TWI695074B - Steel work piece having high hardness and impact resistance and method of forming the same - Google Patents

Abstract

A steel work piece having high hardness and impact resistance and a method of forming the same are provided in the present invention. An alloy material having a high carbon content is subjected to an Austempering operation, a quenching operation and a tempering operation, so as to form the steel work pieces. The steel work piece has high hardness and high toughness, and it can be applied to a hand tool such as a screw driver.

Description

Steel with high hardness and impact resistance and manufacturing method thereof

The invention relates to a steel part and a manufacturing method thereof, and in particular to a hand tool steel part and a manufacturing method thereof, the steel part has both high hardness and high toughness, and can be used for those that need to have impact resistance and wear resistance characteristics Operating environment.

Generally speaking, as small-sized hand tool steel parts such as electric screwdrivers, it is necessary to have both high hardness and high toughness. In view of the fact that if this kind of steel is only quenched and tempered by traditional quenching and tempering methods, its toughness is often insufficient, so heat tempering (that is, heat treatment at a temperature higher than the metamorphic initial temperature (Ms) of the Ma Tian bulk of the steel material) can be used. ) To increase the toughness of the steel material. However, the Ms temperature of currently common steel parts materials is relatively high, and it is necessary to use 300℃ or higher temperature for Voss tempering in order to achieve the effect of constant temperature metamorphosis and tempering. In contrast, this high temperature also easily leads to insufficient hardness of steel parts.

At present, there is a known method that uses tempering and tempering and electrolytic polishing to increase the functionality and fatigue of the bit. The hardness of the bit after tempering is about HRC 52 to HRC 56. In addition, in this method, part of the section is processed to reduce the diameter in the design of the hexagonal rod part of the screwdriver head Reduced diameter midportions to increase the impact resistance of the bit.

However, the current method still cannot meet the requirements of satisfactory steel parts with high hardness and high toughness. Therefore, at present, there is an urgent need to propose a steel part and a manufacturing method thereof, which have sufficient hardness and toughness for application in an operating environment requiring impact resistance and wear resistance characteristics.

According to one aspect of the present invention, a method for manufacturing a steel member with high hardness and impact resistance is proposed. In some embodiments, first of all, providing carbon containing 0.76 weight percent (wt.%) to 0.8 wt.%, silicon from 1.9 wt.% to 3 wt.%, manganese from 0.3 wt.% to 0.5 wt.%, 0.65 wt.% to 12wt.% of chromium, 0.15wt.% to 0.25wt.% of vanadium, inevitable impurities and the balance of iron alloy materials. Next, a heat treatment operation is performed on this alloy material to form a first treatment material having a Vostian iron phase. Then, the first treatment material is subjected to a quenching operation to a first temperature to form a second treatment material, wherein the first temperature is higher than the metamorphic onset temperature (Ms) of the Ma Tian scattered iron alloy material. Next, at the first temperature, a Voss tempering operation is performed on the second treatment material to form a third treatment material having needle-shaped lower-toughened iron. In the third treatment material, the volume fraction of the needle-like toughened iron is 15% to 30% of the metallographic structure. After that, the third treatment material is subjected to a quenching operation and a tempering operation to form a steel piece.

According to some embodiments of the present invention, the heat treatment operation is performed at a second temperature higher than 855°C.

According to some embodiments of the present invention, one of the quenching operations has a cooling rate of at least 150°C/sec.

According to some embodiments of the present invention, the first temperature is 235°C to 245°C.

According to some embodiments of the invention, the quenching operation includes cooling the third treatment material to room temperature.

According to some embodiments of the present invention, the tempering operation is maintained at 180°C to 200°C.

According to some embodiments of the present invention, the alloy material further includes 0.1 wt.% to 0.4 wt.% molybdenum.

According to some embodiments of the present invention, the Voss tempering operation is performed for 1 to 30 minutes.

According to some embodiments of the present invention, the quenching operation further includes leaving the third processing material at room temperature.

