JP2019111573A - Die repair weld material - Google Patents

Abstract

To provide a die repair weld material spreadable easily on the mold surface.SOLUTION: A die repair weld material contains, in terms of mass%, 0.20%≤C≤0.25%, 0.05%≤Si≤0.15%, 0.75%≤Mn≤0.95%, 5.70%≤Cr≤6.00%, 2.40%≤Mo≤2.60%, 0.60%≤V≤0.70%, and having a residue comprising Fe and inevitable impurities. Preferably, a melting point of the die repair weld material is 1,700°C or lower. More preferably, at a room temperature, hardness of a weld zone is 45 HRC or more, and a thermal conductivity is 25 W/(m K) or more.SELECTED DRAWING: Figure 1

Description

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

  In a mold used for forming a metal material, if the mold is damaged due to the use of the mold, the damaged portion will affect the subsequent forming. For example, in a mold used for die casting of a metal material, injection and cooling of a high-temperature molten metal into the mold are repeated, and damage such as cracking or cracking occurs in the mold due to heat check. Such damage to the mold surface can be transferred to the product. Therefore, after removing the damaged part of the mold, repair welding is performed so as to fill the part.

  For example, Patent Document 1 discloses a mold repair welding material used for repair welding of a die for die casting. In patent document 1, it is aiming at improving the lamination | stacking property of a welding material, ensuring the heat check resistance of a metal mold | die, and the lifetime of a metal mold | die by adjustment of the component composition of a metal mold repair welding material. By improving the laminating property of the welding material, it is believed that the welding material can be secured to the thickness of the welding material without excessively spreading on the mold surface at the time of welding.

JP 2017-24053 A

  As in the material disclosed in Patent Document 1 above, the fact that the mold repair welding material has a high laminating property keeps the mold repair weld material in a highly raised state without spreading too much on the mold surface. It means that. However, if there is damage to a wide area of the surface of the mold, or if a long crack occurs, etc., it is necessary to repair and repair the large area. In such a case, if it is difficult for the mold repair welding material to spread on the mold surface, it is necessary to carry out the repair welding at a large number of locations and to repeat the repair welding for each location a number of times. Then, repair welding will take a long time. In particular, when repair welding is continuously performed on a large number of dies, the repair welding of the dies can not be completed in a short time, and it becomes difficult to increase the operation rate of the repair welding operation. In these cases, it is desirable to use a mold repair weld material that tends to spread on the mold surface so that repair welding of the required area can be completed with a reduced number of welds.

  The problem to be solved by the present invention is to provide a mold repair welding material which is easy to spread on the mold surface.

  In order to solve the above problems, the mold repair welding material according to the present invention is, by mass%, 0.20% ≦ C ≦ 0.25%, 0.05% ≦ Si ≦ 0.15%, 0.75 % ≦ Mn ≦ 0.95%, 5.70% ≦ Cr ≦ 6.00%, 2.40% ≦ Mo ≦ 2.60%, 0.60% ≦ V ≦ 0.70%, the balance being It consists of Fe and unavoidable impurities.

  Here, in the mold repair welding material, the melting point is preferably 1700 ° C. or less.

  The hardness of the welded portion may be 45 HRC or more at room temperature.

  The thermal conductivity of the welded portion may be 25 W / (m · K) or more at room temperature.

  The ratio H / W of the height H to the width W may be 0.28 or less in a weld formed by three-pass five-layer welding.

  In the mold repair welding material, it is preferable that Ni ≦ 0.25%, Cu ≦ 0.25%, Al ≦ 0.030% in mass%.

  It is good in the said mold repair welding material that it is N <= 0.020%, O <= 0.0015%, P <= 0.030%, S <= 0.010% in mass%.

  According to the mold repair weld material according to the above invention, the molten repair weld material has high fluidity when it is used for repair welding, particularly by adjusting the content of Cr, and gold Spread well on the mold surface. As a result, in one pass welding, a large welding area can be secured, and even in the case of repair welding over a large area, it can be completed with a small number of weldings. The adhesion of the mold repair welding material to the mold surface is also enhanced. In addition, since the mold repair welding material according to the above-described invention can easily form a weld having high hardness and thermal conductivity, the heat check resistance of the weld is also excellent.

