JP2014147965A - Die repair welding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die repair welding material which has excellent hardness, exhibits high heat check resistance when used for repairing a die-casting die, and can improve the life of the die.SOLUTION: A die repair welding material comprises a composition of 0.30<C≤0.50 mass%, 0.05≤Si≤0.80 mass%, 0.50≤Mn≤1.50 mass%, 4.00≤Cr≤9.00 mass%, 0.50≤Mo≤3.00 mass%, and 0.30≤V≤0.70 mass%, with the balance being Fe and inevitable impurities.

Description

  The present invention relates to a mold repair welding material, and more particularly, to a mold repair welding material for repair welding a die casting mold made of hot tool steel.

  As a die casting mold for casting a metal or alloy such as aluminum, magnesium, zinc, lead, etc., hot tool steel represented by JIS SKD61 (hereinafter sometimes referred to simply as SKD61) is widely used. In the above metal die casting, injection and cooling of a high-temperature molten metal into a mold are repeated, and damage such as cracks and cracks such as a heat check occurs in the mold. When such damage occurs on the mold surface, the damage is transferred to the product. Therefore, repair by welding is performed on the damaged portion of the die casting mold.

  Conventionally, maraging steel having a composition of 18.5Ni-4.8Mn-9.0Co-0.1Al-0.6Ti has been used as a welding material for repairing a die-casting die made of hot tool steel. It was. Further, in Patent Document 1, as a repair welding material whose manufacturing cost is lower than that of maraging steel and whose hardness and welding efficiency are improved, C: 0.15 to 0.30%, Si: 0.20-1.00%, Mn; 0.30-1.50%, Cr: 3.6-6.0%, Mo: 0.8-1.5%, V: 0.10-0. A repair welding material containing 80%, the balance being Fe and inevitable elements is disclosed.

JP 2011-245488 A

  In order to improve the heat check resistance of die casting dies that have been repaired using repair welding materials, the repair welding materials are excellent in hardness and at the same level or higher than the hot work tool steel that is the base material. It is necessary to have a high thermal conductivity. If the thermal conductivity of the repair welding material is a low value separated from the thermal conductivity of the hot work tool steel, which is the base material, the part where the repair welding was performed will continue to be heat checked while using the mold. Will crack faster than the base metal, shortening the life of the mold.

  Maraging steel does not have sufficient hardness and has low thermal conductivity. On the other hand, although the repair welding material of patent document 1 is excellent in hardness, its thermal conductivity is low. For this reason, when using maraging steel and the repair welding material of patent document 1 for repair of a die-casting metal mold | die, the heat check resistance of the site | part to which repair welding was performed will become low.

  The problem to be solved by the present invention is a mold repair that is excellent in hardness and exhibits high heat check resistance when used for repair of a die-cast mold and can improve the life of the mold. It is to provide a welding material.

  In order to solve the above-described problems, the mold repair welding material according to the present invention has 0.30 <C ≦ 0.50 mass%, 0.05 ≦ Si ≦ 0.80 mass%, 0.50 ≦ Mn ≦ 1. .50 mass%, 4.00 ≦ Cr ≦ 9.00 mass%, 0.50 ≦ Mo ≦ 3.00 mass%, and 0.30 ≦ V ≦ 0.70 mass% with the balance being Fe and inevitable The main point is that it consists of mechanical impurities.

  Here, the mold repair welding material may further include 0.01 ≦ W ≦ 4.00 mass%.

  The mold repair welding material may further include 0.30 ≦ Co ≦ 3.00 mass%.

  The mold repair welding material further includes 0.0001 ≦ Nb ≦ 0.100 mass%, 0.0001 ≦ Ta ≦ 0.100 mass%, 0.0001 ≦ Ti ≦ 0.100 mass%, 0.0001 ≦ It may include at least one selected from the group consisting of Zr ≦ 0.100 mass%, 0.0005 ≦ Al ≦ 0.1000 mass%, and 0.0020 ≦ N ≦ 0.1500 mass%.

  The mold repair welding material further includes 0.0002 ≦ B ≦ 0.0100 mass%, 0.05 ≦ Cu ≦ 1.50 mass%, and 0.05 ≦ Ni ≦ 1.50 mass%. It may contain at least one selected from

  The mold repair welding material is 0.001 ≦ S ≦ 0.200 mass%, 0.0005 ≦ Ca ≦ 0.2000 mass%, 0.03 ≦ Se ≦ 0.50 mass%, 0.005 ≦ Te ≦. It may contain at least one selected from the group consisting of 0.100% by mass, 0.01 ≦ Bi ≦ 0.30% by mass, and 0.03 ≦ Pb ≦ 0.50% by mass.

