JPS6136070B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is made of high-speed tool steel that can obtain sufficient hardness down to the core even when thick tools with large mass are air quenched, or hardenability that allows sufficient hardness to be obtained even when the cooling rate is slow such as in vacuum quenching. It concerns excellent high-speed tool steel. Regarding this type of high-hardenability high-speed tool steel, one of the present inventors has already invented a steel that has performance not found in conventional steels (Japanese Patent Laid-Open No. 54-68715).
Afterwards, as a result of further research to improve the properties, the content of Cr, Si, and C was 0.8 to 1.3%.
In the range of Si 0.6-2.0%, Cr 5.5-8.0%, Cr
When the chemical composition satisfies the relationship (%)≦4+5Si(%)+4{C(%)-Ceq}, the hardenability is the same as that of the invention steel, but the tempering softening resistance at 550℃ or higher It was discovered that the mechanical strength also increases. Here, Ceq is the theoretical carbon content when W, Mo, and V form carbides in high-speed tool steel, and Ceq = 0.24 + 0.033W
(%) + 0.063Mo (%) + 0.2V (%), {C
(%)-Ceq} means the ease of solid solution of carbon into the matrix. That is, the components of the steel of the present invention are limited as follows. C is a main constituent element in the present invention, and the contents of W, Mo, and V added at the same time, and
Determined according to Cr and Si content. In other words, Ceq
=0.24+0.033W(%)+0.063Mo(%)+0.2V
(%), Cr(%)≦4+5Si(%)+4{C
(%)-Ceq}. In order to satisfy the above conditions, maintain hardenability, and increase hardening-tempering hardness, the carbon content must be at least 0.8%. However, if it exceeds 1.3%, the toughness deteriorates, so C
Must be in the range 0.8-1.3%. Si is also a major constituent element in the present invention. In other words, in order to improve the hardenability of high-speed tool steel, it is necessary to contain 5.5 to 8.0% Cr, but when the Cr content is this high (conventional high-speed tool steel has a content of 3.5 to 4.5%) %) It was confirmed that during the tempering process, precipitation and aggregation of carbides were stopped, and the tempering softening resistance was reduced. This can cause early damage to cutting tools and warm/hot tools where the temperature of the used part rises above the tempering temperature due to frictional heat, etc. Therefore, after examining many chemical compositions, it was discovered that this problem could be solved by incorporating an appropriate amount of Si and adjusting the C content as described above.
i.e. 5.5-8.0% to improve hardenability
It is essential to contain Cr, but in this case, Cr(%)≦4+5Si(%)+4{C(%)−
Ceq}, a new fact was discovered that the tempering softening resistance does not decrease when the contents of Si and C are adjusted. However, if Si is less than 0.6%, the above effects will be small, and if it exceeds 2.0%, machinability will deteriorate, so it must be contained in a range of 0.6 to 2.0%. Cr is an essential element for improving the hardenability of high-speed tool steel, but if it is less than 5.5%, this effect will be small, and if it exceeds 8.0%, cutting durability and toughness will deteriorate. It must be contained in a range of ~8.0%. Also, Cr(%)≦4+5Si(%)+
4 {C (%) - Ceq} Cr, Si and C
In addition to improving the tempering softening resistance as described above, the addition of the above-mentioned alloys results in a finer structure and higher mechanical strength. W and Mo are elements that combine with C to form a double carbide, improving wear resistance, and at the same time solid solution in the matrix to cause tempering and softening. At this time, twice as much W as Mo has an equivalent effect, and in order to sufficiently bring about the above effect, it is necessary to contain W+2Mo in an amount of 12% or more. but,
Excessive content will significantly reduce toughness, so
The content of W and Mo is suitably 12 to 24% as the amount of W+2Mo. Like W and Mo, V combines with C to form a highly hard carbide, contributing to wear resistance and secondary tempering. However, if it is less than 0.5%, this effect will not appear, and if it exceeds 3.5%, the hardenability will decrease and the grindability will also be significantly worse, so V was limited to a range of 0.5 to 3.5%. Mn is an element added as a deoxidizing agent, with an upper limit of 1
%. Ni is 2% when used in cold working tools
The upper limit was set at 2% because the following content improves toughness. When Co is used in tools that particularly require heat resistance or tools that require high tempering hardness, the effect becomes greater when it is contained at 9% or less, so 9% was set as the upper limit. If it exceeds 9%, hot workability and toughness will be reduced. N is contained in an amount of about 0.01 to 0.02% in a normal melting process, but the upper limit was set at 0.10% since N content up to 0.10% has the effect of improving tempering hardness. When one or more of Ti, Nb, Zr, Hf, and Al are contained in a total amount of 0.2% or less, the structure is refined and the toughness is improved. However, even if the content exceeds 0.2%, no further effect is observed, and on the contrary, nonmetallic inclusions increase, so the upper limit was set at 0.2% in total. When B is contained in an amount of 0.2% or less, it has the effect of increasing hardenability and tempering hardness. However, 0.2%
If the B content exceeds 0.2%, the hot workability deteriorates significantly, so the upper limit of the B content was set at 0.2%. Next, an example will be described. Table 1 shows the chemical compositions of representative examples A to F of the steels of the present invention, comparative steel H, and conventional steel G among many experimental compositions. This composition is the result of analyzing a test piece that was melted and solidified in a 10Kg small high-frequency melting furnace and then hot forged. At the same time, hardness and 10R-C notched pea impact test pieces were taken from this hot forged material. For both hardness and charpee tests, the average cooling rate from the quenching temperature to 600°C was set to approximately 600°C to correspond to the actual vacuum quenching process.
Cooling was artificially slow at 60°C/min. In Table 1
The measured values of hardness after tempering at 560°C are shown for Nos. A to F, No. G, and No. H of the steel of the present invention.
The tempering hardness of the steel of the present invention is clearly increased. In addition, the 10R-C notch mechanical strength impact value was also improved, demonstrating the effectiveness of the steel of the present invention.