  Here, in the above-mentioned mold repair welding material, when the melting point is 1700 ° C. or less, the melting point is sufficiently low, so that the mold repair welding material melted at the time of repair welding is solidified until it solidifies. , It is easy to spread the mold surface in the state of having high fluidity. Therefore, it can be used suitably for repair welding over a large area.

  When the hardness of the weld is 45 HRC or more at room temperature, the hardness required as a mold can be easily secured in the weld. Moreover, in the metal mold | die after repair welding, high heat check resistance is securable.

  When the thermal conductivity of the weld is 25 W / (m · K) or more at room temperature, the weld has a sufficiently high thermal conductivity, so that the mold after repair welding has high resistance Heat check performance can be secured.

  When the ratio H / W of height H to width W is 0.28 or less in a weld formed by three-pass five-layer welding, the width is wider than the height of the weld It becomes an indicator that molten repair welding material spreads well on the mold surface.

  In the above-mentioned mold repair welding material, in the case of Ni ≦ 0.25%, Cu ≦ 0.25%, Al ≦ 0.030% by mass%, the spreadability of the mold repair welding material is lowered or The effects of these elements on the properties of the mold repair weld material, such as a decrease in the thermal conductivity of the weld, can be suppressed to a low level.

  In the above-mentioned mold repair welding material, when it is N ≦ 0.020%, O ≦ 0.0015%, P ≦ 0.030%, S ≦ 0.010% by mass%, weld defects in the weld zone The effects of these elements on the properties of the mold repair weld material, such as the formation of the compound and the formation of the compound, can be suppressed to a low level.

It is a test result which shows the relationship between Cr content and melting | fusing point in a metal mold repair welding material. It is a test result which shows the relationship between melting | fusing point and the height of a welding part in a mold repair welding material.

  Hereinafter, a mold repair welding material according to an embodiment of the present invention will be described in detail. The mold repair / welding material according to the present embodiment is a material for repairing a mold including a die for a die by welding, and has the following component composition and characteristics.

  In the present specification, physical property values such as thermal conductivity and hardness described for welds and mold base materials formed using a mold repair welding material are values at room temperature. In addition, the physical property values of the welded portion are values obtained in the as-welded state (the state in which other treatments such as heat treatment and the like are not performed while the welding is performed). The physical properties of the weld may be evaluated on the weld produced by simulating the welding conditions at the time of repairing the mold using the mold repair welding material, for example, overlaying using TIG welding It is preferable to use a weld produced by welding. In addition, when it is difficult to accurately evaluate the physical properties of the metal material that constitutes the weld by the oxide or nitride formed on the surface of the weld, the surface of the weld is appropriately ground or the like. Evaluation should be performed after removing tissue.

<Component composition of mold repair welding material>
The mold repair welding material (hereinafter sometimes referred to simply as repair welding material) according to the present embodiment contains C, Si, Mn, Cr, Mo, and V as essential elements, and the balance is Fe and unavoidable impurities. It consists of Hereinafter, the unit of content of each component element is mass%.

(1) 0.20% ≦ C ≦ 0.25%
The content of C greatly affects the hardness of the repair welding material, and the higher the content, the higher the hardness. If the content of C is 0.20% or more, high hardness such as 45 HRC or more in the as-welded state generally required for dies used for molding of metal materials such as die casting dies. In the weld formed by using the present repair welding material. When the weld has high hardness such as 45 HRC, the heat check resistance of the weld also becomes high.

  On the other hand, even if the content of C is too large, the effect of improving the hardness of the welded portion is saturated. In addition, the thermal conductivity of the welded portion is lowered. There is also a concern about deterioration of the properties of the repair weld material due to the increase of carbides. From these viewpoints, the content of C is set to 0.25% or less. Thereby, it is easy to obtain high thermal conductivity like 25 W / (m · K) or more in the as-welded state. When the welded portion has a high thermal conductivity such as 25 W / (m · K) or more, the heat check resistance of the welded portion is enhanced.

