TWI535863B

TWI535863B - Hot-work tool steel and a process for making a hot-work tool steel

Info

Publication number: TWI535863B
Application number: TW101106919A
Authority: TW
Inventors: 傑根安德森; 漢瑞克傑斯柏森; 漢斯歐樂夫安卓恩; 拉爾斯艾瑞克斯凡森
Original assignee: 伍德赫爾恩股份有限公司
Priority date: 2011-03-04
Filing date: 2012-03-02
Publication date: 2016-06-01
Also published as: CA2828962C; SI2681340T1; JP2014512456A; EP2681340B1; EP2681340A1; PT2681340E; PL2681340T3; TW201303043A; RU2013142584A; BR112013022606A2; US20160115573A1; KR20150047636A; SE536596C2; KR102012950B1; KR20140015445A; KR20170105138A; CN103703150A; US20140056749A1; SE1150200A1; DK2681340T3

Description

熱工作工具鋼及用來製造熱工作工具鋼的方法 Hot working tool steel and method for manufacturing hot working tool steel

本發明係關於低鉻熱工作工具鋼及用來製造低鉻熱工作工具鋼物件之方法。 This invention relates to low chromium hot work tool steels and methods for making low chromium hot work tool steel articles.

術語「熱工作工具」用來表示各種各樣用於在相對較高之溫度下對金屬進行加工或成形的工具，例如：壓鑄工具，諸如模具、嵌件及模芯、入口部件、噴嘴、噴射器元件、活塞、壓力室等；擠出加工操作所用的工具，諸如模具、模座、襯裏、壓力墊及擠壓桿、軸等；熱壓工具，諸如用於對鋁、鎂、銅、銅合金及鋼進行熱壓之工具；塑膠品模型，諸如注射成型、壓縮成型及擠出操作所用之模型；以及熱剪裁工具、箍環/套環及耐磨損部件等意欲在高溫下使用之各種其他類型的工具。對於耐回火性及熱疲勞方面的需求較高的應用，其中的中小型工具使用了低合金熱工作工具鋼。耐回火性為熱工作工具鋼的一種能力，可以在高溫下長時間保持其硬度。熱工作工具鋼形成後可長時間處於高溫下而不改變其強度及硬度，且熱工作工具鋼一般使用大量會形成碳化物之合金。 The term "hot work tool" is used to denote a variety of tools for machining or forming metals at relatively high temperatures, such as die casting tools such as molds, inserts and cores, inlet parts, nozzles, sprays. Components, pistons, pressure chambers, etc.; tools used in extrusion processing operations, such as molds, die holders, linings, pressure pads and extrusion bars, shafts, etc.; hot pressing tools, such as for aluminum, magnesium, copper, copper Tools for hot pressing of alloys and steels; models for plastics, such as those used for injection molding, compression molding and extrusion operations; and various types of tools, such as hot-cutting tools, hoops/loops and wear-resistant parts, intended for use at high temperatures. Other types of tools. For applications requiring high temper resistance and thermal fatigue, the medium and small tools use low alloy hot work tool steel. Tempering resistance is a capability of hot work tool steel that maintains its hardness for extended periods of time at elevated temperatures. Hot work tool steel can be exposed to high temperatures for a long time without changing its strength and hardness, and hot work tool steels generally use a large amount of alloys that form carbides.

工具鋼的另一種類型為高速鋼，此類鋼適用於特定類型的切割工具，即，必須在760℃或760℃以上的高溫下保持其強度及硬度的鋼製件。為減少鎢及鉻之需求量，例如，分別為18 wt-%及4 wt-%，已藉由使用鉬(5-10 wt-%)來形成變種高速鋼。高速鋼之組成物及價格與熱工作鋼不同，且不能取代熱工作鋼。 Another type of tool steel is high speed steel, which is suitable for certain types of cutting tools, ie steel parts that must maintain their strength and hardness at temperatures above 760 ° C or above 760 ° C. In order to reduce the demand for tungsten and chromium, for example, 18 wt-% and 4 wt-%, respectively, have been formed by using molybdenum (5-10 wt-%). Varied high speed steel. The composition and price of high speed steel is different from that of hot working steel and cannot replace hot working steel.

本發明之一目標係提供具有改良之性質型態，尤其具有改良之耐回火性之低鉻熱工作工具鋼。本發明之鋼尤其適於小型工具，製造此類工具所用的鋼組成物不需要具有高的可硬化度。 It is an object of the present invention to provide a low chromium hot work tool steel having improved properties, particularly improved temper resistance. The steel of the present invention is particularly suitable for small tools, and the steel composition used to manufacture such tools does not need to have a high degree of hardenability.

藉由提供如申請專利範圍第1項之低鉻熱工作工具鋼可達到此目標，該低鉻熱工作工具鋼由以下物質組成(單位為wt-%)：C 0.08-0.40、N 0.015-0.30、C+N 0.30-0.50、Cr 1-4、Mo 1.5-3、V 0.8-1.3、Mn 0.5-2、Si 0.1-0.5、視需要而定Ni <3、Co 5、B <0.01、除雜質外，其餘為Fe。 This can be achieved by providing a low chromium hot work tool steel as in claim 1 of the patent scope, which is composed of the following materials (in wt-%): C 0.08-0.40, N 0.015-0.30 , C+N 0.30-0.50, Cr 1-4, Mo 1.5-3, V 0.8-1.3, Mn 0.5-2, Si 0.1-0.5, Ni <3, Co as needed 5, B <0.01, except for impurities, the rest is Fe.

低鉻熱工作工具鋼之較佳具體實例陳述於附屬項申請專利範圍第2至10項中。 Preferred specific examples of the low chromium hot work tool steel are set forth in items 2 to 10 of the scope of the patent application of the subsidiary.

另一目標係提供具有改良之性質型態，尤其是具有改良之耐回火性之低鉻熱工作工具鋼物件。 Another objective is to provide a low chromium hot work tool steel article having an improved property profile, especially with improved temper resistance.

根據本發明，可藉由如申請專利範圍第11項之方法達到此目標，亦即，包含以下步驟之方法：a)提供如申請專利範圍中任一項之低鉻熱工作工具鋼；b)用該鋼組成物形成鋼物件；c)將步驟b)中獲得的鋼物件在至多為1200℃之溫度下沃斯田體化約半小時，然後淬火；以及d)將淬火後的鋼物件回火至少兩次，回火溫度在500℃與700℃之間，每次回火時間約為2小時；本方法之較佳具體實例陳述於附屬項申請專利範圍第12至15項中。 According to the present invention, this object can be attained by the method of claim 11, that is, a method comprising the steps of: a) providing a low chromium hot work tool steel according to any one of the claims; b) Forming the steel article with the steel composition; c) tempering the steel article obtained in step b) at a temperature of up to 1200 ° C for about half an hour, then quenching; and d) returning the quenched steel object back The fire is at least twice, the tempering temperature is between 500 ° C and 700 ° C, and each tempering time is about 2 hours; preferred embodiments of the method are set forth in Items 12 to 15 of the scope of the patent application of the subsidiary.

在具有高鉻含量(即9-12 wt-%)之抗蠕變鋼中，在相對較低之溫度(即1020-1050℃)下可能已溶解碳氮化釩。然而，若鉻含量較低，低於約4-5 wt-%，一次碳氮化釩則會在熔料中形成，事實上之後也不可能溶解。 In creep resistant steels having a high chromium content (i.e., 9-12 wt-%), vanadium carbonitride may have been dissolved at relatively low temperatures (i.e., 1020-1050 ° C). However, if the chromium content is lower, less than about 4-5 wt-%, the primary vanadium carbonitride will form in the melt, and in fact it will not dissolve afterwards.

在本發明之鋼中，應將碳及氮之總量控制在0.30(C+N)0.50之範圍內，其中較佳為0.36(C+N)0.44。標稱含量應約為0.40 wt-%。同時，有利的是將氮含量控制在0.015 N與0.15 N之間(較佳為0.015-0.10)，而較佳可將碳控制在至少0.20 wt-%。較佳範圍陳述於產物請求項中。 In the steel of the present invention, the total amount of carbon and nitrogen should be controlled at 0.30. (C+N) Within the range of 0.50, preferably 0.36 (C+N) 0.44. The nominal content should be approximately 0.40 wt-%. At the same time, it is advantageous to control the nitrogen content between 0.015 N and 0.15 N (preferably 0.015-0.10), and preferably the carbon can be controlled to be at least 0.20 wt-%. The preferred range is stated in the product request.

