JP2006161133A - Method for producing blank for wear resistance excellent in cold-forging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a blank for wear resistance excellent in a cold-forging which is suitable to sliding parts for internal combustion engine requiring the high wear resistance, such as a valve lifter (tappet), a pump lifter or a plunger of a diesel fuel injecting device, etc. <P>SOLUTION: The method for producing the blank for wear resistance excellent in the cold-forging comprises the steps of: cold-rolling a high carbon alloy tool steel and performing continuous annealing thereto; and drawing the steel at 10-20% reduction of area and successively performing one or two times of annealing at 850-900°C to the steel. In the method, the steel blank contains 1.40-1.60% C, 11-13% Cr, 0.5-1.5% Mo+1/2W, 0.2-1.0% V+1/2Nb and the balance Fe with inevitable impurities. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention has excellent cold forgeability suitable for sliding parts for internal combustion engines that require high wear resistance, such as engine valve lifters (tuppets) and diesel fuel injection pump lifters and plungers. The present invention relates to a method for manufacturing a wear-resistant material.

  Conventionally, high-C, high-V cold tool steel is often used for parts that require wear resistance. Cutting is often used in the manufacture of these parts. However, with the recent progress in plastic processing technology and cost reduction requirements, the part manufacturing method is also shifting from cutting to cold forging. is there. Since these steel types have high hardness and contain a large number of hard carbides, they are inferior in workability in the cold, causing defects such as cracks during the manufacturing process. As a method for improving these, for example, as disclosed in JP-A-8-193246 (Patent Document 1), cracks originating from primary carbides are avoided by limiting the range of C and Cr contents. Controlling the properties of the next carbide improves the cold forgeability. Also, as disclosed in Japanese Patent Application Laid-Open No. 2000-63944 (Patent Document 2), after performing cold and warm plastic working, the cracking of carbide is repaired by an optimum heat treatment, and mechanical properties are improved. What to do has been proposed.

JP-A-8-193246 JP 2000-63944 A

However, in Patent Document 1 described above, the primary carbide is coarse because the C and Cr contents are not in the optimum range, and the aggregate size and crack generation rate of the primary carbide aggregate part that is the main crack starting point during cold forging. No correlation has been verified and crack countermeasures are insufficient. Further, Patent Document 2 has a problem that there is no measure for preventing troubles such as die chipping and seizure at the time of drawing, and there is a problem that measures for reducing the hardness at the time of drawing annealing are not incorporated.

  On the other hand, demands for internal combustion engines in recent years include higher output and lower manufacturing costs. For the former, the latter has conventionally been reduced in weight and improved wear resistance for the purpose of high rotation. The transition from cutting to cold forging has been studied. Currently, JIS SKD11 and other materials are used for sliding parts that require wear resistance, and the weight is reduced by making them into one-piece parts. The present situation is that there is a concern about variation in performance as a sliding part due to cracks remaining in the agglomerated portion of the primary carbide after cold forging as well as high cost due to the process.

  Furthermore, in response to the recent increase in environmental problems, improvement of fuel is an indispensable issue, and efforts to reduce friction loss in internal combustion engines have become active. Currently, efforts are being made to reduce frictional resistance by applying surface treatment to sliding parts, but it is not only costly but also has insufficient reliability such as peeling of the surface treatment film. The actual situation is that further studies are underway.

In order to solve the problems as described above, the present invention is a result of intensive and experimental studies on cold forgeability, wear resistance, and seizure resistance, which are required as sliding parts for internal combustion engines. The present invention provides a manufacturing method for preventing defects such as cracks during the manufacturing process due to inferior cold workability. The gist of the present invention is that
(1) Cold rolling characterized in that high carbon alloy tool steel is continuously annealed after coil rolling, then drawn at a reduction in area of 10 to 20%, and subsequently annealed once or twice at 850 to 900 ° C. A method for manufacturing wear-resistant materials with excellent forgeability.

(2) In the method according to (1), C: 1.40 to 1.60%, Cr: 11 to 13%, Mo + 1 / 2W: 0.5 to 1.5%, V + 1 / 2Nb: 0. A method for producing a wear-resistant material excellent in cold forgeability, characterized in that a steel material comprising 2 to 1.0% and the balance comprising Fe and inevitable impurities is processed.
(3) In the method described in (1) above, C: 0.70 to 1.10%, Cr: 7.0 to 9.0%, Mo + 1 / 2W: 1.5 to 3.0%, V + 1 / 2Nb: 0.2 to 2.0% in the manufacturing method of a wear-resistant material excellent in cold forgeability, characterized in that a steel material consisting of Fe and inevitable impurities is processed in the balance. .

