JPS5964748A - High abrasion resistant and highly tough cold working tool steel - Google Patents

Abstract

PURPOSE:To obtain an iron base high C, high Cr, high Fe type martensite cold working tool steel that is excellent in abrasion resistance and high in toughness, by incorporating C, Cr, V, Mo, Si and Mn in a prescribed proportion. CONSTITUTION:The high abrasion resistant and highly tough cold working tool steel consists of 2.0-4.0wt% C, 7.0-17.1wt% Cr, 6.0-14.0wt% V, 0.5-3.0wt% Mo, 2.0wt% or less Mn and the balance of Fe and impurities. This tool steel possesses advantages like a conventional high Cr type material as well as the conventional high V type material. That is, by adding 5% or more V to a high C and high Cr material, the Cr type carbide that crystallizes when it is cast is allowed to crystallize as particles, and as a result the toughness is greatly improved. Further, the carbon and the carbide forming elements are suitably kept balanced on the one hand to improve the abrasion resistance greatly and on the other hand to minimize the lowering of the toughness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a martensitic hardening type cold work tool steel having an iron base, high C, high Cr, and high V, which has excellent wear resistance and high toughness.

Among cold work tool steels, high C゛, high C'r such as 5KD1, 5ICJ) 11 etc. have traditionally been used for applications that require wear resistance.
Steel is mainly used, but even this is not sufficient in terms of wear resistance, and many improvements have been made to the chemical composition of the steel. For example, like Al5ID7, 5 people 1)
1+ with about 4% V added to improve wear resistance by forming VC carbides, and 51cD2 with about 2% W added to improve wear resistance by increasing high temperature softening resistance. etc.

As a measure to improve wear resistance, (1) Increase base hardness.

(2) A large amount of hard particles (for example, carbide particles) are dispersed in the base.

(5) Use an austenite base with a high work hardening index.

However, in the case of using a martensite base (11, (21), these measures deteriorate mechanical properties, so they are rarely implemented in practice. In particular, high C1 high C' In the case of r, the eutectic carbide crystallizes in a network during casting, and this carbide expands into a rod shape in the processing direction during hot working, so there is a limit to increasing the C'r. As a countermeasure for item (5), a method of high-temperature quenching to retain stable residual austenite of 90 modulus or higher to achieve high wear resistance under special wear conditions such as soil wear (σ) (Japanese Patent Publication No. 54-35168) However, this is unlikely to be a general solution.In addition, there is a method of adding elements such as Si and N to make the eutectic grains into pressure granules during casting (
(Special Publication No. 1971-19371), increase base hardness by adding about 4% C″U (Special Publication No. 7I9-112570)
, adding 02 to 10% Ni to improve toughness and wear resistance (%Kai No. 52-575++), 25 to 10% of co.
% to increase tempering softening resistance (JP-A-5L-16)
OB+6), C'.

and C'u are added together (Japanese Patent Application Laid-open No. 79715/1983)
, to control the shape of MC carbide by adding Ti (Special Publication Publication No. 4
7-15581), adding Al to impart a 9-ization effect (Japanese Patent Application Laid-open No. 52-4415), lowering C to improve toughness (Japanese Patent Application Laid-Open No. 47-8801), etc. have been proposed. However, these are all minor improvements.

It cannot be said that the wear resistance is essentially the same as above.

Next, there is a group of iron-based high V-based materials in which a small amount of C゛γ is added to improve wear resistance and hardenability. For example, AISI Type 449 has a weight ratio of 2.4.
56'-0,9Si -0,5un -5,25Cr
-1,5Aio -9,75V.

Type dd6 is 525 f-' −0,3δZ −
0,! l Mn-1, OCr-1, + MO-127
There are alloys that contain a large amount of MC type carbides and have excellent ML wear resistance, but they have a high C content, poor hot workability, and poor grindability. These materials are not often used for high-speed grinding because they are low and difficult to process with a grinding wheel, have poor machinability, and have relatively low hardenability and require oil cooling for thick materials.
Due to its low content, it has low self-hardening properties and low softening resistance at high temperatures, so it cannot be used in applications where the temperature rise is large during use. For this reason (, 15% or less of O is added and %W02
There is an attempt to increase the softening resistance by adding ~10 and MO (Japanese Patent Publication No. 42-26591), and an attempt to add MO with the same <(, '6) (Japanese Patent Publication No. 59-11054), but the softening resistance at high temperatures is Although it would be a great improvement, it has not been implemented in reality.

