阅读说明：本技术 一种高硬度粉末钢及其热处理方法 (High-hardness powder steel and heat treatment method thereof ) 是由 林仕坚 崔靖 孙晓林 吴建华 于 2021-08-13 设计创作，主要内容包括：本发明提供了一种高硬度粉末钢及其热处理方法,所述粉末钢按质量百分比包括：C 1.8-2.5％、Si≤0.2％、Mn≤0.4％、Cr 4.0-5.2％、W 12-14％、V 5.6-6.8％、Co 9-11％,其余为Fe和不可避免的杂质元素。所述粉末钢合金和碳含量高,采用粉末冶金工艺制造,其热处理方法参数主要为：淬火处理为：真空淬火温度为(1100～1200)℃×(0.5～4)h,真空气淬,气体压力4～8bar；深冷处理为：在超低温深冷箱中在-100至-190℃处理(1～10)h；回火处理为：500～600℃保温2～6h,回火2～3次,出炉后空冷。经测试合金硬度可达70-72HRC,碳化物细小弥散、残余奥氏体少,耐磨性和红硬性高,并保持优良的韧性,可用于滚齿刀、高速冲压模等的加工制造,较常规高速钢具有更高的使用寿命。(The invention provides high-hardness powder steel and a heat treatment method thereof, wherein the powder steel comprises the following components in percentage by mass: 1.8 to 2.5 percent of C, less than or equal to 0.2 percent of Si, less than or equal to 0.4 percent of Mn, 4.0 to 5.2 percent of Cr, 12 to 14 percent of W, 5.6 to 6.8 percent of V, 9 to 11 percent of Co, and the balance of Fe and inevitable impurity elements. The powder steel has high alloy and carbon content, is manufactured by adopting a powder metallurgy process, and has the following parameters in the heat treatment method: the quenching treatment comprises the following steps: the vacuum quenching temperature is 1100-1200℃ x (0.5-4) h, and the vacuum gas quenching is carried out at the gas pressure of 4-8 bar; the cryogenic treatment comprises the following steps: treating for 1-10 h at-100 to-190 ℃ in an ultralow temperature deep cooling box; the tempering treatment comprises the following steps: keeping the temperature at 500-600 ℃ for 2-6 h, tempering for 2-3 times, and air cooling after discharging. The alloy hardness can reach 70-72HRC through testing, the carbide is fine and dispersed, the residual austenite is less, the wear resistance and the red hardness are high, the excellent toughness is kept, the alloy can be used for processing and manufacturing a hobbing cutter, a high-speed stamping die and the like, and the service life is longer than that of the conventional high-speed steel.)

1. A high-hardness powder steel characterized by: the alloy is manufactured by adopting a powder metallurgy process, and the powder steel comprises the following components in percentage by mass: 1.8 to 2.5 percent of C, less than or equal to 0.2 percent of Si, less than or equal to 0.4 percent of Mn, 4.0 to 5.2 percent of Cr, 12 to 14 percent of W, 5.6 to 6.8 percent of V, 9 to 11 percent of Co, and the balance of Fe and inevitable impurity elements.

2. The high-hardness powder steel according to claim 1, wherein: the powder steel comprises the following elements in percentage by mass: 2.3% of C, 0.07% of Si, 0.05% of Mn, 4.2% of Cr, 12.2% of W, 5.7% of V, 9.5% of Co, and the balance of Fe and inevitable impurity elements.

3. The high-hardness powder steel according to claim 1, wherein: the powder steel comprises the following elements in percentage by mass: 2.1% of C, 0.05% of Si, 0.1% of Mn, 4.8% of Cr, 12.9% of W, 6.1% of V and 10.3% of Co, and the balance of Fe and inevitable impurity elements.

4. A heat treatment method of high hardness powder steel according to any one of claims 1 to 3, comprising the steps of:

(1) the quenching treatment comprises the following steps: the vacuum quenching temperature is (1080-1200) DEG C (x) (0.5-4) h, and the vacuum gas quenching is carried out at the gas pressure of 4-8 bar;

(2) the cryogenic treatment comprises the following steps: treating for 1-10 h at-100 to-190 ℃ in an ultralow temperature deep cooling box;

(3) the tempering treatment comprises the following steps: keeping the temperature at 500-600 ℃ for 2-6 h, tempering for 2-3 times, and air cooling after discharging.

5. The heat treatment method of high-hardness powder steel according to claim 4, characterized in that: after heat treatment, the hardness of the powder steel is 64-72 HRC.

6. The heat treatment method of high-hardness powder steel according to claim 4, characterized in that: after heat treatment, the unnotched impact of the prepared 10 multiplied by 55mm part is 5 to 12J.

Technical Field

The invention relates to the technical field of powder steel, in particular to high-hardness powder steel and a heat treatment method thereof.

