JPS61117250A - High speed tool steel having superior weldability - Google Patents

Abstract

PURPOSE:To obtain the high speed tool steel having superior weldability, by specifying the chemical composition of the steel and also by specifying the relation between the quantity of oxygen and the quantity of nitrogen in the steel. CONSTITUTION:The high speed tool steel consists of, by weight, 0.5-4.5% C, <2% Si, <1% Mn, 3-6% Cr, 1-15% V, <15% Co, <25% W and/or <12.5% Mo, and the balance Fe with inevitable impurities; where C%-(0.06Cr%+0.063Mo%+0.033W%+0.2V%) is -0.1-0.2%. At the same time, the quantity of oxygen, (O)ppm, and the quantity of nitrogen, (N)ppm, are in the relation represented by a formula. In this way, the high speed tool steel to which electron beam welding is applicable can be obtained.

Description

[Detailed description of the invention]

The present invention relates to a high-speed tool steel manufactured by powder metallurgy that exhibits excellent weldability when welding, particularly electron beam welding and laser beam welding. High speed tool! I4 is a tool steel that has excellent wear resistance, heat resistance, and strength, but it is not only expensive, but also has poor toughness and fatigue strength when heat treated to fully demonstrate its properties. However, it is possible to reduce the cost of a tool by welding it with an inexpensive steel or a steel that has high toughness and fatigue strength, or to weld it with a high-speed tool steel that exhibits the respective characteristics of the high-speed tool steel and the base material. Manufacturing tools is being carried out. A metal band saw is a typical example of a method for manufacturing such a cutting tool. The metal band saw has a cutting edge that is directly involved in cutting.
The back part not only supports the cutting force applied to the cutting edge, but also receives repeated tensile stress due to bending, so it requires high tensile strength, toughness, and fatigue strength. Ru. Although it is difficult to satisfy the technical requirements of each part to a high degree using the same material, the roles of each part are divided, and the blade material is made of high-speed tool steel that has excellent wear resistance and heat resistance. By using steel with excellent tensile strength, toughness, and fatigue strength as the backing material, welding it into one piece, and then processing it into a Pantone shape, the above-mentioned high requirements can be met. Electron beam welding is generally used to weld the blade material and back material of a band saw. As is well known, the electron beam welding method uses a narrowly focused electron beam usually in a vacuum.
Di-welding is performed by melting the welded part with extremely high energy density, and it is possible to weld between the same and different types of ferrous and non-ferrous materials (including high melting point materials). (2) Welded part (3) The area affected by welding heat can be localized. (4) High purity welds can be obtained. (5) The weld penetration depth can be increased. Furthermore, since the depth can be precisely controlled, it is possible to weld from extremely thin plates to thick plates.For example, it is extremely advantageous for welding the blade material and back material of the aforementioned Metal Pantone. The technical feature of the electron beam welding method is that it heats and melts a narrow region in a vacuum with high energy density, which eliminates gaseous elemental impurities such as oxygen and nitrogen contained in the molten part. This leads to the release of alloy components with high vapor pressure, impurities, and their compounds into the welding atmosphere.Oxygen as an impurity contained in steel is partially dissolved in the Fe' matrix, and Nitrogen exists as non-metallic inclusions such as C3, 8102, and some nitrogen exists as a solid solution in the F8 base, as well as nitrides such as AjlN, and a portion of nitrogen as a solid solution in carbides.By electron beam, The welded part is heated to a high temperature.
Upon melting, oxygen reacts with the carbon in the steel and gasifies in the form of CO and nitrogen primarily in the form of N2. The atomic weight of oxygen is 1
6. Since the atomic form of nitrogen is 14, oxygen is approximately 2 times the size of nitrogen.
Generates twice the amount of gas (capacity). If the gas generation rate is high, the molten metal will scatter,
Furthermore, if the release into the welding atmosphere is insufficient, blowholes may remain and cause welding defects. A technique for adding increased amounts of AJ to the Pantone backing material for the purpose of preventing the occurrence of welding defects (for example, Japanese Patent Publication No. 32778/1983) has shown that, but due to the characteristics of the electron beam welding method mentioned above, It is difficult to prevent oxygen and nitrogen from being released as gases such as CO1N2, so by keeping the amount of oxygen and nitrogen contained in the molten part low, gas generation does not occur suddenly and the welding atmosphere is maintained smoothly. Fortunately, in recent years, advances in steelmaking technology, especially the application of vacuum degassing, have made it possible to obtain high-quality welds such as high-speed tool steel. In steel, it has become common practice to control the content of oxygen and nitrogen in steel to a low level, and the occurrence of welding defects such as those mentioned above has become rarer.On the other hand, recent technological advances in high-speed tool steel High-speed tool steel manufactured by powder metallurgy (hereinafter referred to as powder high-speed tool steel) has almost no segregation, fine carbides, and high strength. It has excellent usability characteristics such as high toughness and good workability in cutting and grinding.It also produces high-quality steel with high alloy components, especially steel with high V content, which is difficult to produce using conventional methods. In addition, metal pantones used for cutting difficult-to-cut materials such as highly hard tempered steel and shaped steel have recently been in demand.Such metal pantones are also made of powdered high-speed steel. There are many methods currently used industrially to produce high-speed tool steel powder, but here are a few representative ones: (11) Gas atomization (gas atomization) (2) Water atomization-reduction method (3) Metal oxide/pulverization/mixing □ reduction method. However, such powdered high-speed tool steels cannot be manufactured due to the characteristics of the manufacturing method. Compared to high-speed tool steel manufactured by the conventional method (ingot method) (hereinafter referred to as conventional high-speed tool steel), the amount of oxygen contained in the steel is