(2) 0.05% ≦ Si ≦ 0.15%
When the content of Si increases, the thermal conductivity of the repair welding material decreases. Therefore, in the repair welding material, from the viewpoint of improving the thermal conductivity, the content of Si is preferably small, and is limited to 0.15% or less.

  The content of Si is preferably as small as possible from the viewpoint of improving the thermal conductivity and the like, but Si is an element that is inevitably contained for component adjustment and refining in the manufacturing process of steel materials. Since it is very difficult industrially to make content of Si in a repair welding material less than 0.05%, content of Si is made into 0.05% or more.

(3) 0.75% ≦ Mn ≦ 0.95%
By including Mn, the hardenability of the repair welding material is improved. In the welded portion formed using the repair weld material that has undergone hardening, the content of Mn is set to 0.75% or more from the viewpoint of obtaining a hardness such as 45 HRC or more in the as-welded state.

  On the other hand, if too much Mn is contained, the thermal conductivity of the repair welding material is lowered. From the viewpoint of securing a high thermal conductivity, the content of Mn is made 0.95% or less.

(4) 5.70% ≦ Cr ≦ 6.00%
The content of Cr greatly affects the melting point of the repair welding material. As shown in the subsequent examples, in the region where the content of Cr is less than 5.7%, the melting point tends to be higher as the content of Cr decreases. When the melting point of the repair welding material becomes high, the melted repair welding material becomes difficult to spread. Therefore, the content of Cr is made 5.70% or more from the viewpoint of keeping the melting point low and securing the spreadability of the repair welding material. Further, Cr is an element for improving the hardness and high temperature strength of the welded portion, and by containing 5.70% or more, it becomes easy to achieve the hardness and high temperature strength which gives sufficient heat check resistance.

  On the other hand, as shown in the later examples, the melting point of the repair welding material tends to be high even if the content of Cr is too large. Therefore, the content of Cr is set to 6.00% or less from the viewpoint of suppressing the rise of the melting point of the repair welding material and securing the ease of spreading. In addition, when the content of Cr is increased, the thermal conductivity of the welded portion is lowered. By setting the content of Cr to 6.00% or less, the thermal conductivity of the welded portion can be increased, and the heat check can be easily suppressed.

  Thus, by setting the Cr content to 5.70% or more and 6.00% or less, the melting point is lowered to 1700 ° C. or less, and the spreadability of the melted repair welding material is enhanced. Can. At the same time, it is easy to ensure high thermal conductivity such as 25 W / (m · K) or more and high hardness such as 45 HRC or more, and it is possible to improve the heat check resistance of the welded portion.

(5) 2.40% ≦ Mo ≦ 2.60%
Mo is an element having the effect of improving the hardenability, and by adding Mo, it is possible to form a welded portion with high hardness using the repair welding material manufactured through hardening. Si and Mn are also elements that improve the hardenability, but as described above, it is not preferable to add large amounts of Si and Mn to the repair welding material from the viewpoint of improving the thermal conductivity etc. Need to ensure. By setting the content of Mo to 2.40% or more, hardness such as 45 HRC or more can be achieved in the as-welded state. In addition, Mo also has the effect of facilitating the spreading of the melted repair welding material, and by securing the content of Mo to 2.40% or more, the ease of spreading necessary for repair welding in a large area is secured. It will be easier.

  On the other hand, when the content of Mo is too large, the thermal conductivity of the repair welding material is lowered. Therefore, in the repair welding material, the content of Mo is made 2.60% or less from the viewpoint of securing the thermal conductivity.

(6) 0.60% ≦ V ≦ 0.70%
V has the effect of refining the crystal grains in the repair welding material. When welding is performed using a repair welding material, the metal material is rapidly cooled from the liquid state at the weld, so the crystal grains tend to be coarsened. Coarsening can be suppressed. In the repair welding material, by refining the crystal grains, it is possible to obtain the effect of suppressing the cracking that occurs in the weld during the welding operation. From the viewpoint of sufficiently obtaining the effect of grain refinement, the content of V is set to 0.60% or more.

