JP2010051982A - Welding material for repairing mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding material, which is most suitable for repairing the mold disclosed in Japanese Published Patent Application No.2007-146278, and specifically has excellent mirror-finishing property while keeping the performance of the mold even after welding to repair the mold, and further which makes equal the hardness of a welded part and that of the base material of the mold to suppress unevenness in embossing or uneven wear in forming. <P>SOLUTION: A mold is made of steel containing, by mass%, 0.10-0.25% C, ≤1.00% Si, ≤2.00% Mn, 0.60-1.50% Ni, >1.00% and ≤2.50% Cr, Mo and/or W alone or in combination to satisfy 0.10-1.00% of (Mo+1/2W), 0.03-0.15% V, 0.50-2.00% Cu, 0.007-0.05% S, and the balance Fe with inevitable impurities. A welding material for repairing the mold is composed of the steel containing, by mass%, 0.07-0.25% C, 0.40-1.00% Si, ≤2.00% Mn, 0.40-1.50% Ni, >0.80% and ≤2.50% Cr, Mo and/or W alone or in combination to satisfy 0.08-1.00% of (Mo+1/2W), 0.02-0.15% V, 0.10-0.45% Cu, ≤0.005% S, and the balance Fe with inevitable impurities. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention uses a steel for molds mainly used for plastic molding, which has extremely excellent toughness, machinability and hardness, and also has excellent polishing finish and wear resistance. Thus, the present invention relates to a welding material that exhibits excellent repair characteristics only when the mold is used for welding repair.

As steel for plastic molding dies,
(1) Good mirror finish and low tendency to generate pinholes and other fine pits.
(2) Good texture processing,
(3) Good corrosion resistance and rust resistance,
(4) Good strength, wear resistance and toughness,
(5) Good machinability,
Etc. are required. Therefore, the present applicant has proposed a steel for molds having these characteristics at a high level (see Patent Document 1). If this is supplied in a pre-hardened state with a hardness of 34 to 45 HRC, it can be used as a mold by performing polishing finishing after die-cutting as it is.

  Plastic molding dies are relatively frequently repaired by welding when repairing or redesigning the plastic mold. Therefore, excellent weldability is also important for mold steel. Here, excellent weldability means that excellent mirror finish and texture workability are maintained even after welding, as a matter of course that no cracking occurs during welding. And even if the mold surface after welding repair is worn during its molding use, it is important that the wear progresses uniformly. That is, it is difficult for the hardness of the heat-affected portion by welding to be higher or lower than the tempered (target) hardness. Therefore, the mold steel described in Patent Document 1 also has excellent weldability due to its qualified alloy design.

Therefore, in the field of the plastic molding die of the present case, the above properties can be maximized even for the above-mentioned steel for molds having excellent welding properties (that is, the hardness of the welded portion is the mold). It is important to combine it with an optimal weld repair material that can fit within the tempered hardness of the steel. Therefore, the welding material used for repairing molds, etc. has a component composition that is similar to that of molds because there is no difference between the characteristics of the weld and the mold base material. May be used.
JP 2007-146278 A

  Therefore, in the case of a metal mold made of steel of Patent Document 1 proposed by the present applicant, if welding repair is performed with a material having the same component composition in accordance with the above technical idea, cracks during welding are also confirmed. In spite of this, excellent mirror surface was maintained even after mirror finishing after welding. However, when welding extremely fine parts, there were cases where the welds were rapidly solidified and slightly harder than the mold base. Such welds having different hardnesses have a convex pattern, which degrades the surface finish of the molded product. Furthermore, depending on the degree of the hardness difference, there is a concern about unevenness during embossing and non-uniform progression of mold wear as described above, and in particular, high-quality surface finishes such as transparent parts are required. There is room for improvement in the selection of welding materials.

  Therefore, in view of the above-described requirements, an object of the present invention is to provide a welding material having an optimal combination for repair and the like, limited to the mold made of Patent Document 1 proposed by the present applicant. Specifically, while maintaining the performance of the mold, it has excellent mirror finish even after welding, and also can suppress unevenness during embossing and uneven wear during molding, It is providing the welding material which can make the hardness of a part and the hardness of a metal mold | die base material equivalent.

  First, the present inventor made concrete the component composition to be welded repair object of the present invention as the mold (steel) proposed in Patent Document 1. And about this metal mold | die, the composition of the welding material and the relationship between the structure and hardness after welding were examined in detail. As a result, the welding material is designed to reduce the cracking susceptibility by regulating the amount of S and to improve the flowability of the molten metal by optimizing the amount of Si. It has been found that the reduction of the amount of Cu is important for reducing the sensitivity of all cracks. In addition to this, the inventors have found that fine adjustment to reduce the content of other elements slightly from that of the mold is effective, and have reached the present invention.

