JPS6075549A - Free-cutting alloy tool steel - Google Patents

Abstract

PURPOSE:To obtain a tool steel having remarkably improved machinability, mechanical property, and heat checking property by adding Zr to the titled tool steel for such as die having a specified compsn., and regulating the proportion of O+N and the content of Zr compd. coexisting with sulphide to specified proportion. CONSTITUTION:The tool steel has a compsn. consisting of by wt% 0.015-0.50 C, 0.1-1.5 Si, 0.1-1.5 Mn, 0.5-8.0 Cr, 0.5-5.0 Mo, 0.1-2.0 V, 0.05-0.2 S, 0.005- 0.2 Zr, 0.01-0.03 O+N. Further >=70% of the Zr compd. i.e. ZrO2 and ZrN are coexisting with sulphide. Furthermore, appropriate amt. of Se, Fe, Ca, Mg may be added if necessary. In the steel of this invention, the shape, size, and distribution of sulphide are made uniform by the inoculating effect of Zr compd. on sulphide, and the effect is fully exhibited by the coexistence of >=70% ZrO2+ZrN with sulphide, and aimed tool steel is then obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alloy tool steel used for press molds, die casting molds, plastic molds, etc.

A new free-cutting alloy tool steel that has significantly improved heat-checking resistance and deterioration in impact value, which were considered to be the biggest drawbacks of conventional free-cutting alloy tool steels.

It is related to.

It greatly influences the market value of metal materials.

The material has excellent material properties and has a long service life in practical use.

In addition, it is easy to process such as die engraving.

can be given. Rigidity is particularly important for die casting molds, plastic molds, and press type 10 steel that are cut into complex shapes.

By adding certain elements, mold engraving is possible even in a tempered state.

A free-cutting alloy tool steel has been developed that allows for smooth cutting. However, since conventional steels of this kind can be carved into molds in a refining state, they suffer less deformation during heat treatment, but problems remain in terms of heat-checking resistance and toughness.

The conventionally known free-cutting component is S + N4 + T4 r
BL+A, +Pb, etc.

There are S, N4. T4 is sulfide, selenide, respectively.

Formation of non-metallic inclusions of chirlide and its internal image.

The small notch effect gives machinability, and BL+4+Pb is a metal component.

Provides rigidity due to the lubrication effect of the inclusions. this.

Among these elements, elements such as Bbr and Pb that exist as metal inclusions have low melting points, making the material unstable at high temperatures.

conventional free-cutting alloy tool steel.

is S, S4. T4. A free-cutting component of At may be added alone or in combination.

However, when these free-cutting ingredients are added, the center side.

There is a risk of deteriorating the product's impact resistance and fatigue strength, as well as reducing hot workability.

When a free-cutting component is added, the problem is how to significantly reduce the decrease in toughness.

The present invention has 0.1-0.5% C, 0.1-1.5% S.
L, 0.1-1.5% M-, 0.5-8.0% C
rt 0.5-5.0% Mo, 0.1-2.0%.

V of 0.05-0.2%, S of 0.005-0.
2% zr, 0.01-0.03゜% 0+N and more Z
Free-machining alloy tool steel in which 70%15 or more of the compounds ZrO* and ZrN coexisted with sulfides and 840.05 to 0.15% as necessary p T4 o, os ~ 015
One type of %.

Or 2 types, C60,001~0.01%y My
0.001 to 0.01% of one kind or two kinds are contained to impart free machinability to steel.

Due to the combined effect of (0+N), existing free-cutting alloy tool steel...

This greatly improves the deterioration in heat-checking resistance and impact resistance, which were considered to be serious defects in steel, and also improves machinability.

Next, the reason for limiting the component range will be explained. .

If the amount of C is less than 0.15%, the required hardness as a hot work tool steel cannot be obtained, and if it exceeds 0.5%, the toughness decreases.

However, there is a high risk of cracking during use.

Sp is contained as a deoxidizer and also improves oxidation resistance.

is valid above. If it is less than 0.1%, there is no deoxidizing effect on steel manufacturing.

If it is not obtained and exceeds 1.5%, the effect of improving oxidation resistance will be small1.
0, and on the other hand, the rigidity deteriorates, making it impractical. Mn
In addition to being added as a deoxidizing agent like SL, it is also added as a deoxidizing agent.

It has a remarkable effect on improving human resources. Also, M? LS type.

Forms sulfides and contributes to improving free machinability. deer.

If it is less than 0.1%, it has no effect, and if it exceeds 1.5%, it increases annealing hardness and deteriorates stiffness, as well as deteriorating oxidation/oxidation resistance and hot properties.

Cr is an important element for hot work tool steel and is necessary because it increases strength at high temperatures, hardenability, and oxidation resistance.

