TWI280284B - Hot-working tool steel - Google Patents

Abstract

The present invention relates to a hot-working tool steel which comprising C: 0.10 to 0.70%, Si: 0.10 to 0.80%, Mn: 0.30 to 1.00%, P: 0.007 to 0.020%, Cr: 3.00 to 7.00%, W and Mo individual or composite (1/2W+Mo): 0.20 to 12.00%, V: 0.10 to 3.00%, Ni: 0.05 to 0.80%, Co: 6.50% below, S: 0.150% below and the rest quantity consisting of Fe and unavoidable impurities essentially. Furthermore, the purity of non-metal inclusions are 0.020% below and the ratio of superficial area of carbide and non-metal inclusion which the particle size is more than 1.0 mum is 0.004% below. The hot crack resistance and melting loss of the hot-working tool steel were promoted and simultaneously the machinability was improved after the above technologic treatment.

Description

1280284 Level ,1: Description of the Invention (Description of the Invention) The technical field, prior art, contents, embodiments and drawings of the invention belong to the technical field of the invention. The present invention relates to a hot forging die. Hot-working tool steels such as extrusion dies and die-casting dies, especially heat-resistant tool steels that control carbide and non-metallic inclusions to improve machinability, heat crack resistance and melt resistance. [Prior Art] In the prior art, a technique for improving the toughness of a hot tool steel by improving the purity of a non-metallic inclusion has been disclosed (Japanese Patent No. 2,800,926, Unexamined-Japanese-Patent No. 11-61331). In addition, there is a technique for improving the machinability by increasing the number of inclusions and making the shape of the inclusions spherical (Electrical Steel, Vol. 64, No. 3, pp. 191 to 201, Fig. 2 and Fig. 4, special opening) 1Bu 6 1 3 3 No. 1 and Special Kaiping No. 10-6 05 8 No. 5). However, the above-mentioned prior art evaluates inclusions according to standards such as JISG05 5 5 or ASTM E45-76, and therefore only the type and number of inclusions are specified, and the size of inclusions cannot be quantitatively evaluated. A technique for improving the machinability by adjusting the composition has been proposed (Japanese Patent Laid-Open No. Hei 10-60 5 8 5, No. 9-217147, No. 4-358040, and No. 11-269603). In addition, some technical solutions have been proposed to improve the machinability by improving the organization (Hot -6 - 1280284, Vol. 39, No. 5, pp. 225-226, Japanese Patent No. 2,806,622). However, these known techniques do not take into account the size of carbides and non-metallic inclusions, so they sacrifice other properties and only improve machinability. SUMMARY OF THE INVENTION An object of the present invention is to provide an inter-heat tool steel which remarkably improves machinability while improving heat-resistant crack resistance and melt-resistance by appropriately limiting the sizes of carbides and non-metallic inclusions. The hot tool steel of the present invention contains C: 0.10 to 0.70% by mass, Si: 0.10 to 0.80% by mass, and Μη: 0·30 to 1.00% by mass. : 0.007 to 0.020 mass%, to: 3.00 to 7.00 mass%, 1 and "lanthanum alone or composite (1/2 to + 仏〇): 0.20 to 12.00% by mass, V: 0.10 to 3.00% by mass, Ni: 0.05 ~0.80% by mass, S: 0.150% by mass or less, the balance is basically composed of Fe and unavoidable impurities, and the purity of non-metallic inclusions (JISG0555) is dA60M00 below 0.020%, dB60><400 0.020% or less, dC60M00 is 0.020% or less, and d(A + B + C) is 0.045% or less. Meanwhile, at the time of annealing, the area ratio of carbides and non-metallic inclusions having a particle diameter of more than 1.0 μm is 0.004. In addition, it is preferable to contain Co: 6.50 mass% or less. In the hot tool steel, the area ratio of carbides and non-metallic inclusions having a particle diameter of 1.0 μm or less during annealing is 1 0.5 % or more. In addition, in the hot tool steel, in the case of quenching and tempering, the area ratio of the carbides and non-metallic inclusions having a particle diameter of more than 1. 〇 micron is preferably 0.04% or less. In the hot tool steel, when quenching and tempering, the carbide having a particle diameter of 1.0 μm or less The area ratio of the non-metallic inclusions is preferably 0.03 % or more. The heat-exchanger tool steel of the present invention can further exhibit the effects of the present invention, that is, C: 0.3 5 to 0.40% by mass, Si : 0.55 to 0.65 mass%, Mn: 0.35 to 0.45 mass%, P: 0.007 to 0.010 mass%, Cr: 4.60 to 5.00 mass%, W and Mo, alone or composite (1/2W + M〇): 1.60 to 1.80 Mass %, V: 0.40 to 0.60% by mass, Ni: 0.08 to 0.15 mass%, and S: 0.005 mass% or less. The present invention improves heat crack resistance by appropriately limiting the size of carbides and non-metallic inclusions. The melt resistance is improved, and the machinability is improved. However, the machinability is remarkably deteriorated due to the composition of the steel material, and the steel for reducing inclusions is reduced in order to improve the properties