JP2917468B2 - Plastic molding pre-hardened steel for mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a plastic molded pre-hardened mold steel excellent in mirror finish and texture.

(Prior art) Metal stamping dies are used in the manufacture of various parts, from automobile parts to electric parts that require high precision, but recently there is a tendency to produce many kinds and small quantities. At the same time, strict conditions such as simplification of mold making, cost reduction, and high precision have been required.

Conventionally, various proposals have been made for plastic mold steel, and there is also a proposal for use in a pre-hardened state (see, for example, JP-A-63-1831587).

(Problems to be Solved by the Invention) However, the conventionally proposed steel for plastic molding dies has striped segregation in its structure, has low toughness in proportion to hardness, and has mirror finish and grain finish. It turned out that there was still a problem that sex was not enough.

Therefore, the present invention has been made in view of the above-described situation in the related art. That is, an object of the present invention is to provide a plastic molded pre-hardened mold steel excellent in mirror finish and grain workability.

(Means for Solving the Problems) As a result of the study, the present inventors have found that stripping segregation by reducing the amounts of Si and P in an alloy composition conventionally known as a plastic molding pre-hardened mold steel. It was found that mold steel having a uniform structure was obtained by reducing the occurrence of, and when used as a pre-hardened mold steel, it had excellent mirror finish and texture.
The present invention has been completed.

The first plastic-molded pre-hardened mold steel of the present invention contains C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less, and Mn: 0.5% by weight.
~ 2.0 wt%, P: 0.01 wt% or less, Ni: 2.5 ~ 3.5 wt%,
Mo: 0.1-0.4% by weight, Al: 0.7-1.5% by weight, Cu: 0.7-2.5
% By weight is the basic alloy composition and the balance is Fe.

The basic alloy composition may further contain one or both of the following (1) and (2):

(1) Nb + Ta: 0.3% by weight or less, Ti: 0.5% by weight or less, V: 0.
At least one selected from 5% by weight or less and Zr: 0.5% by weight or less.

(2) Pb: 0.01 to 0.3% by weight, Bi: 0.01 to 0.3% by weight, Se:
At least one selected from 0.01 to 0.4% by weight, Te: 0.01 to 0.3% by weight and S: 0.015% by weight or less.

The second prestic molded pre-hardened mold steel of the present invention comprises: C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less, Mn: 0.5% by weight.
~ 2.0 wt%, P: 0.01 wt% or less, Ni: 2.5 ~ 3.5 wt%,
Mo: 0.1-0.4% by weight, Al: 0.7-1.5% by weight, Cu: 0.7-2.5
%, Cr: 0.1 to 2.5% by weight as a base alloy composition, and further selected from W: 0.5% by weight or less, Co: 0.5% by weight or less, Be: 0.5% by weight or less, and B: 0.01% by weight or less At least one kind is composed of the balance Fe.

The basic alloy composition may further contain one or both of the above (1) and (2).

Next, the composition range of the alloy composition in the present invention and the reasons for limitation will be described.

C: 0.05 to 0.18% by weight: C keeps the quenched structure in a massive upper bainite structure with good machinability, and provides a precipitation effect based on the precipitation of carbide in tempering. On the other hand, when added excessively, the matrix forms a martensite structure, and excessive carbides are formed, thereby impairing machinability and reducing toughness after pre-hardening. Therefore, it is necessary to limit to the above range.

Si: 0.1% by weight or less: Since Si can reduce the occurrence of stripe-like segregation and reduce the size of carbides by lowering its amount, It must be set to less than weight%.

Mn: 0.5 to 2.0% by weight: When performing pre-hardening treatment, it is necessary to perform quenching cooling by air cooling in order to minimize bending during quenching of steel materials. Therefore, 0.5% by weight or more is added. However, if added in an excessively large amount, the workability is impaired.
It must be set to 2.0% by weight.

P: 0.01% by weight or less: P also has the effect of reducing the occurrence of stripe-like segregation by lowering its amount. Therefore, in order to produce this effect, P needs to be 0.01% by weight or less.

Ni: 2.5 to 3.5% by weight: Ni enhances the hardenability of bainite, suppresses the formation of ferrite, and precipitates a Ni-Al intermetallic compound during tempering to increase the hardness. However, if the amount is too large, the bainite transformation temperature is lowered, the bainite structure is refined, and the machinability is reduced.

Mo: 0.1 to 0.40% by weight: Mo is an element necessary for improving toughness, and a small amount of Mo
Is added in an amount of 0.1% by weight or more in order to ensure the action because a uniform microstructure is produced. However, 0.40
If the content is more than 10% by weight, the hardness increases and the machinability deteriorates, which is not preferable as plastic mold steel.