當氮含量在約0.05 wt-%至0.10 wt-%之範圍內達到平衡時，會形成碳氮化釩，碳氮化物會在沃斯田體化步驟中部分溶解，然後在回火步驟中析出為奈米大小之顆粒。碳氮化釩之熱穩定性優於碳化釩，因此會顯著改良低鉻熱工作工具鋼物件之耐回火性。此外，回火至少兩次後，回火曲線(顯示硬度隨回火溫度變化)會具有更高的二次峰。 When the nitrogen content reaches equilibrium in the range of about 0.05 wt-% to 0.10 wt-%, vanadium carbonitride is formed, the carbonitride is partially dissolved in the Vostian body formation step, and then precipitated in the tempering step. It is a particle of nanometer size. carbon The thermal stability of vanadium nitride is superior to that of vanadium carbide, so the tempering resistance of low chromium hot work tool steel parts can be significantly improved. In addition, after tempering at least twice, the tempering curve (showing a change in hardness with tempering temperature) will have a higher secondary peak.

在本發明之最佳具體實例中，氮含量較佳約為0.05 wt-%。該值所提供之效能優於較高值。與較高含量相比，約為0.05 wt-%的氮含量更有可能在淬火過程中引起二次硬化，從而使鋼具有高硬度。然而，研究顯示約為0.10 wt-%的氮含量會使二次硬化峰偏移至略高的回火溫度，該現象為有利現象。較佳範圍陳述於產物請求項中。 In a preferred embodiment of the invention, the nitrogen content is preferably about 0.05 wt-%. This value provides better performance than the higher value. A nitrogen content of about 0.05 wt-% is more likely to cause secondary hardening during the quenching process than the higher content, thereby giving the steel a high hardness. However, studies have shown that a nitrogen content of about 0.10 wt-% shifts the secondary hardening peak to a slightly higher tempering temperature, which is a favorable phenomenon. The preferred range is stated in the product request.

另外，已執行之測試及模型化計算顯示，沃斯田體化溫度需要隨著氮含量的升高而升高。 In addition, the tests performed and the model calculations show that the temperature of the Worth field needs to increase as the nitrogen content increases.

鉻能提昇鋼的可硬化度及耐蝕性。鉻含量過低，則會降低鋼的耐蝕性。因此，鋼中之最小鉻含量被設定為1 wt-%。為了避免形成不需要的富鉻碳化物/碳氮化物，例如M₂₃C₆，最大鉻含量之被設定為4 wt-%。鉻含量較佳應為不超過3 wt-%，更佳為不超過2.6 wt-%。本發明之一具體實例中，鉻含量為1.5-1.7 wt-%。較佳範圍陳述於產物請求項中。低鉻含量會延遲微觀結構中碳化鉻之析出，其有利於形成熱穩定性更佳之富釩碳氮化物。因而減緩了材料的回復速度，並改良了耐回火性。 Chromium can improve the hardenability and corrosion resistance of steel. Too low a chromium content will reduce the corrosion resistance of the steel. Therefore, the minimum chromium content in the steel is set to 1 wt-%. In order to avoid the formation of unwanted chromium-rich carbides/carbonitrides, such as M ₂₃ C ₆ , the maximum chromium content is set to 4 wt-%. The chromium content should preferably be no more than 3 wt-%, more preferably no more than 2.6 wt-%. In one embodiment of the invention, the chromium content is from 1.5 to 1.7 wt-%. The preferred range is stated in the product request. The low chromium content delays the precipitation of chromium carbide in the microstructure, which is advantageous for the formation of vanadium-rich carbonitrides with better thermal stability. This slows down the recovery of the material and improves tempering resistance.

為了使鋼具有足夠的析出可能性，從而使鋼具有足夠的耐回火性以及所需的高溫強度性質，鋼中所含之釩的量至少應為0.8 wt-%。為了避免形成過多的M(C,N)析出物，釩含量的為上限為1.3 wt-%，其中M(C,N)析出物會增加風險以致熱處理後基質中殘餘粗大的未溶解析出物，並且會進一步增加風險以致基質中的碳及氮被損耗。釩含量較佳在1.0 wt-%與1.3 wt-%之間。較佳範圍陳述於產物請求項中。 In order for the steel to have sufficient precipitation potential so that the steel has sufficient temper resistance and the required high temperature strength properties, the amount of vanadium contained in the steel should be at least 0.8 wt-%. In order to avoid the formation of excessive M(C,N) precipitates, the upper limit of the vanadium content is 1.3 wt-%, wherein the M(C,N) precipitates increase the wind. It is dangerous to leave large undissolved precipitates in the matrix after heat treatment, and further increases the risk that carbon and nitrogen in the matrix are lost. The vanadium content is preferably between 1.0 wt-% and 1.3 wt-%. The preferred range is stated in the product request.

為了得到所需MC相，比率Cr/V應較佳為小於2，更佳為小於1.8。其原因在於，Cr被視為不利於MC相。 In order to obtain the desired MC phase, the ratio Cr/V should preferably be less than 2, more preferably less than 1.8. The reason for this is that Cr is considered to be detrimental to the MC phase.

鋼中存在之矽的量應在0.1-0.5 wt-%之間，較佳為0.2-0.4 wt-%。保持低的矽含量可使介穩定M₃C碳化物初步析出。該等碳化物將給後來析出的所需M(C,N)顆粒提供碳。亦避免了在晶粒邊界及晶格邊界中析出不需要的富鉻M₂₃C₆顆粒。較佳範圍陳述於產物請求項中。 The amount of rhenium present in the steel should be between 0.1 and 0.5 wt-%, preferably between 0.2 and 0.4 wt-%. Maintaining a low niobium content allows for the initial precipitation of metastable M ₃ C carbides. The carbides will provide carbon to the desired M(C,N) particles that are later deposited. Unwanted chromium-rich M ₂₃ C ₆ particles are also precipitated in grain boundaries and lattice boundaries. The preferred range is stated in the product request.

錳的存在是為了使鋼具有足夠的可硬化度，尤其在鋼中鉻含量及鉬含量相對較低之情況下。鋼中錳含量在0.5 wt-%與2 wt-%之間，較佳為1.0 wt-%與2.0 wt-%之間。較佳範圍陳述於產物請求項中。 Manganese is present in order to provide steel with sufficient hardenability, especially in the case of relatively low chromium content and low molybdenum content in steel. The manganese content in the steel is between 0.5 wt-% and 2 wt-%, preferably between 1.0 wt-% and 2.0 wt-%. The preferred range is stated in the product request.

為了在回火過程中提供二次硬化並提昇可硬化度，鋼中鉬含量應在1.5 wt-%與3 wt-%之間，較佳為2.2-2.8 wt-%。較佳範圍陳述於產物請求項中。部分鉬可以本身已知之方式取代鎢，但是鋼較佳應不含任何有意添加之鎢，亦即，所含之鎢的量不應超過雜質含量，此係因為存在該元素會引起某些缺陷。 In order to provide secondary hardening and increase hardenability during tempering, the molybdenum content in the steel should be between 1.5 wt-% and 3 wt-%, preferably 2.2-2.8 wt-%. The preferred range is stated in the product request. Part of the molybdenum may be substituted for tungsten in a manner known per se, but the steel preferably does not contain any intentionally added tungsten, i.e., the amount of tungsten contained should not exceed the impurity content, which is due to the presence of the element causing certain defects.