of heat crack resistance, melt resistance, and machinability. The size of carbides and inclusions that simultaneously improve machinability and thermal crack resistance and melt resistance are defined. That is, the main components of the hot tool steel are not changed, and the inclusions are controlled by limiting the purity of the impurities. In the form, the shape and the number of the carbides are controlled by the pre-heat treatment, so that the machinability, the heat-resistant crack resistance and the melt-resistance can be simultaneously improved. -8 - 1280284 [Embodiment] The present invention will be described in further detail below. When the inclusions are reduced, the heat crack resistance can be improved. However, depending on the composition of the steel, the improvement effect is not the same, and the machinability is remarkably deteriorated. Therefore, it is difficult to achieve both thermal crack resistance and machinability. The present inventors have found that if the particle diameters of carbides and non-metallic inclusions are controlled, heat crack resistance and machinability can be achieved. In the conventional method of extending the life of the tool, the more the number of inclusions, the better the machinability is known. However, the present inventors have found that in the quenched and tempered steel having a hardness exceeding 45 HRC, the machinability is good in some cases, and the machinability is poor in some cases. Therefore, the inventors believe that by appropriately controlling the particle size and amount of carbides and non-metallic inclusions in a state of good purity, the machinability can be improved without impairing other properties. Steels with large particle sizes of carbides and non-metallic inclusions have deteriorated machinability, and the more micro-carbides and non-metallic inclusions below 1.0 μm, the greater the improvement effect. Further, the effect of improving the carbonized matter precipitated into the matrix is larger than that of the eutectic carbide. As a non-metallic inclusion, compared with A 1 2 0 3, particles such as B-based nitride and B-based oxide, MnS, and A1N, and having an aspect ratio of 1.3 or less, have an effect of prolonging the life of the cutting tool and improving. The effect of cutting tool life variation and the effect of improving melt resistance and heat crack resistance. Moreover, the coarse non-metallic inclusions -9- 1280284 and carbides significantly deteriorate the melt resistance and heat crack resistance. In order to obtain an inter-heat tool steel that is improved in machinability, reduced in variation, and refractory, heat-resistant and fatigue-resistant, it is important to make carbides and non-metallic inclusions small in size, carbides and The distribution of non-metallic inclusions is very uniform, and in addition to the amount of inclusions described in the well-known literature, by controlling the size of inclusions, variation in machinability can be reduced, and damage resistance and heat crack resistance can be improved. For the melt resistance and the heat crack resistance, the particle size range of the carbides and non-metallic inclusions which do not affect the initial heat has an influence on the melt resistance and the heat crack resistance, and the particle diameter exceeds 1. 〇 Carbide and non-metallic inclusions of rice. Therefore, in the present invention, the amount of carbides and non-metallic inclusions having a particle diameter exceeding 1.0 μm is reduced, and carbides and non-metallic inclusions having a particle diameter of 1.0 μm or less which have a large effect of improving machinability are increased. The morphology and amount of carbide and non-metallic inclusions can be controlled by heating at 1 0 50 to 119 (TC for 1 minute-hour) before annealing, and then controlling furnace cooling, air cooling, oil, etc. The cooling condition is realized. The composition of the hot tool steel of the present invention is defined below according to the definition of the inclusion. The composition of the hot tool steel: C: 0.10~0.70% by mass, preferably 0.35~0.40% by mass The melt-forming 5 micro-solidification of 20 cold and 1280284 c in the matrix during quenching heating provides the required quenching hardness, and in addition, special carbides form special carbides during tempering, and By the precipitation of such special carbides, the softening resistance and the high-temperature strength at the time of tempering are imparted. Further, c forms residual carbides, provides wear resistance at high temperatures, and has an effect of preventing coarsening of crystal grains during quenching and heating. When the amount of carbide is excessively increased, the toughness required for the hot tool cannot be maintained, and the high temperature strength is lowered, so that it is limited to 0.70 mass% or less, and when the content is too low, The additive effect can not be obtained, thus defining its 0.10 mass% or more preferably, C content of 0.35~0.40% by mass.