Another aspect of the present invention provides a steel piece with high hardness and impact resistance, which is manufactured by the foregoing method for manufacturing a steel piece with high hardness and impact resistance. This steel with high hardness and impact resistance has a needle-like toughened iron with a volume fraction of 15% to 30% of the metallographic structure.

110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130

210‧‧‧Heat treatment operation

211‧‧‧Quick cooling operation

220‧‧‧Tempering operation

Section 221‧‧‧

230‧‧‧Quenching operation

240‧‧‧Tempering operation

T1, T2, T4‧‧‧Temperature

T3‧‧‧Room temperature

Ms‧‧‧Matian powder metamorphic onset temperature

In order to make the above and other objects, features, advantages and embodiments of the present invention more obvious and understandable, the drawings are described in detail as follows: [FIG. 1A] and [FIG. 1B] are described according to some embodiments of the present invention. Schematic flow chart of the manufacturing method of steel parts with high hardness and impact resistance.

[Fig. 2] A schematic diagram of a heat treatment process of a method for manufacturing a steel member with high hardness and impact resistance according to some embodiments of the present invention.

[FIG. 3A] A schematic diagram of a screwdriver head of Example 6 and Comparative Examples 2 to 4.

[FIG. 3B] It is a schematic diagram of the screwdriver head of Example 7 and Comparative Example 5. [FIG.

[Fig. 4] It is the expansion curve of the semi-finished spheroidized material having composition No. 1 in Table 1.

[FIG. 5A] to [FIG. 5D] are electron micrographs of the metallurgical structure of the steel parts of Examples 3 to 5 and Comparative Example 1, respectively, after water tempering after Voss tempering.

[FIG. 6A] and [FIG. 6B] are electron micrographs of the metallographic structure of the screwdriver heads of Comparative Example 5 and Example 7, respectively.

The invention aims to provide a steel piece and a manufacturing method thereof. In some embodiments, the Ms temperature of the alloy material is reduced by the composition of the alloy material, and combined with an appropriate heat treatment process, the steel member can have both high hardness and high toughness. In addition, the steel can be used as a hand tool such as a screwdriver, and it can be used in an operating environment that requires wear resistance and impact resistance.

Please refer to FIG. 1A and FIG. 1B first, which is a schematic flowchart of a method for manufacturing a steel member with high hardness and impact resistance according to some embodiments of the present invention. First, as shown in step 110 of FIG. 1A, an alloy material is provided. In some embodiments, the alloy material includes at least 0.76 weight percent (wt.%) to 0.8 wt.% carbon, 1.9 wt.% to 3 wt.% silicon, 0.3 wt.% to 0.5 wt.% manganese , 0.65wt.% to 12wt.% chromium, 0.15wt.% to 0.25wt.% vanadium, inevitable impurities, and the balance of iron. In still other embodiments, the alloy material may further include 0.1 wt.% to 0.4 wt.% molybdenum.

The carbon affects the properties of steel such as strength, plasticity, toughness, workability, and hardenability. Generally speaking, the higher the hardness of the steel parts, the better the wear resistance, and when the carbon content of the alloy material falls within the above content range, the strength of the steel parts increases with the carbon content, but relatively, the toughness and plasticity are also Reduce, so by adjusting the carbon content of alloy materials, to achieve the appropriate hardness, toughness and plasticity of steel parts. When the carbon content is too high, it will cause the steel parts to be difficult to process; on the contrary, if the carbon content is insufficient, the steel parts have insufficient hardness. In addition, carbon is also the main element that affects the Ms temperature (details will be described later), and the carbon in the above content range helps to reduce the Ms temperature.