  On the other hand, when V is contained too much, coarse nitrides having a particle size of more than 10 μm are easily formed. From the viewpoint of suppressing the wear of the mold due to the formation of coarse nitrides, the content of V is set to 0.70% or less.

  The repair welding material according to the present embodiment contains the predetermined amounts of C, Si, Mn, Cr, Mo, and V, and the balance is composed of Fe and unavoidable impurities. Here, the following elements and upper limit amounts are assumed as unavoidable impurities.

(7) Ni ≦ 0.25%
(8) Cu ≦ 0.25%
When manufacturing repair welding materials industrially, Ni and Cu unavoidably mix in repair welding materials from raw materials, such as iron scrap and alloy iron. However, if the amount is less than the above upper limit value, even if it is contained, the spreadability on the surface of the mold, hardness and thermal conductivity of the weld, and the like significantly affect the characteristics as the repair welding material It is difficult to become. Therefore, it is preferable to restrain to the content within the said each upper limit.

(9) Al ≦ 0.030%
Al is also an element which is inevitably mixed in the raw materials at the time of production of the repair welding material. However, in order to make it difficult to spread the melted repair welding material, Al is preferably smaller in content. If the content is 0.030% or less, sufficient spreadability can be ensured even if Al is mixed.

(10) N ≦ 0.020%
(11) O 0.001 0.0015%
Since N and O dissolve in Fe from the atmosphere when manufacturing steel products industrially, they are unavoidably mixed in repair welding materials. However, if the contents of N and O become too high, blow holes (welding defects) are generated during welding. Then, N and O form nitrides and oxides of the metal element in the repair welding material, respectively. Metal nitrides and metal oxides, especially those with large particle sizes, are prone to wear of repair welded molds. Therefore, it is preferable to reduce the contents of N and O as much as possible. By suppressing the content of N to 0.020% or less and the content of O to 0.0015% or less, formation of coarse nitrides and oxides can be effectively suppressed. Moreover, in the manufacturing process of the repair welding material, since the manufacturing cost increases as the content of N and O is reduced, the content of N and O is set to the above upper limit from the viewpoint of avoiding an excessive increase in the manufacturing cost. It is preferable to manage within a range.

(12) P ≦ 0.030%
(13) S ≦ 0.010%
P and S are also inevitably mixed in the repair welding material due to the raw material and the like. However, if the amount is less than the above upper limit value, even if it is contained, the spreadability on the surface of the mold, hardness and thermal conductivity of the weld, and the like significantly affect the characteristics as the repair welding material It is difficult to become. Therefore, it is preferable to restrain to the content within the said each upper limit.

  Besides the above-mentioned Ni, Cu, Al, N, O, P, S, the following unavoidable impurities may be mentioned. That is, Co <0.3%, W <0.10%, Nb <0.10%, Ta <0.01%, Ti <0.10%, Zr <0.01%, B <0.010% , Ca <0.010%, Se <0.03%, Te <0.01%, Bi <0.01%, Pb <0.03%, Mg <0.02%, REM <0.10%, etc. Is assumed.

<Characteristics of mold repair welding material>
In the mold repair welding material according to the present embodiment, by having the above-described component composition, the melted repair weld material is easily spread on the mold surface at the time of repair welding, particularly by adjusting the content of Cr. There is.

  When performing repair welding on the mold surface, if the melted repair welding material does not spread easily on the mold surface, it is necessary to weld at a large number of places in order to repair weld the required area on the mold surface There is. In addition, in welding at each location, a large number of welding passes are required. Then, to complete the repair welding, the welding operation has to be performed many times, which takes a long time. In particular, when a long crack has occurred, the area requiring repair welding is large, or when it is necessary to carry out repair welding on a large number of molds, the efficiency of the repair welding becomes extremely low.