Si: 0.10 to 0.80% by mass, preferably 0.55 to 0.65 mass% When S i is less than 0.1% by mass, microsegregation does not occur, and machinability is deteriorated. When Si exceeds 0.80 mass%, band segregation is severe. In the cutting edge of the cutting tool, the toughness is lowered, so that the Si content is limited to 0.10 to 0.80% by mass, preferably 0.55 to 0.65 mass%. Μη: 0.30 to 1.00% by mass, preferably 0.35 to 0.45 mass% Μη is solid-solved in the matrix, and the effect of improving the hardenability is large. In order to obtain the effect of addition, the amount of Μη added must be 0.30% by mass or more. When the amount of ruthenium added exceeds 1.0% by mass, the annealing hardness is too high, the machinability is lowered, and the A1 transition point is excessively lowered. Therefore, the amount of Μη added is from 0.30 to 1.00% by mass, preferably from 0.35 to 0.45% by mass. -11 - 1280284 P: 0.007 to 0.020% by mass, preferably 0.007 to 0.010% by mass P is segregated between particles during solidification, and is indispensable for improving the degree of segregation of the strip portion after hot working. As a basic element for maintaining good cutting performance characteristic of the present invention, the P content must be 0.007% by mass or more. However, when P is excessively added, the toughness is lowered, and in order to suppress the decrease in toughness, the upper limit P of P is made 0.020% by mass, preferably 0.007 to 0.010% by mass.

Cr: 3.00 to 7.00% by mass, preferably 4.60 to 5.00% by mass

Cr is the most important element for providing the hardenability necessary as a tool. In addition, Cr improves oxidation resistance and raises the A1 transition point, and forms residual carbides, suppresses coarsening of crystal grains during quenching and heating, and improves wear resistance. When tempering, special carbides are precipitated, and softening resistance at elevated temperature is improved. It has an effect of increasing the high-temperature strength, and the addition amount thereof should be 3.00% by mass or more. When Cr is excessively excessive, Cr carbide is excessively formed, and the high-temperature strength is lowered. Therefore, the amount of Cr should be 7.00% by mass or less, preferably 4.60 to 5.00% by mass. W and Mo: 0.20 mass (l/2W + Mo)S 12.00% by mass, preferably 1.60 mass (l/2W + Mo)S 1.80% by mass W and Mo form a special carbide which can be prevented by forming residual carbide The structure is coarsened during quenching and heating, and fine special carbides are precipitated during tempering, and temper softening resistance and high temperature strength are enhanced, and thus are the most important additive elements. Moreover, W and Mo have the effect of increasing the A 1 transition point. W improves the high temperature strength and wear resistance -12- 1280284 The effect of the property is particularly large, and the enthalpy is more advantageous in terms of toughness than W. When Mo and W are too large, coarse carbides are formed and the toughness is lowered. Therefore, when W and Mo are added alone or in combination, (1/2W + MO) should be 0.20% by mass or more and 12.00% by mass or less. V : 0 . 1 0 to 3.0 0% by mass, preferably 0.4 0 to 0.6 0% by mass V is a strong and strong carbide-forming element, and the effect of forming residual carbides and miniaturizing crystal grains is large, and Improve wear resistance at high temperatures. In addition, when tempering, fine carbides are precipitated in the matrix, and by adding together with W and Μ, the effect of increasing the strength in the high temperature region of 60 to 600 ° C is high, and the A 1 transition point is improved. The role. When V is excessively added, coarse carbides are formed, resulting in a decrease in toughness, so the upper limit is made 3.00% or less. 0质量质量以上。 In order to obtain the effect of V, the content of V must be more than 0.1% by mass. A preferred content range is from 0.40 to 0.60% by mass.

