structure chart is a structure chart having Ni equivalent and Cr equivalent as parameters, and it has been found that an isohardness difference line where hardness differences before and after supercooling treatment are equal can be drawn in the structure chart.

Based on this fact, the present invention is based on this fact that the basic composition of the welding material is Nis and Cr in addition to the Ms temperature.
It is an object of the present invention to provide a welding material defined by equivalent parameters and a method for determining its composition.

[0007]

In order to achieve the above-mentioned object, the present invention is a welding material for hardfacing, which is hardened by supercooling after being welded to a cast iron base material, and the basic composition of the material is , The hardness difference before and after the supercooling treatment in the state of the weld overlay is a predetermined value or more, Ni equivalent and Cr equivalent included in the region of the Schaeffler structure chart are satisfied, and the martensitic transformation start temperature is equal to or lower than a predetermined temperature. It is characterized by setting so that

Further, a welding material for hardfacing, which is hardened by supercooling after being welded to a cast iron base material, wherein the basic composition of the material is the hardness before and after the supercooling treatment in the state of the weld overlay. A region where the difference is equal to or more than a predetermined value is defined in the Schaeffler structure chart, and the Ni equivalent and the Cr equivalent become values within the region of the Schaeffler structure diagram and the martensite transformation start temperature becomes equal to or lower than a predetermined temperature. It is characterized in that the composition is obtained, and the basic composition of the welding material is determined so that this composition is obtained in the state where the weld overlay is applied.

[0009]

In the Schaeffler structure diagram shown in FIG. 1A, LA indicates a boundary line between an austenite region containing only austenite and a region containing austenite and martensite at room temperature. Further, even within the austenite region, when the Ni equivalent shown on the vertical axis is increased, carbide begins to precipitate in the structure. The limit at which this carbide does not precipitate is Ni equivalent = 34, and the boundary line is indicated by LC. Therefore, the composition of the welding material must be a region sandwiched between LA and LC. Next, the range X including the intersection of LA and LC is enlarged and shown in FIG. The numerical value indicated by "□" in the figure indicates the hardness difference before and after the supercooling treatment by HRC, and it can be seen that the hardness difference increases as it approaches the intersection of LA and LC. Incidentally, LH is an equal hardness difference line connecting the points having the same hardness difference. Therefore, the Ni equivalent and the Cr equivalent are set so that they fall within a region of a substantially inverted triangle surrounded by LH, LA, and LC of a desired hardness difference, and the Ni equivalent is a component composition in which the Ms temperature becomes a predetermined temperature. The component composition satisfying the set values of Cr and Cr equivalent may be the basic component composition.

[0010]

EXAMPLE Here, the Ms temperature is calculated by the following formula, and the Ms
The ratio of each basic component was determined so that the temperature was 50 to 60 ° C. An example of the basic component composition is shown below.

Ms (° C.) = 538 −317 × C−33 × Mn−17
XNi-28xCr-11xMo-11Si-11xW Basic component composition (% by weight) C Mn Ni Cr Mo Si W 1.1 1.0 0.5 0.5 3.0 0 1.0 0 Co is 0.2% and B is 0.01
% Create a sample with addition, and actually perform weld overlay,
The hardness after overlaying and the hardness after supercooling treatment were measured. still,
The Ni equivalent and the Cr equivalent are calculated by the following formula.

Ni equivalent = 30 × C + 0.5 × Mn + Ni Cr equivalent = Cr + Mo + 1.5 Si The Ms temperature of the above sample is 52.8 ° C., and the Ni equivalent is 3
4, the Cr equivalent was 4.5. This corresponds to point P in FIG. 1B, and is in a region surrounded by the equal hardness difference lines LH20 and LC and LA having a hardness difference of 20 in HRC.
Further, the hardness after overlaying was HRC34, and it was confirmed that when the supercooling treatment is performed, the hardness increases to HRC57, and a hardness difference of 23 (HRC) occurs before and after the supercooling treatment.

Next, for comparison, a comparative material having the following basic composition was prepared.