The content of Cr2°.3.0 is 0.5 to 8.0% depending on the requirements, but contents outside this range have little effect and are rarely put into practical use.

Mo and ■ greatly increase heat resistance and hot abrasion resistance.

It is an effective element for hot work tool steels, and normally 0.5 to 5.0% M and 0.1 to 2.0% M are added. Containing it has little effect.

S is an essential element for improving rigidity. Many.

If it is too high, the toughness and hot workability will be impaired, so it should be 0.2% or more.

If the content is too low, the above effects cannot be obtained, so the content should be 0.0% or more.

Zr is an essential element for improving machinability and heat checking resistance. Added Zr becomes sulfide.

Zr0t or ZrN, which has an effective inoculum effect against.

Ru. This inoculation effect results in very good uniformity in the size and distribution of the sulfides. This uniformity.

This improves stiffness and heat checking resistance. The effect of this Zr addition is not sufficient if it is less than 0.005%. Moreover, when it exceeds 0.2%, the effect is saturated and ZrO* and ZrO*, which do not coexist with sulfide and exist in the base, are saturated.

and ZrN increases, resulting in increased stiffness and heat checking resistance.

There is a risk of harming the performance of the product. Therefore, Zr is 0.00
s, 4t.

・　4　・ ~0.20%.

0 and N are constituent elements of Zr0t and ZrN, and are responsible for the inoculating action of Zr compounds Zr0t and ZrN, which is a feature of the present invention.

It is an essential element. 70% or more of ZrO2, ZrN, etc.

In order for Zr to coexist with sulfide and perform an effective inoculating action, the content of (0+N) must be strictly controlled to 0.01° to 0.03% along with 0.005 to 0.2% Zr. Must be. O+N.

If it is less than 0.01%, the inoculation effect is not sufficient and it is in the form of sulfide.

Uniformity of severity and distribution cannot be achieved. Ma.

When 0+N exceeds 0.05%, the amount of independent oxides or nitrides that do not coexist with sulfides increases, causing damage to machinery.

There is a risk of deteriorating the physical properties. Therefore 0+N
was set at 0.01 to 0.03%.

S4 improves mechanical properties and stiffness. death.

If the amount exceeds 0.15%, the toughness decreases significantly, so
The 5th limit was set to 0.15%. If it is less than 0.006%, the effect is small or absent, so the lower limit was set at 0.05%.

Like S4, T4 has improved mechanical properties and rigidity.

let However, the effect of improving stiffness exceeds 0.15%.

upper limit, because the less the mechanical properties decrease, the more noticeable it becomes.

was set at 0.15%. If it is less than 0.03%, the effect will be small.

Therefore, the lower limit was set at 0.05%.

The effect of Ca 1MP is the inoculation of Zr compound against S'd4.

This improves the mechanical anisotropy by suppressing the stretchability of the sulfides during rolling processing through the production of Ca S and Mis. It is something. If the amount is too large, deoxidation by Ca and My will proceed excessively, making it impossible to obtain the inoculation effect.

Therefore, both should be 0.010% or less. Above if too low.

Since no effect can be obtained, the content should be 0.001% or more in all cases.20 Below, the steel of the present invention will be explained in detail with examples.Table J shows the chemical composition of the test materials.

Tables 1 and 2 show the proportions of Zr compounds coexisting with sulfides.

Table 2 From Table 2, in the steel of the present invention, Zr compounds account for 70% or more.

It can be seen that S'd< coexists with S'd<. Comparative steel.

Hard compounds other than Zr compounds (e.g. 7v!, O
, , M, O) are individually dispersed in the base, which promotes mechanical wear of the tool during cutting. Therefore, there is a high possibility that the tool life will be shortened. On the other hand, the invention steel.

In this case, the coexistence of the Zr compound with S'c14 causes chip breakage to occur more easily than in 5'ctc K during cutting.
tool blade.

This reduces the chance of the tip coming into direct contact with the Zr compound.

・　7　・ Extension of tool life can be expected. Also, Zr compounds.

In this way, by coexisting with S'mu, the first. Figure 2.

As shown in the figure, the distribution and shape of S′ in the cast structure.

has been significantly improved. Figure 1 shows comparison steel.

(1) and FIG. 2 are micrographs of the invention steel (4).

51 Rigidity JIS -5KI (9 bits (cutting edge shape 8° - 15° -
6＠−6°−.

20@-15"-0.5R) and feed 0.5wl7
Turning was carried out under dry cutting conditions of /rcv + depth of cut 1 and 9°. 20 minute bye.

■ Cutting speed that provides long life. Values and comparison steel 41110
Table 3 shows the degree of rigidity improvement for the four values of 42.

・　8　・ From Table 3, the stiffness of the steel of the present invention is greater than that of the comparative steel.