為了得到二次碳化物之理想析出順序及理想析出可能性，比率Mo/V應較佳處於1.8-2.3之範圍內，較佳為1.9-2.1。已知Mo能使M₂C相穩定，並且藉由調節Mo及V 的含量以使比率Mo/V屬於1.8-2.3之範圍內，亦會形成富鉬M₂C，與富釩MC相相比，該富鉬M₂C相具有更高的晶粒粗化速率。 In order to obtain an ideal precipitation order of secondary carbides and an ideal precipitation probability, the ratio Mo/V should preferably be in the range of 1.8 to 2.3, preferably 1.9 to 2.1. It is known that Mo can stabilize the M ₂ C phase, and by adjusting the contents of Mo and V such that the ratio Mo/V falls within the range of 1.8-2.3, a molybdenum-rich M ₂ C is also formed, compared with the vanadium-rich MC phase. The molybdenum-rich M ₂ C phase has a higher grain coarsening rate.

鋼中所含之鎳元素及鈷元素的量可分別達到3 wt-%及5 wt-%。鈷可提昇鋼在高溫下的硬度，此有利於鋼的某些應用。若要添加鈷，其有效添加量約為4 wt-%。鎳可增加鋼的耐蝕性、可硬化度及韌性。較佳範圍陳述於產物請求項中。 The amount of nickel and cobalt contained in the steel may reach 3 wt-% and 5 wt-%, respectively. Cobalt increases the hardness of steel at elevated temperatures, which is beneficial for certain applications of steel. To add cobalt, the effective addition amount is about 4 wt-%. Nickel increases the corrosion resistance, hardenability and toughness of steel. The preferred range is stated in the product request.

原則上，進行沃斯田體化之溫度可在軟化退火溫度820℃與最高沃斯田體化溫度1200℃之間，但進行鋼物件之沃斯田體化之溫度較佳約為1050-1150℃，較佳為1080-1150℃，典型地為1100℃。內部測試顯示，較高的沃斯田體化溫度會使回火硬度偏移至較高溫度，亦即，會使二次硬化峰偏移至較高溫度，此意味著將在初始回火溫度較高的情況下達到所需硬度。因而改良了材料的耐回火性，並提高了工具的工作溫度。 In principle, the temperature at which the Worth field is formed can be between 820 ° C and the highest Worth field temperature of 1200 ° C, but the temperature of the Worth formation of the steel object is preferably about 1050-1150. °C, preferably 1080-1150 ° C, typically 1100 ° C. Internal tests have shown that a higher Worth field temperature shifts the tempering hardness to a higher temperature, ie, the secondary hardening peak is shifted to a higher temperature, which means that it will be at the initial tempering temperature. The required hardness is achieved at higher temperatures. This improves the tempering resistance of the material and increases the operating temperature of the tool.

較佳對淬火後的鋼物件進行至少兩次回火，回火溫度在550℃與680℃之間，每次的停留時間為2小時。在鋼組成物之最佳具體實例中，進行回火之溫度在600℃與650℃之間，較佳為625℃與650℃之間。 Preferably, the quenched steel article is tempered at least twice, and the tempering temperature is between 550 ° C and 680 ° C, and the residence time is 2 hours each time. In the most preferred embodiment of the steel composition, the temperature for tempering is between 600 ° C and 650 ° C, preferably between 625 ° C and 650 ° C.

若要使氮含量在0.05-0.10 wt-%之範圍內，可用習知澆鑄方法藉由如下步驟加入氮：首先形成熔料，澆鑄熔料以形成鋼錠，且藉由熱處理使鋼錠均質化。氮的添加會產生粗大的一次富釩M(C,N)析出物，而此等析出物會使材料硬度不均勻。然而，若降低氮含量並在隨後的鍛造之前進行均質化熱處理，則不會出現粗大的一次碳氮化物。 To make the nitrogen content in the range of 0.05-0.10 wt-%, nitrogen can be added by a conventional casting method by first forming a melt, casting the melt to form a steel ingot, and homogenizing the steel ingot by heat treatment. The addition of nitrogen produces coarse primary vanadium-rich M (C, N) precipitates, which can harden the material. The degree is not uniform. However, if the nitrogen content is lowered and a homogenization heat treatment is performed before the subsequent forging, coarse primary carbonitride does not occur.

在變種鋼中，氮含量亦可能高於針對較佳具體實例所指示之含量。在此變種鋼中，氮含量可達到0.30 wt-%。為獲得更高之氮含量，僅使用習知澆鑄方法是不夠的。取而代之，可藉由如下步驟加入氮：首先製造基本上為所需組成物(除了氮以外)之鋼粉，然後用含氮流體(例如氮氣)對此粉末進行固態氮化，其後在約1150℃之溫度及約76 MPa之壓力下將此粉末均衡地熱壓成鋼錠。藉由用粉末冶金法製造工具鋼，可避免出現粗大的一次碳化物之問題。 In the variant steel, the nitrogen content may also be higher than indicated for the preferred embodiment. In this variant steel, the nitrogen content can reach 0.30 wt-%. In order to obtain a higher nitrogen content, it is not sufficient to use only conventional casting methods. Alternatively, nitrogen can be added by first producing a steel powder that is substantially the desired composition (other than nitrogen) and then solid-nitriding the powder with a nitrogen-containing fluid (e.g., nitrogen), followed by about 1150 The powder was uniformly hot pressed into a steel ingot at a temperature of ° C and a pressure of about 76 MPa. By manufacturing tool steel by powder metallurgy, the problem of coarse primary carbides can be avoided.

較佳將鋼錠在約1270℃之溫度下鍛造，然後在約820℃之溫度下軟化退火，隨後以每小時10℃之速率冷卻至650℃之溫度，然後在空氣中自由冷卻，以使鋼錠預備進行沃斯田體化。 Preferably, the ingot is forged at a temperature of about 1270 ° C, then soft annealed at a temperature of about 820 ° C, then cooled to a temperature of 650 ° C at a rate of 10 ° C per hour, and then freely cooled in air to prepare the ingot Carry out the Worth field.

本發明之鋼具有顯著改良之耐回火性，使得鋼物件在熱工作應用中具有更長之使用壽命。如上文所述，氮含量較佳約為0.05 wt-%，而鉻含量較佳小於3 wt-%，亦即1.2-2.6或1.3-2.3。 The steel of the present invention has significantly improved temper resistance, allowing steel articles to have a longer service life in hot working applications. As mentioned above, the nitrogen content is preferably about 0.05 wt-%, and the chromium content is preferably less than 3 wt-%, i.e., 1.2-2.6 or 1.3-2.3.

本發明之鋼物件較佳亦應滿足以下要求中的一些要求：-優良的耐回火性，-優良的高溫強度，-優良的熱導性，-不具有高出可接受範圍之熱膨脹係數。 The steel article of the present invention preferably also satisfies some of the following requirements: - excellent temper resistance, - excellent high temperature strength, - excellent thermal conductivity, - does not have a coefficient of thermal expansion higher than an acceptable range.

下文將參照較佳的具體實例及附圖更詳細地對本發明進行描述。 The invention will be described in more detail hereinafter with reference to preferred embodiments and the accompanying drawings.

鉬釩合金熱工作工具鋼能很好地抵抗熱疲勞、軟化及高溫蠕變。表1所示為此類先前技術鋼的例示性標稱化學組成物(wt-%)。 Molybdenum-vanadium alloy hot work tool steel is very resistant to thermal fatigue, softening and high temperature creep. Table 1 shows exemplary nominal chemical compositions (wt-%) of such prior art steels.

表1之各種鋼之所以具有高溫性質，其原因被認為是回火過程中有奈米大小之碳化釩析出。此等堅硬的MC型碳化物(2900 HV)使材料得到二次硬化。圖1所示為例示性先前技術工具鋼之回火曲線(硬度與回火溫度)。此等樣本在1030℃進行沃斯田體化，然後在不同溫度下回火兩次；溫度範圍在200℃至700℃之間，回火時間為2+2小時。自圖中可以看出，在500℃至650℃之溫度間隔內，在550℃處出現明顯的二次硬化峰。之後的研究亦顯示：在625℃回火過程中，例示性先前技術工具鋼中明顯析出了介穩定富鉬M₂C，此有利於達成二次硬化的作用。 The reason why the various steels of Table 1 have high-temperature properties is considered to be the precipitation of nano-sized vanadium carbide during tempering. These hard MC-type carbides (2900 HV) give the material a secondary hardening. Figure 1 shows the tempering curve (hardness and tempering temperature) of an exemplary prior art tool steel. These samples were subjected to Vostian at 1030 ° C and then tempered twice at different temperatures; the temperature ranged from 200 ° C to 700 ° C and the tempering time was 2+ 2 hours. As can be seen from the figure, a significant secondary hardening peak occurs at 550 ° C in the temperature interval of 500 ° C to 650 ° C. Subsequent studies have also shown that during tempering at 625 °C, metastable molybdenum-rich M ₂ C is clearly precipitated in the exemplary prior art tool steel, which is beneficial for achieving secondary hardening.