  According to the mold repair welding material according to the present invention, especially by optimizing the contents of C and Si, and also by optimizing the contents of Mn, Cr, Mo, V, In addition to excellent hardness, it has high thermal conductivity compared to hot work tool steel. For this reason, when it uses for repair welding which uses hot tool steel as a base material, and repeats heating and cooling, it is prevented that a crack arises in a welding part and high heat check resistance is acquired.

  On the other hand, the thermal conductivity of the mold repair welding material does not become too high compared to the thermal conductivity of the base metal made of hot tool steel. It is also possible to avoid the occurrence of weld cracks (cracks at the boundary between the base material and the weld material). In this way, the mold repair welding material has a reasonably high thermal conductivity compared to the base metal, thereby improving the heat check resistance and preventing weld cracking, thereby extending the life of the die casting mold. It becomes possible to improve. Moreover, the metal mold | die repair material concerning the said invention is equipped with high machinability simultaneously.

  Here, when the mold repair material according to the invention further contains the predetermined amount of W, the strength of the material can be improved.

  In addition, when the mold repair material according to the invention further contains the predetermined amount of Co, the strength of the material can be improved.

  When the mold repair material according to the invention further includes at least one selected from the group consisting of the predetermined amount of Nb, Ta, Ti, Zr, Al, and N, the strength of the material Toughness can be improved.

  When the mold repair material according to the invention further contains at least one selected from the group consisting of the predetermined amounts of B, Cu, and Ni, the hardenability of the material can be improved.

  When the mold repair material according to the invention further contains at least one selected from the group consisting of the predetermined amount of S, Ca, Se, Te, Bi, and Pb, the machinability of the material Can be improved.

It is a graph which shows the dependence with respect to C content of thermal conductivity. It is a graph which shows the dependence with respect to Si content of thermal conductivity. It is a graph which shows the dependence with respect to Si content of machinability. It is a figure which shows the shape of the test piece used for the heat check acceleration test, (a) is a top view, (b) is a side view (The dimension unit in a figure is mm). It is a photograph which shows the result of a heat check acceleration test, (a1), (a2) is Example A09, (b1), (b2) is Comparative Example 1, (c1), (c2) is Comparative Example 2, (d1) ) And (d2) are those of the test piece of Comparative Example 3. (A1) to (d1) show the state after 5000 cycles, and (a2) to (d2) show the state after 10000 cycles. It is a photograph which shows the result of the heat check acceleration test of the test piece of Example A09, (a) shows the case with no prognostic heat, and (b) shows the case with prognostic heat. It is a figure which shows the shape of the test piece used for the weld crack evaluation test, (a) is a top view, (b) is sectional drawing (The dimension unit in a figure is mm). It is a photograph which shows the result of a weld crack evaluation test, (a) shows the case with no prognostic heat and (b) shows the case with prognostic heat.

  Hereinafter, a mold repair welding material according to an embodiment of the present invention will be described in detail.

(Component composition)
The mold repair welding material according to this embodiment (hereinafter sometimes referred to simply as repair welding material) contains C, Si, Mn, Cr, Mo, V as essential elements, with the balance being Fe and inevitable impurities. Consists of. The content of each component element and the reason for limitation will be described below.

(1) 0.30 <C ≦ 0.50 mass%
C greatly affects the thermal conductivity of the repair welding material, and if the content is small, the thermal conductivity increases. When the C content is 0.30% by mass or less, the thermal conductivity of the repair welding material is too high than the thermal conductivity of the hot tool steel as the base material, so that the repair welding material is used during welding. The thermal stress increases and weld cracks occur. On the other hand, if the C content exceeds 0.50% by mass, the thermal conductivity of the repair welding material becomes too lower than the thermal conductivity of the hot work tool steel, which is the base material. Cracks are likely to occur in the welded portion that has been repeatedly heated and cooled in this step. That is, the heat check resistance of the welded portion is lowered. Therefore, in order to avoid both the occurrence of weld cracking due to the difference in thermal conductivity with the hot work tool steel as the base material and the deterioration of the heat check resistance, the C content is 0.30 <C ≦ 0. 50% by mass. At the same time, the C content greatly affects the hardness of the repair welding material, but if it is within the range of this content, an appropriate hardness (410 to 550 Hv) can be achieved as a mold repair welding material. .