Background

High-speed tool steel is widely used for manufacturing tools such as turning tools, milling cutters, press dies, and broaches, and plays a very important role in industrial manufacturing. The high-speed tool steel mainly contains carbide forming elements such as tungsten, molybdenum, chromium, vanadium, cobalt and the like and more than 1% of carbon element, and the elements are dissolved in a matrix or form carbide, so that the high-speed tool steel can still keep high hardness under high-speed cutting or stamping, and the hardness of the high-speed tool steel is generally between 60HRC and 68 HRC.

High carbon and carbide forming elements in the alloy tend to cause large size eutectic carbides to form during solidification, placing very high demands on the size of the bulk carbides and the carbide non-uniformity in high speed tool steels.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides high-hardness powder steel and a heat treatment method thereof, solves the problems of insufficient hardness, poor red hardness and wear resistance of conventional high-speed steel, low toughness and high cost of hard alloy, and improves the service life and cost performance of the alloy.

The technical scheme adopted by the invention is as follows: the high-hardness powder steel and the heat treatment method thereof are characterized in that the alloy is manufactured by adopting a powder metallurgy process, and the powder steel comprises the following components in percentage by mass: 1.8 to 2.5 percent of C, less than or equal to 0.2 percent of Si, less than or equal to 0.4 percent of Mn, 4.0 to 5.2 percent of Cr, 12 to 14 percent of W, 5.6 to 6.8 percent of V, 9 to 11 percent of Co, and the balance of Fe and inevitable impurity elements.

Preferably, the powder steel comprises the following elements in percentage by mass: 2.3% of C, 0.07% of Si, 0.05% of Mn, 4.2% of Cr, 12.2% of W, 5.7% of V, 9.5% of Co, and the balance of Fe and inevitable impurity elements.

Preferably, the powder steel comprises the following elements in percentage by mass: 2.1% of C, 0.05% of Si, 0.1% of Mn, 4.8% of Cr, 12.9% of W, 6.1% of V and 10.3% of Co, and the balance of Fe and inevitable impurity elements.

The invention also discloses a heat treatment process of the high-hardness powder steel, which specifically comprises the following steps:

(1) the quenching treatment comprises the following steps: the vacuum quenching temperature is 1100-1200℃ x (0.5-4) h, and the vacuum gas quenching is carried out at the gas pressure of 4-8 bar;

(2) the cryogenic treatment comprises the following steps: treating for 1-10 h at-100 to-190 ℃ in an ultralow temperature deep cooling box;

(3) the tempering treatment comprises the following steps: keeping the temperature at 500-600 ℃ for 2-6 h, tempering for 2-3 times, and air cooling after discharging.

Under the same condition, the product has longer service life compared with the hard alloy, and can meet the working conditions of turning tools, milling cutters, high-speed stamping dies and the like with higher requirements on hardness and toughness. The preparation by the powder metallurgy process controls the unevenness of the carbide in the high-speed steel and controls the size of the large carbide within 2 grades.

The hardness of the powder steel after the powder steel is subjected to heat treatment is 64-72 HRC. The unnotched impact energy of the prepared 10 multiplied by 55mm part is 5 to 12J, wherein the highest hardness can reach 70 to 72HRC, and the part has very high hardness and higher toughness.

The invention has the following beneficial effects:

first, the present invention increases the alloy hardness, red hardness and wear resistance by increasing the tungsten, vanadium and carbon content in the alloy, wherein the high cobalt content ensures that the alloy has superior red hardness. The invention adopts the powder metallurgy process to smelt the high-speed tool steel to realize the effective control of the size and the unevenness of carbide, and the hardness can reach more than 70HRC after the proper heat treatment process. Compared with high-speed steel such as M42, ASP2023, ASP2060 and the like, the high-speed steel has higher hardness and better wear resistance and red hardness.

Secondly, the carbide in the powder steel is dispersed and refined, the crystal grains and the martensite are fine, the red hardness and the wear resistance are obviously higher than those of traditional high-speed steel such as M42, ASP2023 and the like and powder high-speed steel, the toughness is obviously higher than that of hard alloy, and the service life of the powder steel used for hobbing cutters, high-speed stamping dies and the like is greatly prolonged.

Drawings

FIG. 1 is a flow chart illustrating a heat treatment method of high hardness powder steel according to the present invention.

FIG. 2 shows the hardness and impact energy of the high hardness powder steel of the present invention.

FIG. 3 shows the structure of the high-hardness powder steel according to the present invention after quenching.

FIG. 4 is a structure of the high-hardness powder steel according to the present invention after final heat treatment.

Fig. 5 shows the shape of the punched product of table 2.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to fig. 1 to 5 and embodiments 1 to 3, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Specific embodiments of the present invention are described below.

Example 1: the high-hardness powder steel comprises the following elements in percentage by mass: 2.0% of C, 0.05% of Si, 0.05% of Mn, 4.9% of Cr, 12.5% of W, 5.7% of V, 9.5% of Co, and the balance of Fe and inevitable impurity elements.