  That is, this invention is mass%, C: 0.10-0.25%, Si: 1.00% or less, Mn: 2.00% or less, Ni: 0.60-1.50%, Cr: More than 1.00% and not more than 2.50%, Mo and W are single or composite, Mo + 1 / 2W: 0.10 to 1.00%, V: 0.03 to 0.15%, Cu: 0.50 2.00%, S: 0.007 to 0.05%, the balance is a welding material for repairing a mold made of steel of Fe and unavoidable impurities, the component composition of the welding material is mass% , C: 0.07 to 0.25%, Si: 0.40 to 1.00%, Mn: 2.00% or less, Ni: 0.40 to 1.50%, Cr: more than 0.80% 2. 50% or less, Mo and W alone or in combination, Mo + 1 / 2W: 0.08 to 1.00%, V: 0.02 to 0.15%, Cu: 0.0. 0~0.45%, S: 0.005% or less, the balance being welding material for a mold repair characterized by comprising Fe and unavoidable impurities steel.

  And preferably, the working effect of the present invention is maximized by setting the target hardness of the mold to 34 to 45 HRC.

  According to the present invention, conventional welding repairs are strictly prohibited due to the strict quality required for molds, such as molding of transparent resin parts and resins with good transferability, and new molds must be produced at the time of replacement. Even if not obtained, regeneration by welding repair is possible, and it can meet the recent strong demand for cost reduction. Furthermore, since uneven wear during molding is less likely to occur, the life of the mold can be extended by conventional welding.

  As described above, the basic features of the present invention are that the composition of the mold made of Patent Document 1 is the composition of the welding material, in particular, the regulation of the amount of S and the optimization of the amount of Si, and the amount of Cu. By performing the reduction management, various weldability improvements, in particular, the hardness control of the welded portion can be achieved.

  First, the mold that is the object of the welding repair of the present invention will be described. The mold for use in the present invention has already been proposed by the applicant of the present application, and its component composition is “known” as described in Patent Document 1. In other words, the steel for molds of Patent Document 1 has extremely excellent toughness, machinability and hardness, and excellent polishing finish and wear resistance due to its qualified alloy design. It also has weldability. Therefore, in the present invention, it is possible to extend the life of a mold having excellent characteristics by providing an optimum welding material for repairing the known mold.

The component composition of the mold for use in the present invention is as follows in mass%.
C: 0.10 to 0.25%,
Si: 1.00% or less,
Mn: 2.00% or less,
Ni: 0.60 to 1.50%,
Cr: more than 1.00% and 2.50% or less,
Mo and W are single or composite, Mo + 1 / 2W: 0.10 to 1.00%,
V: 0.03-0.15%,
Cu: 0.50 to 2.00%,
S: 0.007 to 0.05%,
The remainder: Fe and inevitable impurities

Hereinafter, the reason for component limitation (mass%) of the welding material for repairing the mold of the present invention will be described.
C is an element that determines basic solidification hardness, including cracking susceptibility of welds. Therefore, with respect to the C amount of the mold (0.10 to 0.25%), 0.07 to 0.00 is necessary to reduce cracking susceptibility of the rapidly solidified weld and to prevent excessive hardening. 25%. Preferably, it is 0.10 to 0.20% with respect to the C amount of the mold 0.13 to 0.20%. It is more desirable that the C amount of the welding material of the present invention is equal to or reduced with respect to the C amount of the mold.

  Si is an important element for the welding material because it improves the flowability of the molten metal and improves the corrosion resistance. In other words, for the Si amount (less than 1.00%) of the mold, the mechanical characteristics are similarly reduced, so that the amount is still 1.00% or less, and adjustment within this range is possible. If the amount is too small, the above effect cannot be obtained. Therefore, Si of the present invention is made 0.40 to 1.00%. Preferably, it is 0.50 to 1.00%.

  Similarly, Mn is an element that adjusts the structure, hardness, etc. with respect to the Mn amount (2.00% or less) of the mold, and can be adjusted within this range as 2.00% or less. It is. Preferably, the Mn content of the mold is 0.80 to 2.00% with respect to 1.00% to 2.00%, more preferably 1.00 to 2.10% with respect to 1.20 to 2.00%. 00%. It is more desirable that the Mn amount of the welding material of the present invention is equal to or reduced with respect to the Mn amount of the mold.