熱工作工具鋼能在高溫下長時間保持其硬度之能力，即耐回火性，通常與初始回火溫度相關；若材料所處溫度遠低於初始回火溫度，則材料不會軟化。材料所處溫度越接近或高於初始回火溫度，軟化就越明顯。 The ability of hot work tool steel to maintain its hardness at high temperatures for a long time, ie temper resistance, is usually related to the initial tempering temperature; if the temperature of the material is much lower than the initial tempering temperature, the material will not soften. The temperature at which the material is placed Softening is more pronounced near or above the initial tempering temperature.

若二次硬化峰可偏移至更高的溫度下，則此情況意味著可在初始回火溫度更高的情況下達到所需硬度(例如，44-46 HRC)。因而能改良材料的耐回火性，並提高工具的工作溫度。 If the secondary hardening peak can be shifted to a higher temperature, this means that the desired hardness (for example, 44-46 HRC) can be achieved with a higher initial tempering temperature. Therefore, the tempering resistance of the material can be improved and the working temperature of the tool can be improved.

關於高鉻鋼之早期研究表明：在向此類鋼中添加了氮的情況下，硬度在回火過程中可變得更高。將樣本Cr 15、Mo 1、C 0.6及Cr 15、Mo 1、C 0.29、N 0.35在1050℃進行溶液處理，然後進行水淬火並用液氮冷卻，然後在不同的溫度下回火2小時。自圖2可看出，添加氮後，峰值硬度顯著提高。關於含氮鋼，其麻田散體之初始硬度較低，但此種鋼在回火過程中獲得的硬度比不含氮鋼要高。 Early studies on high chromium steels have shown that hardness can be made higher during tempering in the case of adding nitrogen to such steels. The samples Cr 15, Mo 1, C 0.6 and Cr 15, Mo 1, C 0.29, N 0.35 were solution treated at 1050 ° C, then water quenched and cooled with liquid nitrogen, and then tempered at different temperatures for 2 hours. As can be seen from Figure 2, the peak hardness is significantly increased after the addition of nitrogen. Regarding nitrogen-containing steels, the initial hardness of the Matian bulk is lower, but the hardness of such steel during tempering is higher than that of nitrogen-free steel.

此現象的原因是，由於沃斯田體相中鉻之溶解度有所增加，因此氮使得鉻更均勻地分佈在基質中。淬火後，麻田散體相保留了沃斯田體相中鉻之均勻分佈特性，且在回火過程中，析出的氮化鉻的分佈十分細微，從而對材料產生更強的硬化作用。 The reason for this phenomenon is that nitrogen increases the chromium more uniformly in the matrix due to the increased solubility of chromium in the Vostian bulk phase. After quenching, the loose phase of Ma Tian retains the uniform distribution of chromium in the body phase of Vostian, and during the tempering process, the distribution of chromium nitride precipitated is very fine, which produces a stronger hardening effect on the material.

此外，用氮取代部分碳可使麻田散體鋼基質的硬度更高。開始時，氮的添加會產生更多的殘餘沃斯田體。然而，之後藉由冷加工可將此沃斯田體轉變成麻田散體，如此便可獲得高達68 HRC之硬度。 In addition, the replacement of a portion of the carbon with nitrogen allows for a higher hardness of the Matian bulk steel matrix. At the beginning, the addition of nitrogen produces more residual Worth. However, this Worth field can then be converted into a Matian bulk by cold working, so that a hardness of up to 68 HRC can be obtained.

低鉻含量似乎對耐回火性有積極的影響。對鉻含量分別為1.5 wt-%及5.0 wt-%之兩種不同熱工作工具鋼進行對比顯示：低鉻含量會延遲微觀結構中碳化鉻之析出，其有利於形成熱穩定性更佳之富釩MC。因而減緩了材料的回復速度，並改良了耐回火性。 Low chromium content seems to have a positive effect on tempering resistance. Comparison of two different hot work tool steels with chromium contents of 1.5 wt-% and 5.0 wt-% respectively shows that low chromium content delays the precipitation of chromium carbide in the microstructure, which has Conducive to the formation of vanadium-rich MC with better thermal stability. This slows down the recovery of the material and improves tempering resistance.

然而，參看圖3，對鉻含量為9-12 wt-%、N含量為0.06 wt-%之典型抗蠕變鋼之研究顯示：低鉻含量戲劇性地對MX(X為C+N)顆粒起到了穩定化作用。若在1100℃進行沃斯田體化，則所有M(C,N)顆粒都會溶解於鉻含量為10 wt-%之鋼中。若鉻含量降低至2.5 wt-%(比照圖1之例示性低鉻工具鋼)，則會有大量M(C,N)依舊存在於沃斯田體中。顯然，低鉻含量會導致在沃斯田體化處理過程中僅有少量填隙粒子會溶解於沃斯田體中。 However, referring to Figure 3, a study of typical creep resistant steels with a chromium content of 9-12 wt-% and an N content of 0.06 wt-% shows that the low chromium content dramatically plays a role in MX (X is C+N) particles. Stabilization is achieved. If Worth formation is carried out at 1100 ° C, all M (C, N) particles are dissolved in steel with a chromium content of 10 wt-%. If the chromium content is reduced to 2.5 wt-% (cf. the exemplary low chromium tool steel of Figure 1), a large amount of M(C, N) will still be present in the Vostian field. Obviously, low chromium content will cause only a small amount of interstitial particles to dissolve in the Worth field during the Worth field process.

根據本發明，藉由執行以下方法步驟來製造耐回火性有所增加之低鉻熱工作工具鋼：a)向低鉻熱工作工具鋼之熔料組成物中加入氮，從而提供如方法請求項中任一項之鋼組成物；b)用該鋼組成物形成鋼物件；c)將步驟b)中獲得的鋼物件在至多為1200℃之溫度下沃斯田體化約半小時，然後淬火；以及d)將淬火後的鋼物件回火至少兩次，回火溫度在500℃與700℃之間，每次回火時間約為2小時；就本技術領域之傳統理解而言，此等結果令人意外，因為目前流行的學說為：鉻含量的降低會導致可硬化度降低以及一次M(C,N)顆粒難以溶解。 According to the present invention, a low chromium hot work tool steel having increased tempering resistance is produced by performing the following method steps: a) adding nitrogen to the melt composition of the low chromium hot work tool steel to provide a method request a steel composition according to any one of the items; b) forming a steel article from the steel composition; c) subjecting the steel article obtained in step b) to a Worth field at a temperature of at most 1200 ° C for about half an hour, and then Quenching; and d) tempering the quenched steel article at least twice, the tempering temperature is between 500 ° C and 700 ° C, and each tempering time is about 2 hours; as is conventionally understood in the art, such The results are surprising because the current popular doctrine is that a reduction in chromium content leads to a decrease in hardenability and a difficulty in dissolving the primary M(C,N) particles.

在具有高鉻含量(即9-12 wt-%)之抗蠕變鋼中，在相對較低之溫度(即1020-1050℃)下可能已溶解碳氮化釩。然而，若鉻含量較低，小於約4-5 wt-%，初始碳氮化釩則會在熔料中形成，事實上之後也不可能溶解。 In creep resistant steels having a high chromium content (i.e., 9-12 wt-%), vanadium carbonitride may have been dissolved at relatively low temperatures (i.e., 1020-1050 ° C). Of course However, if the chromium content is lower, less than about 4-5 wt-%, the initial vanadium carbonitride will form in the melt, and in fact it will not dissolve afterwards.