Ni: 0.05 to 0.80% by mass, preferably 0.08 to 0.15% by mass

Ni is dissolved in the matrix to improve the toughness and improve the hardenability, and therefore 0.05% by mass or more should be added. When the amount of Ni is too large, the annealing hardness is too high, the machinability is lowered, and the A 1 transition point is excessively lowered, and the segregation is remarkably deteriorated. Therefore, the upper limit of Ni is set to 0.80 mass%. It is preferably 0.0 8 to 0.15 mass%. C 〇: 6.5 0 mass% or less C 〇 is dissolved in the matrix and has an effect of increasing the high-temperature strength, and thus can be contained as needed. In addition, C 〇 increases the solid solution limit of carbides in the 13-1280284 Worth iron during quenching heating, increases the amount of precipitation of special carbides during tempering, and increases the agglomeration resistance of carbides precipitated at the time of temperature rise. Improve the performance of high temperature strength properties. Further, due to the temperature rise during use of the tool, Co forms a dense oxide film having a good adhesion on the surface, and has an effect of improving wear resistance and solder resistance at high temperatures. When C is too large, the toughness is lowered. Therefore, when Co is contained, the content should be 6.50% by mass or less. S: 0.15% by mass or less, preferably 0.05% by mass or less S forms a sulfide such as ΜnS, which is distributed in the hot working direction to cause a decrease in toughness in the radial direction. Therefore, in order to maintain the toughness in the radial direction, the upper limit S of S should be 0.150% by mass or less, preferably 0.005% by mass or less. A s, S η, S b, C u, Β and B i are concentrated at the intergranular position during solidification, and the banding degree of segregation after hot working is increased, resulting in a decrease in toughness in the T direction, and segregation during heat treatment. The toughness is reduced at or between the iron particles in the Worthfield. Moreover, Pb is distributed in the direction of hot working, so that the toughness in the T direction is lowered.

For the above reasons, the contents of As, Sn, Sb, Cu, B, Pb and Bi should be limited to a particularly low level, and the inventors have found through investigation that the total amount of these elements is less than 0.13%, even if these impurities are contained. Elements can also achieve the objects of the present invention. For each component, the content limit is desirably: As 0.00 5 % or less, Sn 0.003 % or less, SbO.0015 % or less, Cu 0.08 % or less, B -14-1280284 0.0005 % or less, Pb 0.0002 % or less, Bi. Below 0.0001%, other impurity elements include Ti, Al, and N. Among them, Ti and Ti are strong carbide forming elements, and the miniaturization of crystal grains and the precipitation of micro-carbides with high agglutination resistance during tempering have the effects of improving the softening resistance and high temperature in the high temperature region above 65 °C. However, when Nb and Ti are excessively large, coarse and insoluble carbides are formed, resulting in a decrease in toughness, and therefore they are each required to be 0.5% or less. Further, N is dissolved in the matrix and the carbide to make the knot finer and to improve the toughness. Further, N is a Worthite iron forming element. Even in the case of a low C, it is possible to prevent residual iron during quenching and heating, and is an alloy composition having good toughness. However, the hot component steel such as Cr has a content in the alloy composition range, so N must be 0.20 mass% or less. Inclusions According to the purity specified in JIS G0 5 5 5, the inclusions of the A system are deformed inclusions, including Mn S and citrate. These A-based products remarkably deteriorate the heat-resistant crack resistance and the melt-resistance, and therefore, the A-based product must be 0.02% or less, preferably 0%. The B-series inclusions form a group in the direction of discontinuous granular inclusions, including alumina and carbonitride. In addition, the C-based inclusions are viscous and deformed in an irregularly dispersed form, including oxides and carbonitrides. These B-series inclusions and C-clamps, Nb micro-, with strength to solid content of granules, retention of fertilizer N is limited, viscous inclusions in the addition of non-granular impurities -15 - 1280284 to make the machinability deteriorate Therefore, the content must be below 0 · 0 2 0 %, preferably Ο %. Moreover, the sum of these inclusions d (Α + B + c ) must be less than 5 4 5 %. In