  In addition, when there is much content of C, there exists a tendency for the machinability of repair welding material to fall. Therefore, from the viewpoint of achieving both sufficiently high thermal conductivity and high machinability in comparison with hot tool steel, the C content is preferably 0.30 <C ≦ 0.40 mass%. .

(2) 0.05 ≦ Si ≦ 0.80 mass%
Si contributes to increasing softening resistance in repair welding materials. If the softening resistance of the repair welding material is small, a heat check is likely to occur at the weld. When the Si content is less than 0.05% by mass, the softening resistance of the repair welding material decreases, and the heat check resistance of the welded portion decreases. On the other hand, if the Si content is less than 0.05% by mass, the thermal conductivity becomes too high as compared with hot tool steel, and weld cracks are likely to occur. On the other hand, the greater the Si content, the lower the thermal conductivity. When the Si content exceeds 0.80% by mass, the thermal conductivity is too low compared to the hot tool steel as the base material. Then, due to the difference in thermal conductivity with the base material, the heat check resistance of the welded portion is lowered. Therefore, from the viewpoint of improving heat check resistance and preventing weld cracking, the Si content is set to 0.05 ≦ Si ≦ 0.80 mass%.

  In addition, since there is a tendency for machinability to decrease when the content of Si decreases, from the viewpoint of balancing both sufficiently high thermal conductivity and high machinability in comparison with hot tool steel, The content of Si is preferably 0.30 ≦ Si ≦ 0.60 mass%, and more preferably 0.40 ≦ Si ≦ 0.60 mass%.

(3) 0.50 ≦ Mn ≦ 1.50 mass%
Mn improves the hardness of the mold repair welding material. Moreover, since Mn improves hardenability, the hardness can be further improved by quenching, and the impact value can also be improved. If the Mn content is less than 0.50% by mass, it is difficult to ensure hardness and the hardenability is insufficient. On the other hand, if the Mn content exceeds 1.50% by mass, the weld becomes too hard and the thermal conductivity is lowered. In addition, the impact value is reduced. Therefore, the Mn content is set to 0.50 ≦ Mn ≦ 1.50% by mass so that necessary and sufficient hardness can be ensured and high thermal conductivity can be obtained. Considering the balance between hardness and thermal conductivity, the Mn content is preferably 0.50 ≦ Mn ≦ 0.90 mass%.

(4) 4.00 ≦ Cr ≦ 9.00 mass%
Cr is an element that improves heat check resistance and contributes to improving hardenability, hardness, and impact value. When the Cr content is less than 4.00 mass%, the heat check property is lowered, and sufficient hardness cannot be obtained. On the other hand, since heat conductivity falls by containing many Cr, when content exceeds 9.00 mass%, heat conductivity will become low too much. Also, the hardness increases too much. Therefore, the Cr content is 4.00 ≦ Cr ≦ 9.00 mass%. From the viewpoint of balance between thermal conductivity and hardness, the Cr content is preferably 4.5 ≦ Cr ≦ 6.0% by mass.

(5) 0.50 ≦ Mo ≦ 3.00 mass%
Mo contributes to improving the softening resistance as well as improving the hardness of the repair welding material. When the Mo content is less than 0.50% by mass, sufficient hardness cannot be obtained, softening resistance is reduced, and heat check resistance of the welded portion is lowered. On the other hand, if the Mo content exceeds 3.00 mass%, the hardness will increase too much. Therefore, the Mo content is set to 0.50 ≦ Mo ≦ 3.00 mass%. From the balance between heat check resistance and preferable hardness, the Mo content is preferably 0.75 ≦ Mo ≦ 1.75% by mass.

(6) 0.30 ≦ V ≦ 0.70 mass%
V improves the hardness and impact value of the repair weld material by forming carbides. Moreover, the softening accompanying the heating of a metal mold | die can be suppressed. When the content of V is less than 0.30% by mass, it is difficult to obtain the effect of improving hardness and softening resistance. On the other hand, if the content of V exceeds 0.70 mass%, the hardness will increase too much. Moreover, high thermal conductivity cannot be obtained. Therefore, the content of V is set to 0.30 ≦ V ≦ 0.70 mass%. In view of a suitable balance between hardness and thermal conductivity, the V content is preferably 0.45 ≦ V ≦ 0.70 mass%.

  Furthermore, in addition to the above essential elements, the mold repair welding material according to the present embodiment may optionally contain a selection element selected from the following within a range of the following content.

(7) 0.01 ≦ W ≦ 4.00 mass%
W is a selective element that can be added to increase strength by precipitation of carbide (precipitation hardening). If the W content is less than 0.01% by mass, the effect of increasing the strength is small. On the other hand, if the W content exceeds 4.00% by mass, the effect is saturated and the cost is significantly increased. Therefore, the W content is set to 0.01 ≦ W ≦ 4.00 mass%.

(8) 0.30 ≦ Co ≦ 3.00 mass%
Co is a selective element that can be added to increase the strength by solid solution in the base material (solid solution hardening). If the Co content is less than 0.30% by mass, the effect of increasing the strength is small. On the other hand, if the Co content exceeds 3.00% by mass, the effect is saturated and the cost is significantly increased. Therefore, the Co content is set to 0.30 ≦ Co ≦ 3.00 mass%.

(9) 0.0001 ≦ Nb ≦ 0.100 mass%,
0.0001 ≦ Ta ≦ 0.100 mass%,
0.0001 ≦ Ti ≦ 0.100 mass%,
0.0001 ≦ Zr ≦ 0.100 mass%,
0.0005 ≦ Al ≦ 0.1000 mass%, and
At least one or more selected from the group consisting of 0.0020 ≦ N ≦ 0.1500 mass% Nb, Ta, Ti, Zr, Al, and N are added in order to refine crystal grains and increase strength and toughness. Is a selective element that can. If any element is less than a predetermined amount, the effect of improving strength and toughness is small. On the other hand, when the amount exceeds a predetermined amount, carbides, nitrides, and oxides are excessively generated, which leads to a decrease in toughness.

(10) 0.0002 ≦ B ≦ 0.0100 mass%,
0.05 ≦ Cu ≦ 1.50 mass%, and
At least one selected from the group consisting of 0.05 ≦ Ni ≦ 1.50 mass% B, Cu, and Ni are selective elements that can be added to improve hardenability. If any element is less than the predetermined amount, the effect of improving the hardenability is small. Moreover, if it exceeds a predetermined amount, the effect is saturated and the actual profit is poor. In particular, excessive addition of Cu and Ni lowers the thermal conductivity.

(11) 0.001 ≦ S ≦ 0.200 mass%,
0.0005 ≦ Ca ≦ 0.2000 mass%,
0.03 ≦ Se ≦ 0.50 mass%,
0.005 ≦ Te ≦ 0.100 mass%,
0.01 ≦ Bi ≦ 0.30 mass%, and
At least one selected from the group consisting of 0.03 ≦ Pb ≦ 0.50% by mass S, Ca, Se, Te, Bi, and Pb can be added to improve machinability. It is a selective element. If any element is less than a predetermined amount, the machinability improving effect is small. Moreover, when it exceeds a predetermined amount, cracks are likely to occur.

(Effect of component composition)
The mold repair welding material according to the present embodiment, having the above composition, is sufficiently high to improve heat check resistance in comparison with the thermal conductivity of hot tool steel represented by SKD61, and It has a moderately high thermal conductivity that is suppressed to a value that is low enough to prevent weld cracking. This is achieved in particular by optimizing the C content and the Si content. That is, by providing a predetermined lower limit value for the C and Si content, the thermal conductivity is improved, and by providing a predetermined upper limit value for the C and Si content, it is excessive as compared with hot tool steel. The increase in thermal conductivity is prevented. Both heat check resistance and weld cracking depend on the overall composition of the alloy composition, and the degree of thermal conductivity is not determined only by the level of thermal conductivity. In comparison with the thermal conductivity of the base metal, if it is too low, high heat check resistance cannot be obtained, and if it is too high, cracking of the weld tends to occur.

  Specifically, the thermal conductivity of the hot tool steel represented by SKD61 is generally 23 W / m / K or more and less than 24 W / m / K, and a hot tool steel having such a thermal conductivity is used. In the repair welding material used as a base material, in order to effectively improve heat check resistance and prevent weld cracking, the repair welding material preferably has a thermal conductivity of 24 to 30 W / m / K. . As will be shown later in Examples, the repair welding material having the above composition realizes such a thermal conductivity. The thermal conductivity of the repair welding material is more preferably 25 to 28 W / m / K from the viewpoint of more effectively achieving both improvement of heat check resistance and prevention of weld cracking.

  And the repair welding material concerning this embodiment is equipped with high machinability mainly by content of Si being more than predetermined value. When performing repair welding of the mold using the repair welding material, the repair welding material preferably has high machinability because it includes a step of removing the raised portion after the build-up welding.

  Furthermore, it is generally preferred that the repair welding material for the die casting mold has a hardness of about 410 to 550 Hv. If it is lower than this range, it is not sufficient as the hardness to withstand the use as a die casting mold, and conversely, if it is too hard, it is not preferable from the viewpoint of heat treatment after welding. Cr, Mo, V contained in the repair welding material according to the present embodiment has the effect of increasing the hardness, but together with the optimization of the content of C and Si, the content of Cr, Mo, V Is optimized within a predetermined range, the above preferable hardness can be realized. In addition, Cr, Mo, V are contained in a large amount to lower the thermal conductivity of the repair welding material, but the content is defined in the above range, while maintaining a preferable hardness while maintaining the base material. In comparison with the thermal conductivity of the hot work tool steel, a sufficiently high thermal conductivity is achieved.

(Production method)
The repair welding material according to the present embodiment includes, for example, an ingot made from a molten metal in which predetermined components are dissolved at a predetermined composition ratio, heated to 900 ° C. to 1250 ° C., and subjected to forging and rolling. (Welding rod) can be manufactured. Moreover, you may wire-draw etc. to the material after rolling.

  Furthermore, it is preferable that the repair welding material is manufactured through a quenching / tempering process. By adjusting the quenching and tempering conditions, a repair welding material having a desired hardness can be obtained. In the case of the repair welding material according to the present embodiment, the quenching and tempering conditions may be selected so as to have a hardness of 410 to 550 Hv as described above. Specifically, as a quenching condition, a method of rapidly cooling after holding at 1000 to 1050 ° C. for 0.5 to 5 hours can be exemplified. Moreover, as a condition of tempering, the form hold | maintained at 500-650 degreeC for 1 to 10 hours can be illustrated.

(Die-cast die repair welding method)
The repair welding material according to the present embodiment can be suitably used for overlay welding for repairing a die casting mold made of hot tool steel such as SKD61. The repair welding material according to the present embodiment can be suitably applied to both TIG welding and laser welding. The repair welding material is usually used in the form of a welding rod, but the diameter of the welding rod is preferably 02 to 4.0 mm.

  Usually, in repair welding of a die-casting die, prognostic heat is performed to prevent weld cracking. That is, preheating for heating the mold base material before welding and post-heating for heating the welded portion after welding are performed. However, the repair welding material according to the present embodiment has a thermal conductivity close to that of hot tool steel due to the effect of having a predetermined component composition, and the occurrence of weld cracks due to the difference in thermal conductivity is effective. Is prevented. Therefore, the occurrence of weld cracks can be avoided without performing prognostic heat. That is, if the repair welding material concerning this embodiment is used, a welding process can be simplified by not performing prognostic heat.

  However, in the repair welding material according to the present embodiment, prognostic heating may be performed as in the case of conventional materials. Then, welding cracks can be prevented more reliably. In addition, the heat check resistance of the welded portion is hardly affected by the presence or absence of prognostic heat, and excellent heat check resistance can be obtained whether or not prognostic heat is applied. In the case of performing the prognostic heat, a mode in which preheating is performed at 350 to 450 ° C. for 0.5 to 5 hours and afterheating is performed at 500 to 650 ° C. for 1 to 10 hours can be shown as suitable. .

  After performing build-up welding and performing prognostic heat treatment as necessary, the raised portion of the welded portion is removed by machining, and the repaired welded portion is finished flush with the mold surface.

  Examples of the present invention and comparative examples are shown below. In addition, this invention is not limited by these Examples.

  The repair welding material according to each example and comparative example is a shape required for each test by producing an ingot from a molten metal prepared to have the composition shown in the respective examples, performing forging (900 to 1200 ° C.), and rolling. Obtained as a sample piece. Furthermore, quenching (1000 to 1050 ° C., 0.5 to 10 hours) and tempering (550 to 600 ° C., 1 to 10 hours) were performed.

<Example 1: Examination of C content>
In order to optimize the C content from the viewpoint of thermal conductivity, the dependence of the thermal conductivity on the C content was evaluated. That is, the C content is varied in the range of 0.1 to 1.0 mass% every 0.1 mass%, and C, Si: 0.35 mass%, Mn: 0.83 mass%, Cr: 5 A repair welding material containing 0.03% by mass, Mo: 1.21% by mass, and V: 0.59% by mass with the balance being Fe and inevitable impurities was prepared, and the thermal conductivity was measured. Here, the thermal conductivity was measured at room temperature using a laser flash method by preparing a sample piece of φ20 mm × 2 mm from a wire having a diameter of 20 mm.