發明者已經發現：當低鉻鋼中氮含量在約0.015 wt-%至0.30 wt-%之範圍內達到平衡時，會形成碳氮化釩，碳氮化釩會在沃斯田體化步驟中部分溶解，然後在回火步驟中析出為奈米大小之顆粒。顆粒的大小約為1 μm至10 μm。在某些狀況下，當氮含量較低時(典型地為0.05 wt-%)，顆粒的平均大小小於1 μm。碳氮化釩之熱穩定性優於碳化釩，因此會顯著改良低鉻熱工作工具鋼物件之耐回火性。此外，回火至少兩次後，回火曲線(顯示硬度隨回火溫度變化)會具有更高的二次峰。 The inventors have discovered that when the nitrogen content of the low chromium steel reaches equilibrium in the range of about 0.015 wt-% to 0.30 wt-%, vanadium carbonitride is formed, which will be in the Vostian process. Partially dissolved and then precipitated into nanometer sized particles in the tempering step. The size of the particles is approximately 1 μm to 10 μm. In some cases, when the nitrogen content is low (typically 0.05 wt-%), the average size of the particles is less than 1 μm. The thermal stability of vanadium carbonitride is superior to that of vanadium carbide, which significantly improves the tempering resistance of steel parts of low chromium hot work tools. In addition, after tempering at least twice, the tempering curve (showing a change in hardness with tempering temperature) will have a higher secondary peak.

在鋼的較佳具體實例中，氮含量較佳約為0.05 wt-%。該值所提供之效能優於較高值。與較高含量相比，約為0.05 wt-%的氮含量更有可能在淬火過程中引起二次硬化。 In a preferred embodiment of the steel, the nitrogen content is preferably about 0.05 wt-%. This value provides better performance than the higher value. A nitrogen content of about 0.05 wt-% is more likely to cause secondary hardening during quenching than at higher levels.

在較佳具體實例中，鉻含量較佳為1.5-1.7 wt-%。低鉻含量會延遲微觀結構中碳化鉻之析出，其有利於形成熱穩定性更佳之富釩碳氮化物。因而減緩了材料的回復速度，並改良了耐回火性。 In a preferred embodiment, the chromium content is preferably from 1.5 to 1.7 wt-%. The low chromium content delays the precipitation of chromium carbide in the microstructure, which is advantageous for the formation of vanadium-rich carbonitrides with better thermal stability. This slows down the recovery of the material and improves tempering resistance.

原則上，進行沃斯田體化之溫度可在軟化退火溫度820℃與最高沃斯田體化溫度1200℃之間。在一較佳具體實例中，即，在氮含量約為0.05 wt-%而鉻含量約為1.5 wt-%至1.7 wt-%的組成物中，進行鋼物件之沃斯田體化之溫度較佳約為1050℃至1150℃，較佳為1100℃。內部測試顯示，較高的沃斯田體化溫度會使回火硬度偏移至較高溫度，亦即，會使二次硬化峰偏移至較高溫度，此意味著將在初始回火溫度較高的情況下達到所需硬度。因此會改良材料的耐回火性，並會提高工具的工作溫度。 In principle, the temperature at which the Worth formation is carried out can be between a softening annealing temperature of 820 ° C and a maximum Woustian body temperature of 1200 ° C. In a preferred embodiment, that is, in a composition having a nitrogen content of about 0.05 wt-% and a chromium content of about 1.5 wt-% to 1.7 wt-%, the temperature of the Worstian body of the steel article is compared. It is preferably from about 1050 ° C to 1150 ° C, preferably 1100 ° C. Internal tests have shown that higher Worth field temperatures can shift the tempering hardness to higher temperatures. That is, the secondary hardening peak is shifted to a higher temperature, which means that the desired hardness will be achieved with a higher initial tempering temperature. This will improve the temper resistance of the material and will increase the operating temperature of the tool.

若要使氮含量在0.05-0.10 wt-%之範圍內，可用習知澆鑄方法藉由如下步驟加入氮：首先形成熔料，並澆鑄熔料以形成鋼錠，然後藉由熱處理使鋼錠均質化。氮的添加會產出粗大的一次富釩M(C,N)析出物，而此等析出物會使材料硬度不均勻。然而，若降低氮含量並在隨後之鍛造之前進行均質化熱處理，則不會出現粗大的一次碳氮化物。 To make the nitrogen content in the range of 0.05-0.10 wt-%, nitrogen can be added by a conventional casting method by first forming a melt, casting the melt to form a steel ingot, and then homogenizing the steel ingot by heat treatment. The addition of nitrogen produces a coarse primary vanadium-rich M (C, N) precipitate which causes the material to be non-uniform in hardness. However, if the nitrogen content is lowered and the homogenization heat treatment is performed before the subsequent forging, coarse primary carbonitride does not occur.

在本發明之較佳具體實例中，氮含量較佳約為0.05 wt-%。該值所提供之效能優於較高值。與較高含量相比，約為0.05 wt-%的氮含量更有可能在淬火過程中引起二次硬化，從而使鋼具有高硬度。然而，研究顯示約為0.10 wt-%的氮含量會使二次硬化峰偏移至略高的回火溫度，此現象為有利現象。另外，已執行之測試及模型化計算顯示，沃斯田體化溫度需要隨著氮含量的升高而升高。 In a preferred embodiment of the invention, the nitrogen content is preferably about 0.05 wt-%. This value provides better performance than the higher value. A nitrogen content of about 0.05 wt-% is more likely to cause secondary hardening during the quenching process than the higher content, thereby giving the steel a high hardness. However, studies have shown that a nitrogen content of about 0.10 wt-% shifts the secondary hardening peak to a slightly higher tempering temperature, which is a favorable phenomenon. In addition, the tests performed and the model calculations show that the temperature of the Worth field needs to increase as the nitrogen content increases.

在變種鋼中，氮含量亦可能高於針對較佳具體實例所指示之含量。在此變種鋼中，氮含量可達到0.30 wt-%。為獲得更高之氮含量，僅使用習知澆鑄方法是不夠的。取而代之，可藉由如下步驟加入氮：首先製造基本上為所需組成物(除了氮以外)之鋼粉，然後用氮氣對此粉末進行固態氮化，其後在約1150℃之溫度及約76 MPa之壓力下將此粉末均衡地熱壓成鋼錠。藉由用粉末冶金法製造工具鋼，可避免出現粗大的一次碳化物之問題。 In the variant steel, the nitrogen content may also be higher than indicated for the preferred embodiment. In this variant steel, the nitrogen content can reach 0.30 wt-%. In order to obtain a higher nitrogen content, it is not sufficient to use only conventional casting methods. Instead, nitrogen can be added by: first making the substantially desired group The steel powder of the product (except nitrogen) is then solid-nitrided with nitrogen, and then the powder is uniformly hot pressed into a steel ingot at a temperature of about 1150 ° C and a pressure of about 76 MPa. By manufacturing tool steel by powder metallurgy, the problem of coarse primary carbides can be avoided.

較佳將鋼錠在約1270℃之溫度下鍛造，然後在約820℃之溫度下軟化退火，隨後以每小時10℃之速率冷卻至650℃，然後在空氮中自由冷卻以使鋼錠預備進行沃斯田體化。 Preferably, the steel ingot is forged at a temperature of about 1270 ° C, then soft-annealed at a temperature of about 820 ° C, then cooled to 650 ° C at a rate of 10 ° C per hour, and then freely cooled in an empty nitrogen to prepare the steel ingot. Sitian body.

實施例1 Example 1

下表2所示為三種不同合金N0.05、N0.10及N0.30中之化學組成物(單位為wt-%)。N0.05表示氮含量為0.05 wt-%之材料，N0.10及N0.30以此類推。注意，此等組成物為試驗鋼錠之實際組成物。 Table 2 below shows the chemical compositions (in wt-%) of three different alloys N0.05, N0.10 and N0.30. N0.05 represents a material having a nitrogen content of 0.05 wt-%, and N0.10 and N0.30 are deduced by analogy. Note that these compositions are the actual compositions of the test steel ingots.