(1) Quenching treatment: the powder steel is put into a vacuum quenching furnace and then heated up, the heating rate does not exceed 300 ℃/h, the temperature is kept at 600 ℃ for 1h, then the temperature is raised to 870 ℃ and kept for 0.5h, then the vacuum gas quenching is carried out after the temperature is kept at 1150 ℃ for 1h, and the gas pressure is 8 bar;

(2) cryogenic treatment: when the cooling temperature is as low as 80 ℃, putting the powder steel into an ultralow temperature deep cooling box, and treating for 4 hours at-120 ℃;

(3) tempering treatment: putting the powder steel into a box furnace, keeping the temperature at 520-540 ℃ for 2h, taking out of the furnace, air cooling, and tempering for 2-3 times;

(4) the unnotched impact energy was 10J when the hardness of the powder steel after heat treatment was 66 HRC.

Example 2: the high-hardness powder steel comprises the following elements in percentage by mass: 2.3% of C, 0.07% of Si, 0.05% of Mn, 4.2% of Cr, 12.2% of W, 5.7% of V, 9.5% of Co, and the balance of Fe and inevitable impurity elements.

(1) Quenching treatment: the powder steel is put into a vacuum quenching furnace and heated up, the heating rate does not exceed 300 ℃/h, the temperature is kept at 550 ℃ for 1h, then the temperature is raised to 850 ℃ and kept for 0.5h, then the temperature is kept at 1160 ℃ for 1h, and then vacuum gas quenching is carried out, and the gas pressure is 7 bar;

(2) cryogenic treatment: when the cooling temperature is as low as 80 ℃, putting the powder steel into an ultralow temperature deep cooling box, and treating for 4 hours at-120 ℃;

(3) tempering treatment: putting the powder steel into a box furnace, keeping the temperature at 500 ℃ for 2h, discharging from the furnace, air cooling, and tempering for 2-3 times;

(4) the unnotched impact energy was 8J when the hardness of the powder steel after heat treatment was 68 HRC.

Example 3: the high-hardness powder steel comprises the following elements in percentage by mass: 2.1% of C, 0.05% of Si, 0.1% of Mn, 4.8% of Cr, 12.9% of W, 6.1% of V and 10.3% of Co, and the balance of Fe and inevitable impurity elements.

(1) Quenching treatment: the powder steel is put into a vacuum quenching furnace and heated up, the heating rate does not exceed 300 ℃/h, the temperature is kept at 600 ℃ for 1h, then the temperature is raised to 850 ℃ and kept for 0.5h, then the temperature is kept at 1180 ℃ for 1h, and then vacuum gas quenching is carried out, wherein the gas pressure is 6 bar;

(2) cryogenic treatment: when the cooling temperature is as low as 80 ℃, putting the powder steel into an ultralow temperature deep cooling box, and treating for 5 hours at-150 ℃;

(3) tempering treatment: and (3) putting the powder steel into a box furnace, keeping the temperature of 500-520 ℃ for 2 hours, taking the steel out of the furnace, air cooling and tempering for 2-3 times.

(4) The unnotched impact energy was 7J when the hardness of the powder steel after heat treatment was 70 HRC.

Experimental example: the high-hardness powder steel of the invention and powder steel such as ASP2023 are made into a die and then are stamped into a conventional part structure shown in figure 5. The toughness and the service life of different steel grades are compared by analyzing the parameters of the hardness of the die, the unnotched impact energy, the stamping die frequency, the failure mode and the like of the experimental die,

TABLE 1 comparison of unnotched impact energy of the examples with the prior alloys

In the present application, the 66HRC data set shown in FIG. 2 is example 1, the 68HRC data set shown is example 2, and the 70HRC data set shown is example 3. Although the hardness of some cemented carbide in table 1 can reach 70HRC, its lower impact energy is not suitable for high load condition.

TABLE 2 comparison of service life for stainless steel stamping

From table 2, it can be seen that the high hardness powder steel of the present invention has a hardness of 64HRC, a stamping number of 6000, a service life and a wear resistance significantly higher than those of ASP2023 powder steel for 5000 times, and at this time, the main failure mode of the high hardness powder steel of the present invention is wear.

When the hardness of the high-hardness powder steel is increased to 66HRC, the stamping times reach 16000 times, the ASP2060 stamping times is 5000, namely abrasion and tooth breakage occur, and the high-hardness powder steel does not have tooth breakage and is related to higher impact energy of the steel type.

When the hardness of the high-hardness powder steel is increased to 68HRC, no obvious abrasion occurs, the service life reaches 29000 die times, tooth breakage occurs when ASP2060 punches 8000 times, and the service life is higher if the high-hardness powder steel does not abnormally crack.

In conclusion, the high-hardness powder steel disclosed by the invention not only has the hardness of 70-72HRC, but also has extremely high wear resistance and impact toughness under the high-hardness condition that the hardness is 64-68HRC, and the service life of a stamping die is obviously prolonged. In the prior art, ASP2023 has high unnotched impact energy but low hardness and wear resistance, ASP2060 can reach 68HRC but low wear resistance and impact resistance, and the hard alloy in Table 1 has high hardness and wear resistance but low unnotched impact energy.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.