JPS6075552A - Age-hardening austenitic hot working tool steel - Google Patents

Abstract

PURPOSE:To obtain the titled inexpensive hot working tool steel having superior wear resistance and toughness at high temp. by adding specified percentages of C, Si, Mn, Cr, Ni, V, Mo, W, Ti and Nb to Fe. CONSTITUTION:An austenitic hot working tool steel consisting of, by weight, 0.35-0.60% C, <=0.05% Si, 14.0-20.0% Mn, 2.0-8.0% Cr, 1.5-3.5% Ni and 0.5- 3.5% V as essential components, one or more among 0.01-4.0% Mo, 0.01-4.0% W, 0.001-0.5% Ti, 0.001-0.5% Zr and 0.001-0.5% Nb, and the balance Fe with trace impurities is prepd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot work tool steel, and more particularly to an age hardenable austenitic hot work tool steel that has excellent wear resistance and toughness at high temperatures. be.

Conventional hot work tool steels include; JXB BKDb/ and 6.
JOR type hot work tool steel represented by 2, and 0.3 of BKD7! ro-jor-JMo series hot work tool steel, k
Precipitation hardening hot work tool steels of EMbPII (DO, , lO-JNi-JMo system and H0..20-301=-JMo system are known. It is also known that since carbide is precipitated on a site base or a bainite base, the hardness rapidly decreases at around 310°C.

On the other hand, when the temperature of the workpiece material such as copper alloy is 100 degrees Celsius or higher, J-work 8 5KDj is used.

AIf3 H/DE is used, but these hot work tool steels are all martensitic and cannot avoid softening.

Therefore, an austenitic hot work tool steel with high high-temperature strength is required as a hot work tool steel for such work materials, and for this purpose, 8UHAAO etc. are used rather than J, but this is expensive. There are some difficulties.

On the other hand, conventionally known age-hardening austenitic hot work tool steels, which are relatively lower than this, have low toughness;
It has the disadvantage that breakage is likely to occur during use.

SUMMARY OF THE INVENTION An object of the present invention is to obtain a modified age-hardening austenitic hot work tool steel that eliminates these drawbacks of various conventionally known hot work tool steels.

The present inventor conducted various studies to achieve this objective, and as a result, discovered that age-hardening austenitic hot work tool steel having the following chemical components is optimal.

In other words, this cicada invention is 0θ,...? j-0,40%, S
1θ, 0.2 or less, M n /Il, 0-. 20.0
%, Orλ, θ~! , 0%, N1/J ~, 7. j
96, vo, ss ~ s, z% as the basic components,
To this, Moo, o/~y, o L WOoo / ~
4', θchi, T i Ooo 0 / ~0. ! r%
,Z r6′,00//~O,j%,1ibO,00
The present invention is characterized by an age-hardening type austenitic hot work tool steel containing seven or more of the following: / to o, r, and the remainder substantially consisting of 're and trace amounts of impurities.

Hereinafter, the present invention will be explained in detail based on examples thereof.

First, the hot work tool steel according to the present invention is characterized by having the chemical composition as described above, and the reason for limiting the chemical composition and composition range of the steel according to the present invention will be explained here.

0 strengthens the austenite base of steel, combines with carbide-forming elements Or, MO, W, V, and Nb, causes age hardening, significantly hardens the steel, and is effective in improving wear resistance. There is. In order to fully demonstrate these effects, Cρ, 3j-chi or more is required, but too much will impair toughness, so o,,ys~0.40 (7
Limited to 6.

Since Sl is an element that impairs toughness at high temperatures, the content of Sl should be reduced as much as possible in production, and o, o! By setting r% to r% or less, the shift leap characteristics are improved.

Mn is added to change the wood-like microstructure to austenite, and since this element provides a highly stable austenite base and high temperature strength (3), it is an important element in the steel of the present invention. playing a role. This stable austenite can also be obtained with Mn of /4'4 or less, but if it is too small, the toughness will be insufficient, so the setting should be tlIq6 or more, and if it is too large, the maximum hardness of age hardening will be lowered and the high temperature strength will be reduced. decreases, so 1
．． Let it be 20q6.