  However, since the repair welding material according to the present embodiment is easily spread on the surface of the mold due to the effect of its component composition, the welded portion can be formed in a large area by one welding operation. Then, in order to repair and repair the required area on the mold surface, it is possible to reduce the places where welding is performed and to reduce the number of welding passes at each place. Then, a large area repair welding can be completed with a small number of welding operations, and the time required for the repair welding can be shortened. This improves the efficiency of repair welding. The highly weldable repair welding material as described in Patent Document 1 can be suitably used when repair welding is performed on a small area area, whereas the repair welding material according to the present embodiment is used. Is particularly suitable for use when repair welding is required for a large area, such as when a long crack has occurred, or when it is necessary to carry out repair welding continuously for a large number of dies. Can. Furthermore, since the repair welding material according to the present embodiment is likely to spread on the mold surface, it contacts the mold surface over a wide area, and the adhesion of the weld to the mold surface also increases.

  As an index of the spreadability of the repair welding material on the mold surface, the height ratio H / W in the weld formed on the mold surface can be used. Here, H is the height of the weld and W is the width of the weld. For example, a repair weld material is used on the surface of a flat mold base material to form a linear weld by overlay welding, and welding is performed from the surface of the mold base in the cross section of the weld The distance to the top of the portion may be height H, and the width dimension (dimension in the direction orthogonal to the welding direction) of the weld at the interface where the weld and the mold base material contact each other may be width W. Then, the height ratio H / W may be calculated by normalizing the height H with the width W. The smaller the value of the height ratio H / W, the better the molten repair weld material spreads on the mold surface.

  For example, when three-pass five-layer build-up welding is performed, that is, three linear welds are formed on the surface of a flat die base material, and five welds are laminated in each pass. At the time of welding, the height ratio H / W may be 0.30 or less in the obtained welded portion. Furthermore, the height ratio H / W is preferably 0.28 or less and 0.25 or less.

  The spreadability of the repair welding material has a correlation with the melting point of the repair welding material, and the lower the melting point, the more easily the molten repair welding material spreads. This is, for example, when the output of heating by a welding torch or the like for melting the repair welding material is made constant when performing repair welding, the melting point exceeds the melting point as the repair welding material has a lower melting point Thus, the temperature at which the material is heated becomes high, and the repaired weld material which is in a molten and high temperature state acquires high fluidity. Furthermore, the lower the melting point of the repair weld material, the longer it will take for the repair weld material melted on the mold surface to cool and solidify, allowing the repair weld material to spread across the mold surface It is because the time which is in the state which maintained sex becomes long.

  For example, if the melting point of the repair welding material is 1700 ° C. or less, the repair welding material tends to spread sufficiently well on the mold surface. It is particularly preferable that the melting point is 1670 ° C. or less, further 1650 ° C. or less, or 1600 ° C. or less. The melting point of the repair welding material depends on the component composition of the repair welding material, and has a high correlation particularly with the content of Cr as shown in the following examples.

  Furthermore, the repair welding material according to the present embodiment has high thermal conductivity because the content of C, Si, and Mn is particularly suppressed to a low level by having the above-described component composition. For example, a welded portion welded using the repair welding material according to the present embodiment can have a thermal conductivity of 25 W / (m · K) or more in the as-welded state. Generally, SKD 61 and SKD 11 used for repair welding of molds are not the ones whose components are optimized as welding materials, and the thermal conductivity is 18 to 25 W / (m · K), but the repair according to this embodiment The weld material exhibits a higher thermal conductivity than this.

  Due to the high thermal conductivity of the welded portion, the temperature of the surface layer portion of the welded portion is likely to decrease even when the weld portion is heated due to injection of the molten metal at the time of die casting, etc. The temperature gradient does not easily increase. Then, in the welded portion, the thermal stress can be suppressed to a low level, and the occurrence of the heat check can be suppressed. In the repair welding material in the present embodiment, if the welded portion has a thermal conductivity of 25 W / (m · K) or more, the occurrence of heat check can be effectively suppressed. In the mold after repair welding, it is easy to avoid the occurrence of damage to the mold again by suppressing the occurrence of heat check. The thermal conductivity is particularly preferably 27 W / (m · K) or more, and further preferably 30 W / (m · K) or more. From the viewpoint of suppressing the heat check, the heat conductivity is preferably as high as possible, and the upper limit is not particularly provided.