The silicon is an important reducing agent and deoxidizer in the steelmaking process. It can be dissolved in ferrite iron and Vostian iron to improve the hardness and strength of steel parts. Its role is second only to phosphorus, and it is better than manganese, nickel, Chromium, tungsten, molybdenum, vanadium and other elements. In addition, because silicon has the effect of solid solution strengthening, it can improve the elastic limit, yield reduction ratio and fatigue strength of steel parts. Due to the improvement of this elastic limit, the ability of steel parts to resist torsional deformation is increased. However, when the content of silicon is too much, it will significantly reduce the plasticity and toughness of the steel parts, and it will also cause the phase transition temperature Ac3 of the alloy material to increase significantly, resulting in an increase in the cost required to ferrite the alloy material Vostian .

The manganese can improve the hardening energy of the steel parts and improve the hot workability of the steel parts. Manganese can form high melting point manganese sulfide (MnS) with sulfur during the smelting process, so it can prevent the thermal embrittlement of iron sulfide (FeS), thereby reducing or eliminating the adverse effects caused by sulfur. In addition, since manganese can be infinitely dissolved in iron, it is added While manganese strengthens the strength of steel parts, it has less effect on plasticity, and the price of manganese is relatively low, so manganese is often added to the alloy as a strengthening element. However, too much manganese will still reduce the plasticity and weldability of steel parts, and will increase the tendency of steel grains to coarsen and the sensitivity of temper brittleness. Furthermore, if too much non-metallic intermediary MnS is formed, it is also easy to become a source of fatigue and reduce the fatigue life of steel parts. Therefore, the manganese content is preferably within the disclosed content range.

The chromium can improve the hardening energy of the steel parts, so that the steel parts can have better comprehensive mechanical properties after quenching and tempering, for example: better tempering stability and secondary hardening, so that the hardness and resistance of the steel parts The wearability is improved, but the steel parts are not brittle. In addition, chromium is a strong carbide forming element, so it can make steel parts difficult to decarburize. In addition, the high content of chromium can also make steel parts have good high temperature oxidation resistance, oxidation resistance, thermal strength, good surface processing quality and surface wear resistance.

The vanadium can be used as a deoxidizer for steel, and the precipitates of vanadium can refine grains and improve the strength and toughness of steel parts. In addition, the carbide formed by vanadium and carbon can improve the resistance of steel parts to hydrogen corrosion under high temperature and high pressure. If vanadium is not added or the amount is too small, the hardness and toughness of the steel parts will be insufficient.

The molybdenum improves the hardening energy and thermal strength of steel parts, and can reduce or prevent the temper brittleness of steel parts. In the process of quenching and tempering (such as Vos tempering and/or quenching and tempering), containing molybdenum helps to quench and deepen the treatment materials of large cross-sectional area, so it can improve the tempering resistance or tempering of steel parts Stability, so that the treatment material can be tempered at a higher temperature, thereby more effectively removing or reducing residual stress and improving plasticity.

The inevitable impurities include phosphorus, sulfur or other common Impurity elements. Although phosphorus is beneficial to the solid solution strengthening and cold work hardening of ferrite iron, which can improve the strength and hardness of steel parts, the presence of phosphorus will significantly reduce the plasticity, impact toughness and other properties of steel parts. Especially at low temperatures, phosphorus can significantly embrittle steel parts (called cold embrittlement), which deteriorates the cold workability and weldability of steel parts. Therefore, in the present invention, the phosphorus content of the alloy material is preferably not more than 200 ppm. Sulfur in alloy materials will exist in steel parts in the form of iron sulfide, and iron sulfide and iron will form compounds with low melting points, resulting in iron sulfide in the process of hot processing steel parts using the melting point of iron sulfide. Premature melting leads to cracking of steel parts (called hot brittleness). In addition, the presence of sulfur will reduce the ductility and toughness of the steel parts, so that cracks will occur when forging and rolling steel parts. At the same time, sulfur is not conducive to welding performance and corrosion resistance. Therefore, in the present invention, the sulfur content of the alloy material is preferably not more than 100 ppm.