  Ni is 0.40 to 1.50% as an element for adjusting the structure and toughness of the welded portion with respect to the Ni amount of the mold (0.60 to 1.50%). Can be adjusted. Preferably, it is 0.40 to 1.20% with respect to Ni amount 0.60 to 1.20% of the mold. It is more desirable that the amount of Ni in the welding material of the present invention is equal to or reduced with respect to the amount of Ni in the mold.

  Cr is an element that adjusts the main characteristics such as the structure, hardness, and corrosion resistance of the welded portion with respect to the Cr amount of the mold (over 1.00 to 2.50%). 50% and adjustment within this range is possible. Preferably, the amount of Cr in the mold is 1.20 to 2.20% with respect to 1.40 to 2.20%, more preferably 1.40 to 2.20% with respect to 1.60 to 2.00%. 00%. It is more desirable that the Cr amount of the welding material of the present invention is equal to or reduced with respect to the Cr amount of the mold.

  Mo and / or W is equivalent to the Mo equivalent of the mold (from 0.10 to 1.00% in the relationship of Mo + 1 / 2W) as an element for adjusting the hardness and corrosion resistance of the welded portion. And 0.080 to 1.00%, and adjustment within this range is possible. Preferably, it is 0.08 to 0.70% with respect to Mo equivalent of 0.10 to 0.70% of the mold. It is more desirable that the Mo equivalent of the welding material of the present invention is equal to or reduced with respect to the Mo equivalent of the mold.

  V is 0.02% as an element that suppresses the coarsening of crystal grains and adjusts the toughness and wear resistance of the welded portion with respect to the V amount (0.03 to 0.15%) of the mold. It can be adjusted to 0.15% within this range. Preferably, it is 0.03 to 0.12% with respect to the V amount 0.05 to 0.12% of the mold. It is more desirable that the V amount of the welding material of the present invention is equal to or reduced with respect to the V amount of the mold.

  For the welding material of the present invention, Cu has a high effect of increasing the cracking susceptibility of the welded portion and increasing the hardness of the welded portion, and therefore strongly affects the hardness adjustment between the mold base material and the welded portion. It is an important element that affects. Therefore, the Cu content of the welding material needs to be reduced with respect to the Cu content (0.50 to 2.00%) of the mold. And in this invention, it regulates to the quantity which is less than the Cu minimum of 0.45% or less of a metal mold | die. However, if the amount is too small, it approaches a structure (upper bainite) different from the target structure of the mold (lower bainite), and further causes a decrease in corrosion resistance. Preferably it is 0.20% or more.

  S is an element that increases cracking sensitivity. Here, for the mold to be used in the present invention, a certain amount of S is necessary to combine the machinability and the mirror finish, but the welded portion of the present invention has a certain amount of S. Machinability is not required. Therefore, it is necessary to regulate the S amount (0.007 to 0.05%) of the mold because the welding material gives priority to the reduction of crack sensitivity. Therefore, the amount of S of the welding material of the present invention is limited to 0.005% or less and below the lower limit of the mold S. Desirably, it is 0.004% or less.

  In addition, in the mold provided for the present invention, in order to maintain and improve its excellent cold plastic workability, mirror surface workability, machinability and polishability, Al, O (oxygen), It is desirable to regulate N (nitrogen). And it is preferable to regulate similarly also in the welding material of this invention.

Al is usually used as a deoxidizing element at the time of melting. However, in the mold and / or welding material of the present invention, Al ₂ O ₃ present in the steel decreases the mirror surface workability, so that 0 It is preferable to regulate to 10% or less. More preferably, it is 0.05% or less, and 0.01% or less, and further preferably 0.002% or less.

O (oxygen) is an element that forms an oxide in steel, and causes a significant deterioration in cold plastic workability and polishability. Particularly for the mold and / or welding material of the present invention, it is effective to suppress the formation of the above Al ₂ O ₃ , so the upper limit of O is regulated to 0.005%, preferably 0.003%. It is preferable. In order to improve the polishability, it is also desirable to control the regulation to be even lower, for example, 0.001% or less. However, in aiming at reduction of Al ₂ O ₃ , if the above-mentioned Al low amount management is already adopted, in addition to this, the low amount management of the O amount itself is not particularly strictly required. Therefore, it is sufficiently allowed to exceed 0.001%.

