JPS60194045A - Ejector pin for plastic - Google Patents

Abstract

PURPOSE:To provide the titled ejector pin having good toughness and wear resistance by subjecting a bar material which consists of a steel having the specific compsn. consisting of C, Si, Mn, Ni, Mo, Al, Ti, Co and iron and is subjected to a soln. heat treatment to a nitriding treatment at an adequate temp. after forming. CONSTITUTION:A softened bar material which is made of the steel consisting of <=0.03wt% C, <=0.20% Si, <=0.20% Mn, 15.0-20.0% Ni, 2.9-5.0% Mo, 0.02- 0.25% Al, 1.25-2.0% Ti, 2.1-4.0% Co and the balance iron and impurities and is subjected to a soln. heat treatment is worked to a prescribed shape by machining, etc. The formed article is thereafter subjected to a nitriding treatment at about 470 deg.C to harden the surface and at the same time to induce age hardening in the inride. The plastic ejector pin having excellent resistance to wear and seizure and good toughness is thus obtd. The expansion by the nitriding treatment is negated by shrinkage owing to the age hardening by which the dimensional change is substantially eliminated. The dimensional accuracy in the diameter of the small-diameter pin for a precision plastic die is thus easily improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a small diameter extrusion pin of φθq to φ2θ for precision plastic molds.

Conventionally, as extrusion pins for plastics, generally 8 to 8
．． 2/, SKD/, etc., which are quenched and tempered to a hardness of around HRC60, and medium carbon steel 8
KDA/ is used after being quenched and tempered and then nitrided. However, 8KS 2 /, S
KD// has low toughness and cannot be used in bottles with a smaller diameter than a φ2θ sieve as it may cause breakage. In addition, 8KD 6/ is HR O 4 3; after tempering to around 5θθ~5
Although it is used after being nitrided at 70°C, the dimensional accuracy of the diameter of the small diameter pin is limited (θ, -θ) to avoid expansion due to nitriding.
It is difficult to increase θθj Mn), and the toughness is also slightly insufficient.

The present invention was made in view of these problems, and
The object of the present invention is to provide an extruded pin which has excellent toughness and wear resistance compared to conventional extruded pins, and can be used as an extremely thin extruded pin with a diameter of φθq to φ2θ.

That is, the present invention has a weight percentage of 0003% or less, 8iθ
Below θ, MnO,, below 2θ, Nil! ;, 0
~260%, -Mo, Zri~, 5:0%, Bθθ, 2~
4.2! %, Ti/, Jj--! , θchi, Oo2/ ~
After processing a solution-treated steel bar consisting of IAθchi, balance iron and impurities into a specified shape, it is nitrided at a temperature of around 70°C for 4 tons, and at the same time the surface is hardened and the interior is aged. It is hardened and has very good toughness, as well as excellent wear resistance and seizure resistance. In addition, the extruded pin of the present invention has the characteristic that the expansion caused by nitriding treatment is canceled out by the contraction caused by age hardening, so there is no dimensional change at all, and it is easy to improve the dimensional accuracy of the diameter of the small diameter bottle. It also has

Next, the reasons for limiting the composition of the extrusion pin according to the present invention will be described.

Since C impairs the toughness of low carbon martensite, 603
% or less. Although Si and Mn have a deoxidizing effect, if the content exceeds 0.2%, the toughness decreases, so the content of each of them was set to θλ or less. Ni is necessary to create a martensitic structure and to stabilize martensite up to the aging temperature, but if it is less than /iθ, it has no effect, and if it exceeds -θ, it will form retained austenite. Since there is a hail, I decided to set /ma θ to 2θθ. On is Mo
1.2. lts
If it is less than 2.7, there will be no effect, and even if it exceeds 2.7, there will be little improvement in the effect, so it was set at 2.7 to 2.7.

Mo is necessary to form intermetallic compounds with Fe and Ni and to cause precipitation hardening by aging treatment, but if it is less than 2 degrees, it has no effect, and if it exceeds Sθ, the toughness decreases. ~S, limited to Oqb. An is added as a deoxidizing agent and also improves age hardenability.
θθ− to θkojts.

Ti is necessary to form the intermetallic compound N i3 T t and cause age hardening, but /, 2! If it is less than -, there is no effect, and if it exceeds 20%, the toughness decreases, so it was set as i, 2s-4θ. Steel with the above composition is
Solution treatment, that is, air cooling from about 52θ℃, softens the hardness to HROJθ ~ 32, making cutting easy.Also, aging treatment, that is, heating to 0℃ for 3 hours, reduces low carbon martensite. Intermetallic compounds precipitate on the substrate and age harden before and after HROjJ, but
Nitrogen is used because it lacks wear resistance when used as an extrusion pin.

We decided to apply surface hardening by oxidation. Generally, steel exhibits expansion due to nitriding treatment, but in the case of the present invention, the nitriding temperature matches the aging treatment temperature, and the expansion due to nitriding is canceled out by contraction due to precipitation hardening. will be explained using examples. 1st
The table shows the chemical composition of the extrusion pin according to the present invention and the conventional extrusion bottle.

In addition, φ0 made of steel with the chemical composition shown in Table 1 and Table 1.
This figure shows the durability test results for the stepped extrusion pin No. 1. The extruded pin of the present invention with symbol A has a surface hardness of Hvg9θ and an internal hardness of HRC! ;2 was shown.

Table 1: Extrusion bottle chemical composition Table 2: Extrusion pin durability test results Table 2: 1. O, when tested in a precision mold for packaging plastic, /θ, 0θθ shot and Sθ
, indicates the presence or absence of breakage of the ejector pin after the θθθ shot.
It was confirmed that even after the θθ shot, it did not break and had excellent toughness. There were also no problems with wear.

As explained above, the extrusion pin of the present invention has a weight ratio of 0.
603% or less, 8i0. ．． 2θchi or less, MnO, 2θchi or less, Ni / ma θ ~ ko θθchi, Mo, Z rima θchi,
A2θθ, 2~θ25chi, Ti/:, 2j-, 2,0%
, Oo, Z/~gu θchi, after processing a solution-treated steel bar consisting of the remainder iron and impurities into a predetermined shape, 97
This product is nitrided at a temperature of around 0°C to harden the surface and age harden the inside.It has excellent toughness and wear resistance, and is nitrided and age hardened at the same time. Because of this, there is almost no dimensional change, and the dimensional precision of the diameter is very high, making it ideal as an extrusion pin for ultra-fine pins of φU θ■ or less.

Claims (1)

[Claims] In weight%, Cθθ3 or less, 8rO, 2θ or less, Mn
Below θ, Ni150 to θθ, Moa2. the law of nature~
S, O=S, Anθθ, 2~θ2schi, Ti1.2j~
! θchi, Ooyu/~guθchi, After processing a solution-treated steel bar consisting of the remainder iron and impurities into a predetermined shape,
An extruded pin for plastics having good toughness and wear resistance, characterized by being subjected to nitriding treatment at a temperature of around 970°C to cause both surface hardening and internal age hardening.