JPS6227556A - Steel for knockout pin having high toughness and wear resistance - Google Patents

Abstract

PURPOSE:To obtain a steel for knockout pins with small diameter excellent in wear resistance and toughness and used for metallic mold for plastic molding by incorporating specific percentage of C, Si, Mn, Ni, Mo, Co, Al and Ti to Fe. CONSTITUTION:The steel containing, by weight, 0.21-0.45% C, <=0.20% Si, <=0.20% Mn, 16.0-19.0% Ni, 3.0-6.0% Mo, 11.0-14.0% Co, 0.02-0.25% Al and Ti in the amounts where the upper limit is regulated to the value represented by Tibal%=4C%+1.6 and the lower limit Tibal%X1.2 and having the balance consisting of Fe and small amounts of impurities is prepared. This steel has high toughness as well as wear resistance equal to that of nitrided 18 Ni marageing steel, so that it can be used as a knockout pin having a diame ter as small as <=about phi1.0mm.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention IIIJ relates to a high toughness, wear-resistant extrusion pin steel used in plastic molds.

(Prior art) Steel for extrusion pins must have small heat treatment deformation, easy heat treatment, sufficient toughness so as not to break during use, high wear resistance, and good wear resistance. It is also required that the dimensions do not change during long-term use.

Conventionally, high carbon tool steel such as 5KS21.5KD11 is generally used as the steel for extrusion pins used in plastic molds, and is hardened and tempered to a hardness of around 11c60. ing. 5KS21
and SK[]11 have high wear resistance but low toughness;
φ1. will cause a breakage accident. It cannot be used for extrusion pins with a small diameter of Oa or F.

Therefore, 18-year old maraging steel is currently used as the steel for small diameter extrusion pins. 18Ni Ma) Lt
Nissing steel is C0103% or less, Ni18%
, Ho5%.

It is a low carbon martensitic steel with a chemical composition of 9% Co, 6% TiO, 1% AIo, and is easy to process as it softens to around 1h300 through liquefaction treatment.
After gas nitriding treatment at 470°C for 2 hours (hours), the surface hardness increased to 11v900 and the internal hardness increased to IIv540, showing good wear resistance and toughness, and the dimensional change caused by the nitriding treatment was extremely small. Has characteristics.

However, in the case of 18N i maraging steel, the cost of nitriding treatment is high and the wear resistance of the extrusion pin end face is insufficient, which limits its use.

(Technical Problem) The present invention has been made in view of these problems,
It is an object of the present invention to provide a steel for extruded pins that has wear resistance and high toughness equivalent to nitrided 18N1 maru machining steel without nitriding.

(Technical means) ■The above 1] The present invention achieves the target (I hanging%, C021~
0.45%, Si 0.20% or less, Hno, 20% or less, Ni 16.0-190%, MO3,0-6.0
%, Co11.0-14.0%, 810.0:)-
Contains 0.25% and 11 content is riba1%-4C
The lower limit is the value shown by %+1.6, and T i ba 1
% x 12 as the upper limit, with the balance consisting of iron and some impurities]? This article focuses on steel for wear extrusion pins.

■18N1 maraging steel is a low carbon martensite matrix with Fl)z No, Ni, No and N:3
It is a type of steel whose strength is increased by precipitation hardening of Ti intermetallic compounds, and it has high toughness, but when used for extrusion pins, it has the disadvantage of poor #4 wear resistance.

The Ministry of Invention only applies to the aging process J:Tete Ik? As a result of research aimed at creating a steel for extrusion pins that is precipitation hardened to C58 or higher and does not require nitriding, it has been found that in order to increase the wear resistance of maraging steel, it is necessary to create a hard special steel with a low carbon martensitic matrix. It was discovered that a structure in which carbide TiC is dispersed was sufficient, and the above-mentioned steel composition was conceived.

(2) Next, the reasons for limiting the composition of the steel according to the present invention will be described.