  N is an element that forms nitrides in steel. If the nitride is excessively formed, the toughness, machinability and polishability of the mold and welding material are significantly deteriorated. Therefore, it is effective to regulate N in steel to be low, and it is preferable to regulate the N content in the mold and / or welding material of the present invention to 0.06% or less. More preferably, it is 0.02% or less, More preferably, it is 0.005% or less.

  In addition, the welding material of the present invention is similar to the mold, Nb: 0.5% or less (preferably 0.01 to 0.1%), Ti: 0.15% or less, Zr: 0.15% or less, Any one or more of Ta: 0.15% or less can be added.

  Zr: 0.003-0.2%, Ca: 0.0005-0.01%, Pb: 0.03-0.2%, Se: 0.03-0.2%, Te: 0.0. Add one or more of 01 to 0.15%, Bi: 0.01 to 0.2%, In: 0.005 to 0.5%, Ce: 0.01 to 0.1% can do.

  Furthermore, Y, La, Nd, Sm, and other REM elements can be contained in a total amount of 0.0005 to 0.3%.

  If it is the welding material of this invention, the welding part by the use will be easy to adjust especially to the hardness range with respect to the metal mold | die tempered to the hardness of 34-45HRC.

  First, a 15 mm × 100 mm × 100 mm base material having a hardness of 38.6 HRC was prepared as a mold for use in the present invention. As welding materials, a welding rod B (comparative example) of 2.0 mm × 2.0 mm × 300 mmL made from the same material as the base material and a welding rod A (Φ2.5 mm × 300 mmL) made from another material ( An example of the present invention was prepared. The respective components are shown in Table 1.

  Next, as shown in FIG. 1, the base material was subjected to semicircular machining with a radius of 3 mm at two places, and overlay welding by TIG welding using the welding rods A and B was performed on the machining portion. The welding conditions are preheating 250 ° C., afterheating 400 ° C., welding current 80-120 A, and Ar gas flow rate 10 L / min. Then, the excess build-up part is removed by parallel polishing, and the mirror finish is performed by paper → diamond compound method, which is a general mirror finish, and then the overall mirror finish is evaluated and the mother of the mirror finish The Vickers hardness (load: 300 g) of the material part, the heat affected part and the welded part was measured. The evaluation of the specularity is based on a molding mold in the transparent resin field where the required level of specular finish is strict, with a level that does not cause a problem in use being ◯, a usable level being △, and an unusable level being x. This was done in a staged evaluation.

  Moreover, the sample after parallel grinding | polishing was prepared similarly to the above, and after carrying out # 800 paper grinding | polishing, the fine satin finish processing was performed and the texturing workability was evaluated. The evaluation method is based on a molding die in the matte resin field where the required level of embossing is strict, with a level where there is no problem in use as ◯, a usable level as △, and an unusable level as x. It was done by evaluation. The above test results are summarized in Table 2.

  As shown in Table 2, when the welding rod A according to the present invention was used, there was almost no difference in hardness from the base material part to the welded part, and the mirror finish and the textured workability were also good. On the other hand, when the welding rod B was used, the mirror finish and the textured workability were within the allowable ranges, but the hardness of the welded portion was slightly increased. In addition, about the crack of a welding part, the generation | occurrence | production was not confirmed irrespective of which welding rod was used.

  The welding material for repairing the mold according to the present invention is not only a combination with the mold made of Patent Document 1, but also in a field where strict characteristics are required such that the component must be the same or similar to the mold. Otherwise, it can be used as a welding material for other molds.

It is a figure explaining the welding method used in the Example of this invention.

Claims (2)

In mass%, C: 0.10 to 0.25%, Si: 1.00% or less, Mn: 2.00% or less, Ni: 0.60 to 1.50%, Cr: more than 1.00% 2. 50% or less, Mo and W are single or composite, Mo + 1 / 2W: 0.10 to 1.00%, V: 0.03 to 0.15%, Cu: 0.50 to 2.00%, S : 0.007 to 0.05%, the balance is a welding material for repairing a mold made of steel of Fe and inevitable impurities,
The component composition of the welding material is mass%, C: 0.07 to 0.25%, Si: 0.40 to 1.00%, Mn: 2.00% or less, Ni: 0.40 to 1. 50%, Cr: more than 0.80% and not more than 2.50%, Mo and W alone or in combination, Mo + 1 / 2W: 0.08-1.00%, V: 0.02-0.15%, Cu : 0.10 to 0.45%, S: 0.005% or less, the balance being made of Fe and steel of inevitable impurities, a welding material for repairing molds. The mold repair welding material according to claim 1, wherein the mold has a hardness of 34 to 45 HRC.