  The repair welding material according to the present embodiment preferably has a hardness of 45 HRC or more in the as-welded state at the formed weld. A hardness of 45 HRC or more is sufficient for a mold that has undergone repair welding to withstand use as a mold. In addition, when the welded portion has a high hardness such as 45 HRC or more, cracking and cracking are less likely to occur, and the occurrence of heat check can be suppressed. The hardness of the welded portion is more preferably 47 HRC or more.

  On the other hand, even if the hardness of the weld is too high, there is a concern about the occurrence of large cracks. Therefore, the hardness of the welded portion is preferably 54 HRC or less. More preferably, it is 52 HRC or less.

<Manufacturing method of mold repair welding material>
In the repair welding material according to the present embodiment, for example, an ingot is produced from a molten metal in which a predetermined component is melted at a predetermined composition ratio, heated to 900 ° C. to 1250 ° C., forged, and rolled. It can be manufactured as (welding rod). Moreover, you may perform wire drawing etc. to the material after rolling. If preparation of a molten metal and preparation of an ingot are performed under reduced pressure, it is easy to hold down the concentration of N and O in the repair welding material to be produced.

  Furthermore, it is preferable to manufacture this repair welding material through annealing as a heat treatment process. As annealing conditions, spheroidizing annealing which heats at 800-950 ° C for 3 hours or more, and carries out gradual cooling to 700 ° C or less with a cooling rate of 50 ° C / hour or less, heating at 600-780 ° C for 5 hours or more And low temperature annealing with air cooling and water cooling can be exemplified.

<Method of repair welding of mold>
The repair welding material according to the present embodiment can be suitably used for repair welding of a mold. This repair welding material can be suitably applied to both TIG welding and laser welding.

  In the mold, after removing the damaged part by machining such as cutting appropriately to the place where the repair is necessary due to the occurrence of damage such as a crack, overlaying using the present repair welding material Welding should be done. Then, the raised portion of the weld may be removed by machining such as cutting or grinding to finish the weld flush with the surface of the mold and adjust the shape of the mold. If necessary, prognostic heat treatment may be performed on the weld.

  The type of mold to be repaired by the repair welding material is not particularly limited, but it is preferably used for a die casting mold. In die casting, injection and cooling of a high-temperature molten metal are repeated to the mold, and damage such as heat check is likely to occur. Even if such damage occurs over a large area, the ease of spreading of the repair weld material can be used to complete the repair welding with a reduced number of welds. In addition, the weld formed by this repair welding material has high thermal conductivity and hardness, and is less likely to cause a heat check, so that the heat check again occurs in the mold subjected to the repair welding due to the heat check. , Can be suppressed.

  The metal material (mold base material) constituting the mold to be repaired is also not particularly limited. However, the mold base material preferably has a hardness of 42 HRC or more, and further 45 HRC or more. The mold base material having such hardness can suppress the occurrence of heat check in the mold base material. As a result, even if damage occurs due to heat check on the surface of the mold base material, the area is kept small and the number of times of welding is small along with the effect of having the characteristic that the repair welding material easily spreads. Then, it becomes easy to complete the repair welding. Moreover, it becomes easy to endure repeated use, suppressing generation | occurrence | production of a heat check as the whole metal mold which went through repair welding.

  On the other hand, the hardness of the mold base material is preferably 50 HRC or less, and more preferably 48 HRC or less. If the hardness of the mold base material exceeds 50 HRC, the toughness decreases and the possibility of occurrence of a large crack increases.

  The thermal conductivity of the mold base material is preferably 23 W / (m · K) or more. If the thermal conductivity is high not only in the weld portion of the repair weld material but also in the mold base material, the heat of the surface portion of the weld portion and the mold in the mold after repair welding is the inside of the weld portion and the metal. It is because it is easy to be dissipated inside the mold and to avoid the occurrence of heat check. On the other hand, the thermal conductivity of the mold base material is preferably 27 W / (m · K) or less. Even when the mold size becomes large, in order to obtain the necessary hardness after heat treatment, the mold base material needs to have excellent hardenability, and elements such as C, Mn, Cr, Mo, etc. that enhance the hardenability Is well-balancedly added in an amount that provides sufficient hardenability, it is easy to obtain a thermal conductivity less than the above value.