  In FIG. 1, the thermal conductivity measured about the repair welding material which has each C content is shown. According to this, the lower the C content, the higher the thermal conductivity. As mentioned above, in comparison with the thermal conductivity of hot work tool steel, the heat conductivity of the repair welding material is too low and the heat conductivity of the repair welding material is too high. In order to avoid cracking of the weld due to, it is preferable that the repair welding material has a thermal conductivity of 24 to 30 W / m / K. In FIG. 1, if the C content is 0.3 to 0.5% by mass, the thermal conductivity is in this range, and the dependence of the thermal conductivity on the C content is compared to other content regions. It is very gradual and can stably obtain high thermal conductivity. From this, it is understood that the C content may be 0.30 <C ≦ 0.50 mass%. Especially, it is preferable that it is 0.30 <C <= 0.40 mass% in the point that it has high heat conductivity and can improve heat check resistance effectively.

<Example 2: Examination of Si content>
In order to optimize the Si content from the viewpoints of thermal conductivity and machinability, the dependence of the thermal conductivity and machinability on the Si content was evaluated. That is, the content of Si is varied in increments of 0.1% by mass within the range of 0.1 to 1.0% by mass, and Si, C: 0.35% by mass, Mn: 0.81% by mass, Cr: A repair welding material containing 5.73% by mass, Mo: 1.23% by mass, and V: 0.61% by mass with the balance being Fe and inevitable impurities is prepared, and the thermal conductivity and machinability are evaluated. went. The thermal conductivity was measured at room temperature by a laser flash method by preparing a sample piece of φ20 mm × 2 mm from a wire having a diameter of 20 mm. The machinability was evaluated as the distance by which the material was scraped before the carbide coating tool reached the end of its life.

  In FIG. 2, the thermal conductivity measured about the repair welding material which has each Si content is shown. According to this, the smaller the Si content, the higher the thermal conductivity, having a thermal conductivity of 24-30 W / m / K in the region of 0.1-0.8% by mass, In relation to the thermal conductivity of steel, high heat check resistance and prevention of weld cracking can be achieved.

  FIG. 3 shows the relationship between the Si content and machinability. According to this, the machinability is improved as the Si content increases. In general, when the Si content exceeds 0.8% by mass, the effect of improving machinability is saturated.

  Based on the above results, in order to obtain a good balance between the desired thermal conductivity and high machinability in relation to the thermal conductivity of the hot work tool steel, the Si content is 0.05 ≦ Si ≦. What is necessary is just to set it as 0.80 mass%. More preferably, 0.40 ≦ Si ≦ 0.60 mass% may be satisfied.

<Example 3: Comparison of characteristics of various repair welding materials>
Based on the examination results of the contents of C and Si, steel materials according to Examples and Comparative Examples having various compositions shown in Tables 1 to 3 were produced, and the characteristics were compared. Examples A01 to A18 contain only essential elements. On the other hand, Examples B01 to B04 (Group B), C01 to C04 (Group C), D01 to D04 (Group D), and E01 to E06 (Group E) contain a selective element in addition to the essential elements. It is classified into groups according to the type of additive element contained. Comparative Example 1 corresponds to Example 1 of Patent Document 1, Comparative Example 2 corresponds to SKD61, and Comparative Example 3 corresponds to maraging steel.

  About the repair welding material concerning the said Example and comparative example, the characteristic evaluation was performed as follows.

(Measurement of thermal conductivity)
A sample piece of φ20 mm × 2 mm was prepared from a wire rod having a diameter of 20 mm, and the thermal conductivity was measured at room temperature using a laser flash method. The obtained values are shown in Table 4.

(Evaluation of heat check resistance)
As shown in FIG. 4, a sample piece S1 in which a build-up weld W made of each repair welding material was formed on a base material B made of SKD61, and a heat check acceleration test was performed. Here, as the base material B, a 50 HRC hard material obtained by sequentially performing tempering at 1030 ° C. for 2 hours, gas fan cooling (equivalent to water cooling), tempering at 600 ° C. for 2 hours, and air cooling in a vacuum furnace. SKD61 having a thickness was used. Moreover, the build-up welding part W was produced by using each repair welding material as a wire 12 mm in diameter, and performing TIG welding with the welding current 100A.

  In the heat check acceleration test, the sample piece S1 is fixed to the testing machine through the screw hole H, and the sample piece S1 is heated to 500 ° C. for 6 seconds by high-frequency induction heating while rotating at a rotation speed of 300 rpm. Water was sprayed for 2 seconds to cool, and a cycle of air blowing for 15 seconds was continuously performed. After 5000 cycles and 10000 cycles, the surface of the sample piece S1 was observed to evaluate the number and length of cracks generated. A case where the number of cracks having a length of 5 mm or more was 2 or more at 5000 cycles or 4 or more at 10,000 cycles was defined as defective “x”. In addition, when the number of cracks having a length of 5 mm or more in 10000 cycles was 3 or less, good “◯” and 1 or less were particularly good “以下”. Table 4 shows the evaluation results obtained by conducting the above test without performing prognostic heat during welding. Moreover, about Example A09 and Comparative Examples 1-3, the sample piece surface at the time of 5000 cycle progress ((a1)-(d1) of FIG. 5) and 10000 cycles ((a2)-(d2) of FIG. 5). The photograph of is shown in FIG.

  Moreover, in order to evaluate the influence which prognosis heat has on heat check resistance, as a representative, the same applies to Example A09 for sample pieces that were preheated at 500 ° C. × 1 hour and post-heated at 500 ° C. × 1 hour. The heat check acceleration test was conducted. FIG. 6 shows a photograph of the surface of the sample piece after the lapse of 5000 cycles for cases (a) and (b) where no prognostic heat is performed.

(Measurement of weld hardness)
The hardness of the welded part formed by TIG welding with a welding current of 100 A was measured according to the Vickers hardness test method of JIS Z2233 using each repair welding material (wire material with a diameter of 12 mm). The test load was 200 g.

(Evaluation of weld cracks)
A sample piece S2 shown in FIG. 7 was produced and evaluated for weld cracking. That is, a groove portion having a substantially U-shaped cross section is formed in the central portion of the base material B made of SKD61 similar to that used for the heat check resistance evaluation, and each repair welding material (wire having a diameter of 12 mm) is formed in this groove portion. The build-up weld W was formed by TIG welding with a welding current of 100A. Then, the sample piece S2 is visually observed, and a case where no crack is generated on the build-up weld W and the boundary between the build-up weld W and the base material B is determined as “good”, A case where a crack occurred in at least one of the samples was defined as a defective “x”.

  Table 4 shows the evaluation results. Here, about each Example, the prognostic heat is not performed in the case of welding. On the other hand, each comparative example was preheated at 500 ° C. for 1 hour and post-heated at 500 ° C. for 1 hour.

  Further, in order to evaluate the effect of prognostic heat in the repair welding material according to the example, in addition to the case where the prognostic heat is not performed for the sample piece of Example A09, preheating at 500 ° C. × 1 hour and 500 ° C. × 1 hour Evaluation of weld cracking was also performed on sample pieces subjected to after-heating in an atmosphere furnace (atmosphere: nitrogen). FIG. 8 shows photographs of the sample piece surface when the prognostic heat is not performed (a) and when (b).

(Evaluation results)
In Table 4, the evaluation result of the repair welding material concerning each Example and a comparative example is shown.

  According to Table 4, the repair welding material according to each example having a component composition within the range defined in the present invention is the thermal conductivity, heat check resistance, hardness after welding, In any evaluation of cracks, excellent characteristics are shown. On the other hand, the repair welding material concerning each comparative example does not have the component composition prescribed | regulated to this invention, and sufficient characteristics are not acquired in the one part or all evaluation item. Below, the analysis about the result of each characteristic evaluation is shown.

  The repair welding material according to each example has a heat in the range of 24-30 W / m / K, which is higher than the thermal conductivity of the hot tool steel and not too high compared to the thermal conductivity of the hot tool steel. It has conductivity. Correspondingly, the repair welding material according to each example has good heat check resistance and resistance to cracking of the welded portion.

  Regarding the heat check resistance, in FIG. 5, in the sample pieces according to each comparative example, cracks were observed even at 5000 cycles, and crack generation further progressed at 10,000 cycles, whereas the samples according to Example A09. In the sample piece, no crack was observed at 5000 cycles, and even at 10,000 cycles, there were only two cracks at the end of the overlay weld (the left end in the figure), where heat check is relatively likely to occur. Only. As shown in Table 4, the repair welding material according to Example A09 has a sufficiently high thermal conductivity of 26.9 W / m / K, whereas the repair welding material according to each comparative example is This corresponds to having a low thermal conductivity of less than 24 W / m / K or more.

  Thus, the repair welding material according to the embodiment of the present invention has extremely high heat check resistance as compared with the conventional repair welding material. This is due to the effect of adjusting the thermal conductivity by optimizing the content of each essential element. In particular, the contents of C and Si have a great influence on the magnitude of the thermal conductivity and the heat check resistance that is greatly affected by the thermal conductivity. According to Table 4, Examples A02, A04 to A10, and B in which the content of these elements is in the range of 0.30 <C ≦ 0.40 mass% and 0.40 ≦ Si ≦ 0.60 mass%. In the repair welding material according to each of the examples of Group E, a thermal conductivity of 25 to 28 W / m / K is obtained, and particularly good (◎) heat check resistance is achieved.

  In addition, according to FIG. 6, the crack by a heat check is not observed after 5000 cycles progress, regardless of the presence or absence of the prognostic heat at the time of welding, and the equally high heat check resistance is acquired. That is, the presence or absence of prognostic heat does not particularly affect the heat check resistance.

  Next, with respect to cracking of the welded portion, the repair welding material according to each example did not crack (circle in Table 4), whereas the repair welding material according to comparative example 3 cracked. (× in Table 4). Here, it should be noted that the sample pieces used for the evaluation of each example are not subjected to prognostic heating, whereas the sample pieces used for the evaluation of comparative examples are subjected to prognostic heating. In general, the prognostic heat at the time of welding has the effect of preventing weld cracking, and in the repair welding material according to each example, even though such prognostic heat is not performed, a comparative example that has undergone prognostic heat The weld cracking is prevented to a higher degree than the repair welding material. In FIG. 8, when comparing the form of the welded portion when the prognostic heat is applied to the repair welding material of Example A09 (b) and when not (a), the build-up is performed regardless of the presence or absence of the prognostic heat. No cracks were observed on the welded portion (horizontal irregular shape in the center of the photo) or on the boundary between the build-up weld and the base material. That is, in the repair welding material according to the embodiment of the present invention, welding cracks can be highly prevented without performing prognostic heat.

  Furthermore, the hardness after welding can be adjusted to some extent depending on the quenching and tempering conditions in the manufacturing process of the repair welding material, but all of the repair welding materials according to the examples are made of hot tool steel. A value of 410 to 550 Hv suitable for use in repair welding of die casting molds has been achieved. In the maraging steel of Comparative Example 3 which is greatly different in composition from the repair welding material according to the example, the hardness in this range is not obtained.

  Finally, the repair welding material according to each example of the groups B to E contains an essential element having almost the same configuration as that of Example A08, and further added with a selective element. In all evaluation items of thermal conductivity, heat check resistance, hardness after welding, and cracks in the welded portion, high characteristics obtained by the effect of essential elements are maintained even by addition of selective elements. In comparison with Example A08, the selected element mainly contributes to improving the hardness after welding.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

S1, S2 Specimen B Base material W Overlay weld

Claims (6)

0.30 <C ≦ 0.50 mass%,
0.05 ≦ Si ≦ 0.80 mass%,
0.50 ≦ Mn ≦ 1.50 mass%,
4.00 ≦ Cr ≦ 9.00 mass%,
0.50 ≦ Mo ≦ 3.00 mass%, and
Including 0.30 ≦ V ≦ 0.70 mass%,
A mold repair welding material characterized in that the balance consists of Fe and inevitable impurities.   Furthermore, 0.01 <= W <= 4.00 mass% is contained, The metal mold | die repair welding material of Claim 1 characterized by the above-mentioned.   Furthermore, 0.30 <= Co <= 3.00 mass%, The metal mold repair welding material of Claim 1 or 2 characterized by the above-mentioned. further,
0.0001 ≦ Nb ≦ 0.100 mass%,
0.0001 ≦ Ta ≦ 0.100 mass%,
0.0001 ≦ Ti ≦ 0.100 mass%,
0.0001 ≦ Zr ≦ 0.100 mass%,
0.0005 ≦ Al ≦ 0.1000 mass%, and
4. The mold repair welding material according to claim 1, comprising at least one selected from the group consisting of 0.0020 ≦ N ≦ 0.1500 mass%. 5. further,
0.0002 ≦ B ≦ 0.0100 mass%,
0.05 ≦ Cu ≦ 1.50 mass%, and
5. The mold repair welding material according to claim 1, comprising at least one selected from the group consisting of 0.05 ≦ Ni ≦ 1.50 mass%. further,
0.001 ≦ S ≦ 0.200 mass%,
0.0005 ≦ Ca ≦ 0.2000 mass%,
0.03 ≦ Se ≦ 0.50 mass%,
0.005 ≦ Te ≦ 0.100 mass%,
0.01 ≦ Bi ≦ 0.30 mass%, and
6. The mold repair welding material according to claim 1, comprising at least one selected from the group consisting of 0.03 ≦ Pb ≦ 0.50 mass%.