As mentioned above, conventional high wear-resistant tool steels for cold working are basically high C' and high C''r thread steels containing 1 to 2% carbon.

Crycxr-type carbide is dispersed into the martensite base, and this includes 2% or less of Si, 3% or less of W, and Mo.

A group of materials with 5% or less V added, a high C, high V system containing 25-3.5% carbon and 29-12%, and with 5% or less C°γ and No, W It is classified as a second group of materials. The former has relatively low wear resistance but medium toughness and excellent hardenability. The latter has high wear resistance but low toughness and poor hardenability. As a result, it is difficult to say that the material completely satisfies the requirements for high collapse resistance and high toughness.

In contrast, the material of the present invention has a weight ratio of C'i, s ~ 3.5%.
.

Si2% or less, Mn2% or less, C'r10-15%, V
5-15%, W or MO is 7F+2 No amount te 0.5
~5%, balance may include impurities and iron, depending on purpose 5%
Materials containing Co below or below Co and Ni below coefficient 5, compared to conventional high C
It has characteristics that combine the advantages of both 'r type materials and high V type materials. The gist of the invention is a high-C, high-C'r material [
It was discovered that by adding 5% or more of V in combination, C'r threads crystallized into carbide carbides during casting.5.
This can greatly improve toughness, and by maintaining an appropriate balance between carbon and carbide-forming elements, wear resistance can be greatly improved while minimizing deterioration of toughness. The degree of subsequent hardening is significantly increased, and the resistance to temper softening at high temperatures is extremely high. It has been discovered that by compacting by extrusion or hot isostatic pressure, uniform fine and granular carbides can be dispersed and a balance between wear resistance and toughness can be achieved.

The present invention will be explained below by way of examples.

Table 1 shows the chemical analysis results of experimentally blown 21cA,+. A151 C'lαss 449. Al5I
Six types, D7, 5KD11, were used as comparative steels, and the rest were all invented steels. The invention steel was blown in the atmosphere using a 50Ky/Ch4' high-frequency melting furnace, and then alloy powder was created by N2 gas atomization.

Table 1: After sizing into 52 mesh powder, filling it into a 515C mild steel capsule, sealing it under a vacuum of 10-'7 orγ, and hot isostatic compaction for 2 hours in a 4R atmosphere at a temperature of 1100υ and 1000 atm. I did it. Thereafter, various test pieces were cut out by hot forging and stretching at a processing ratio of 16. For comparative steel, a test piece was cut from a commercially available steel of approximately 7IOφ made by a conventional melt metallurgy method.

Table 2 shows the quenching hardness, tempering hardness, and fracture stress measurement results of each material by bending test.

The quenching hardness was determined by holding the sample in an electric furnace for 30 minutes at two temperatures of 1,000, 1, and 100°C, and then cooling it in oil. 1000E
.

Regarding the quenching hardness at both temperatures of 1100° C., both the steels of the present invention have higher hardness than the comparative steel types. This tendency is particularly noticeable in high temperature quenching at 1100°C.

Among these, there are cases where the absolute value of hardness exceeds RRC67.0 with considerable frequency. Tempering hardness is 1000E oil-cooled 2
00'C1hrX2 tempering, 110011: Oil cooling 5
The experiment was carried out under two conditions: 50°C and x1Arx2 times.

The characteristics of the steel of the present invention are noticeable in high-temperature quenching and high-temperature tempering materials. V2~Va, Ai+, (,'1.C2,
Kt.

Table 2 P1-P2. In materials such as Sl and F2, it is possible to obtain a high tempering hardness of 1lnc66.0 or more, which is unimaginable with American cold work tool steel.

Figure 1 shows as an example the change in hardness of F3 steel depending on the quenching temperature and tempering temperature.
The subsequent hardening phenomenon becomes noticeable, and the hardening process starts from 1125℃ to 560℃.
In υ tempering, the maximum hardness is close to that of HpC6B. This is 5
It is comparable to that of high speed tool steel containing ~8% Co. The effect of increasing r' in the steel is particularly remarkable, and increases in Mo, C''r, Si, etc. also increase the temper softening resistance.The mechanical properties are as follows:
1 invention steel has IIR when tempered at temperatures above ℃
The transverse fracture stress value was shown in the range of C62 to C65.