In some embodiments, the composition of the above alloy material affects the Ms temperature. Therefore, the present invention consists of adjusting the composition of the above alloy material to achieve a predetermined lower Ms temperature. In some examples, the Ms temperature of the present invention is about 230°C. In other embodiments, the Ms temperature can be calculated by the following formula (1) or (2).

Ms (℃)=550-350[C]-40[Mn]-20[Cr]-17[Ni]-10[Mo]-5[W]-10[Cu]-35[V]+15[Co ]+30[Al] (1)

Ms (℃)=538-317[C]-33[Mn]-28[Cr]-17[Ni]-11[Mo]-11[W]-11[Si] (2)

In formula (1) and formula (2), square brackets ([]) indicate the content of individual elements. From the above formula (1) and formula (2), it can be seen that the carbon content has the largest influence on the Ms temperature, followed by manganese.

Next, as shown in step 112 of FIG. 1A, the alloy material is made into a disc element. In some embodiments, the operation of forming the disk element may include, but is not limited to, vacuum melting and casting to form alloy blanks, alloy blank straightening, rough rolling, finish rolling, finishing, welding and other steps. The above steps are generally in the art. The knowledgeable person knows, so I won't repeat them here.

Next, as shown in step 114 of FIG. 1A, a spheroidizing step is performed on the disk element. In some embodiments, this spheroidization step can be performed, for example, at 765°C to 785°C. After this spheroidization step, insoluble spherical carbides can remain, which can improve wear resistance. For example: the hardness of the disk element can reach HRB 98.

Then, as shown in step 116 of FIG. 1A, the ball-shaped disk element is drawn for the first time. In some examples, the disk element may be drawn into the shape of a hexagonal column, for practical application of the steel member of the present invention. However, due to the high carbon content of the alloy material, in general, the wire drawing step can be repeated to obtain semi-finished spheroidized materials having a predetermined shape.

Between the secondary thread drawing steps, as shown in step 118 of FIG. 1A, an annealing step is performed. In some embodiments, this annealing step may be performed, for example, at 670°C to 690°C.

After that, as shown in step 120 of FIG. 1A, a second thread drawing is performed. This time the drawing line can be regarded as fine drawing to obtain semi-finished products of pelletized material with a predetermined shape. Then, as shown in step 122 of FIG. 1A, the semi-finished product after cutting and drawing the thread is a hexagonal rod, which is the semi-finished product of the spheroidizing material.

Next, please refer to FIG. 1B and FIG. 2 together, where FIG. 2 is the manufacture of a steel piece with high hardness and impact resistance according to some embodiments of the present invention Schematic diagram of the heat treatment process of the manufacturing method. As shown in step 124, a heat treatment operation 210 is performed on the semi-manufactured spheroidized material to form a first treatment material having a Vostian iron phase. In some embodiments, the heat treatment operation 210 is performed at a temperature higher than the phase transition temperature (Ac3) of the alloy material. For example, the heat treatment operation 210 may be performed at a temperature T1 higher than 855°C. In some embodiments, the phase transition temperature Ac3 of the alloy material may be 850°C to 875°C. In the heat treatment operation 210, a Vostian iron phase is formed in the semi-finished spheroidized material.

Then, as shown in step 126 of FIG. 1B, the first processing material is subjected to a quenching operation 211 to a temperature T2 to form a second processing material. In some embodiments, the cooling rate of the quenching operation 211 is at least 150°C/sec. As shown in FIG. 2, if the cooling rate of the quenching operation 211 is too low, during the cooling process, soft ferrite iron may be generated inside the second processing material, resulting in insufficient strength of the steel parts. In addition, in order to prevent soft iron ferrite from forming on the surface and core of the first treatment material, the size of the semi-finished spheroidized material used for the heat treatment process should not be too large, for example, its diameter should not be greater than 10 mm. On the other hand, if the cooling rate is too fast, it may cause the steel parts to be brittle, so the cooling rate of the quenching operation 211 may be about 150°C/sec to about 200°C/sec. In some embodiments, the temperature T2 may be slightly higher than the Ms temperature of the aforementioned alloy material, for example, the temperature T2 may be 235°C to 245°C.

