KR100412643B1 - Cast alloy steel for a press mould - Google Patents

Abstract

Disclosed is a cast alloy steel for a press die. The disclosed cast alloy steels for press dies include C; 1.40 to 1.50 wt%, Si; 0.4-0.6 wt%, Mn; Up to 0.6 wt%, P; Up to 0.03 wt%, S; Up to 0.03 wt%, Cr; 11.0 to 12.0 wt%, Mo; 0.8 to 1.2 wt%, W; 0.4-0.6 wt%, and V; It is characterized by containing 0.07-0.15 wt%, remainder Fe, and other unavoidable impurities. According to the present invention, the processing time is short and the machinability is excellent.

Description

Casting Alloy Steel for Press Molds {CAST ALLOY STEEL FOR A PRESS MOULD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cast alloy steel for press dies, and more particularly, to cast alloy steel for press dies with improved workability and improved castability.

In general, SKD forging alloy is used as a tool steel for die and cutting. The SKD single alloy contains about 13% Cr and is widely used as a precision mold material, but it is difficult to apply in terms of cost to be used as a plastic mold or a structural steel for cutting.

In particular, in the case of a mold and a tool steel, there is a big economic loss such as the loss of materials and processing costs due to the purchase of a forged alloy.

One example of such a single alloy is shown in Tables 1 and 2 below. Here, Table 1 and Table 2 show the components and mechanical properties of the SKD11 single alloy.

C Si Mn P S Cr Mo W V Fe 1.40-1.60 0.40max 0.60max 0.03max 0.03max 11-13 0.80 to 1.20 0.20 to 0.50 Balance

Tensile Strength (Kg / ㎡) Material Hardness (HB) Heat treatment (Q.T) 241 and below HRc62min

By the way, in order to manufacture a mold using such a conventional single-component alloy for press mold, it is used by processing each material. As a result, the machining amount is increased, and the machining time is increased, which causes cost increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a cast alloy steel for a press die in which workability is improved and casting property is improved to reduce cost.

1 is a comparison table of the component analysis results of the cast alloy steel for press dies according to the present invention.

Casting alloy steel for press mold of the present invention for achieving the above object is C; 1.40 to 1.50 wt%, Si; 0.4-0.6 wt%, Mn; Up to 0.6 wt%, P; Up to 0.03 wt%, S; Up to 0.03 wt%, Cr; 11.0 to 12.0 wt%, Mo; 0.8 to 1.2 wt%, W; 0.4-0.6 wt%, and V; It is characterized by containing 0.07-0.15 wt%, remainder Fe, and other unavoidable impurities.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Casting alloy steel for press dies according to the present invention, C; 1.40 to 1.50 wt%, Si; 0.4-0.6 wt%, Mn; Up to 0.6 wt%, P; Up to 0.03 wt%, S; Up to 0.03 wt%, Cr; 11.0 to 12.0 wt%, Mo; 0.8 to 1.2 wt%, W; 0.4-0.6 wt%, and V; 0.07 to 0.15 wt%, remainder Fe, and other unavoidable impurities.

This is summarized in Table 3 below.

C Si Mn P S Cr Mo W V Fe 1.4 to 1.5 0.4 to 0.6 0.6max 0.03max 0.03max 11.0 to 12.0 0.8 to 1.2 0.4 to 0.6 0.07 to 0.15 Balance

And the mechanical properties of the cast alloy steel for a press die according to the present invention constituting such a component is shown in Table 4 below.

Tensile Strength (Kg / ㎡) Material Hardness (HB) Heat treatment (Q.T) 700 or more 200-240 HRc62 ~ 64

In view of the material hardness and hardness after quenching / tempering (QT) of Table 4, the cast alloy steel for a press die according to the present invention has the same mechanical properties as the forging (SKD11), and of course, Casting is possible accordingly.

And the forging (SKD11) performs only the vacuum heat treatment, while the cast alloy steel for press mold according to the present invention, as well as the vacuum heat treatment can be flame treatment.

In addition, heat treatment after the 8 hours at 900 ℃ to facilitate the machining, the furnace has the mechanical properties as shown in Table 4.