  As a mold base material which can be used suitably, SKD61, SKD6, SKD7, SKT4 etc. can be illustrated.

  Examples of the present invention and comparative examples are shown below. The present invention is not limited by these examples. All the tests below are conducted at room temperature in the air unless otherwise stated.

<Test 1: Relationship between Cr Content and Melting Point>
First, the relationship between the content of Cr in the repair welding material and the melting point was examined.

(Preparation of sample)
Repair welding materials with different contents of Cr were produced. Specifically, it contains C: 0.23%, Si: 0.10%, Mn: 0.85%, Mo: 2.52%, V: 0.62% and Cr, with the balance being Fe and unavoidable. Of repair weld materials consisting of chemical impurities. The content of Cr was varied in the range of 5.40% to 6.20%.

  In the preparation of the repair welding material, 5 kg of molten metal was prepared in a vacuum induction furnace so as to have a predetermined component composition, and casting was performed to prepare an ingot. The obtained ingot was heated at 1200 ° C. for 10 hours, and then hot forging was performed until it became φ80 mm. After forging, air cooling was performed, and after reaching 100 ° C., low temperature annealing was performed by heating again at 700 ° C. for 20 hours and air cooling. From the repair welding material thus obtained, a test piece of φ2 mm × 135 mm was produced by wire cutting.

(Measurement of melting point)
The melting point of each of the repair welding materials prepared above was measured by thermogravimetric differential thermal analysis (TG-DTA).

(Test results)
FIG. 1 shows the relationship between the Cr content and the melting point. According to FIG. 1, it can be seen that the melting point of the repair welding material has a high correlation with the content of Cr. Generally, in the region where the content of Cr is 5.7% or less, the melting point is lowered by increasing the content of Cr, but in the region where the content of Cr is higher than that, the content of Cr increases Along with, the melting point is rising. A melting point of 1700 ° C. or less is obtained in the region of Cr ≦ 6.0%.

<Test 2: Relationship between component composition of repair welding material and various characteristics>
Next, the content of component elements other than Cr is also changed, and the component composition of the repair welding material and the characteristics of the repair welding material, that is, the melting point of the repair welding material, and the hardness, thermal conductivity and shape of the weld portion I examined the relationship with.

(Preparation of sample)
A repair weld material containing the component elements shown in Table 1 and the balance of Fe and unavoidable impurities was prepared in the same manner as in Test 1 above. And the same test piece was produced.

  The surface of a φ30 mm × 15 mm mold base material prepared using the test piece prepared above as a welding rod and produced with hot tool steel SKD 61 (hardness: 50 HRC, thermal conductivity: 23 W / (m · K)) Then, TIG welding was performed. As a condition at the time of welding, welding current was set to 100 to 150 A, and welding of three passes and five layers was performed. Weaving was not performed and neither preheating nor postheating was performed. The temperature between passes was 300 ° C. or less, and overlay welding was performed under the conditions of reverse mode.

(Evaluation of characteristics)
Measurement of Melting Point In the same manner as in Test 1 above, the melting point of the repair welding material was measured.

-Measurement of hardness of welded portion After removing about 1 mm of the surface from the surface of the built-up welded portion by grinding, using the Rockwell C scale, the hardness of the surface of the welded portion Was measured.

-Measurement of the thermal conductivity of a welding part The test piece of (phi) 10 mm x 1 mm was shaved out by lathe processing from the build-up welding part produced above, and laser flash-type thermal conductivity measurement was performed.

-Evaluation of the shape of a welding part The cross section of the cladding welding part was cut out, and the height (H) of the cladding welding part from the surface of a metal mold | die base material was measured. In addition, the width (W) of the weld overlay at the interface in contact with the mold base material was also measured, and the height ratio H / W was calculated.

(Test results)
Table 1 summarizes the component composition of the repair welding material according to each example and the comparative example and the evaluation result of each characteristic. Furthermore, FIG. 2 shows the relationship between the melting point and the height (H) of the weld overlay in the examples and comparative examples in which the melting point is 1700 ° C. or less.