Basic composition (% by weight) C Mn Ni Cr Mo Si W 1.0 0.5 0.5 3.0 3.0 0.7 0.7 0 0.7% Co was added. Ms temperature / N of the comparative material
The i equivalent and Cr equivalent have the following values.

Ms temperature = 112.8 Ni equivalent = 30.25 Cr equivalent = 4.05 This corresponds to point C1 in FIG. 1 (b), the hardness after overlaying is HRC41, and the supercooling treatment is performed. HRC54
The hardness increases only up to 13 (HR
Only the hardness difference of C) occurred. It is considered that this is because martensite had already occurred after the buildup, and therefore the hardness after the buildup did not decrease so much and the difference in hardness did not increase.

Further, for comparison, another comparative material having the following basic composition was prepared.

Basic Component Composition (% by Weight) C Mn Ni Cr Mo Si W 1.1 1.5 1.0 1.0 4.5 0 1.0 0 Co was added at 1.0%. Ms temperature / N of the comparative material
The i equivalent and Cr equivalent have the following values.

Ms temperature = -14.2 Ni equivalent = 34.75 Cr equivalent = 6.0 This corresponds to point C2 in FIG. 1 (b), the hardness after overlaying is HRC27, and it is undercooled. HRC40 when treated
The hardness increases only up to 13 (HR
Only the hardness difference of C) occurred. It is considered that this was because the value of LC in the figure exceeded and carbide was deposited after the buildup, and the desired hardness could not be obtained.

By the way, as shown in FIG. 2, even if the welding material is multi-layered on the base material 1, for example, two layers and three beads are built up, and the beads 2a and 2b in the inner layer portion are wound with carbon in the cast iron base material, In the bead 2c of the outer layer portion which is built up with the same welding material, the component composition becomes the same as that of the welding material, and there is no problem.

Further, as shown in FIG. 3, when the bead 2 is built up in a single layer on the base metal 1, carbon elutes from the base metal 1 to the bead 2, so that the component composition of the welding material is The amount of carbon in the inside is reduced in advance by the amount eluted from the base material 1, and the dissolved carbon is combined in the state of weld overlay to obtain a predetermined component composition.

[0021]

As is apparent from the above results, according to the present invention, the hardness after the buildup is low and the cutting process can be easily performed, and then the hardness can be increased by the supercooling treatment. The basic constituent composition of a material can be determined without actually making a test piece and measuring the hardness.

[Brief description of drawings]

FIG. 1A is a Schaeffler organization chart, and FIG. 1B is an enlarged view of the range X.

FIG. 2 is a cross-sectional view of a built-up portion with multiple layers.

FIG. 3 is a cross-sectional view of a built-up portion having a single layer.

Claims (3)

[Claims] 1. A welding material for hardfacing, which is hardened by supercooling after being welded to a cast iron base material, wherein the basic composition of the material is the hardness before and after the supercooling treatment in the state of the weld overlay. For hardfacing, characterized by satisfying the Ni and Cr equivalents contained in the region of the Schaeffler structure chart where the difference is a predetermined value or more and setting the martensite transformation start temperature to be a predetermined temperature or lower. Welding material. 2. A region of the Schaeffler structure chart is an austenite region, having a Ni equivalent of 34 or less, and a difference between hardness after welding and hardness after supercooling treatment is HRC (Rockwell hardness C scale). ) Is 20 or more regions, the welding material for hardfacing according to claim 1, characterized in that. 3. A welding material for hardfacing, which is hardened by supercooling after being welded to a cast iron base material, wherein the basic composition of the material is the hardness before and after the supercooling treatment in the state of the weld overlay. A region where the difference is equal to or more than a predetermined value is defined in the Schaeffler structure chart, and the Ni equivalent and the Cr equivalent become values within the region of the Schaeffler structure diagram and the martensite transformation start temperature becomes equal to or lower than a predetermined temperature. A method for determining the composition of a welding material for hardfacing, which comprises determining the composition and determining the basic component composition of the welding material so that this composition is obtained in the state of the weld overlay.