C combines with Ti to form a special carbide and is effective in improving wear resistance, but if it is less than 0.21%, the effect is small, and if it exceeds 0.45%, toughness decreases, so 0.
The content was set at 21% to 0.45%. Although Si and Hn have a deoxidizing effect, if their content exceeds 0.20%, the toughness decreases, so they are each kept at 0.20% 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 16%, the effect will be small, and if it exceeds 19%, residual austenite will be formed. Therefore, it was set at 16.0 to 19.0%.

Ho is necessary to create intermetallic compounds such as e and Ni and to cause precipitation hardening, but if it is less than 3.0%, the effect will be small, and if it exceeds 6%, the toughness will be impaired, so 3.0 =
It was set at 6.0%. A1 is added as a deoxidizing agent and also improves age hardening properties, but the range of this purpose is 0.02
~0.25%. Ti is an intermetallic compound N! An addition of 1.6% or more is required to form 3Ti and cause precipitation hardening. , [i also combines with C to form a special carbide C and -C improves wear resistance, but Ti1 combined with C
Since i is 40%, the Ti content is Tibal%-4
It is necessary to set the value shown by C%+1.6 as the lower limit.

The reason why the upper limit is set to 1 iba 1% x 1.2 is that if T1 increases beyond this point, the toughness will decrease.

(Operations and effects of the invention) In the above configuration, Ti has a very strong affinity with C, and C is added to maraging steel containing Ti.
J, this C is combined with [1 to form 1iC. In this case, the amount of Fj removed to form TiC is 11%-4C%. In addition, -C111 addition, which requires 1116% or more to cause precipitation hardening, is (4c% + 1.6 to (4c% + 16) x
1.2) % J:=<;le. Ding IC is 1lv30
Since it has a high hardness of 0.00, it is possible to make a maraging steel with appropriately dispersed TiCl particles (Ni'f) which can be easily abrasive.

As described above, the present invention provides C0.21 to 0.45%, Si
0°20% or more, Mn 0.20% or less, Ni 160-1
9.0%, Ho3゜0~60%, Co11.0-
14.0%, 81002~0.25%, (1) The lower limit of the content is the value shown by Tibal% - 4C% + 1.6, the upper limit is Tiba 1% x 12, and the balance is iron. Since it is a steel consisting of a small amount of impurities, it is relatively soft with lk<C34 in the liquefied state, and hardens to IkC58.5 by weather treatment.Moreover, hard special carbide ■iC is dispersed in the martensitic matrix. It has high wear resistance and good toughness, making it suitable for use in small-diameter extrusion bottles.

(Example) Examples of the present invention will be described below, but the present invention is not limited to the contents thereof. Table 1 shows the chemical composition of various steels. Symbol A is steel for extrusion bottles according to the present invention, B is 18N
1 maraging steel, symbol C is 5KD11. Next, Table 2 shows the heat treatment hardness and Charpy impact value. It can be seen that the Charpy impact value of the steel of the present invention, code A, is slightly inferior to the 18 old maraging steel of code B, but is significantly superior to 5KD11.

Table 3 shows the results using the heat-treated test pieces shown in Table 2.
Using the 5uJ2 annealed material as the mating material, a wear theory was conducted using the Okoshi type wear test I, and the ratio 1♦ wear value at each rotation speed was determined.
Although slightly inferior, it is clear that the number of specific wear parts is significantly lower than that of the 18N1 maraging steel with symbol B, and the wear resistance is excellent.

Claims (1)

[Claims] In weight%, C 0.21-0.45%, Si 0.20
% or less, Mn 0.20% or less, Ni 16.0-19
．． 0%, Mo 3.0-6.0%, Co 11.0-1
4.0%, Al 0.02-0.25%, the lower limit of the Ti content is Tibal% = 4c% + 1.6, the upper limit is Tibal% x 1.2, and the balance is iron. A high-toughness wear-resistant extruded pin steel with some impurities.