Next, as shown in step 128 of FIG. 1B, at a temperature T2, the second treatment material is subjected to a Vos tempering operation (or constant temperature quenching) 220 to form a third treatment material having needle-shaped toughened iron . The Voss tempering operation 220 includes a segment 221 that generates needle-shaped toughened iron. In other words, the Voss tempering operation 220 needs to be performed in addition to the specific temperature. The temperature can be achieved for a specific length of time. In some embodiments, the Voss tempering operation 220 is performed for 1 to 30 minutes. Carrying out the Vos tempering operation 220 within the range of the above temperature T2 and time can appropriately increase the volume fraction of the needle-like toughened iron in the third treatment material, thereby increasing the toughness of the steel and improving the steel Impact resistance. In addition, since the Ms temperature of the alloy material is low, the Voss tempering operation 220 can also be performed at a relatively low temperature, so that the disadvantage of insufficient hardness of conventional steel parts can be improved. In some embodiments, after this Voss tempering operation 220, the volume fraction of the needle-like toughened iron in the third treatment material is 15% to 30% of the metallographic structure. In other embodiments, the Voss tempering operation 220 may be performed in a salt bath, for example, which may use a common constant temperature bath.

The longer the tempering operation of Voss 220, the higher the content of toughened iron under the needle shape, the lower the hardness of the steel. If the toughened iron is deformed completely, the hardness will be softer (for example, less than HRC 58). Therefore, in application, it is better not to make the fully-toughened iron metamorphic, but after adopting the partially-toughened iron metamorphic, supplemented by other heat treatment methods to obtain a metallographic structure with both toughness and hardness. Further, in order to avoid the constant temperature metamorphic process of the Voss tempering operation resulting in the rapid softening of the hardness of the steel parts, the temperature of the Voss tempering operation is preferably 245°C or lower, more preferably 240°C or lower.

Next, as shown in step 130 of FIG. 1B, a quenching operation 230 and a tempering operation 240 are performed on the third processed material to form a steel piece. In some embodiments, the quenching operation 230 includes cooling the third processing material. In some examples, the quenching operation 230 may be oil quenching or additive water quenching, or the third treatment material may be cooled to room temperature and then subjected to cryogenic treatment. In some real In the embodiment, the quenching operation 230 is to cool the third treatment material to room temperature T3. In some embodiments, the quenching operation 230 further includes leaving the third processing material at room temperature T3. The room temperature T3 may be, for example, about 15°C to about 25°C. The quenching operation 230 can stop the aforementioned Voss tempering operation 220 to avoid generating too many needle-like toughened irons, resulting in insufficient hardness of the steel parts.

However, this quenching operation 230 still causes the toughness of the steel parts to decrease, so a further tempering operation 240 is performed to form a tempered martensite and improve the toughness of the steel parts. The tempering operation 240 is performed at a temperature T4 higher than room temperature T3 and lower than Ms temperature T2. In some embodiments, the temperature T4 may be, for example, 180°C to 200°C. In some embodiments, after the tempering operation 240, the fourth treatment material may be cooled again to room temperature T3.

Overall, in addition to the partial transformation by the above-mentioned Voss tempering operation 220, the present invention produces toughened lower-toughened iron, and also the quenching and tempering operation is carried out on the remaining non-metamorphic Vostian iron. The metallographic structure of steel is mixed with toughened iron structure with toughness and tempered hemp scattered iron structure with hardness. The quenched quenching is applied to the third treatment material where the part of the toughened iron metamorphosis occurs, so that the untransformed residual Vostian iron phase transformation is transformed into the Matian loose iron. Because the Matian loose iron is not tough, the third treatment after quenching The material needs to be heated to a temperature range not exceeding the Ms temperature for tempering operation 240. Preferably, low-temperature tempering can be carried out at a temperature not greater than 200°C to obtain a hardened tempered hemp scattered iron structure.