In addition, the cast alloy steel for a press die according to the present invention is a material used as insert steel (Insert Steel) in the process of forming a steel sheet, and has excellent vacuum heat treatment, and after the heat treatment, ion nitriding and PVD (TiN, CrN) coating It is a material developed for the purpose of which the hardness is required HB 210 ~ 240 before the heat treatment, and HRC 62 ~ 64 after the heat treatment. The material is characterized by the addition of tungsten (W) as the steel sheet becomes high strength and the mold is less sensitive to temperature and requires abrasion resistance. Since the process was developed and the components were adjusted to enable casting, the amount of processing was reduced by more than 30%. When developing such materials, the experimental method was tested in various ways to minimize problems in actual use while changing each component. Referring to FIG. 1, the test method was divided into A1 to A4 in large categories, and the test was classified into three types while changing components in detail. The total experiments were carried out in 12 methods, and each specimen was tested for workability, heat treatment, weldability, and abrasion resistance to obtain Table 3 as described above for the final alloy design. Is 700 Mpa, the material hardness before the heat treatment is HB 200 ~ 240, after the heat treatment was heat treated to HRC 62 ~ 64, the components shown in Table 3 are required to meet the conditions of Table 4 and to meet the practical use. The amount of C (carbon) determines the strength during heat treatment of the material, and the required strength (700 Mpa) can be easily obtained when the amount of carbon becomes 1.4 ~ 1.5wt% during the heat treatment. When the amount of carbon increases, cracks are likely to occur after the heat treatment. Therefore, the upper and lower limits of the amount of carbon are strictly defined. Increasing the amount of Si improves castability and enhances the deoxidation effect, but if the amount is too large, the impact value and workability may be reduced. In addition, cracks are easily generated during welding, making preheating and postheating conditions too difficult. Therefore, the amount of Si was lowered to 0.40 to 0.60 wt%, and Mn has the effect of increasing the hardenability and combining with S to improve the machinability. However, the amount of Mn was limited to 0.6 wt% or less because the addition of much Cr improved the wear resistance when using the high strength steel sheet. Therefore, cracks are also reduced during welding. In addition, P and S are brittle because they cause brittleness when they are added in a large amount. Cr and V are carbide forming elements, which increase the wear resistance of the mold. Ingredient. Since V is expensive, more Cr was added with similar properties. And V is a grain refinement element up to 0.25wt% to improve the hardenability and increase the toughness. When it exceeds 0.3 wt%, the upper and lower limits are set as shown in Table 3 because the hardenability can be reduced.W is an element that improves high temperature hardness. To prevent it. By adding ingredients that are not present in existing SKD11, wear resistance can be improved at high temperature. The upper and lower limits of the components were added and tested as the components of the remarks not shown in Fig. 1, and after 12 experiments, the final upper and lower limits were determined. When each component shows too much difference, the desired physical properties cannot be obtained properly, and problems occur during welding and heat treatment. Therefore, the results are determined as shown in Table 3. The meaning of FIG. 1 is four times (A1 to A4). It means that each component was cast during the experiment. In test A1, test 1, test 2, and test 3 change the existing standard components and add test 1 by adding additional elements (Ni, Nb, Cu, W), and test 2 determines the amount of Si, Mn, Cr, and Mo. Means to test by changing In addition, test 3 is a case in which the amount of Si is lowered and other components are changed slightly than test 2, and the specimen is made. The total test is 12 kinds, and the optimum solution is derived by testing the weldability, heat treatment, and abrasion resistance according to the components. Mo, V, Ni, and Nb as a reinforcing element to improve the hardenability, to refine the grains and to suppress grain coarsening in the present invention, these alloying elements were added as shown in Table 3.

In addition, in the description of the experiment, as shown in the component analysis results of the cast alloy steel for the press die according to the present invention of Figure 1, the non-hardened layer structure of the annealing state in the four alloys were almost similar, but the spheroidized carbide together with pearlite In the case of hardened layer, A1, A2, A3 alloy showed uniform martensite structure, but A4 alloy had coarse structure of coarse pearlite and martensite structure.

In comparison, the non-hardened layer of the single alloy (SKD11) was composed of spheroidized pearlite and coarse carbide (Cr carbide), and the hardened layer was composed of martensite matrix and carbide.

In the macrostructure analysis, the entire specimens were observed by etching the marks to analyze the overall structure and defects of the entire flame-hardened specimens. Flame-heat-treated specimens were mirror-polished with corrosion solution (50mlHCl + 50mlH2O2) for at least 30 minutes, and then the surface layer was descaled to remove antioxidant (WD-40) to prevent oxidation. After sprinkling, the distribution of the overall defects, structures, and dendritic structures was observed, and the cured layer depth was measured from the change of the overall color in macro etching.

This cured layer depth was measured directly on the specimen at 1 cm intervals to determine the cured layer depth as the average depth of the cured layer. The mark etched specimen showed good dendritic structure in the developed cast steel specimen, and the hardened part appeared black after the macro etch.

Here, the single alloy (SKD11) compared with the present invention was found to have a deep hardened layer as a whole. The main alloy according to the present invention dissolved well without major defects as a whole. In addition, the single compound (SKD11) showed a uniform structure without the dendritic structure, the dendritic structure was well developed in the main alloy according to the present invention.

Therefore, in the case of cast specimens, segregation between dendrite and dendritic phase in the specimen can be predicted, so that if the flame temperature is not sufficient during flame heat treatment, the dendritic region with low carbon content does not form uniform austenite but is cooled to give a uniform martensite structure. I don't think I can get it.

On the other hand, in the case of the main alloy, it is thought that sufficient temperature should be maintained in order to obtain a uniform austenite structure during flame heat treatment in consideration of segregation.

As described above, the cast alloy steel for a press die according to the present invention has the following effects.

It is possible to cast according to the shape, so the processing time is short, the machinability is excellent, and the mechanical property (characteristic) is excellent like the forging product.

Vacuum heat treatment and flame heat treatment are available for improved heat treatment.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (1)

C; 1.40 to 1.50 wt%, Si; 0.4-0.6 wt%, Mn; Up to 0.6 wt%, P; Up to 0.03 wt%, S; Up to 0.03 wt%, Cr; 11.0 to 12.0 wt%, Mo; 0.8 to 1.2 wt%, W; 0.4-0.6 wt%, and V; A cast alloy steel for a press die comprising 0.07 to 0.15 wt%, balance Fe and other unavoidable impurities.