Comparative steel cannot achieve this kind of hardness, so llR657
The breaking stress values ranged from ~60.

It is clear that the steel of the present invention has higher mechanical properties than the steel of the present invention.

The reason why high alloy steels such as the steel of the present invention have such excellent toughness is the difference in microstructure.

FIG. 2 shows a typical example of σ-1t3. b-Δl5I11r
The X400 microstructure of i9°c-5 D11 is shown. In the steel of the present invention, both the chromium carbide and the MC-type vanadium carbide are completely spheroidized, each grain size is fine, and the distribution is uniform. On the other hand, AJSJd49 has a structure in which rod-shaped chromium carbide and irregularly shaped vanadium carbide are mixed.
S person 1) + 1 shows a structure in which large square-shaped loam carbides are arranged in the processing direction.

As described above, in the steel of the present invention, float carbides can be made spheroidized by adding 7% or more of V, and further made fine and homogeneous by using ultra-rapidly solidified alloy powder, which is a major factor in achieving high toughness. This is a contributing factor.

Table 3 shows the measurement results for one representative steel regarding hardenability, which is an important usage characteristic of cold die steel.The evaluation method is
'￥! The absolute value of the hardness after cooling for 15 minutes and iQ minutes was used. Here, the half-cooling time is the austenitizing vorticity (1050
It is the time it takes to cool down from 525 to half that temperature (at 525), and is a parameter that indicates the cooling rate. The half-cooling time of 5 minutes corresponds to the cooling rate of the center of the 17Of steel bar during oil cooling, and 10 minutes corresponds to the cooling rate of the center of the 24o/m steel bar during oil cooling. It is clear that the steel of the present invention has higher hardenability than the comparative steels.

Table 3 Figure 5 shows the results of the Okoshi type wear test for representative steels.

The test conditions were a contact load of 6 with SN6M2+ as the mating material,
The specific wear amount was measured at a friction distance of 1100 m and a friction speed of 1~' m/Sec.

It is clear that the adjustable steel has significantly better wear resistance than the comparative steel. In particular, as the P° content 4' increases, the wear resistance improves.

FIG. 6 shows the measurement results of representative steels subjected to corrosion wear tests as plastic molding materials.

A schematic diagram of the test apparatus is shown in FIG. In Fig. 15, the boundary is partitioned with an iron plate, the lower PCAES plastic resin 3 of the container 2 with the pipe connection port 10 is filled with glass powder 4, and the entire container 2 is placed in an electric furnace 5.
Heat to 40E. By heating, the resin 5 melts and decomposes,
A gas such as S (/2, C'12.BI', B2S, etc.) is generated and mixed into the glass powder 4 through the connection port 1.The test piece 6 is set so as to be completely buried in the glass powder. It is connected to a motor (not shown) and rotated in the glass powder.The number of revolutions is about d501?PM.The temperature during the corrosion test is adjusted to the desired temperature using a thermocouple 7. The upper part has a gas vent 8. The test piece was taken out every 50 hours and the M-shape reduction rate was calculated and the wear loss was compared.

The excellent corrosion resistance of the invented steel is also evident against corrosion wear.

Next, the reason for limiting the ingredients will be explained.

(, °r is an important constituent element that dissolves in the matrix and increases corrosion resistance and hardenability, as well as temper softening resistance, and the remainder forms carbide and contributes to imparting wear resistance.Content 7
If V is less than 6%, the corrosion resistance and quenching resistance will be poor, and the solid solution ability of V in the matrix will be reduced. Even if V is added in an amount of 6% or more, the secondary hardenability will be decreased, so the lower limit amount was set at 7%. -1: When it exceeds 165%, the tempering hardness decreases, network-like carbides begin to crystallize, and the carbide granulation effect due to the addition of V decreases. At the same time, hot workability also decreases, so 165
The upper limit is %.

V is an important element next to C゛γ which constitutes the present invention. It forms extremely hard Ai C-type carbides in steel, which greatly impairs the improvement of wear resistance. Moreover, addition of 6% or more has the effect of granulating chromium carbide. If the addition of V is below this limit, the secondary curing property is low and the granulation effect is small, so the lower limit is set at 6%. Further, if the upper limit is 14% or more, hot working becomes impossible.

C is an indispensable element for imparting strength and wear resistance to the steel of the present invention.