In terms of crystal structure, since the bases of the toughened iron and tempered Ma Tian scattered iron are all body-centered cubic ferrite grains, the structure will not be significantly soft/ The hard phase interface can reduce the generation of fatigue sources; furthermore, the lower toughened iron that is generated first in the base can be regarded as a barrier for crack transmission or a buffer for increased plasticity. When steel parts (such as screwdrivers) are subjected to fatigue testing , Because the fatigue cracks are hindered by the toughened iron that is scattered everywhere and has toughness, it can improve the fatigue life; when the steel parts are subjected to torsion tests, the lower toughened iron provides plastic deformation buffer, so the torsion breaking angle can be increased, and Increase the impact resistance of steel parts.

The steel parts produced by the above manufacturing method have needle-like toughened iron with a volume fraction of 15% to 30% of the metallographic structure. This steel has both high strength and high toughness, for example, it can have a hardness of HRC 58 or more, and its torque value, torsion angle or fracture angle, depending on the specifications of the steel, have different values, but it is relatively good toughness .

In the following, a plurality of embodiments are used to explain the method for manufacturing the steel piece with high hardness and impact resistance according to the present invention and the properties of the steel piece.

Example 1

First, an alloy material having the composition as No. 1 in Table 1 is cast into a small steel embryo by vacuum melting, and the small steel embryo is forged into a 145mm×145mm cross section from a square embryo having a cross section of 210mm×210mm, And its length is about 1.2m. After that, this small steel blank is welded with other small steel blanks and rolled into a disc element with a diameter of 8 mm. Next, the disk element was hot rolled and annealed to draw a hexagonal bar with a side length of 1/4". After that, the hexagonal bar was spheroidized at 765°C to 785°C. Then the first wire drawing was performed , Annealing, second drawing and cutting processes to form semi-finished spheroidized materials, in which the annealing temperature is 670 ℃ to 690 ℃. Then, at a temperature higher than 855 ℃, the semi-finished spheroidized materials are heat-treated. Next , At 150℃/sec Cooling speed, rapid quenching operation. Afterwards, the quenched semi-finished spheroidized material was subjected to a Vos tempering operation at about 240° C. for 1 minute to obtain an intermediate material with needle-like toughened iron. After quenching the intermediate material to room temperature, the temperature is maintained at 180°C to 200°C for tempering operation. After that, the above material was cooled again to room temperature, that is, the steel piece of Example 1 was obtained. The hardness and Ms temperature of this steel were tested, and the results are shown in Table 2.

Examples 2 to 5 and Comparative Example 1

Examples 2 to 5 and Comparative Example 1 were carried out using the same method as Example 1, but Examples 2 to 5 and Comparative Example 1 changed the time of the Voss tempering operation, of which Examples 2 to 5 and Comparative Example 1 were Perform Vos tempering operations for 2, 5, 10, 30, and 60 minutes. The steel parts of the above Examples 2 to 5 and Comparative Example 1 were tested for hardness respectively, and the results are shown in Table 2.

Example 6

Example 6 is carried out in the same manner as in Example 1, and the manufactured steel parts are powerful screwdrivers with 50L PH2 specifications (diameter of 1/4") as shown in FIG. 3A. The steel parts of Example 6 are Carry out hardness, torsion value, fatigue and fracture angle under 11.3N.m and other characteristic tests. The results are shown in Table 3.

Comparative Examples 2 to 4

Comparative Examples 2 to 4 are screwdriver heads prepared using commercially available steel materials BT9865V, S2, and 73MoV5-2, respectively, where the carbon content of the steel material BT9865V is 0.67wt.% and the carbon content of the steel material S2 is about 0.67wt .%, and the carbon content of steel 73MoV5-2 is about 0.73wt.%. The screwdriver heads of Comparative Examples 2 to 4 were tempered to have a hardness equivalent to that of Example 6, and the torque values of the screwdriver heads of Example 6 and Comparative Examples 2 to 4 were compared at 11.3N. The characteristics of fatigue life and fracture angle under m are shown in Table 3.