目標係保持除碳及氮以外之所有合金元素之含量。與表1之標準低鉻熱工作工具鋼相比，鉻含量亦略有減少。另外，鉬含量略有減小，錳含量有所增加。關於碳及氮，目標係使此等元素的含量之總和約為0.40 wt-%，且已相對較好地達成了此目標。 The target is to maintain the content of all alloying elements except carbon and nitrogen. The chromium content is also slightly reduced compared to the standard low chromium hot work tool steel of Table 1. In addition, the molybdenum content is slightly reduced and the manganese content is increased. With regard to carbon and nitrogen, the target is to make the sum of the contents of these elements approximately 0.40 wt-%, and this goal has been relatively well achieved.

回火階段主要涉及介穩定相，而先前的電子顯微法研究已顯示：在回火溫度間隔內，亦即400℃至700℃，介穩定相存在於標準低鉻熱工作工具鋼中。此等碳化物相主要為富釩MC(FCC)及富鉬M₂C(HCP)。亦已發現一定量的富鉻M₇C₃存在於標準低鉻熱工作工具鋼中。 The tempering phase mainly involves the interstitial phase, and previous electron microscopy studies have shown that during the tempering temperature interval, ie 400 ° C to 700 ° C, the metastable phase is present in the standard low chromium hot work tool steel. These carbide phases are mainly vanadium-rich MC (FCC) and molybdenum-rich M ₂ C (HCP). A certain amount of chromium-rich M ₇ C ₃ has also been found in standard low chromium hot work tool steels.

進行以下計算以便決定此等含氮合金是否有可能硬化，亦即，在沃斯田體化溫度下，是否有足夠的合金元素能被溶解到沃斯田體基質中，從而在淬火過程中形成麻田散體。因此，所關注的溫度間隔係介於軟化退火溫度(820℃)與指定的最高實用沃斯田體化溫度(1200℃)之間。 The following calculations are made to determine if these nitrogen-containing alloys are likely to harden, that is, at the Worth field temperature, whether sufficient alloying elements can be dissolved into the Worth matrix matrix to form during quenching Ma Tian loose body. Therefore, the temperature interval of interest is between the softening annealing temperature (820 ° C) and the specified highest practical Vostian body temperature (1200 ° C).

圖4所示為此等平衡計算之結果。此處顯示M₆C、M(C,N)及bcc基質之莫耳分數隨溫度變化。平衡相為沃斯田體。實曲線表示N0.05；虛曲線表示N0.10，點曲線表示N0.30。注意，合金N0.30中M(C,N)的高含量一直到1200℃。如所預期，溫度超過850℃時，bcc相不穩定。有意思的是，可以看到表示M(C,N)量之平衡曲線的斜率隨著氮含量的增加而降低。此意味著使M(C,N)溶解在N0.30中比溶解在N0.05中更難。因此，在1100℃進行沃斯田體化之後，預期N0.30基質中碳、氮及釩的量比在N0.05基質中更低。 Figure 4 shows the results of this equilibrium calculation. The mole fractions of M ₆ C, M(C, N) and bcc matrices are shown here as a function of temperature. The equilibrium phase is the Worth field. The solid curve represents N0.05; the dashed curve represents N0.10, and the dotted curve represents N0.30. Note that the high content of M(C,N) in alloy N0.30 is up to 1200 °C. As expected, the bcc phase was unstable at temperatures above 850 °C. Interestingly, it can be seen that the slope of the equilibrium curve representing the amount of M(C,N) decreases as the nitrogen content increases. This means that it is more difficult to dissolve M(C,N) in N0.30 than in N0.05. Therefore, after the Worth fielding at 1100 ° C, the amount of carbon, nitrogen and vanadium in the N0.30 matrix is expected to be lower than in the N0.05 matrix.

由於富鉬M₆C相僅溶解碳而不溶解氮，因此其受N0.10及N0.30中較低碳含量的影響，因而M₆C的量隨著碳含量的降低而降低。亦應注意，在所用沃斯田體化溫度下，M₆C全部溶解。 Since the molybdenum-rich M ₆ C phase dissolves only carbon and does not dissolve nitrogen, it is affected by the lower carbon content of N0.10 and N0.30, and thus the amount of M ₆ C decreases as the carbon content decreases. It should also be noted that at the Worstian body temperature used, M ₆ C is completely dissolved.

在回火溫度區域內執行的計算僅僅係為了估計N0.05、N0.10及N0.30之二次析出可能性。已發現的平衡充其量能顯示，經過足夠長時間後，何種相會存在於材料中。先前的研究已顯示：實務上，標準低鉻熱工作工具鋼中存在某種自生回火。此意味著M₃C(雪明碳體)會在沃斯田體化過程之後析出。 The calculations performed in the tempering temperature region are only for estimating the secondary precipitation possibilities of N0.05, N0.10, and N0.30. The balance that has been found can at best show which phase will be present in the material after a sufficiently long time. Previous studies have shown that there is some spontaneous tempering in the standard low chromium hot work tool steel. This means that M ₃ C (Snowy Carbon) will precipitate after the Worth formation process.

圖5所示為在回火溫度區域內計算所得出之結果。實曲線表示N0.05；虛曲線表示N0.10，點曲線表示N0.30。二次硬化通常在500℃與650℃之間發生，而在此溫度間隔內，N0.05與N0.10之間M(C,N)量之差值不大。另一方面，N0.30所含的M(C,N)量較高且幾乎恆定，其可能係由於N0.30中釩含量及氮含量較高。 Figure 5 shows the results calculated in the tempering temperature region. The solid curve represents N0.05; the dashed curve represents N0.10, and the dotted curve represents N0.30. Secondary hardening typically occurs between 500 ° C and 650 ° C, and during this temperature interval, the difference in M (C, N) between N 0.05 and N 0.1 0 is small. On the other hand, the amount of M(C,N) contained in N0.30 is relatively high and almost constant, which may be due to the higher vanadium content and nitrogen content in N0.30.

與N0.10相比，N0.05中的較高碳含量產生了更多與基質平衡之M₂C相。N0.30中M₂C要少的多。 The higher carbon content in N0.05 produced more M ₂ C phases in equilibrium with the matrix than N0.10. M ₂ C is much less in N0.30.

根據先前的計算，應該可以估計在特定溫度下進行沃斯田體化之後此等合金中發生二次析出的可能性。該可能性取決於，在回火溫度下的介穩定平衡與沃斯田體化溫度下的平衡之間，M(C,N)相及M₂C相的量的差值。表3所示為此等差值，用以說明三種不同合金之二次析出可能性。該等值的單位為莫耳百分數。 Based on previous calculations, it should be possible to estimate the likelihood of secondary precipitation in such alloys after Worth fielding at a particular temperature. This possibility depends on the difference between the amount of M(C,N) phase and M ₂ C phase between the metastable equilibrium at the tempering temperature and the equilibrium at the Worth field temperature. Table 3 shows the difference between the two to illustrate the possibility of secondary precipitation of three different alloys. The unit of the equivalent is the percentage of moles.

表3所示結果表明：N0.05具有最佳硬化反應，因為在1100℃時N0.05中存在之M(C,N)相的量較低，亦即，許多合金元素可溶於沃斯田體基質。亦表明N0.05在625℃溫度下進行回火的過程中最有可能發生良好的二次硬化。 The results shown in Table 3 indicate that N0.05 has the best hardening reaction because the amount of M(C,N) phase present in N0.05 is lower at 1100 ° C, that is, many alloying elements are soluble in Voss Field matrix. It is also shown that N0.05 is most likely to undergo good secondary hardening during tempering at a temperature of 625 °C.

實施例2 Example 2

N0.05及N0.10兩種合金按照習知方法被澆鑄成50 kg的小型鋼錠。N0.10為第一試驗合金，在鍛造過程之前沒有對此鋼錠進行均質化處理。在鍛造之前在1300℃對第二試驗合金N0.05進行了15小時之均質化處理。第三試驗合金N0.30之氮含量過高，以致於無法藉由習知澆鑄法來製造該合金。因此，使用粉末冶金法來產生此合金。首先製造鋼粉，然後用加壓N₂氣體對此粉末進行固態氮化。隨後在1150℃以76 MPa之壓力對此粉末進行熱均衡加壓(HIP)。 N0.05 and N0.10 alloys were cast into small steel ingots of 50 kg according to a conventional method. N0.10 is the first test alloy, and the ingot was not homogenized before the forging process. The second test alloy N0.05 was homogenized at 1300 ° C for 15 hours prior to forging. The nitrogen content of the third test alloy N0.30 was too high to manufacture the alloy by a conventional casting method. Therefore, powder metallurgy is used to produce this alloy. The steel powder is first produced and then solidified by solid state nitriding with pressurized N ₂ gas. This powder was then subjected to heat equalization (HIP) at 1150 ° C at a pressure of 76 MPa.