The nitrogen content is typically much higher, and nitrogen may even be utilized as an active alloying component. Further, most of the oxygen exists as non-metallic inclusions, but when using the powder method, unlike when using the conventional method, the non-metallic inclusions are very fine and do not have any particular effect on properties. However, when welding, particularly electron beam welding, is applied, a major problem arises in that a good weld cannot be obtained due to the generation of a large amount of gas during welding. Of course, it is not impossible to reduce the oxygen and nitrogen content in the steel to a level close to that of conventional high-speed tool steel by adding technical innovations to the above-mentioned Izun production method, but the number of steps will increase. It is also true that this will lead to a significant increase in costs, such as an increase in production efficiency, a decrease in production efficiency, and an increase in energy costs. Also,
The application conditions of the electron beam welding method have been changed to increase the gas release rate,
In other words, if the welding speed is changed to a lower level, it is not impossible to reduce the problems caused by gas release, but it can also cause other problems, and it is also unlikely to lead to a decrease in welding efficiency and an increase in costs. There are no males. The present invention is based on the results of an investigation into the relationship between the occurrence of welding defects due to the scattering of molten metal due to boiling or residual blowholes when electron beam welding is applied, and the amount of oxygen and nitrogen in the steel that causes these problems. Oxygen i Co contained in
) ppm, nitrogen amount (Nl'ppm O relationship is expressed as 2 (o
]+[:N]<zoo, we aim to provide powder high-speed tool steel to which electron beam welding can be applied under almost the same conditions as conventional high-speed tool steel without causing a significant increase in cost. It is something to do. The alloy components of the high speed tool steel according to the present invention will be explained below. C strengthens the base by heat treatment, and K, Cr,
It forms hard carbides with carbide-forming elements such as Mo, W, V, Ti, N'b, and Zr, and is an essential alloying component for high-speed tool steel that imparts wear resistance. Depending on the characteristics that the high-speed tool steel should have in response to the intended use, it is necessary to include an alloy amount according to the following relational expression between the amount of other alloy components. 0%-(0,06Cr%+0.063M0%+o,o3
aw%+0.2V%+〇, 14Nb%+0.257i%
+0.142r%) 1.1% to 0.2% 0.5 to 4 to satisfy the range of other alloy component amounts in the steel of the present invention
．． S to 4.5%. Cr improves hardenability and increases cutting durability, but
If it is less than 3%, this effect will be small, and if it exceeds 6 inches, the heat resistance and toughness will decrease, so the Cr content is limited to 30 to 6.0%. W and Mo are the most important alloy components for high-speed tool steel. That is, both W and Mo combine with C to form M, C carbides, a part of which dissolves solidly in the matrix during heating for quenching, and precipitates as fine M, C carbides during tempering. It has the property of strengthening the matrix and imparting heat resistance, and some of it also provides excellent wear resistance as a hard residual carbide. Note that W and Mo have almost the same properties, but due to the difference in atomic weight, 1% by weight of Mo has an effect of approximately 2% by weight of W, so the effect can be set by (W% + 2 Mo%). I can do it. (W%+2Mo%) from 5.0 to 25
．． It is best to set it to 0. If the content is less than s, o%, the effect will be insufficient, and if it exceeds 25.0%, not only will no increase in the effect be expected, but it will also lead to an increase in cost and a decrease in toughness. In addition, since W and Mo do not necessarily need to be added simultaneously, in this case, the W content is 25% or less, and the Mo content is 1
It is best to limit it to 2.5 inches or less. V combines with C to form a hard carbide and significantly improve wear resistance. Furthermore, since it is difficult to form a solid solution during heating for quenching, especially when the content of W and Mo is small, the effect of preventing coarsening of crystal grains is remarkable. In conventional high-speed tool steels, when the V content increases, the grindability decreases significantly, so in many cases it is set to 1 to 3 g, but when using the powder method, the carbides are fine and there is less deterioration in the grindability. Therefore, it is possible to improve wear resistance by adding a large amount of V. In the steel of the present invention, it is limited to 1.0 to 15.0%. The reason is that less than 1.0ch is less effective and 15.0ch is less effective.
This is because even if it is added in excess of 1, no increase in the effect can be expected, and the cost increases, the grindability deteriorates, and the toughness decreases significantly. Like V, Nb, Ti, and Zr combine with C to form hard carbides, and have a remarkable effect of significantly improving wear resistance and preventing crystal grain coarsening.
It is preferable to include one species or two or more species and limit the total to 3096 or less. Since V, which has the same effect as Nb, Ti, and Zr, is contained in an amount of 10% or more, it is not necessary to contain these elements. When contained, Nb, Ti, and Zr carbides exhibit an angular shape unlike V carbides, and when present in large amounts, they significantly reduce toughness. Although CO has the effect of increasing heat resistance and significantly increasing cutting durability, it conversely reduces toughness. If heat resistance is not important as a required characteristic, the addition of CO is not necessary, but the addition of CO shows a remarkable effect in applications that require heat resistance, such as cutting difficult-to-cut materials. . However, if it is added in excess of 15%, no increase in the effect is expected and the toughness will be reduced, so the content should be limited to 0 to 15%. Si is added as a deoxidizing agent, but if it exceeds 2.0%, the toughness decreases, so it is preferably kept at 2.0% or less. Furthermore, Mn is added as a deoxidizing agent and desulfurizing agent.
Since there is no effect if it is used in excess of 1.0%. The amount of oxygen contained in the steel is (') ppms, the amount of nitrogen is (N
) ppm, 2 (0) + I:N:]<
Limited to 200. When applying electron beam welding to powdered high-speed tool steel, it is desirable that the amount of oxygen and nitrogen in the steel be low in order to prevent welding defects and maintain welding efficiency. The amount of oxygen is the same as that of high speed steel.
Reducing the amount of nitrogen would result in a significant increase in cost. From this point of view, it is desirable that the allowable amounts of oxygen and nitrogen be as high as possible for welding. As explained in the examples below, when performing electron beam welding on powdered high-speed tool steel under practical conditions, 2