Example 7

Example 7 is carried out in the same manner as in Example 1, except that the alloy material composed of No. 2 in Table 1 is used, and the manufactured steel parts have a 50L PH2 specification (diameter of 1/4” as shown in FIG. 3B )'S strong impact resistant pneumatic screwdriver head. The screwdriver head of Example 7 was tested for hardness, torsion value and breaking angle and other characteristics (ten repetitions), and the results are shown in Table 4.

Comparative example 5

Comparative Example 5 is a screwdriver head made of commercially available steel material BT9865V, which is not subjected to a tempering operation, and is subjected to a quenching and tempering operation after heat treatment. The carbon content of the steel material BT9865V is 0.67 wt.%. The screwdriver heads of Comparative Example 5 were tested for characteristics such as hardness, torque value and breaking angle, and the results are shown in Table 4.

First of all, please refer to FIG. 4 first, which uses an expansion meter to measure the expansion curve of the semi-finished spheroidized material having the composition of No. 1 in Table 1 at a heating rate of 0.5° C./s. According to Figure 4, the Ac3 temperature of the semi-finished spheroidized material composed of No. 1 is about 855°C, and the Ms temperature is about 230°C. In particular, the No. 2 spheroidized material semi-finished product also has similar Ac3 temperature and Ms temperature. Therefore, Examples 1 to 7 and Comparative Examples 1 to 5 of the present invention performed heat treatment and Voss tempering operations with reference to these temperatures.

Next, please refer to Table 2 and FIGS. 5A to 5D, where FIGS. 5A to 5D are the metallurgical structures obtained by carrying out water quenching of the steel parts of Examples 3 to 5 and Comparative Example 1, respectively, after the Voss tempering Of the electron microscope. As shown in FIGS. 5A to 5D, as the temperature holding time of the Voss tempering operation increases, the content of needle-like toughened iron in the tissue increases, while in Examples 3 to 5 of FIGS. 5A to 5C, the needle shape The volume fraction of the lower toughened iron is about 15% to 30% of the metallographic structure. In addition, as shown in Table 1, as the temperature holding time of the Voss tempering operation increases, the hardness of the steel parts gradually decreases, especially within 30 minutes, the hardness of the steel parts can be maintained About HRC58 or above. However, once it exceeds 30 minutes, for example, 60 minutes in Comparative Example 1, the hardness of the steel part is reduced to HRC 55.1.

Next, according to Table 3, compared to the screwdriver heads made from commercially available steel materials with relatively low carbon content, when the alloy material numbered 1 in Table 1 is made into a strong screwdriver head of a specific specification, it is combined with the specific heat treatment of the present invention During the manufacturing process, the prepared strong screwdriver head can have good hardness and toughness.

In addition, according to Table 4, it can also be seen that, compared to the screwdriver heads made from commercially available steel materials with relatively low carbon content, when the alloy material No. 2 in Table 1 (which has a composition similar to No. 1) is made into another specific The standard impact-resistant pneumatic screwdriver head can also make the prepared impact-resistant pneumatic screwdriver have good hardness and toughness when combined with the specific heat treatment process of the present invention. The screwdriver heads of Example 7 and Comparative Example 5 shown in Table 4 have average torque values comparable to each other, but the screwdriver head of Example 7 is superior to Comparative Example 5 in terms of the performance of average hardness and average torsional breaking angle. . In particular, the average hardness of the screwdriver head of Example 7 can reach HRC 58 or more, and the average torsional breaking angle can reach more than 220°, showing that the screwdriver head of Example 7 has quite excellent fracture toughness.