the present invention, d A 6 Ο χ 4 0 0 = 0 · 0 2 0 % or less, dB 60 x400 = 0.020% UT , dC6 Ο x4 〇Ο = Ο · Ο 2 Ο % or less, d (A + B + C) = 0.045 %WT. Carbide and non-metallic inclusions, when the non-metallic inclusions are less, the area ratio of carbides and non-metallic inclusions with a particle size of more than 1 · 〇 micron can improve the annealing when the annealing state T is 0.04 % or less. Machinability in the state. Further, when the area ratio of the carbide and the non-metallic inclusions having a particle diameter of 1.0 μm or less is 10.5 % or more in the annealed state, the machinability can be further improved. Similarly, in the case where the amount of non-metallic inclusions is small, the area ratio of carbides and non-metallic inclusions having a particle diameter of more than 1 · 〇 micron is 0.02% or less in the quenching and tempering state, and the refractory resistance can be simultaneously improved. Damage, heat crack resistance and machinability. In addition, when the area ratio of carbides and non-metallic inclusions having a particle diameter of less than 〇micron is more than 8% of _ 〇· 〇 in the quenching and tempering state, the resistance to melting and cracking can be further improved. Sex and machinability. Thus, when the area ratio of carbides and non-metallic inclusions having a particle diameter of more than 1.0 μm is less than 4 % of 〇 · 〇 ,, the variation of the cutting tool can be reduced. Such large-sized carbide and non-metallic inclusions 1280284 cause the cutting edge of the tool to be broken when it collides with the cutting tool, and the service life is mutated. As described above, the size of non-metallic inclusions is a problem for machinability. However, when the inclusions are evaluated in accordance with the conventional JIS G05 5 5 or ASTM E45 -7 6, only the types and the number are evaluated, even if they are When the result of the evaluation is good, it does not indicate that the inclusions are minute. The more carbides and non-metallic inclusions having a particle size of 1 · 0 μm or less are present on the segregation zone, the longer the tool life is. The area ratio of carbides and non-metallic inclusions is 1 〇 · 5 % or more in the annealed state, and 〇 · 〇 3 8 % or more in the quenching and tempering state. The effect of the fine carbides having a particle diameter of 1 · 0 μm or less is not limited to carbides, and the same applies to non-metallic inclusions. In order to form minute inclusions having a particle diameter of 1 μm or less, it is preferable to add one or more of Ti, Zr, Ca, Al, Si, B, yttrium and N to 0.00 1 0 to 0.0 0 0 1 . The mass %, by A12〇3, is preferably a fine non-metallic inclusion having a B-based nitride or a B-based oxide, Μ n S and A1N, and an aspect ratio of 1.3 or less. In addition, the purity of non-metallic inclusions is limited to dA6〇x4〇〇 = 〇%, dB60M00 = 0%, dC6〇x 400 = 0% according to the purity specified in JIS G0 5 5 5, which can significantly improve the thermal crack resistance. Hereinafter, the effects of the embodiments of the present invention will be specifically described by comparison with comparative examples outside the scope of the present invention. -17- 1280284 The hot-spot tool steel shown in Tables 1 and 2 below was smelted with a 10 kg vacuum melting furnace (VIF), and the obtained ingot was forged into a 4 〇 x 8 〇 x 2 50 mm with a forging device. The size is then annealed at 83 (TC). The morphology and quantity of carbides and non-metallic inclusions are controlled by passing at 1015~1 240° (: heating for 1 minute to 20 hours, then furnace cooling, air cooling or oil cooling) Realized. -18- 1280284

1280284 <Nm 1/2W +Mo 2.55 5.55 1.90 3.85 1.95 2.60 5.20 6.90 1.60 O r-^ 0.003 0.004 0.004 0.003 0.004 0.004 0.003 0.004 0.003 0.004 0.004 0.004 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.006 0.006 0.008 0.007 0.008 0.010 0.015 0.001 0.003 0.001 0.001 0.003 0.003 0.002 0.003 0.003 0.001 0.002 s 0.50 0.10 0.05 0.06 0.08 0.10 0.40 0.05 0.08 0.13 0.15 2.300 0.000 1.300 2.300 4.000 1.200 0.300 0.000 0.000 0.000 0.000 2.700 3.100 2.800 1.700 0.900 0.600 2.400 1.800 0.000 0.000 0.000 > 0.10 2.50 2.50 0.50 0.10 2.70 1.80 0.10 0.40 0.50 0.60 os 4.00 0.50 3.00 1.50 2.30 4.00 6.00 1.60 or—^ 1.80 6.50 3.50 6.60 4.50 3.20 6.80 5.40 3.00 4.60 4.80 5.00 00 0.001 0.007 0.008 0.009 0.006 0.010 0.014 0.012 0.001 0.003 0.005 Ph 0.0070 0.0100 0.0200 0.0200 0.0080 0.0087 0.0100 0.0007 0.0011 0.0080 0.0070 cs 0.80 0.30 0.95 0.30 0.34 0.70 0.32 0.30 0.35 0.40 0.45 0.67 0.60 0.65 0.50 0.48 0.40 0.30 0.10 0.55 0.60 0.65 U 0.18 0. 20 0.30 0.45 0.52 0.61 0.65 0.70 0.35 0.37 0.40 Bu OO Os o <N mv〇布佩孽丨OOSI· 1280284 In addition, the purity of non-metallic inclusions of all cast materials is below JIS dA0.005 %, d (B + C) 0.02% or less, the ratio of the number of carbides to non-metallic inclusions is 1.3 to 1.0. The material was evaluated by solid-solving at 90 to 1800 °C for 30 minutes, then quenching, and tempering at 5000 to 600 °C for 2 hours. The tempering procedure was repeated twice. . Thus, the hardness was adjusted to 43 ± 1 HRC, the performance of the SKD61 material was 50, and the properties were compared. The determination of carbides and non-metallic inclusions below 1.0 μm is carried out as follows, ie, for the annealed material, the honed sample is immersed in the paleo-acid + 3 % nitric acid solution to expose the metal structure And for the quenched and tempered material, the honed sample is etched with oxalic acid to expose the metal structure. The metal structure was magnified by SEM (scanning electron microscope) at 4,000 times, and the area ratio and the average particle diameter were measured by image analysis. Further, the degree of dispersion is evaluated based on the distance between the carbide and the non-metallic inclusions, which is larger than the area ratio of the non-segregated portion by more than 30%. The determination of carbides and non-metallic inclusions with a particle size of more than 1.0 μm was carried out using uranyl oxalate and then image analysis in a 1 mm2 field of view with a 1,000-fold photograph. The results of the measurement of carbides and non-metallic inclusions are shown in Tables 3 and 4 below and Tables 5 and 6. -21 - 1280284 Table 3 SKD 61 Annealing material quenching and tempering material exceeds Ι.Οηηι Ι.Ομιη total more than Ι.Ομιη Ι.Ομιη below common example 1 0.037 10.5 10.537 0.100 0.018 0.057 2 0.032 11.0 11.032 0.037 0.020 0.047 3 0.028 11.7 11.728 0.032 0.015 0.038 4 0.026 15.0 15.026 0.028 0.010 0.040 5 0.003 32.0 . 32.003 0.002 0.038 0.413 6 0.001 14.0 14.001 0.003 0.410 0.118 Comparative Example 1 0.005 17.0 17.005 0.006 0.222 0.057 2 0.012 21.0 21.012 0.008 0.800 0.808 3 0.009 27.4 27.409 0.004 1.200 1.204 4 0.006 23.0 23.006 0.003 0.400 0.403 5 0.007 22.0 22.007 0.001 0.100 0.101 6 0.003 10.2 10.203 0.01 0.035 0.036 Table 4 The quenched and tempered material of the annealed material exceeds Ι.Ομηι Ι.Ομιη The total sum exceeds Ι.Ομιη Ι.Ομηι below total 7 0.004 9.5 9.504 0.002 0.032 0.032 8 0.002 8.4 8.402 0.002 0.028 0.030 9 0.002 10.4 10.402 0.001 0.012 0.013 10 0.003 8.7 8.703 0.001 0.008 0.009 Real 11 0.001 12.0 12.001 0.003 0.007 0.010 Shi 12 0.004 13.2 13.204 0.004 0.042 0.046 Example 13 0.001 15.2 15.201 0.002 0.046 0.048 14 0.001 13.5 13.501 0.003 0.042 0.045 15 0.000 10.5 10.500 0.000 0.042 0.042 16 0.000 12.3 12.300 0.000 0.054 0.054 17 0.000 10.5 10.500 0.000 0.048 0.048 -22- 1280284 Table 5 SKD 61 Non-metal Inclusions dA dB dC Total Example 1 0.030 0.015 0.012 0.057 2 0.028 0.012 0.007 0.047 3 0.018 0.022 0.008 0.048 4 0.022 0.027 0.021 0.070 5 0.018 0.008 0.008 0.034 6 0.015 0.004 0.003 0.022 Comparative Example 1 0.043 0.023 0.310 0.376 2 0.018 0.023 0.024 0.065 3 0.018 0.016 0.007 0.041 4 0.017 0.010 0.009 0.036 5 0.012 0.012 0.010 0.034 6 0.007 0.009 0.002 0.018 Table 6 Non-metallic inclusions dA dB dC Total 7 0.005 0.012 0.004 0.021 8 0.020 0.007 0.009 0.036 9 0.012 0.007 0.012 0.031 10 0.018 0.009 0.018 0.045 实11 0.007 0.002 0.007 0.016 施12 0.009 0.004 0.009 0.022 Example 13 0.002 0.020 0.012 0.034 14 0.004 0.004 0.020 0.028 15 0.000 0.000 0.000 0.000 16 0.000 0.000 0.00 0.00 0 17 0.000 0.000 0.000 0.000 -23- 1280284 The machinability of the annealed material is evaluated by using a high-end steel end mill with a diameter of 1 〇 mm at a speed of 520 rpm and a feed rate of 74 mm/min. When the amount of cutting is 10 × 1 mm, the life at the time of occurrence of the breakage is obtained, and the life of SK D1 of the conventional example is taken as 100, and is expressed by an index. The l〇xlmm indicates that the test material and the sharp knife are in contact with each other in the longitudinal direction of the sharpening knife by 10 mm, the contact in the axial direction of the vertical boring tool is 1 mm, and the infeed of the test material is 1 Ο X 1 mm. The area is cut. Therefore, a recess having a width of 1 mm and a depth of 10 mm was formed on the side surface of the test material. In addition, the machinability evaluation of the quenched and tempered material is that the steel is quenched and tempered to 48 HRC, and a two-blade end mill with TiAIN coated on a powder cutter high speed steel having a diameter of 10 mm (MMC Cognac VA manufactured by VA) is used. -2SS diameter 6mm), the steel is cut at a speed of 1 062 rpm, a feed rate of 212 mm/min, and a feed amount during cutting is 9 X 0 · 6 mm, and the life of the end mill is determined to be melted. . The life of the conventional example SKD6 11 is taken as 100 and expressed by an index. The thermal cracking test is a method of heating a test material having a diameter of 30 mm and a length of 50 mm by high-frequency induction heating, watering at a surface temperature of 650 ° C, and cooling to 50 ° C, thus repeating 1 000 times, and measuring the average length of cracks. (micron). Then, the life of the conventional example SKD611 is taken as 1 0 0 and expressed by an index. The evaluation of the melt loss property was performed using an aluminum alloy (JIS ADC 12) which is usually used in die casting. The JIS ADC12 is an aluminum alloy used for die-casting products of automobiles (transmission type) and home appliances, and its composition is A1-0.43%, Ζη-〇·2〇%, -24-1280284.

Mn-10.85%, Si-2.00%, Cu-1.01% and Fe-0.24%Mg. The aluminum alloy was placed in a container and heated to 650 ° C to be melted. The test pieces of the examples and the comparative examples having a diameter of 5 mm and a length of 30 mm were placed in the melt to rotate at a speed of 500 rpm, and the ADC 12 was melted. The liquid was kept in this state for 20 minutes, and then the test piece was taken out, and the aluminum alloy adhering to the test piece was removed with sodium hydroxide, and the amount of loss (g) of the test piece was measured from the difference in weight before and after use of the test piece. The life of SKD61© of the conventional example is taken as 100 and expressed by an index. The evaluation results of these machinability, melt resistance and heat crack resistance are shown in Tables 7 and 8 below. Table 7 SKD 61 Cut Angle 11 Resistance to Fusible Heat Resistant Cracking Annealing Material (10HRC) Quenching Material (48HRC) Conventional Example 1 100 100 100 100 2 102 104 100 102 3 105 103 102 104 4 103 107 101 106 5 123 102 98 98 6 120 104 104 99 Comparative Example 1 100 100 100 95 2 97 98 102 101 3 102 99 98 104 4 103 102 99 99 5 100 98 97 101 6 180 186 217 180 -25- 1280284 Table 8 Resistance to fusible heat-resistant cracking annealed material (10HRC) Quenching material (48HRC) 7 180 190 210 184 8 182 184 207 191 9 180 180 214 197 Real 10 183 181 218 194 11 218 180 213 184 Application 12 223 228 222 243 13 220 232 223 254 Example 14 216 251 200 280 15 304 332 220 333 16 332 301 260 345 17 340 351 320 380 S KD1~6 of the conventional example improves the purity of the scrap as a raw material during smelting. Degree, but heat crack resistance, melt resistance and machinability were not improved. Further, in Comparative Examples 1 to 6, although the composition of the components falls within the range defined by the scope of the invention of the present invention, the carbides and inclusions having an annealed material having a particle diameter of more than 1.0 μm may not be 0.004% or less. Improve heat crack resistance, melt resistance and machinability. On the other hand, as shown in Examples 7 to 17, when the first item of the patent application range of the present invention is satisfied, the machinability, the melt resistance and the heat crack resistance of the annealed material and the quenched and tempered material are mixed and retained. The S KD 6 11 of the material is increased by 1.8 times or more. Further, as shown in Examples 1 to 17 , if the second aspect of the invention is satisfied, the machinability of the annealed material, the resistance to melt loss -26-1280284, the heat crack resistance and the retention of inclusions are satisfied. Compared with SKD611, it is 2.0 times higher. However, the effect of improving the machinability and heat crack resistance of the quenched and tempered material cannot be obtained. Further, when the present invention is satisfied as in the third and fourth aspects of the patent application, as shown in Examples 12 to 17, the machinability, the melt resistance and the heat crack resistance of the annealed material and the quenched and tempered material are * S KD 6 11 with inclusions increased by 2,0 times or more. When the inclusions are 0%, as shown in Examples 15 to 17, the machinability, melt resistance and heat crack resistance of the annealed material and the quenched and tempered material are increased by 3.2 times compared with the SKD611 holding the inclusions. the above. As described above, the use of the present invention can significantly improve the machinability, melt resistance and heat crack resistance of the hot tool steel.