In the case of steel that falls under [0] 10 [N] < 200, no welding defects will occur under normal welding conditions, and if this range is exceeded, no welding defects will occur. become. Examples will be described below. Example 1 Electron beam welding was performed under practical conditions using a metal pantone-blade welding device. The welding conditions are shown in Table 1. The blade material for the test was a steel equivalent to TIS 8KH57,
Its dimensions are 0.9g x 1.71L11. Three methods were used to manufacture the test materials, and their oxygen and nitrogen contents are shown in Table 2. The second backing material is made of steel equivalent to JIS 5UPIO and its dimensions are 0.
．． 9g x 24.01fa+, its oxygen and weight content was 10-2099m, and its nitrogen content was 50-60ppm. Pre-welding treatments were carried out based on normal standards. Figure 1 shows the results of the investigation after welding. The solid line in the figure indicates the upper limit of the limited range of the amount of oxygen and nitrogen of the present invention. Within the limited range, no welding defects are observed. If the limited range is exceeded, there may be cases where no welding defects are observed, but there are some cases where the occurrence of welding defects is not observed, and there are cases where they occur continuously. In addition, B has a large amount of oxygen and nitrogen.
Some of the samples made from K had significant boiling and were difficult to weld. Example 2 A welding test was conducted using a blade material of steel equivalent to JIS 5KH59. The contents are shown in Table 3. Further, other conditions were the same as in Example 1. The results are shown in Table 3 and Figure 2. The same content as in Example 1 has been improved. Example 3 A welding test was conducted using a blade material of a steel equivalent to Jls SKH'IO.The details are shown in Table 4. In addition, other conditions are the same as in Example 1. The results are shown in Table 4 and Figure 3, and the same content as in Example 1 was obtained.
ing. As shown in the above examples, if the amount of oxygen and nitrogen contained in the steel is within the claimed range, no welding defects will occur when the electron beam welding method is applied. The present invention was completed after obtaining industrially significant knowledge.