Please refer to FIGS. 6A and 6B, which are electron micrographs of the metallographic structure of the screwdriver heads of Comparative Example 5 and Example 7, respectively. First, as shown in FIG. 6A, since Comparative Example 5 only adopts quenching and tempering operations, its structure is tempered Ma Tian scattered iron. On the other hand, as shown in FIG. 6B, the screwdriver head of Example 7 was subjected to a Vos tempering operation and a quenching and tempering operation, and the resulting structure was a mixed structure of needle-like toughened iron and tempered hemp scattered iron. There is no obvious phase interface between the two organizations, and the organization is more detailed. In addition, the base of the needle-shaped toughened iron and tempered Ma Tian scattered iron have some unsolidified spherical carbide residues, which can help increase the wear resistance of the screwdriver head. Consumable.

By applying the steel parts of the present invention and the manufacturing method thereof, by combining specific alloy materials with specific heat treatment process conditions, steel parts with high hardness and high toughness can be produced. This steel part can be steel for hand tools, for example, can be made into a screwdriver head, and is used in an operating environment that requires wear resistance and impact resistance.

Although the present invention has been disclosed as above in the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs can make various modifications and changes without departing from the spirit and scope of the present invention. Retouching, therefore, the protection scope of the present invention shall be subject to the scope defined in the appended patent application.

210‧‧‧Heat treatment operation

211‧‧‧Quick cooling operation

220‧‧‧Tempering operation

Section 221‧‧‧

230‧‧‧Quenching operation

240‧‧‧Tempering operation

T1, T2, T4‧‧‧Temperature

T3‧‧‧Room temperature

Ms‧‧‧Matian powder metamorphic onset temperature

Claims (8)

A method for manufacturing high hardness and impact resistant steel parts, comprising: providing an alloy material, the alloy material comprising: 0.76 weight percent (wt.%) to 0.8wt.% carbon; 1.9wt.% to 3wt.% Silicon; 0.3wt.% to 0.5wt.% manganese; 0.65wt.% to 12wt.% chromium; 0.15wt.% to 0.25wt.% vanadium; inevitable impurities; and the balance of iron; The alloy material is subjected to a heat treatment operation to form a first treatment material having a Vostian iron phase; a quenching operation is performed on the first treatment material to a first temperature to form a second treatment material, wherein the first The temperature is higher than the metamorphic onset temperature (Ms) of one of the alloy materials Ma Tian scattered iron; at the first temperature, a Voss tempering operation is performed on the second treatment material to form a needle-like toughened iron A third treatment material, wherein in the third treatment material, the integral integral rate of the needle-like toughened iron is 15% to 30% of a metallographic structure; and a quenching operation is performed on the third treatment material and A tempering operation to form a steel part, wherein the tempering operation is carried out at a temperature greater than or equal to 180°C and less than 200°C. High hardness as described in item 1 of patent application A method for manufacturing an impact-resistant steel part, wherein the heat treatment operation is performed at a second temperature higher than 855°C. The method for manufacturing a steel part with high hardness and impact resistance as described in item 1 of the patent application range, wherein one of the quenching operations has a cooling rate of at least 150°C/sec. The method for manufacturing a steel part with high hardness and impact resistance as described in item 1 of the patent application range, wherein the first temperature is 235°C to 245°C. The method for manufacturing a steel part with high hardness and impact resistance as described in item 1 of the patent application scope, wherein the quenching operation includes cooling the third treatment material to a room temperature. The method for manufacturing a steel part with high hardness and impact resistance as described in item 1 of the patent application range, wherein the alloy material further contains 0.1 wt.% to 0.4 wt.% molybdenum. The method for manufacturing a steel part with high hardness and impact resistance as described in item 1 of the patent application scope, wherein the Voss tempering operation is performed for 1 minute to 30 minutes. The manufacturing method of steel parts with high hardness and impact resistance as described in item 5 of the patent application scope, wherein the quenching operation is further included in the chamber The third treatment material was allowed to stand still under temperature.

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