It can be seen that it is excellent. I mentioned this earlier.

Zr addition and (0+N) control as above.

This is due to the fact that the distribution shape of S' is uniform, the non-uniformity of the stiffness of the base is eliminated, and the adverse effects of hard inclusions on the tool 5 are reduced. Also,.

Due to the composite addition of 84, T49My, and C=b, the stiffness is slightly reduced.

be good.

2. Mechanical Properties Samples were machined parallel and perpendicular to the forging and elongation direction and subjected to a room temperature tensile test and a hot impact test.Table 4 shows the results.

It can be seen from Table 4 that the elongation anisotropy (T/L) of the steel of the present invention is significantly improved compared to the comparative steel.

3. Heat checking resistance Heat checking caused by thermal fatigue is a phenomenon that occurs in all hot work tool steels, and is one of the factors that determines the tool life. Table 5 shows 70° for a 14° specimen.
After 15 seconds of immersion in a lead bath at 0C, heat and cool with water.
Repeat 200 times, in cross section.

The heat checking resistance of the steel of the present invention is the result of observing the number and length of the checks.

It turns out that it's much better than that. Table 5 Machinability 1 Mechanical properties and heat resistance mentioned above.

The tonic properties of the steel of the present invention were significantly improved.

There is. The reason for this is the contact of Zr compounds with sulfides.

Shape, size and distribution of sulfides due to seed action.

This is due to the fact that it has become uniform. Furthermore, this effect is 5Zr
More than 70% of O2 and ZTN coexist with sulfides.

It is fully demonstrated by.

[Brief explanation of drawings]

FIG. 1 is a photograph of the cast metal structure of Comparative Steel 1, and FIG. 2 is a photograph of the cast metal structure of the steel of the present invention. +. −]] 轡′″＋−１国体2图10θ・12・Director of the Japan Patent Office Name of the invention Free-cutting alloy tool − Name of the person making the correction Name (5081 Hitachi Metals Co., Ltd. Representative Kono Maoyo Masato Kusunoki (Detailed Description of the Invention), Contents of Amendment 1. The claims section of the specification is corrected as follows: ``1. Weight ratio: 00.1.5 to 050%, 5110.
1-1.5%, Mn0.1-1.5%, Oro, 5-&
O%, Mo0.5-5.0%, 70.1-2.0%, S
O, 05~0.2%, Zr0.005~0.2%, O
-1% o, ol ~ 0.03% further zr compound Zr0
A free-cutting alloy tool steel comprising -% or more of a and ZrN coexisting with sulfides, the balance being iron and impurities. 2 Weight ratio: OO, 15-0.50%, Si0.1-L
5%, Mn0.1-1(11.5%, Oro, 5-ho%, Mo0.5-5.0%
, VO, 1-2.0%, 80.05-0.2%, Z
r0.005~0.2%, o4o, o1 figure, o3z
OJ: IJS e O,03”-0,15%, T e
0.0 is 15% of 1 type or 2 types, OaO,001
~0.01%, one or two of MgO, OO1~0.01%, and further Zr compounds Zr0g and ZrN
A free-cutting alloy tool steel characterized in that 70% or more of the carbon coexists with sulfides, the balance being iron and impurities. ”2 The column for detailed explanation of the invention in the specification is corrected as follows. +11 Specification page 3, line 17 [S e O, 05”-
(], 115%T o 0.05-0.15·1 (2) In the same book, page 6, line 3, "Z rO wealth, ZrN" is corrected to "for S/aθ of (Zr02°zrN)". (3) “ZrN or Zr” in Table 2 on page 8 of Douyo
Correct (0,N)j to ``zrN,I.''That's it, 2

Claims (1)

[Claims] 1 CO, 15-0,50% by weight, SLo, 1-
1.5%p M7L0.1~1.5%, Cr0.5~
80% p Mo0-5-5.0%, VO, 1-2.
0%, ''SO, 05~0.2%, Zr0.005
~0.2%, O+N O, 01~0.03%. Furthermore, more than 70% of the Zr compounds ZrOR and ZrN are sulfur. A free-cutting alloy tool steel consisting of residual iron and impurities, which is characterized by the coexistence of iron and impurities. 2 CO, 15-0.50% by weight, SLo, 1-
1.5% 2M? L0.1-01.5%, CrO,5
~B, rJ%, M. [1.5-5.0%, VO,
1-2,0%, SO, 05-0.2%, Z, 0.00
5-0.2%, 0+NO, 01-0.05% and 840.05-0.15%p T40.05-0.15
%1 or 2 pCa 0.001-0.01%
, M, 0.001-0.01% of one or two of the Zr compounds Zro2 and ZrN1.7
It is characterized by 0% or more coexisting with sulfide. A free-cutting alloy tool consisting of residual iron and impurities. steel.