[Brief explanation of drawings]

The drawings are explanatory diagrams of the relationship between the amount of oxygen and nitrogen in steel and the occurrence of welding defects when electron beam welding is performed under practical conditions. Steel types equivalent to JIS 5KH59, Fig. 3 is JIS
The case of steel type equivalent to 5KHIO is shown. Agent Patent Attorney Jun Kawauchi 1st 2M No. 3 ■ Procedural amendment (spontaneous) August 1, 1985 (l-Mr. Michibu Uga, Director General of the Osusa Agency) Indication of the case 1988 Patent Application No. 127558 No. 2. Name of the invention: High-speed tool steel with excellent weldability. 3. Relationship with the case of the person making the amendment. Name of the patent applicant (
519) Fujikoshi Co., Ltd. 4, Agent address: 25th floor 5, World Trade Center Building, 2-4-1 Hamamatsucho, Minato-ku, Tokyo, Date of amended umbrella: 7, Subject of amendment + Patent claims in the FITFL document Scope column and detailed description of the invention column 8 Contents of amendment (8, 1) Lines 4 to 14 of the specification page (Claims) All amendments are made as per the appendix. (8,2) Page 4, line 12 of the specification and page 5, line 3 of the specification
Correct each line "CO" to "co". (S, 3) "Atomic form" on page 4, line 13 of the specification is corrected to "atomic weight." (84) "Segregation" on page 5, line 16 of the specification is corrected to "segregation." (S, S) On page 6, line 4 of the specification, "Made by Nomo Powder High Speed Steel" is corrected to "Made by Momo Powder High Speed Tool Steel." (86) On page 8, line 18 of the specification, r before "invention steel"
That is, insert CFij. (87) Details @ page 9, line 15, change “5.0% or less” to “
Corrected to ``less than 5.0%''. (88) Specification page 10, line 20 “30%” All “3.
Correct it to θ. (8,9) Page 11, line 4 of the specification: “If J is limited,”
limit. ”. (s, lo) "High speed steel" on page 12, line 7 of the specification is replaced with "
Corrected to "High Speed Tool Steel". (S, U) Specification, page 13, line 11? Correct the following sentence.
"Table 2" shown on page 13, line 12 to line 17 of the Specification is amended as shown in the attached sheet. (S1a) In the second line of page 14 of the specification, "after welding" is corrected to "after welding test." (8, 14) "Table 3" shown on page 14, line 15 to line 19 of the specification will be amended in a separate circular. (S, tS) Correct the entire appendix of "Table 4" shown on page 15, line 6 to line 10 of the specification. cIIIG) Figure i 1st Army 2m and Salary 3 Figure δ"
1 Lie-＾'] and 3 degrees 2, claim weight: C 0.5-4.5-4.5%, 19120% or less, Mn 1.0% or less, Cr 3.0-6.0 %, V
1. o~ts, o%, Co 15% or less, and further 1 of W25 or less, Mo12,5 or less
Contains one or two species (W Chi + 2 Mo) is 5. θ~25
．． 0, 0%-(0,06Cr%+0.063M0
%+0.033W%+0.2V%) is -0.1%~o,
The amount of oxygen contained in the steel is within the range of 2%, and the balance is Fe and unavoidable impurities.

A high-speed tool with excellent weldability manufactured by a powder metallurgy method, characterized in that 2Co]+I:N:]<z o o, where [0] ppm and the amount of nitrogen are (N) ppm. steel. Table 2 Gas content and welding test results of steel test materials equivalent to 5KH57 Table 3 Gas content and welding test results of steel test materials equivalent to 5KH59 Table 4 Gas content and welding test results of Koshin test materials equivalent to SKH10 1 Amendment to figure procedure (method) December 19, 1985 Michibe Uga, Commissioner of the Patent Office1, Indication of the case, Patent Application No. 127558, filed in 19822, Name of the invention: High-speed tool steel with excellent weldability Name (519) Fujikoshi Co., Ltd. (Shipped on December 10, 1985) 7. Contents of the amendment Procedural amendment (as per the attached sheet) August 14, 1985 Director General of the Patent Office Uga Michibe 1. Indication of the case 1982 Patent Application No. 127558 2 Name of the invention High-speed tool steel with excellent weldability 3 Relationship with the case of the person making the amendment Patent applicant name (519) Fujikoshi Co., Ltd. 4 , Residence of agent: 25th floor, World Trade Center Building, 2-4-1 Hamamatsucho, Minato-ku, Tokyo, Japan 6, Number of inventions increased by amendment: None 7,
Claims column of the specification subject to amendment, detailed description of the invention, and drawings

Claims (1)

[Claims] C0.5 to 4.5% by weight, Si 2.0% or less, Mn1
．． 0% or less, Cr3.0-6.0%, V1.0-15.
0%, Co 15% or less, W 25% or less, M
Contains one or two of o12.5% or less, C%-
(0.06Cr%+0.063Mo%+0.033W%
+0.2V%) is within the range of -0.1% to 0.2%, and the balance is Fe and unavoidable impurities. When the amount is [N] ppm, 2 [0] + [N] < 2
A high-speed tool steel with excellent weldability manufactured by a powder metallurgy method characterized by the following characteristics: