JPS63145751A - Maraging steel having excellent mirror finishing - Google Patents

Abstract

PURPOSE:To obtain a maraging steel having excellent mirror finishing, by specifying the comps. of steel contg. Ti and in which the content of C, S, N and O to combine with Ti is restricted. CONSTITUTION:The maraging steel contains, by weight, <=0.0020% C, <=0.05% Si, <=0.05% Mn, <=0.005% P, <=0.0020% S, 3-13% Ni, 0.1-2.0% Ti, 9-15% Cr, <=0.0020% N and <=0.0020% O, satisfies the conditional formula of C+S+N+O<=0.0050, and further contains at need one or more kinds from Co+Mo or Al among 5-16% Co, 2-10% Mo and 0.04-0.4% Al, and the balance consists of Fe with inevitable impurities. Said steel has the excellent mirror finishing and is suitable for a material such as a metallic mold for injection molding.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to maraging steel with excellent mirror finish.
It is used in fields such as plastic injection molds and compact desk mirrors that require an excellent mirror finish.

[Conventional technology]

Excellent mirror finish is required for injection molds for plastic lenses and steel for mirror plates for compact discs. Factors that control mirror finish include scratches from machining before mirror finishing and scratches during final polishing.

Rust formation, cleanliness of mold material, hardness of mold, etc. are listed.

In general, maraging steel has the highest hardness among metal materials and relatively excellent cleanliness, and is often used as molds for plastic lenses and compact discs such as those mentioned above.However, in order to maintain its excellent specularity, Furthermore, it must also have excellent corrosion resistance. Stainless steel maraging steel containing approximately 9% or more of Cr is generally known as a maraging steel with improved corrosion resistance.

Maraging steel usually uses special refining processes such as vacuum melting ffK or remelting to take advantage of its excellent strength, and removes impurity elements and inclusions (such as Mn and S).
Excellent cleanliness can be obtained because the amount of oxides such as i, oxides such as Al, sulfides, etc.) is limited to extremely low values.

It is.

As a conventional technique, for example, Japanese Patent Application Laid-Open No. 49-9465 describes defects such as pinholes and non-metallic inclusions in maraging steel.
A technique has been proposed to improve specularity by making the thickness smaller than μm. As stated in the Mei JIB document, this technology aims to reduce the amount of pinholes and non-metallic inclusions by sufficiently performing deoxidation treatment, and is intended to reduce the amount of oxide-based inclusions. This is what happened.

However, maraging steel usually has Ti added to it to ensure strength. Ti is C, S, N, O
Strong affinity with etc. (TiC, TiS+TiN, Tie,
This results in compounds that are extremely hard to matrices such as

As for the cleanliness of conventional maraging steel.

Compounds of Ti, which is such a strength-increasing element, were not targeted. Therefore, even maraging steel, which is said to have a high level of cleanliness, has traditionally contained a considerable amount of Ti-based compounds.

However, due to recent advances in machining and polishing technology, as well as improvements in the performance of compact discs, lenses, etc., molds are now required to have a mirror finish that is even higher than before. The inventors have revealed that Ti-based compounds also pose a problem.

[Problem that the invention seeks to solve]

The purpose of the present invention is to solve the problems of the prior art described above, and to
In maraging steel containing.

To clarify the relationship between the content of C, S, N, and 0 that combine with Ti to form compounds, the amount of nonmetallic inclusions, and mirror finish properties, and to provide a maraging steel with excellent mirror finish properties. be.

[Means and effects for solving the problems] The above objects of the present invention are achieved by the following two inventions.

The gist of the first invention is as follows.

That is, 1 layer) Accent ratio C: 0.0020% or less Si: 0.05% or less Mn: 0.05% or less p: o, oos% or less S: 0.0020% or less NL: 3 to 1; 3 % Tj: 0.1-2.0% Cr: 9-15% N: 0.0020% or less 0: Contains 0.0020% or less, and satisfies the conditional expression of C+S+N+O≦0.0050, and the remainder is It is a maraging steel with excellent mirror finish, characterized by being composed of Fe and unavoidable impurities.

The gist of the second invention is that, in addition to the same basic components as the first invention, Co: 5-16% Mo: 2-10% Al: 0.04-0.4% 1 of C o + M o or Al
It is a maraging steel with excellent mirror finish properties, which is characterized by containing at least 100% of Fe and the remainder consisting of Fe and unavoidable impurities.

The present inventors have discovered that in maraging steel containing Ti, Tic, TiS, TiN, and TiOz inhibit mirror finish as nonmetallic inclusions, and appropriate C2S to obtain excellent mirror finish has been found. , N, 0 h: · was considered. I will explain the basic test.

Si: 0.02%, Mn: 0.01%, P: 0.0
02%, Ni: 8.2%, Cr: 11.3%, Co: 6
．． 0%, Mo: 2.2%, Ti: 1.0%, Al: 0
．． 0.6% and C, S, N, and O as shown in Table 1. After J, hot working at 1200℃ and 20m
Made of thick steel plate. This steel plate was solution-treated at 860°C,
After aging at 490°C, it was polished in the process shown in FIG. That is, rough machining is performed with a milling machine, then surface grinding is performed until the maximum surface roughness height Rmax is less than 2 μm, followed by polishing with emery #1500, and finally diamond #2000.
Final polishing was performed at 0. After polishing, the surface roughness was determined to be 4 (4), and the results are shown in Table 1. The relationship between the total of 11 of C + S + N + O in Table 1 and the surface roughness is shown in Figure 2. In Fig. 2, the symbol O indicates that the content of each of C, S, N, and O is 20 ρρm or less, and the symbol Δ indicates that one or more of the components exceeds 20 ppm.