[Table] Figure 1 also shows the results of hardness samples quenched at a cooling rate of 60°C/min and then tempered at a temperature of 500 to 600°C. Invention steel No.A is conventional steel
Compared to No.G, extremely high hardness can be obtained at all tempering temperatures. 540 compared to comparative steel No.H
The degree of softening at tempering temperatures above ℃ is small,
High hardness is obtained. That is, the invention steel No.
A indicates that the steel has better resistance to temper softening than comparative steel No. H. As described above, the present invention provides a high-speed tool steel that can obtain sufficiently high hardness even when the cooling rate is slow as in vacuum hardening treatment, and has excellent resistance to softening during high-temperature tempering. .

[Brief explanation of the drawing]

Figure 1 shows after quenching at an average cooling rate of 60℃/min.
It is a figure which shows the hardness when tempering at the temperature of 500-600 degreeC.

Claims (1)

[Claims] 1 C 0.8-1.3%, Si 0.6-2.0%, Cr 5.5-8.0
%, (W+2Mo) 12-24%, V 0.5-3.5%, Mn
1% or less, Co 9% or less, N 0.10% or less, and Ceq = 0.24 + 0.033W (%) + 0.063Mo (%) +
A high-speed tool steel containing C, Si, and Cr amounts that satisfy Cr (%) ≦ 4 + 5 Si (%) + 4 {C (%) - Ceq} at 0.2 V (%), with the balance consisting of Fe and impurities. 2 C 0.8 to 1.2 in claim 1
%, Si 0.7-1.5%, Cr 6.0-8.0%, (W+2Mo)
12-24%, V 1.0-2.5%, Mn 1% or less, Co
High-speed tool steel with N of 9% or less and N of 0.10% or less. 3C 0.8~1.3%, Si 0.6~2.0%, Cr 5.5~8.0
%, (W+2Mo) 12-24%, V 0.5-3.5%, Mn
1% or less, Co 9% or less, N 0.10% or less, Ti,
The total content of one or more of Nb, Zr, Hf, and Al is 0.2% or less, and Ceq=0.24+0.033W
(%) + 0.063Mo (%) + 0.2V (%), Cr (%) ≦
A high-speed tool steel containing C, Si, and Cr amounts that satisfy 4+5Si (%) + 4 {C (%) - Ceq}, with the remainder being Fe and impurities. 4 C 0.8-1.3%, Si 0.6-2.0%, Cr 5.5-8.0
%, (W+2Mo) 12-24%, V 0.5-3.5%, Mn
1% or less, Co 9% or less, N 0.10% or less, B
0.2% or less, and Ceq = 0.24 + 0.033W (%) +
0.063Mo(%)+0.2V(%), Cr(%)≦4+
C that satisfies 5Si (%) + 4 {C (%) - Ceq},