Al: 0.7 to 1.5% by weight: Al raises the bainite transformation temperature to facilitate obtaining a desired massive upper bainite structure, and causes precipitation hardening due to fine precipitation of the Ni-Al intermetallic compound during tempering. However, if the amount is too large, the production of alumina-based inclusions increases, impairing the manufacturability, and also impairing the mirror surface finish and corrosion resistance,
Set within the above range.

Cu: 0.7 to 2.5% by weight: Cu brings about precipitation hardening due to fine precipitation of the Fe-Cu intermetallic compound in the tempering treatment and is an element indispensable to bring about excellent machinability. 0.7% by weight. However, if the amount is too large, the hot workability is reduced, the bainite is refined, and the machinability is impaired. Therefore, it is necessary to set the upper limit to 2.5% by weight.

Cr: 0.1-2.5% by weight: Cr is an effective element for improving corrosion resistance,
It is added depending on the purpose and application, but if the amount is too large, the bainite structure is refined and the machinability is impaired.
Use the above ranges.

W: at least one selected from 0.5% by weight or less, Co: 0.5% by weight or less, Be: 0.5% by weight or less, and B: 0.01% by weight or less: When used in a large mold, its toughness and firing It is effective to appropriately add one or more elements in the above-mentioned range, which are necessary for the re-selection of the accessibility. By adding these components, it is possible to adjust the emulsified hardness and aging hardness, but adding more than necessary increases the price of the material,
The upper limit is set to the above value.

At least one selected from Nb + Ta: 0.3% by weight or less, Ti: 0.5% by weight or less, V: 0.5% by weight or less and Zr: 0.5% by weight or less: These alloy components are refined in grain size and toughened. In addition to being effective in improving notch toughness, addition of a large amount increases aging hardness and solution hardening more than necessary.

Pb: 0.01-0.3% by weight, Bi: 0.01-0.3% by weight, Se: 0.01-
0.4% by weight, at least one element selected from Te: 0.01 to 0.3% by weight and S: 0.015% by weight or less: These elements have an effect of remarkably improving machinability, but when added in an excessively large amount, Since the toughness is impaired, it is appropriately contained in the above range.

The plastic molded pre-hardened mold steel of the present invention,
Supplied after quenching and tempering. The quenching and tempering treatment is performed, for example, by heating to 800 to 950 ° C., quenching by air cooling, and then heating to 500 to 600 ° C. and tempering by air cooling. Of the present invention, quenching, the state which has been subjected to tempering treatment Purehadon work die steel, hardness: HRC35～40, tensile strength: a 130~150kgf / mm ^2, also is in the narrow range microhardness distribution . The hardness HRC is preferably higher, but HRC
If the HRC exceeds 40, machining becomes difficult and problems occur in the machined surface. Therefore, it is desirable to perform quenching and tempering so that the HRC does not exceed 40.

Hereinafter, the present invention will be described with reference to examples.

Test materials were prepared using plastic-molded pre-hardened mold steel consisting of the elemental composition and the balance Fe shown in Table 1 below.

These were further quenched and tempered to obtain a pressed die steel sheet having a predetermined hardness. Using these press die steel sheets, micro hardness distribution (HV max to HV m
in) Mirror finish and grain workability were evaluated. Also, mechanical properties (tensile strength, elongation, drawing, Charpy impact value)
Was examined. Further, a mold was prepared and its service life was measured. Table 2 shows the results.

(Effect of the Invention) The plastic molding prehardened mold steel of the present invention
Since it has an alloy composition in which the contents of Si and P are reduced as described above, the occurrence of striped segregation in conventional plastic molded prehardened mold steel is reduced, and a homogeneous structure having high toughness is obtained. Therefore, the plastic molded pre-hardened steel of the present invention has excellent mirror finish and grain workability.

Claims (8)