First, it combines with V to form a hard MC carbide.

For the generation of this carbide, the amount of V added x 021% of the C content I
11 is required as a minimum, and in addition, it is necessary to add a necessary and sufficient amount to form a solid solution in the matrix, harden the martensite, and combine with 6"r to form a chrono-carbide.

In the range of VZo to 14.0% in the present invention, there is little co-C'=Q
, it is necessary to add C that satisfies 5+021V,
If C' is lower than this, the quenching and tempering hardness will decrease significantly.

A minimum of 2% is required to satisfy the above formula. Moreover, if it exceeds 4%, hot working becomes impossible, so the upper limit is set at 4%.

No is an element that is effective in distributing the carbide pressure with the base, shifting the pearlite transformation temperature over a long period of time in the base, and improving the quenching EL. It also enhances tempering softening resistance and high-temperature strength. Below 0.05%, this effect is almost absent;
%, M6(,' type carbide crystallizes, V
Since this impairs the granulation effect of chromium carbide, the thickness was set to 6 or less. Further, even if Aio is replaced by IF, the same effect will occur.

To achieve the same effect, twice as much W as Mo is used in terms of weight ratio.

Although IVi is an effective element for improving corrosion resistance, it is not an essential constituent element of the present invention.

If it is less than 1%, it is not effective in improving corrosion resistance, and if it is more than 65%, the tempering hardness is actually reduced. For applications where corrosion resistance is particularly required, it can be added at a minimum of 1% and a maximum of 3%.

C'o is also not an essential constituent element like Ni. As shown in FIG. 6, it has the effect of reducing the amount of corrosion and wear under special atmospheric conditions such as during plastic molding. On this occasion,
Adding less than 1.5% is less effective, and adding more than 65% does not increase the effect, so the upper limit is set at 6.5%3.Si is used as a deoxidizing agent, but it increases resistance to temper softening. It has the effect of However, even if it is added in an amount of 2% or more, this effect will not increase and hot workability will be impaired, so the upper limit is set at 2%.

Like Si, Ain is used as a deoxidizing agent and is also effective in improving hardenability, but if it exceeds 2%, it lowers the transformation temperature, makes it difficult to reduce annealing hardness, and reduces hot workability. The upper limit was set at 2%.

In addition to these elements, although not specified in the invention, there are 1'i, Al, which have been disclosed to be effective depending on the application in conventional K C' K C''r cold work tool steels.
, the addition of C'u, the increase in the amount of N, etc. do not particularly impair the gist of the present invention, and it is naturally expected that they will be applied to the steel of the present invention.

As described above, the steel of the present invention can be used in conventional high C, high c'r series or high C
In the field of cold work tool steel, where high V type wear resistance is particularly required, the dramatic improvement in wear resistance has an extremely excellent effect.

The granulation effect of chromium carbide due to the addition of r imparts wear resistance without impairing toughness. Adopting a powder metallurgy method using alloy powder as a starting material for the steel of the present invention has a great effect in improving toughness through uniform refinement of the structure.

