TW200401042A - Steel block for the manufacture of moulds for the injection moulding of plastics materials or for the manufacture of metal-working tools - Google Patents

Abstract

Steel blocks for the manufacture of moulds for the injection moulding of plastics material or for the moulding of metals or for the manufacture of metal-working tools having a thickness > 20 mm, with a completely martensitic or martensito-bainitic structure, of which the hardness at all points is between 370 HB and 450 HB and of which the chemical composition of the steel comprises, in % by weight: 0.12% ≤ C ≤ 0.32%; Si ≤ 0.8%; Mn ≤ 2.5%; Ni ≤ 3%; Cr ≤ 3.5%; Mo + W/2 ≤ 2.2%; V + Nb/2 + Ta/4 ≤ 0.5%; A1 ≤ 0.4%; Ti + Zr/2 ≤ 0.1%; 0.0005% < B < 0.015%; S + Se + Te < 0.2%; Pb + Bi < 0.2%; Ca < 0.1%, the remainder being iron and impurities resulting from production, the chemical composition also satisfying the following equations: 3.2 ≤ Tr ≤ 6.5; 77 ≤ Dr ≤ 85; U ≤ 850; in which, for contents expressed in %: Tr = 1.8 x C + 1.1 x Mn + 0.7 x Ni + 0.6 x Cr + 1.6 x Mo*+ 0.5; Dr = 54 x C0.25 + 24.5 x (Mo*+ 3 x V*)0.30 + 1.58 x Mn + 0.74 x Ni + 1.8 x Si + 12.5 x (Cr)0.20; U = 1600 x C + 100 x (0.25 x Cr + Mo* + 4.5 x V*); R= 3.8 x C + 10 x Si + 3.3 x Mn + 2.4 x Ni + 1.4 x (Cr + Mo*); Mo*= Mo + W/2; V*= V+ Nb/2 + Ta/4; the contents of A1, Ti, Zv, N and B being such that: B ≥ 1/3 x K1 + 0.5 wherein K1= Min (I*;J*); I*= Max (;I) and J*= Max (O;J); I = Min (N; N-0.29(Ti+Zr/2- 5));xc J= Min( N: 0.5( N-0.5(N-0.52 A1+ (N-0.52 A1)2+283)) <SP>1/2</SP>.

Description

200401042 玖 玖, Description of the invention [Technical field to which the invention belongs] The present invention relates to a steel block which can be used, in particular, for manufacturing a mold for plastic injection molding or for manufacturing a metal working tool. [Prior art] Plastic injection molding dies are generally produced from steel with a hardness of about 300 HB. However, when these molds are used in the manufacture of, for example, industrial plastics or thermosetting plastics, it is better to use harder steels that are more resistant to wear. Therefore, a 55 NCDV Type 7 steel containing approximately 0.55% carbon and 175% nickel, chromium, uranium and vanadium is used. This steel makes molds with a hardness of about 400 HB. However, this type of steel has many disadvantages: it is difficult to machine and it is difficult to weld. In addition, such steel often has local segregation and constitutes hard spots, which is not conducive to polishing or chemical graining. These two disadvantages are particularly undesirable because the mold must be made with significant mechanical machinability and the mold can generally be repaired by welding and polishing or pelletizing for reassembly. In addition, these molds must be able to harden the surface with nitriding without compromising the hardness of the mold. These steels are also used, for example, to make metal molds such as lightweight alloys by stamping, forging, or forging, or molds for parts intended for metal processing. To achieve this application, conventional steel molds have the same disadvantages as plastic molds. [Abstract] The purpose of the present invention is to propose a steel (2) (2) 200401042 block for molds or metal working tools to overcome these shortcomings. The steel block is easier to weld, machine cut, and polish than steel blocks of the prior art. And granules, and this steel can be used for the manufacture of parts with a hardness of about 40 0 HB, even after the surface is hardened by nitriding. This indicates that the properties required for the steel block, especially in terms of hardness, must be The chain can be forged at least 5 3 0 ° C. The invention relates to a steel block having a thickness of more than 20 mm and possibly up to 1500 mm. The structure of the steel block is martensite or martensite-bainite, and the hardness of all points is 3 70 HB to 450 Among HB, used for manufacturing molds or metalworking parts, the chemical composition of this steel is expressed as% by weight as follows: 0 12 0% &lt; C &lt; 0 3 2 0%

Si &lt; 0,8% Μη &lt; 2 5%

Ni &lt; 3%

Cr &lt; 3 5%

Mo + W / 2 &lt; 2 2% V + Nb / 2 + Ta / 4 &lt; 0 5% A1 &lt; 0 4%

Ti + Zr / 2 &lt; 0 1%-boron, the content is between 〇ο ο 0 5% to 0 015%,-at least one element of sulfur, selenium and tellurium added as the case requires, the total amount is less than Or equal to 02%,-at least one element of lead and bismuth added as the case requires, the total amount of which is less than or equal to 0%, (3) 200401042 0 1%, the steel-calcium as the case requires, The content is less than or equal to the remainder being iron and the rhenium 'copper' which is produced during production. The chemical composition of the impurity block also conforms to the following equation: 3 2 &lt; Tr &lt; 6 5 77 &lt; Dr &lt; 85 U &lt; 850

Mo * + 3x V * &gt; 0 1% where each content is expressed in% below:

Tr = 1 8x C + 1 lx Μη + 0.7x Ni + 0.6x Cr

Mo * + 0 5

Dr = 54x C 0 2 5 + 2 4 5 x (Mo * + 3x V *) ° 30 + 1 + 0 74x Ni + 1 8x Si + 12 5x (Cr) 0 20 u = 1600 x C + 1 OOx (0 25 x Cr + M 0 * + 4.5x \ R = 3 8x c-f 1 0 x Si + 3 3x M n + 2.4x Ni + 1 丨 *) Mo * = Mo + W / 2 V * = V + Nb / 2 + Ta / 4 Boron, Aluminum, Titanium, and Nitrogen--3 Miles and Miles% B / 1000 &gt; 1/3 x K 1 + 0 5 means + 1.6 x 58x Mn, 4x (Cr K1 = Min (I *, J *)

Max (O, J) I * = Max (Ο, I) and J * (4) 200401042 J = Min {N, 0 5 [N-0 5 2 A1 + ((N-2 8 3) 1'2] } The preferred chemical composition is as follows: R &gt; 11 The preferred chemical composition may also be as follows: R &lt; 2 7x Tr The best silicon content is accurately maintained at 0 4 5%. Preferably U &lt; 7 5 0, Better US 7 0 0, and then 6 5 0 ° In addition, more obviously, when US 7 50, the lower of steel: 0 200% &lt; C &lt; 0 320% Si &lt; 0 3 0% 0 3% &lt; Μη &lt; 1.8% Ni &lt; 2% 0 5% &lt; Cr &lt; 2 5% Mo + W / 2 &lt; 1 8% V + Nb / 2 + Ta / 4 &lt; 0 3 % Mo * + 3x V * &gt; 0 3% Even better, US650, and: 0 220% &lt; C &lt; 0 2 8 0% Si &lt; 0 1 5% 0 8% &lt; Μη &lt; 1 6% Ni &lt; 2% 0 5 2A1) 2 +

The composition of Jiadi US

-10-(5) 200401042 1% &lt; C r &lt; 2 5%

Mo + W / 2 &lt; 1 5% V + Nb / 2 + Ta / 4 &lt; 0 2%

Mo * + 3χ V * &gt; 〇 4% Therefore, Tr &gt; 45 is preferred. The present invention also relates to a steel block mechanical part according to the present invention. At least a part of the surface of the mold part and the hardness of all points are 3 7 0 Η B. The steel according to the present invention is also intended to be used for gold. The present invention will be described in more detail. The description and examples are limited to the following examples. Parts used for mold or metal processing are manufactured. The steel block is mechanically cut to obtain a homogeneous structure, and is trained to obtain the desired hardness and hardness. Hardened steel with high malleability and remarkable hardenability Must have maximum mechanical conductivity. This thermal conductivity helps to improve the combination of different properties of the mold. Originally contradictory, the harder the steel, the harder it is to mechanically cut, and alloy elements such as sulfur, Ming, selenium, tellurium or lead can be added. The surface is granulated, but it must be limited in the steel used for the mold. The addition of these elements is not a completely suitable function. 'The thermal conductivity of the steel and the steel mold cut from the Hardened, between 4 5 0 ΗΒ. It belongs to the manufacture of processed parts. Shown, but the present invention is not affected by the martensitic-bainite ductility uniformly cut by mechanical cutting of solid steel blocks. Therefore, steel must be used. However, these machinability and highest heat transfer productivity. This. In fact, it is known that the mechanical cutting performance is improved by the addition. However, because this is not conducive to surface polishing, and other elements are added. Whatever. It is also known that the quenchability of this steel group varies inversely. (6) (6) 200401042 Therefore, the necessary conditions of these steels are contradictory. However, in a novel method, the inventors have found that a composition range can be found that produces a combination of properties that is substantially better than the properties of conventional steels. On the other hand, the scope of these compositions is defined by the content distribution of each element in the composition and the formula to which it depends. In order to achieve these combined properties, the steel must contain:-〇120% to 0 3 20% carbon to form carbides, which can harden the steel without unduly degrading weldability, toughness, and machinability 'and the carbon content It is preferably between 0 2 0 0% and 0 3 2 0%, more preferably between 0 2 2 0% and 0 2 8 0%;-Silicon, the content is lower than 0 8%, and preferably lower At 0 4 5%, more preferably less than 0 30%, and still more preferably less than 0 15%. Usually this element is used for deoxidation in steel production, but it will adversely affect the thermal conductivity. However, silicon is always present in trace amounts;-Manganese, below 25 ° /. It is preferably between 0.3% and 1.8%, and more preferably between 0.8% and 16% in order to obtain good quenchability without causing excessive segregation. Excessive segregation will reduce the ability to obtain good surface characteristics of the mold. Manganese is always present, at least in trace amounts. In addition, in order to capture sulfur in the form of impurities, the content of manganese is preferably higher than 0.01%. If sulfur is added to improve machinability, the minimum content of manganese must be at least 5 times, and preferably 7 times, relative to sulfur;-Nickel, less than 3%, preferably less than 2%. Nickel increases hardenability but is very expensive. It may be present in trace amounts. However, 'application requires greater toughness and extremely uniform hardness, reducing the manganese content and increasing the nickel content is 値 -12-(7) (7) 200401042. It is obtained by using manganese to nickel as a one to two ratio, which reduces segregation. The advantages are:-complex, content below 35 ° / 〇 ', preferably between 0.05% and 25 ° / 〇', more preferably between 1% and 25%. This element can increase the quenchability ', but too much chromium will increase the concentration of carbides and cause adverse conditions for molybdenum, tungsten, vanadium, niobium, and giant elements. Therefore, chromium can be present in trace amounts;-The sum of the content of molybdenum and / or tungsten is Mo * = Mo + W / 2 is less than 22%, preferably less than 1, and more preferably less than 1.5%. These elements have a significant quenching effect. In addition, this element can substantially reduce intermediate annealing, which is advantageous when the surface of the mold is nitrided for surface treatment at a temperature of at least 500 t. However, excessive molybdenum and tungsten will reduce the machinability;-Add at least one element of vanadium, niobium, and molybdenum as required, and its content is low as the sum of V * = V + Nb / 2 + Ta / 4 At 0 5%, preferably below 0.3%, more preferably below 0.2%. These elements can increase the resistance to intermediate annealing 'especially when exercising at temperatures above 550 ° C. Niobium and hafnium also increase the wear resistance of mold marks. However, excessive amounts will detract from machinability and weldability;-The content of boron 'is from 0 0 0 0 5% to 0.0 1 5%. This element will substantially increase hardenability without adversely affecting thermal conductivity. In addition, when the element encounters a high Vostian ironization temperature during welding, the effect 'disappears' is best repaired by welding. When the content is below 0 000 5%, it is limited by the analysis method, and it has no obvious effect. Above 0 〇i 5% 'It will make the steel brittle without increasing its hardenability;' The content of aluminum added as the case requires is 0 4%, and as appropriate -13 (8) (8) 200401042 If necessary, at least one element of titanium and hafnium is added, and the total of Ti + Zr / 2 can reach 0.01%. These elements are strong oxygen scavengers. In addition, these elements fix nitrogen that is still in the form of impurities. The nitrogen content is at least 0.004% to 0.025%, and may be less than 0045%. Above 0 0 2 5%. However, when boron is contained in the steel material, it is preferable that the nitrogen content be less than 0 2 25%. For boron to fully function, aluminum, titanium or zirconium must be included. Aluminum, titanium, and tungsten can be used alone or in combination of two or three of these elements to protect boron from nitrogen and thereby make boron fully functional. The boron, aluminum, titanium, chromium, and nitrogen contents are expressed in thousandths of a weight percent as follows: B &gt; l / 3x K1 + 〇5 K1 = Min (I *, J *) I * = Max (0, I) And J * = Max (Ο, J) I = Min (N, N-0 29 (Ti + Zr / 2-5)) j = Min {N, 〇5 [N-0 5 2 A1 + ((N- 0 5 2 Al) 2 + 2 8 3) 1/2]}-Copper can be present in trace or impurity form;-Add at least one element of sulfur, selenium, tellurium in small amounts as required, the total of these elements The content must be below 0 200%. However, if an attempt is made to use the steel for the production of molds for polished, chemically grained surfaces, the total content of these elements must be less than 0 25%, or preferably less than 0 005%;-depending on If necessary, at least one element of lead and bismuth is added, and the total amount of these elements is less than 0%. If you are trying to use this steel for polishing and (9) (9) 200401042 to mold the surface of granules, it is better not to include these elements; If the test is to use the steel for the polishing and graining of the mold, because the positive effect of calcium on machinability must be achieved with sulfur, it is best not to include this element. If the steel block must be After polishing or granulation, it is best to limit the calcium content; the remainder of the composition consists of iron and impurities produced in the production. However, it must be noted that the minimum content of all alloying elements in this example is not limited, and even if these elements are not added, these elements can still exist in the form of extremely low levels of at least residues or impurities. Within the limits defined just now, the composition of the steel block must be chosen in order to obtain the required service characteristics. For this purpose, its composition must be as follows:-Tr = 1 8x C + 1 lx Μη + 0 7 χ Ν i + 0 6 χ C r + 1 6 χ Μ * * + 〇5 represents the hardenability of the steel, which 値Must be higher than 3.2, preferably higher than 4 5 to obtain proper quenchability. In particular, T r must be higher than 4 5 to obtain a martensitic-bainite structure on the steel part without any trace pearl structure. The thickness of the steel may exceed 1000 mm, and may even reach 1500. mm;

Dr = 54x C ° 2 5 + 24 5 x (Mo * + 3x V *) 0 3 0 + 1 58x Mn 〇74χ Ni + 1.8x Si + 12.5x (Cr) 020 must be between 7 7 and 8 5 In order to achieve proper hardening by carbides without excessively degrading machinability; • sacrificial system of u = 1 600x c + 100X (° 25x Cr + Mo * + 4 5x V *) can be machined Index of mechanical properties (the lower the U 値, the better the machinability is -15-(10) (10) 200401042), the 値 must be maintained below 8500, preferably below 7500, and more preferably 7〇 0 or less, and more preferably 650 or less;-R = 3 8 XC + 1 〇XS i + 3 3 X Μ η + 2.4 X Ni + 1. 4χ (C r + Μ ο *) will follow the thermal impedance Rate, in other words, the reciprocal of heat conduction must be lower than 2 7 χ T r is better. However, for all requirements for the required characteristics of steel, this number 値 cannot usually be less than Η, but is preferably less than 20, more preferably less than 15, so the present invention relates specifically to R 値Steels greater than 1 1 but as low as possible;-In terms of the above points, the composition must also conform to this equation M 0 * + 3 χ V * 2 0 1%; when U &lt; 7 5 0 and analysis When the results meet the following preferred ranges: 0.2 00% &lt; C &lt; 0 3 20%

Si &lt; 0 3 0% 〇 3% &lt; Μη &lt; 1 8%

Ni &lt; 2% 〇 5% &lt; Cr &lt; 2 5%

Mo + W / 2 &lt; 1 8% V + Nb / 2 + Ta / 4 &lt; 0 3% The splitting result must be: Mo * + 3 χ V * 2 0.3%, when US 6 5 0 and the analysis results meet The following is a more preferable range: 0 22〇〇 / 0 &lt; c &lt; 0 2 8 0% s 1 s: 〇1 5% 0 8% &lt; Μη &lt; 1 6% Νί 5 2% (11) (11) 200401042 1% &lt; Cr &lt; 2 5%

Mo + W / 2 &lt; 1 5% V + Nb / 2 + Ta / 4 &lt; 0 2% The analytical composition must satisfy this equation: Μ 〇 # + 3 x V * 2 0 4%. To use this steel to make molds, the steel is manufactured by conventional methods, cast and hot rolled or hot forged and cut to obtain a steel block with a thickness of more than 20 mm, which may exceed 100 mm and reach 400 mm, if possible 600 mm or even 150 mm. It should be noted that the smallest thickness of steel blocks may be as thin as paper or large flat plates, while the largest thickness is usually forged chain steel blocks. The steel block is subject to circumstances, and the temperature is higher than AC3 and preferably lower than 9 50 ° C. During the exercise or hot rotation, Vossian iron is ironized, especially when the steel contains boron. Oil or water cooling depends on the thickness and hardenability of the steel to obtain a martensite or martensite-bainite structure. Finally, the steel blocks are forged at a temperature above 500 ° C, preferably at least 550 ° C, but must be less than AC :. The resulting hardness is approximately between 3 70 HB and U 4 50 HB. Among such steel blocks, mold parts including polished and optionally grained marks are mechanically cut in a conventional manner. Depending on the circumstances, these parts are surface hardened by, for example, gaseous nitriding. After the gas nitriding, the hardness of this steel is approximately 3 70 HB to 4 50 HB, except for the end of the part which has been nitrided. [Embodiment] (12) (12) 200401042 The following examples are used for comparison. The composition of the analyte is listed in Table 1. The Tr, Dr, U, R, and R / 2 of the analyte are listed in the table. 2. Examples 1, 3 '5, 6, 9 to 15, 5, 17 and 18 represent the present invention, while Examples 2 1 to 26 are used for comparison. This steel is not added with sulfur, selenium, tellurium, lead, bismuth, and calcium. However, these steels contain a small amount of sulfur from 0 0 10% to 0 2 0%. For all steels, the hardness HB has been measured in the exercise-quenched state. In other words, the martensite or martensite-bainite structure in all examples is at 550 T: the forged chain is the only example. 26 Forging at 625 ° C (13) 200401042 Table 1 Example C Si Mn Ni Cr Mo WVB * Al * Ti * N * 1 0 25 0 20 1 2 0 95 2 1 0 65 0 0 15 2 65 0 6 3 0 19 0 15 1 2 0 95 2 1 0 8 0 0 17 2 5 5 7 0 6 5 0 27 0 14 1 5 0 2 1 5 0 85 0 0 17 2 45 0 3 6 0 17 0 12 1 1 0 2 1 7 1 6 0 0 15 2 5 5 5 0 6 9 0 28 0 13 14 0 85 2 05 0 95 0 0 02 1 5 25 15 3 10 0 30 0 09 1 3 0 75 1 9 0 6 0 0 19 1 54 0 1 11 0 24 0 05 1 25 0 3 1 8 0 32 0 67 0 16 3 3 15 7 12 0 15 0 07 1 3 0 9 2 7 0 6 0 7 0 17 2 52 0 7 13 0 23 0 04 0.3 0 1 1.5 0.7 0 0 19 2 60 0 5 14 0 27 0.15 1.7 1 8 1 9 0 5 0 4 0 3 64 0 9 15 0 28 0 11 0 3 0 7 2 9 15 0.5 0 2 5 7 0 5 17 0.24 0 27 1 3 0 6 1 9 0 67 0 0 15 3 63 0 8 18 0.20 0 42 1 2 0 7 2 7 0 2 1 0 0.1 2 85 0 8 2 1 0.43 0.33 1 25 0 3 1 9 0 5 0 0 0 24 0 11 22 0 42 0 30 1 2 0 2 2 1 0 25 0 0 1 0 18 0 15 23 0.43 0 14 1 3 0 1 2 9 0 05 0 0 2 0 20 0 10 24 0 49 0 3 5 1 2 0 2 1 8 0 15 0 0 12 0 20 0 8 25 0 55 0 30 0 8 1 7 1 1 0 45 0 0 1 0 25 0 8 26 0 39 0 3 0 0 57 0 1 3 2 0 94 0 0 19 0 1 50 0 9 Boron, nitrogen, Qin, Ming, expressed in thousandths of a percent. (14) 200401042 Table 2 Examples Tr Dr u RR / 2,7Tr 1 5 24 80 9 5 8 5 13 0 92 3 5 3 7 8 1 549 12 5 0 86 5 4 72 80 9 6 11 10 9 0 85 6 5 74 8 1 1 542 10 6 0 68 9 5 8 9 8 14 603 13 2 0 83 1 0 5.1 82 6 673 11.6 0.85 11 4 65 79 6 567 9 69 0 77 12 5 97 79 1 479 12 8 0 8 13 3.33 77 9 56 1 5 58 0 62 14 6 38 83 6 17 16 1 0 93 15 6.36 84.9 696 11.3 0.66 17 4 99 8 1 3 589 12 9 0 96 18 5 41 8 1 9 5 70 15 4 1 0 5 2 1 4 3 80 6 786 13 1 1 13 22 3 88 8 1 795 12 3 1 18 23 4 09 8 3 1 856 11 7 1 06 24 3 66 8 1 9 898 12 5 1 2 7 25 4.44 84.8 998 14 1 17 26 4 82 87 7 8 84 12 4 0 95 The hardness HVHAZ is also measured near the welding point in the heat affected area, and compared with the hardness Hvbasic ratio of the alkali metal that is not affected by heat -20-(15) 200401042, these results are listed in table 3. Table 3 Examples HB HVH AZ H VHAZ / HVbasic 1 3 9 3 5 5 0 1 2 7 3 3 95 492 1 13 5 402 5 5 5 1 26 6 403 45 8 1.03 9 402 5 77 13 1 10 420 5 9 1 1 28 11 3 90 527 1 23 12 3 7 5 462 1 12 13 3 70 500 1 23 14 420 5 77 1 25 15 43 5 5 77 1 21 17 3 93 5 3 8 1.24 18 402 5 16 1 17 2 1 3 93 7 17 1 66 22 402 708 1 6 23 42 5 726 1 5 5 24 4 10 75 1 1 6 7 2 5 42 5 795 1 7 26 43 5 689 1 58 These two tables show similar hardness (HB) and similar Hardness coefficient -21-(16) (16) 200401042