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Claims (1)

1280284 J- , v . , · · · ·.乂. ·. c, Λ. No. 9 1 1 3 5 3 6 No. 1 "Hot-stool steel" patent case (amended on November 27, 2006) Pick-up, patent application scope 1. A hot-spot tool steel, which is an annealed material, which contains C: 0.10 to 0.70% by mass, Si: 0.10 to 0.80% by mass, Μη: 0·30 to 1.00% by mass, Ρ: 0·007 to 0.020% by mass, Cr: 3.00 to 7.00% by mass, W and Mo alone or in combination ( 1/2\¥ + ^4〇): 0.20 to 12.00% by mass, ^0.10 to 3.00% by mass, Ni: 0.05 to 0.80% by mass, S: 0.150% by mass or less, and the balance is substantially composed of Fe and inevitable impurities. The purity of the non-metallic inclusions (JISG0555) is dA60><400 is 0.020% or less, dB60><400 is 0.020% or less, dC60M00 is 0.020% or less, and d(A + B + C) The area ratio of the carbide having a particle diameter of more than 1.0 μm is 0.004 % or less, and the area ratio of the carbide having a particle diameter of 1.0 μm or less is 8.4 % or more. 2. The hot room tool steel according to item 1 of the patent application, which further contains (: 〇: 6.50% by mass or less. 3. The hot room tool steel according to the first item of the patent application, wherein the particle size is less than 1.0 micron. The area ratio of the carbide is more than 0.5%. 4. The hot tool steel of the second aspect of the patent application, wherein the area ratio of the carbide having a particle diameter of 1.0 μm or less is more than 0.5%. The hot-spot tool steel of the first application of the patent scope is a quenching and tempering material to which quenching and tempering is applied, wherein the particle size exceeds 1. The area ratio of the carbide of 〇1280284 micron is 0.04% or less, and the particle diameter is 1.0. The area ratio of the carbides of the micron or less is 0.007% or more. 6. The hot tool steel of the second aspect of the patent application is a quenched and tempered material to which quenching and tempering is applied, wherein the particle diameter exceeds 1.0 μm. The area ratio of the carbide is 0.04% or less, and the area ratio of the carbide having a particle diameter of 1.0 μm or less is 0.07% or more. 7. The hot-work tool steel according to item 3 of the patent application, the system Quenched and tempered material to which quenching and tempering is applied, wherein the particle size exceeds 1 The area ratio of the carbide of 0 micrometers is 0.04% or less, and the area ratio of the carbide having a particle diameter of 1.0 micrometer or less is 0.07% or more. 8. The hot-work tool steel according to item 4 of the patent application, It is a quenching and tempering material to which quenching and tempering is applied, wherein an area ratio of carbides having a particle diameter of more than 1.0 μm is 0.04% or less, and an area ratio of carbides having a particle diameter of 1.0 μm or less is 0.07%. 9. The hot room tool steel according to item 5 of the patent application, wherein the area ratio of the carbide having a particle diameter of 1.0 μm or less is 0.0 3 8 % or more. 1 〇. The heat of the sixth item of the patent application scope The tool steel, wherein the area ratio of the carbide having a particle diameter of 1.0 μm or less is 0.0 3 8 % or more. 1 1 . The hot tool steel according to item 7 of the patent application, wherein the particle diameter is 1.0 μm or less. The area ratio of the carbide is 0.03 8 % or more. 1 2. The hot room tool steel according to item 8 of the patent application, wherein the area ratio of the carbide having a particle diameter of 1.0 μm or less is 0.0 3 8 % or more. 3. The hot room tool steel according to any one of claims 1 to 12, the chemical composition of which includes C: 0.3 5 to 0.40% by mass, Si: 0.55 to 0.65 mass%, Μικ0.35 to 0.45 mass%, 1280284 P: 0.007 to 0.010% by mass, Cr: 4.60 to 5.00% by mass, W Mo alone or composite (1/2W) + M〇): 1.60 to 1.80 mass SV: 0.40 to 0.60 mass%, Ni: 0.08 to 0.15 mass%, S: 0. mass% or less. And 10, 005