  According to Table 1 and FIG. 2, there is a correlation between the melting point of the repair weld material and the height (H) and height ratio (H / W) of the weld, and the lower the melting point, the higher the weld height. The height and height ratio tend to be smaller. Welds with small height and height ratios are formed by spreading the repaired repair welding material well on the surface of the mold base material. That is, by adjusting the content of the component elements, including Cr whose relationship with the melting point was verified in Test 1, and lowering the melting point of the repair welding material, it becomes a repair welding material that easily spreads on the surface of the mold base material , Welds with low height and height ratio can be formed.

  According to Table 1, all of the repair welding materials according to Examples 1 to 10, including 5.70% to 6.00% of Cr, are component elements within the range defined in the embodiment of the present invention Contains And it has melting | fusing point of 1700 degrees C or less corresponding to those component compositions. By having such a low melting point, the melted repair welding material spreads well on the surface of the mold base material, and a small value of 4.5 mm or less in height of weld and 0.28 or less in height ratio is obtained. It is obtained.

  Furthermore, the welds formed by the repair welding material according to Examples 1 to 10 have a thermal conductivity of 25 W / (m · K) or more and a hardness of 45 HRC or more, corresponding to the component composition. There is. As such, by having high thermal conductivity and hardness, the welded portion is less likely to cause a heat check.

  On the other hand, the repair welding material according to each comparative example does not have the component composition within the range defined in the embodiment of the present invention. Corresponding to this, the height (H) of the weld exceeds 4.5 mm, and the height ratio (H / W) also exceeds 0.28. The melting points are all over 1700 ° C. That is, the repair welding material according to each comparative example is less likely to spread on the surface of the mold base material than the repair welding material according to each example, corresponding to the component composition thereof. And the difficulty in spreading is considered to be due to the high melting point. The range of the melting point height according to the embodiment of the present invention is mainly that the Cr and Mo content is 5.70% ≦ Cr ≦ 6.00% and 2.40% ≦ Mo ≦ 2.60%. It is thought that it is because it is off. The component composition of Comparative Example 8 corresponds to SKD61.

  Furthermore, in each comparative example, the thermal conductivity of the weld is less than 25 W / (m · K). This can be roughly corresponded to the content of C, Si, Mn, and Mo. The set of Example 8 and Comparative Example 9 and the set of Example 3 and Comparative Example 10 have component compositions close to each other except for the content of C, but the content of C is too large. Comparative Example 9 10, the height and the height ratio of the welded portion are larger than those of Examples 8 and 3, respectively, and the thermal conductivity is lower.

  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.

Claims (7)

In mass%,
0.20% ≦ C ≦ 0.25%,
0.05% ≦ Si ≦ 0.15%,
0.75% ≦ Mn ≦ 0.95%,
5.70% ≦ Cr ≦ 6.00%,
2.40% ≦ Mo ≦ 2.60%,
Contains 0.60% ≦ V ≦ 0.70%,
A mold repair welding material, the balance of which consists of Fe and unavoidable impurities.   A melting point is 1700 ° C or less, The mold repair welding material according to claim 1 characterized by the above-mentioned.   The mold repair welding material according to claim 1 or 2, wherein the hardness of the weld is 45 HRC or more at room temperature.   The mold repair welding material according to any one of claims 1 to 3, wherein the thermal conductivity of the welded portion is 25 W / (m · K) or more at room temperature.   The ratio H / W of the height H to the width W is 0.28 or less in a weld formed by overlay welding of three passes and five layers, according to any one of claims 1 to 4. Mold repair welding material as described. In mass%,
Ni ≦ 0.25%,
Cu ≦ 0.25%,
The mold repair welding material according to any one of claims 1 to 5, wherein Al 0.0 0.030%. In mass%,
N ≦ 0.020%,
O ≦ 0.0015%,
P ≦ 0.030%,
The mold repair welding material according to any one of claims 1 to 6, wherein S 0.0 0.010%.

Images