Dr, the steel according to the present invention has better machinability (lower U-factor) than the comparative steel. In addition, because the hardness of HAZ is low and the ratio of Η V H A Z / H v b a s i c is low, the steel of the present invention is more suitable for repairing by welding, and is more suitable for polishing after repairing. In the steel block according to the present invention, if the carbon content is less than or equal to 0%, the hardness in terms of HAZ HVHAZ will still be less than 65 0HV and less than 600HV, and if the carbon is less than or equal to 03%, HVHAZ / Hvbasic The ratio will still be below 15 and below 13. Furthermore, in most examples, the quenchability Tr is higher than that of the comparative steel, and can exceed 45, or even 5 or 6, while maintaining other good properties, which makes the thickness of the ingot manufactured. It can reach 1 500 mm, and make the properties of the steel block meet the standards required for manufacturing molds or metal processing parts. These steel ingots are suitable for use in the production of parts for plastic injection molding dies or parts for metal dies such as light alloys. This steel block is also suitable for manufacturing metalworking tool parts.

Claims (1)

(1) (1) 200401042 Scope of patent application 1 A steel block 'used to manufacture plastic injection molding or metal forming tools or used to manufacture metal processed parts' The steel block has a thickness greater than 20 mm, Its structure is completely martensite or martensite-bainite structure, and the hardness of all points is between 37 HB and 45 JPJB, and by weight ° /. In total, the chemical composition of the steel block includes: 0 12% &lt; C &lt; 0 3 2% Si &lt; 0 8% Μη &lt; 2 5% Ni &lt; 3% Cr &lt; 3 5% Mo + W / 2 &lt; 2 2% V + Nb / 2 + Ta / 4 &lt; 0 5% A1 &lt; 0.4% T i + Z r / 2 &lt; 0 1% -boron, content of 0 0 0 0 5% to 0 0 1 5 ° /. Between-one or more elements of sulfur, _ and tellurium are added as the case requires, the total amount of these elements is less than or equal to 02%,-one or more of lead and bismuth are added as the case requires A variety of elements, the total amount of these elements is less than or equal to 02%,-if necessary, calcium is added, the content is less than or equal to 01%, the remainder is iron and impurities produced during production, copper is an impurity, The chemical composition of the block also conforms to the following equation: 3 2 &lt; Tr &lt; 6 5 -23-(2) (2) 200401042 77 &lt; Dr &lt; 85 U &lt; 850 Mo * + 3x V * &gt; 0 1 % In the formula, each content is expressed in% as follows: Tr = 1 8x C + 1 lx Μη + 0 7x Ni + 0 6x Cr + 1 6x Mo * + 0 5 Dr = 54x C ° 2 5 + 2 4 5 x (Mo * + 3 x V *) ° 3 0 + 1 5 8 x Mn + 0 74x Ni + 1 8x Si + 12 5x (Cr) 0 20 U = 1 600x C + 1 OOx (0.25x Cr + Mo * + 4.5x V ”R = 3 8x C + 1 Ox Si + 3 3 x Mn + 2 4x Ni + 1 4x (Cr + Mo *) Mo * = Mo + W / 2 V * = V + Nb / 2 + Ta / 4 boron The content of aluminum, titanium, chromium and nitrogen in thousandths of a weight percent is expressed as follows: B &gt; l / 3x K1 + 0 5 K1 = Min (I *, J *) I * = Max (Ο, I) and J * = Max (Ο, J) 1 = Min (N, N-0 29 (Ti + Zr / 2-5)) J = Min {N, 0 5 [N-0 5 2 A1 + ((N-0 5 2 Al) 2 + 2 8 3) 1/2]}. 2 If the ingot of the application scope item 1, its chemical composition is: R &gt; 11 3 As the application scope item 1 Or the steel block of item 2, where: -24-(3) (3) 200401042 R &lt; 20 4 If the steel block of item 1 of the scope of application, where R &lt; 2 7x Tr 5 The ingot of the item, the content of silicon 'is less than 0 4 5 weight: the amount% (6 as in the second ingot of the second Erfeng Meng range, in which U &lt; 7 5 0. 7 For example, the steel block of item 6 in the range of the three main sundials, where U &lt; 700 ° 8 As for the steel block of item 7 of the range 3 of the main three sundial ranges, U &lt; 65 0 ° 9 As the application range; No. 6 to 8-steel block of any one, which; 0 220% &lt; C &lt; 0 320% Si &lt; 0 3 0% 0.3% &lt; Μη &lt; 1.8% Ni &lt; 2% 0 5% &lt; Cr &lt; 2 5% Mo + W / 2 &lt; 1.8% V + Nb / 2 + Ta / 4 &lt; 0.3% Mo * + 3x V * &gt; 0 3% 10 If the steel block of the application scope item 8 has the following composition: 0 220% &lt; C &lt; 0 280% Si &lt; 0 15% 0 8% &lt; Μη &lt; 1 6% Ni &lt; 2% 1% &lt; C r &lt; 2 5% (4) (4) 200401042 Mo + W / 2 &lt; 1 5% V + Nb / 2 + Ta / 4 &lt; 0 2% Mo * + 3x V * &gt; 0 4% 11 As for the steel ingot in item 9 of the application scope, of which T r &gt; 45. 12 The steel ingot as described in item 10 of the scope of application, wherein T r &gt; 45. 13 A steel mold part mechanically cut from a steel block according to any one of the application scope 1 to 12, at least a part of the surface is hardened by nitriding, and the hardness of all points is between 3 70 HB To 45 0HB. -26-200401042 Lu, (a), the designated representative of this case is: Figure _ (b), the representative symbols of this representative diagram are briefly explained: 柒, if there is a chemical formula in this case, please reveal the chemical formula that can best show the characteristics of the invention : The chemical formula designated in this case is: the chemical formula