(57) [Claims] C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less,
Mn: 0.5 to 2.0% by weight, P: 0.01% by weight or less, Ni: 2.5 to 3.5% by weight, Mo: 0.1 to 0.4% by weight, Al: 0.7 to 1.5% by weight, Cu: 0.7
Pre-hardened plastic mold steel, characterized in that the steel consists of about 2.5% by weight and the balance Fe. 2. C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less,
Mn: 0.5 to 2.0% by weight, P: 0.01% by weight or less, Ni: 2.5 to 3.5% by weight, Mo: 0.1 to 0.4% by weight, Al: 0.7 to 1.5% by weight, Cu: 0.7
Up to 2.5% by weight as a basic alloy component, and further, Nb + Ta: 0.3% by weight or less, Ti: 0.5% by weight or less, V: 0.5% by weight or less and Z
r: A plastic molded prehardened mold steel containing at least one selected from 0.5% by weight or less and the balance being Fe. 3. C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less,
Mn: 0.5 to 2.0% by weight, P: 0.01% by weight or less, Ni: 2.5 to 3.5% by weight, Mo: 0.1 to 0.4% by weight, Al: 0.7 to 1.5% by weight, Cu: 0.7
~ 2.5% by weight as a basic alloy component, and Pb: 0.01 ~ 0.3
Wt%, Bi: 0.01-0.3 wt%, Se: 0.01-0.4 wt%, T
e: A plastic molded prehardened mold steel containing at least one selected from the group consisting of 0.01 to 0.3% by weight and S: 0.015% by weight or less, with the balance being Fe. 4. C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less,
Mn: 0.5 to 2.0% by weight, P: 0.01% by weight or less, Ni: 2.5 to 3.5% by weight, Mo: 0.1 to 0.4% by weight, Al: 0.7 to 1.5% by weight, Cu: 0.7
Up to 2.5% by weight as a basic alloy component, and further, Nb + Ta: 0.3% by weight or less, Ti: 0.5% by weight or less, V: 0.5% by weight or less and Z
r: at least one selected from 0.5% by weight or less, Pb: 0.01 to 0.3% by weight, Bi: 0.01 to 0.3% by weight, Se: 0.0
1 to 0.4% by weight, Te: 0.01 to 0.3% by weight and S: 0.015% by weight or less.
A plastic molded pre-hardened steel for molds. 5. C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less,
Mn: 0.5 to 2.0% by weight, P: 0.01% by weight or less, Ni: 2.5 to 3.5% by weight, Mo: 0.1 to 0.4% by weight, Al: 0.7 to 1.5% by weight, Cu: 0.7
~ 2.5% by weight, Cr: 0.1 ~ 2.5% by weight as the base alloy component,
Further, it is characterized by containing at least one selected from W: 0.5% by weight or less, Co: 0.5% by weight or less, Be: 0.5% by weight or less, and B: 0.01% by weight or less, with the balance being Fe. Plastic molded pre-hardened mold steel. 6. C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less,
Mn: 0.5 to 2.0% by weight, P: 0.01% by weight or less, Ni: 2.5 to 3.5% by weight, Mo: 0.1 to 0.4% by weight, Al: 0.7 to 1.5% by weight, Cu: 0.7
~ 2.5% by weight, Cr: 0.1 ~ 2.5% by weight as the base alloy component,
Further, at least one selected from W: 0.5% by weight or less, Co: 0.5% by weight or less, Be: 0.5% by weight or less, and B: 0.01% by weight or less, and Nb + Ta: 0.3% by weight or less, Ti: 0.5% by weight %, At least one selected from the group consisting of V: 0.5% by weight and Zr: 0.5% by weight and a balance of Fe. 7. C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less,
Mn: 0.5 to 2.0% by weight, P: 0.01% by weight or less, Ni: 2.5 to 3.5% by weight, Mo: 0.1 to 0.4% by weight, Al: 0.7 to 1.5% by weight, Cu: 0.7
~ 2.5% by weight, Cr: 0.1 ~ 2.5% by weight as the base alloy component,
Furthermore, at least one selected from W: 0.5% by weight or less, Co: 0.5% by weight or less, Be: 0.5% by weight or less and B: 0.01% by weight or less, Pb: 0.01 to 0.3% by weight, Bi: 0.01% ~ 0.3
A pre-hardened plastic molding die containing at least one selected from the group consisting of 0.01% to 0.4% by weight, Se: 0.01 to 0.4% by weight, Se: 0.01 to 0.3% by weight and S: 0.015% by weight or less, with the balance being Fe. For steel. 8. C: 0.05 to 0.18% by weight, Si: 0.1% by weight or less,
Mn: 0.5 to 2.0% by weight, P: 0.01% by weight or less, Ni: 2.5 to 3.5% by weight, Mo: 0.1 to 0.4% by weight, Al: 0.7 to 1.5% by weight, Cu: 0.7
~ 2.5% by weight, Cr: 0.1 ~ 2.5% by weight as the base alloy component,
Furthermore, at least one selected from W: 0.5% by weight or less, Co: 0.5% by weight or less, Be: 0.5% by weight or less, B: 0.01% by weight or less, Nb + Ta: 0.3% by weight or less, Ti: 0.5% by weight Hereinafter, V: at least one selected from 0.5% by weight or less and Zr: 0.5% by weight or less, and Pb: 0.01 to 0.3% by weight,
Bi: 0.01-0.3% by weight, Se: 0.01-0.4% by weight, Te: 0.01-
A plastic molded prehardened mold steel containing at least one selected from the group consisting of 0.3% by weight and S: 0.015% by weight or less, with the balance being Fe.