三種鋼錠均在1270℃進行鍛造，然後切割出尺寸為15×15×8 mm之樣本。藉由在820℃首先進行軟化退火而對此等樣本進行熱處理；退火後進行冷卻的順序為，以每小時10℃之速率冷卻至650℃，然後在空氣中自由冷卻。軟化退火之後，對N0.05在1100℃進行沃斯田體化30分鐘。為了補償較差之析出可能性，對N0.10在1150℃進行沃斯田體化30分鐘，對N0.30在1200℃進行沃斯田體化30分鐘。三種合金各提供9個樣本，在以下溫度對該等樣本進行回火：450℃、525℃、550℃、575℃、600℃、625℃、650℃、675℃及700℃。均熱時間為兩小時，回火兩次，亦即，總回火時間為四小時。熱處理之後，量測該等樣本之硬度。為了進一步研究樣本中未溶解顆粒之形態、分佈及大小，執行掃描電子顯微法(SEM)。所用SEM儀器為FEI Quanta 600 F。 All three ingots were forged at 1270 ° C and then cut into samples of size 15 × 15 × 8 mm. The samples were subjected to heat treatment by first performing softening annealing at 820 ° C; the order of cooling after annealing was to cool to 650 ° C at a rate of 10 ° C per hour, and then freely cooled in air. After softening annealing, Worsfield was subjected to N0.05 at 1100 ° C for 30 minutes. In order to compensate for the poor possibility of precipitation, the Vostian body was subjected to N0.10 at 1150 ° C for 30 minutes, and N0.30 was subjected to Vostian for 30 minutes at 1200 ° C. Nine samples were provided for each of the three alloys, and the samples were tempered at the following temperatures: 450 ° C, 525 ° C, 550 ° C, 575 ° C, 600 ° C, 625 ° C, 650 ° C, 675 ° C, and 700 ° C. The soaking time is two hours and tempering twice, that is, the total tempering time is four hours. After the heat treatment, the hardness of the samples was measured. To further investigate the morphology, distribution and size of the undissolved particles in the sample, scanning electron microscopy (SEM) was performed. The SEM instrument used was a FEI Quanta 600 F.

硬度量測Hardness measurement

圖6所示為硬度量測之結果。自圖中可以看出，在500℃至650℃之溫度間隔內，三種合金均具有二次硬化峰。全部回火均進行2+2小時。在淬火後的狀態下，N0.05的硬度最高(53 HRC)，而N0.10及N0.30之硬度略低。然而，三種合金均被視為可硬化的。N0.05的硬度曲線與標準低鉻熱工作工具鋼之硬度曲線非常相似，如圖1所示，標準低鉻熱工作工具鋼之最大硬度值約為54 HRC。 Figure 6 shows the results of the hardness measurement. It can be seen from the figure that the three alloys have secondary hardening peaks in the temperature interval of 500 ° C to 650 ° C. All tempering was carried out for 2+2 hours. In the state after quenching, N0.05 has the highest hardness (53 HRC), while N0.10 and N0.30 have a slightly lower hardness. However, all three alloys are considered to be hardenable. The hardness curve of N0.05 is very similar to that of the standard low chromium hot work tool steel. As shown in Figure 1, the standard low chromium hot work tool steel has a maximum hardness value of about 54 HRC.

N0.10的二次硬化峰似乎略有偏移，處於更高的溫度下，峰值硬度出現在600℃。N0.05及N0.30的峰值硬度出現在550℃。 The secondary hardening peak of N0.10 appears to be slightly offset, and at a higher temperature, the peak hardness appears at 600 °C. The peak hardness of N0.05 and N0.30 Now 550 ° C.

掃描電子顯微法Scanning electron microscopy

按照習知方法澆鑄之N0.05(氮含量最低的合金)中未溶解的M(C,N)顆粒之平均大小小於1 μm。該大小與鋼中普通未溶解之碳化物相當。參看圖7，在N0.05中容易找到另一相，該相為氧化鋁與硫化錳之混合物。圖7為SEM圖像(反向散射)，所示為N0.05中微小的未溶解M(C,N)析出物2，以及氧化物-硫化物之混合球狀顆粒1。該樣本已在1100℃進行沃斯田體化30分鐘，並在625℃回火2+2小時。 The average size of the undissolved M(C,N) particles in the N0.05 (the alloy with the lowest nitrogen content) cast by the conventional method is less than 1 μm. This size is comparable to the usual undissolved carbide in steel. Referring to Figure 7, another phase is readily found in N0.05, which is a mixture of alumina and manganese sulfide. Fig. 7 is an SEM image (backscatter) showing a small undissolved M(C,N) precipitate 2 in N0.05, and an oxide-sulfide mixed spherical particle 1. The sample has been subjected to Vostian for 30 minutes at 1100 ° C and tempered at 625 ° C for 2+ 2 hours.

N0.05(以及N0.10)中之所以包括許多非金屬雜質，是因為所有的試驗鋼錠均係在開放氛圍中製造及澆鑄而成。 Many non-metallic impurities are included in N0.05 (and N0.10) because all test steel ingots are manufactured and cast in an open atmosphere.

在1150℃進行沃斯田體化30分鐘並在625℃回火2+2小時之後，N0.10中M(C,N)顆粒之最常見大小為，圓當量直徑(ECD)在5 μm與10 μm之間。參看圖8，在前沃斯田體晶粒邊界處常常可以找到更大的一次碳化物3(在熔料中析出)，圖8為反向散射SEM圖像，所示為合金N0.10中在前沃斯田體晶粒邊界處未溶解之一次M(C,N)。該樣本在1150℃進行沃斯田體化30分鐘，並在625℃回火2+2小時。 After the Vostian texturization at 1150 ° C for 30 minutes and tempering at 625 ° C for 2+ 2 hours, the most common size of M (C, N) particles in N0.10 is, the equivalent circle diameter (ECD) is 5 μm and Between 10 μm. Referring to Figure 8, a larger primary carbide 3 (precipitated in the melt) is often found at the grain boundary of the former Woustian field, and Figure 8 is a backscattered SEM image showing the former in the alloy N0.10. One time M(C,N) at the grain boundary of the Worth field. The sample was subjected to Vostian for 30 minutes at 1150 ° C and tempered at 625 ° C for 2+ 2 hours.

圖9為N0.10中的一次M(C,N)顆粒4之SEM細節顯微圖。使用牛津儀器提供的INCA特徵軟體，可在SEM中自動發現此等顆粒。此等顆粒之邊緣清晰，此表明此等顆粒已自熔料中析出。圖像中的白色區域為富鉬M₆C顆粒5。注意，在此情況下，樣本為軟化退火後的N0.10。 Figure 9 is a SEM detail micrograph of primary M(C,N) particles 4 in N0.10. These particles can be automatically found in the SEM using the INCA feature software provided by Oxford Instruments. The edges of these particles are clear, indicating that these particles have precipitated from the melt. The white areas in the image are molybdenum-rich M ₆ C particles 5. Note that in this case, the sample is N0.10 after softening annealing.

在用粉末冶金法製造之N0.30中，未溶解的M(C,N)顆粒6之大小分佈(ECD)介於1 μm與5 μm之間，最常見之大小為2 μm，因此，儘管N0.30之氮含量較高，但此等顆粒仍然較小。參看圖10，該等顆粒均勻地分佈在微觀結構中。然而，如圖11所示，其中存在一些M(C,N)叢集7。 Undissolved M(C,N) in N0.30 manufactured by powder metallurgy The size distribution (ECD) of the granules is between 1 μm and 5 μm, the most common size being 2 μm, so these particles are still small despite the higher nitrogen content of N0.30. Referring to Figure 10, the particles are evenly distributed in the microstructure. However, as shown in FIG. 11, there are some M(C, N) clusters 7 therein.