Incidentally, it is generally known that the mirror finish is caused by the unevenness of the surface, and that its superiority or inferiority can be evaluated based on the surface roughness.

From FIG. 2, it can be seen that excellent surface roughness is obtained and excellent mirror finish is obtained only when the total amount of C+S+N+O is 50 ppm or less and the amounts of C, S, N, and O are each 20 ρρm or less. Therefore, in the present invention, C, S
, N, and O are each 0.0020% or less and the total is 0.0020% or less.
It was limited to 0.050% or less.

Next, the reasons for limiting other components are as follows.

Sj, Mn, P: Table 1 Sj, Mn, P reduce the toughness of maraging steel, so they are 0.05%, 0.05%, o, and oos%, respectively.
Limited to the following.

Ni: Ni is an element necessary to form a martensitic matrix with excellent toughness in stainless-type maraging steel, and for this purpose 3% or more is required.
%, the Ms point decreases and the austenite phase is stabilized, so Nj was set in the range of 3 to 13%.

Ti: Ti is an essential element that contributes to precipitation hardening due to aging treatment in stainless steel maraging steel, and is necessary to obtain high hardness as mold steel. For this purpose, Tj is required to be 0.1% or more, and on the other hand, if it exceeds 2.0%, it causes embrittlement, so Tj is set in the range of 0.1 to 2.0%.

Cr: C is an essential element for improving corrosion resistance, and for this purpose, 9% or more is required, but since exceeding 15% inhibits toughness, it is limited to a range of 9 to 15%.

The above Ce b l + Mn, P e S + N 1
．． Although each limited amount of Tx, Cr, and N HO is the basic component of the present invention, the object of the present invention can be more effectively achieved if it further contains a limited amount of one or more selected from Co + Mo or Al. can be achieved. The reason for its addition and limitation is as follows.

CO: Co is an effective element for reducing the solid solubility of MO, promoting precipitation of Ni, Mo, etc., and further increasing hardness. Since this causes embrittlement, the content of CO was set in the range of 5 to 16%.

Mo: Mo is an element that contributes to precipitation strengthening and further increases hardness, and for this purpose, 2% or more is required.

Since MO content exceeds 10%, it causes embrittlement, so MO was limited to a range of 2 to 10%.

AI = Al is an element that contributes to precipitation hardening and is effective in further increasing hardness, and for this purpose it needs to be 0.04% or more, but if it exceeds 0.4%, it will cause embrittlement, so Al is 0.0
The range was 4% to 0.4%.

Note that in addition to the above-mentioned components, the present invention may also contain Zr and B as necessary.
, Cu, Nb, etc., do not cause any adverse effects.

In addition, the steel of the present invention is subjected to vacuum oxygen decarburization (VOD) after preliminary refining and dephosphorization using an electric furnace or a converter, for example.
to reduce C and N, and then remelt in vacuum (MAR).
It can be manufactured by a process of removing gas components such as oxygen.

〔Example〕

After vacuum melting the steel whose components are shown in Table 2, it was hot rolled into a 20IIWl thick steel plate, and heat treated under the conditions shown in Table 2,
As in the case of the basic experiment, polishing was performed in the process shown in FIG. 1, and the hardness and surface roughness were measured, and the results are also shown in Table 2.

In Table 2, it is clear that the steel of the present invention has a much superior surface roughness Jσ compared to the conventional steel that does not satisfy the conditions of the present invention, and has excellent mirror finish. be.

〔Effect of the invention〕

As is clear from the above examples, the present invention makes it possible to produce a maraging steel with excellent mirror finish by limiting the components of the Ti-containing maraging steel, particularly to the contents of C, S, N, and 0. By providing a mold with excellent mirror finish, it is expected that the performance of molded products such as plastic lenses and compact discs will be improved.

[Brief explanation of the drawing]

Figure 1 shows surface polishing process Ri Y in basic experiments. FIG. 2 is a relationship diagram showing the relationship between the total amount of C+S+N+O and surface roughness of a steel plate. Agent Patent Attorney Takeo Nakaji 1 Figure 0 20 40 60 80
+O0C+S+N+O(ppm)

Claims (2)

[Claims] (1) Weight ratio C: 0.0020% or less Si: 0.05% or less Mn: 0.05% or less P: 0.005% or less S: 0.0020% or less Ni: 3 to 13% Ti: Contains 0.1 to 2.0% Cr: 9 to 15% N: 0.0020% or less O: 0.0020% or less, and satisfies the conditional expression C+S+N+O≦0.0050, with the remainder being Fe and unavoidable A maraging steel with an excellent mirror finish, characterized by its composition of impurities. (2) Weight ratio C: 0.0020% or less Si: 0.05% or less Mn: 0.05% or less P: 0.005% or less S: 0.0020% or less Ni: 3 to 13% Ti: Contains 0.1 to 2.0% Cr: 9 to 15% N: 0.0020% or less O: 0.0020% or less, and satisfies the conditional expression of C+S+N+O≦0.0050, and further Co: 5 to 16% Mo: 2 to 10% Al: 0.04 to 0.4% A mirror surface characterized by containing one or more of Co+Mo or Al selected from 0.04 to 0.4%, with the remainder consisting of Fe and inevitable impurities. Maraging steel with excellent finish.