Or is added in order to combine with O to form a double carbide and contribute to wear resistance, and also to be dissolved in the austenite matrix to increase high-temperature strength. In order to fully exhibit this effect in combination with toughness, the content is limited to a range of: t% to f%.

Although N1 tends to reduce age hardenability, it is extremely effective in improving toughness. Shikamu Ni/,,! t
If the temperature is less than 100%, the effect will be small, and if it is more than 100%, the decrease in aging hardness will be small. It is added to cause melt strengthening, cause age hardening due to carbide precipitation, (4') improve wear resistance, and further maintain high temperature strength. However, below o and r%, the effect is small; 3. s
If it exceeds 3.%, the toughness will decrease. r%
The following shall apply.

MO combines with O to generate carbides and strengthens the austenite matrix as a solid solution, thereby increasing wear resistance and high-temperature hardness. However, if the amount is too small, there will be no effect, and if the amount is too large, the toughness will decrease, so it is limited to the ranges of o, oi-da, and 0chi.

W shows the same effect as Mo, is excellent in carbide generation and solid solution strengthening of austenite base, and has a 0.0/~
≠, limited to 0%.

Ti, Zr, and Nb are effective in strongly deoxidizing the molten metal, and are also fixed as 0 and M·0 carbides, forming very hard carbides and improving wear resistance.

However, if it is contained in a large amount, it will adversely affect the toughness, so the tool steel according to the present invention is limited to θ,s% or less.
Although the steel has the above-mentioned chemical composition and composition range, the steel of the present invention will be described next with reference to Examples.

Table 1 shows J-K13 EI as the conventional steel used in the experiment.
The chemical components of KDj- and 6 and experimental samples of the present invention are shown.

Table 2 shows the hardness (Hv) when the samples shown in Table 1 are aged or tempered after being rapidly cooled from the standard solution treatment temperature or quenching temperature. In the case of the steel of the present invention, it was confirmed that the maximum hardness was exhibited by aging at 7SO℃, and there was only a slight decrease in hardness even at higher aging temperatures. Ha, bo
Hardness rapidly decreases during tempering at temperatures above 0°C.

As a result, when the working temperature reaches 700° C. or higher, plastic flow tends to occur due to insufficient hot strength, and wear also tends to occur.

Table λ (de) Next, these samples were subjected to a high temperature tensile test, a Charpy impact test, and a creep 2-punch test (750℃
, /Okf/l/♂ rupture time) and compared their high temperature strength, ductility and toughness. The result is the third
This is just an illustration.

From the results in Table 3, it is clear that the tensile strength and creep rupture time at 700°C and the Charpy impact value at room temperature of the steel of the present invention are higher than that of martensitic JIS Japan KD.
It can be seen that this is superior compared to & and 61.

As described above, the present invention has various mechanical strengths at high temperatures that are superior to conventionally known hot work tool steels, precipitation hardening hot work tool steels, martensitic hot work tool steels, etc. The present invention also provides an improved age hardenable austenitic hot work tool steel that has lower friction compared to austenitic hot work tool steels such as 31-day 5UH440.

Patent applicant Mitsubishi Steel Corporation (/θ)

Claims (1)

[Claims] IQθ, Jj ~0.40%, slo, or% or less, M
n/41.0~. 20. θchi, Orko, 0. ~za, 0
%, Ni/, j~j, 1%, VO, Z~3. s % is the basic alloy component and Mo0.0/N+1. θchi, WO0θ
/-Il, 0%,'riO,00/ ~0. k%, Z
rO,001~O,! f%, Nb0.0θ/~O0, and the remainder is substantially F.
An age-hardening austenitic hot work tool steel characterized by comprising e and trace impurities.