High-speed tool steel containing Si and Cr, with the balance consisting of Fe and impurities. 5 C 0.8-1.3%, Si 0.6-2.0%, Cr 5.5-8.0
%, (W+2Mo) 12-24%, V 0.5-3.5%, Mn
1% or less, Co 9% or less, N 0.10% or less, B
0.2% or less, one or more of Ti, Nb, Zr, Hf, Al in total 0.2% or less, and Ceq = 0.24
+0.033W (%) +0.063Mo (%) +0.2V (%),
A high-speed tool steel containing C, Si, and Cr amounts that satisfy Cr (%) ≦ 4 + 5 Si (%) + 4 {C (%) - Ceq}, with the remainder being Fe and impurities. 6 C 0.8-1.3%, Si 0.6-2.0%, Cr 5.5-8.0
%, (W+2Mo) 12-24%, V 0.5-3.5%, Mn
1% or less, Ni 2% or less, Co 9% or less, N
0.10% or less, and Ceq = 0.24 + 0.033W (%) +
0.063Mo(%)+0.2V(%), Cr(%)≦4+
C that satisfies 5Si (%) + 4 {C (%) - Ceq},
High-speed tool steel containing Si and Cr, with the balance consisting of Fe and impurities. 7 C 0.8 to 1.2 in claim 6
%, Si 0.7-1.5%, Cr 6.0-8.0%, (W+2Mo)
12-24%, V 1.0-2.5%, Mn 1% or less, Ni
High-speed tool steel with a content of 2% or less, Co 9% or less, and N 0.10% or less. 8 C 0.8~1.3%, Si 0.6~2.0%, Cr 5.5~8.0
%, (W+2Mo) 12-24%, V 0.5-3.5%, Mn
1% or less, Ni 2% or less, Co 9% or less, N
0.10% or less, one or more of Ti, Nb, Zr, Hf, Al in total 0.2% or less, and Ceq=
0.24 + 0.033W (%) + 0.063Mo (%) + 0.2V (%)
So, Cr(%)≦4+5Si(%)+4{C(%)−
Contains C, Si, and Cr amounts that satisfy
High speed tool steel consisting of Fe and impurities. 9 C 0.8-1.3%, Si 0.6-2.0%, Cr 5.5-8.0
%, (W+2Mo) 12-24%, V 0.5-3.5%, Mn
1% or less, Ni 2% or less, Co 9% or less, N
0.10% or less, B 0.2% or less, and Ceq=0.24+
At 0.033W (%) + 0.063Mo (%) + 0.2V, Cr
(%)≦4+5Si(%)+4 {C(%)-Ceq} A high-speed tool steel containing C, Si, and Cr amounts that satisfy the following relationship, with the remainder being Fe and impurities. 10 C 0.8~1.3%, Si 0.6~2.0%, Cr 5.5~
8.0%, (W+2Mo) 12~24%, V 0.5~3.5%,
Mn 1% or less, Ni 2% or less, Co 9% or less, N
0.10% or less, B 0.2% or less, Ti, Nb, Zr,
A total of 0.2% of one or more of Hf and Al
Below, and Ceq=0.24+0.033W(%)+
0.063Mo(%)+0.2V(%), Cr(%)≦4+
C that satisfies 5Si (%) + 4 {C (%) - Ceq},
High-speed tool steel containing Si and Cr, with the balance consisting of Fe and impurities.