用EDS來量測所有三種合金中未溶解之M(C,N)相顆粒之化學組成物，量測結果顯示於表4中，表4所示為合金N0.05、N0.10及N0.30中M(C,N)顆粒之化學組成物。該等值之單位為原子百分數。注意，儘管EDS對於輕元素(如碳及氮)之精確度並不很高，但是可知，可根據標稱組成物推測M(C,N)相中除碳及氮以外的元素。表中提供的±值是由INCA程式(牛津儀器)提供的。已記錄之一些鐵很可能來自周圍的基質，對合金N0.05尤其如此。 EDS was used to measure the chemical composition of undissolved M(C,N) phase particles in all three alloys. The measurement results are shown in Table 4. Table 4 shows alloys N0.05, N0.10 and N0. The chemical composition of M(C,N) particles in 30. The unit of the equivalent is the atomic percentage. Note that although EDS is not very accurate for light elements such as carbon and nitrogen, it is known that elements other than carbon and nitrogen in the M(C,N) phase can be estimated from the nominal composition. The ± values provided in the table are provided by the INCA program (Oxford Instruments). Some of the iron that has been recorded is likely to come from the surrounding matrix, especially for alloy N0.05.

產業利用性 Industrial utilization

在需要得到可在高溫下及長時間段內使用的熱工作鋼工具的情況下，本發明之方法及低鉻熱工作工具鋼適用。 The method of the present invention and the low chromium hot work tool steel are suitable in the case where it is desired to obtain a hot working steel tool that can be used at high temperatures and for long periods of time.

1‧‧‧氧化物-硫化物之混合球狀顆粒 1‧‧‧Oxide-sulfide mixed spherical particles

2‧‧‧微小的未溶解M(C,N)析出物 2‧‧‧ Minor undissolved M(C,N) precipitates

3‧‧‧更大的一次碳化物 3‧‧‧Greater primary carbide

4‧‧‧一次M(C,N)顆粒 4‧‧‧One time M(C,N) particles

5‧‧‧富鉬M₆C顆粒 5‧‧‧Molybdenum-rich M ₆ C particles

6‧‧‧未溶解的M(C,N)顆粒 6‧‧‧Undissolved M(C,N) particles

7‧‧‧M(C,N)叢集 7‧‧‧M(C,N) clusters

圖1所示為不含氮的例示性先前技術低鉻熱工作工具鋼之硬度與回火溫度的關係。 Figure 1 shows an exemplary prior art low chromium hot work tool without nitrogen. The relationship between the hardness of steel and the tempering temperature.

圖2所示為先前技術的各種鋼在不同回火溫度下的硬度，此等鋼分別為Cr 15、Mo 1、C 0.6及Cr 15、Mo 1、C 0.29、N 0.35(含量單位為wt-%)。 Figure 2 shows the hardness of various steels of the prior art at different tempering temperatures, such as Cr 15, Mo 1, C 0.6 and Cr 15, Mo 1, C 0.29, N 0.35 (content is wt- %).

圖3所示為沃斯田體中鉻含量變低對M(C,N)穩定性的影響。 Figure 3 shows the effect of low chromium content in the Worth field on the stability of M(C,N).

圖4所示為M₆C、M(C,N)及bcc基質之莫耳分數隨溫度變化。(平衡相：沃斯田體基質。) Figure 4 shows the molar fraction of M ₆ C, M (C, N) and bcc matrices as a function of temperature. (Equilibrium phase: Worth field matrix.)

圖5所示為M(C,N)相及介穩定M₂C之量隨溫度變化。(平衡相：肥粒鐵。) Figure 5 shows the amount of M(C,N) phase and metastable M ₂ C as a function of temperature. (Equilibrium phase: fat iron.)

圖6所示為試驗合金N0.05、N0.10及N0.30之硬度與回火溫度的關係之曲線。 Figure 6 is a graph showing the relationship between the hardness of the test alloys N0.05, N0.10 and N0.30 and the tempering temperature.

圖7為反向散射SEM圖像，所示為N0.05中微小的未溶解M(C,N)析出物及氧化物與硫化物之混合球狀顆粒。 Figure 7 is a backscattered SEM image showing tiny undissolved M(C,N) precipitates and mixed spherical particles of oxide and sulfide in N0.05.

圖8為反向散射SEM圖像，所示為合金N0.10中之前沃斯田體晶粒邊界處未溶解之一次M(C,N)。 Figure 8 is a backscattered SEM image showing the first M(C,N) undissolved at the grain boundary of the Worth field before the alloy N0.10.

圖9為反向散射SEM圖像，所示為軟化退火後的N0.10中的一次顆粒。 Figure 9 is a backscatter SEM image showing primary particles in N0.10 after softening annealing.

圖10為反向散射SEM圖像，所示為未溶解之M(C,N)顆粒在N0.30中均勻分佈。 Figure 10 is a backscattered SEM image showing the undissolved M(C,N) particles uniformly distributed in N0.30.

圖11為反向散射SEM圖像，所示為N0.30中出現了一些未溶解之M(C,N)叢集。 Figure 11 is a backscattered SEM image showing some undissolved M(C,N) clusters in N0.30.

Claims

一種用於在高溫下對金屬進行加工或成形中之一者的低鉻熱工作工具鋼物件，由以下物質組成(單位為wt-%)：視需要而定除雜質外，其餘為Fe。 A low chromium hot work tool steel article for processing or forming metal at elevated temperatures consisting of: (wt-%): As needed Except for impurities, the rest is Fe.

如申請專利範圍第1項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件滿足以下條件中的一或多者(單位為wt-%)： For example, in the low chrome hot work tool steel article of claim 1, the low chrome hot work tool steel article satisfies one or more of the following conditions (unit: wt-%):

如申請專利範圍第2項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件滿足以下條件中的一或多者(單位為 wt-%)： For example, the low chromium hot work tool steel article of claim 2, the low chromium hot work tool steel article meets one or more of the following conditions (in wt-%):

如申請專利範圍第3項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件滿足以下條件(單位為wt-%)：Mo 2.2-2.9。 For example, in the low-chromium hot work tool steel article of claim 3, the low chromium hot work tool steel article satisfies the following conditions (unit: wt-%): Mo 2.2-2.9.

如申請專利範圍第4項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件滿足以下條件(單位為wt-%)：Mo 2.2-2.8。 For example, in the low-chromium hot work tool steel article of claim 4, the low-chromium hot work tool steel article satisfies the following conditions (unit: wt-%): Mo 2.2-2.8.

如申請專利範圍第1項或第2項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件滿足以下條件中的一或多者(單位為wt-%)： If the low chromium hot work tool steel article of claim 1 or 2 is applied for, the low chromium hot work tool steel article meets one or more of the following conditions (unit: wt-%):

如申請專利範圍第6項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件滿足以下條件中的一或多者(單位為wt-%)： For example, in the case of the low chromium hot work tool steel article of claim 6, the low chromium hot work tool steel article meets one or more of the following conditions (unit: wt-%):

如申請專利範圍第8項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件滿足以下條件中的一或多者(單位為wt-%)： For example, the low chromium hot work tool steel article of claim 8 of the patent scope meets one or more of the following conditions (in wt-%):

如申請專利範圍第10項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件滿足以下條件中的一或多者(單位為wt-%)： For example, in the low chrome hot work tool steel article of claim 10, the low chrome hot work tool steel article satisfies one or more of the following conditions (in wt-%):

如申請專利範圍第1項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件由以下物質組成(單位為wt-%)：C 0.20-0.35、視需要而定 For example, in the low chrome hot work tool steel article of claim 1 of the patent scope, the low chrome hot work tool steel article is composed of the following materials (unit: wt-%): C 0.20-0.35, As needed

如申請專利範圍第1項之低鉻熱工作工具鋼物件，該低鉻熱工作工具鋼物件由以下物質組成(單位為wt-%)：視需要而定 For example, in the case of the low chrome hot work tool steel article of claim 1, the low chromium hot work tool steel article is composed of the following materials (unit: wt-%): As needed