It is a material that greatly contributes to extending the lifespan of molds such as punching metals, dirt wear molds, rolls, and plastic molds.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the hardness of the steel of the present invention at different quenching and tempering temperatures, and FIG. 2 is a micrograph showing the microstructures of the steel of the present invention and comparative steel, where a is steel of the invention V3 and b is steel of the invention. C is comparative steel, qlSIaaq, 5KI)11, respectively. Fig. 3 is a diagram showing the friction velocity and specific wear coefficient of the Okoshi type wear test of the inventive steel and the comparative steel, and Fig. 4 is a diagram showing the corrosion wear test of the inventive steel and the comparative steel as materials for plastic molding. FIG. 5 is a schematic diagram of the apparatus used for the corrosion wear test. 1: gas passage, 2: container, 5: ABS plastic resin Nigaras powder, 5: electric furnace, 6I test piece, 7: thermocouple. ;t IV Rule-2cLX4t'ρ S, C, Metj-17U Fig. 3 O 4 Fu θ Otsu Dao 5 Showa 57f1111j1. 'I Application No. 17'0545
(7) Contents of the amendment by the person who added 4' High Ni Thread High Toughness Cold Work Tool Compensation 11'' to the name 1. The claims in the specification are corrected as follows. 1. Weight ratio: ozo~4.0%, Or7.0~clothing%,
■6.0~14.0%, MOo, 5~3.0%, S12
．． A cold work tool steel with high wear resistance and high toughness, consisting of 0% or less, Mn&O% or less, the balance Fθ and impurities. 2L T1! Amount ratio TO20~4.0%, Or7.0
~17.1%, 76.0~140%, Mo0.5~3.
0%, Sij? , 0% or less, MnfiLo% or less, and further add some or all of Mo0.5 to 3.0% to Wl, 0 to 6
．． In the range of 0% and -! A cold work tool steel with high wear resistance and high toughness, consisting of the balance Fe and impurities subtracted by the equation (%W) - (%Mo2). 3. Weight ratio: 02PO to 40%, Or7.0 to 17.
1%, 760-140%, Mo0.5-3.0%, Si
Highly wear-resistant, high-toughness cold work tool steel 02 consisting of 2.0% or less Mn, 2.0% or less Mn, and 1.0 to 3.5% 00 or Hl, with the remainder being Fe and impurities. Correct the column as follows. fll On page 5 of the specification, line 4, "to the base" is corrected to "to the base." (2) The text from page 5, line 14, ``ol, 5~'' to line 18, ``the following'' on page 5 of the same book, is corrected as follows. "020-40%, S12.0% or less, Mn2-0% or less, Or7.0-17.1%, 760-140%, W or MO is 1.0-6.0 in W-1-2Mo amount %, including the balance impurities and iron, depending on the purpose 1.5-30% 00
(3) Correct “5%” on page 5, line 20 of the same book to “6%” 0 (4) Correct “1aucsJ” on page 13, line 8 of the same book to l’-A
Corrected to BsJ. (5) In the same book, page 14, line 7, "less than" is corrected to "less than". (6) “In the same book, page 14, line 10 and page 13, “
16,5" are respectively corrected to "17.1". (The first line of page 15 of the same book, ``Hot working becomes impossible if it exceeds this.'' is corrected to ``Since hot working becomes impossible if it exceeds that, it is set at 14%.''). (8) The same book, page 15, line 10, “7.OJ” to “6.0
” is corrected. (9) 1, page 15, line 19, “less than” is replaced with “less than”
Correct. 0Ill Same 1. Page 16, line 2, “3% or less” is changed to “
,05-3.0%". (11) 1, page 16, line 6, "Invention of the present application" is corrected to "first and second of the present application". αδ Correct “less than” in line 8 of page 16 of the same 1 to “less than”. Side N1, page 16, line 8 to line 9 z) Correct "more than" to "beyond". Q4) l751m! 1st page, line 10 “3j, r
Corrected to 3.5j. 05) After “Similarly” on page 16, line 12 of the same 1, “
In the first and second inventions, " is added. 0 Ibid., page 16, line 15 of the same book, “1.5% or less” was changed to “1.5% or less”.
．． Correct to "less than 0." 071 The same book, page 16, line 16 “3.5% or more”
Corrected to "over 35%." 0Q From line 15 to line 17 on page 16 of the same book, “
The upper limit is 3.5%. ", ", 1.0 to 3.5%." a! 1 The same book, page 16, line 19, “more than”
Correct to "beyond". 3. Replace Figure 1 of the drawings with Figure 1 of the angle of view.

Claims (1)

[Claims] 1. C2.0 to 4.0% by weight, Cr7. o~16
5%m V6.0~14.0%, klo 0.5~5
．． 0%*si2. A cold work tool steel with high wear resistance and high toughness, consisting of 0% or less, Mn 2.0% or less, and the balance being Fa and impurities. 2. C2.0-4.0% by weight, Cr 7.0-1
6.5%wV6.0~14.0%, No 0.5~3
．． 0%@St 2.0% or less sun 2.0% or less, further K No o, some or all of s ~ 3.0% is Fl, in the range of 0 ~ 6.0%, Gatsu i (%W)=C%
A high wear-resistant, high-toughness cold work tool steel consisting of impurities and the balance Fe substituted with the equation: Mo). 6. C' 2.0-4.0% by weight, Cr7.0
He165% I V6.0 He14.0% j N
O0.5~3.0%tSL2.0% or less, Mn2o% or less, further containing 15~5.0% C'o or Ni, balance Fe
High wear resistance and high toughness cold work tool steel consisting of and impurities.