  As described above, according to the present invention, it is possible to reduce the cost by manufacturing from a coil material and to achieve an extremely excellent effect capable of expanding sales to cold forging applications.

Hereinafter, the present invention will be described in detail.
As a method according to the present invention, heat treatment is performed once or twice for the purpose of softening before drawing in order to prevent troubles such as die chipping and seizure during drawing. Thereafter, drawing and annealing are performed to reduce the hardness. This is because moderate distortion is generated inside the steel material and spheroidization of the carbide is promoted. Further, by performing annealing a plurality of times, further effects are obtained and stable softening hardness is obtained.

Hereinafter, the reasons for limiting the component composition according to the present invention will be described.
C: 0.70 to 1.60%
C needs to be 0.70% or more in order to ensure the hardness after quenching and tempering. However, addition exceeding 1.60% coarsens the primary carbide, increases the size of the agglomerated portion of the primary carbide, and remarkably deteriorates the cold forgeability. Therefore, the range was made 0.70 to 1.60%.

Cr: 7-13%
Cr needs to be 7% or more to ensure hardenability and wear resistance. However, addition exceeding 13% coarsens the primary carbide, increases the size of the agglomerated portion of the primary carbide, and remarkably deteriorates the cold forgeability. Therefore, the range was 7 to 13%.

Mo + 1 / 2W: 0.5-3.0%
Mo and W are required to be 0.5% or more in order to ensure hardenability and improve wear resistance and seizure resistance due to precipitated carbides during high temperature tempering. However, if it exceeds 3.0%, the agglomeration of precipitated carbides becomes remarkable, and seizure resistance and toughness are reduced. Therefore, the range was made 0.5 to 3.0%.

V + 1 / 2Nb: 0.2-2.0%
V and Nb improve wear resistance and seizure resistance by dispersing and precipitating fine carbides in steel during secondary hardening by high temperature tempering. In order to obtain this effect, 0.2% or more is necessary. However, if the addition exceeds 2.0%, the agglomeration of the precipitated carbides becomes remarkable, and seizure resistance and toughness deteriorate. Therefore, the range was made 0.2 to 2.0%.

  After continuous annealing, it is pulled out with a reduction in area of 10 to 20%. However, if the area reduction rate is less than 10%, the strain remaining in the steel material is insufficient and the degree of softening is small. If it exceeds 20%, the risk of chipping and seizure at the time of drawing increases. Subsequently, annealing is performed once or twice at 850 to 900 ° C. The reason is to promote the spheroidization of the carbide. When the temperature is lower than 850 ° C., the softening is insufficient, and when the temperature exceeds 900 ° C., the hardness increases. Therefore, the temperature range was set to 850 to 900 ° C.

Hereinafter, the present invention will be specifically described with reference to examples.
Invention steels A to D and comparative steels E, F, and G shown in Table 1 were each produced in a 1-t vacuum melting furnace, and after ingot forming and billet forging and rolling, a φ18 coil material was obtained. Then, after cold working under the annealing conditions and area reduction ratio shown in Table 2, the annealing hardness and cold workability after annealing were subsequently adjusted to 60 HRC by quenching and tempering. Table 2 shows the results of the wear resistance of the quality materials. In the wear resistance test, the amount of wear was measured at a friction distance of 200 m, a final load of 61.7 N, and a friction speed of 2.44 m / s. As a result, ◯ marks are excellent in wear resistance, and X marks are inferior in wear resistance. Further, regarding the cold workability, ◯ indicates that it is excellent, Δ indicates that it is poor, and X indicates that it is bad.

  As shown in Table 2, no. Nos. 1 to 11 are steels of the present invention. Nos. 12 to 16 are comparative steels. 17 to 18 are conventional products. Comparative Example No. No. 12 has a low area reduction rate, is not different from the conventional material, has a high annealing hardness, and has poor cold workability. Comparative steel No. Since No. 13 has a low annealing temperature, the annealing hardness is hard and the cold workability is poor. Comparative steel No. In contrast, since No. 14 has a high annealing temperature, the annealing hardness is high and the cold workability is poor. Comparative steel No. Since both 15 and 16 had a high area reduction rate, die baking occurred and the process was stopped. Conventional product No. 17 and 18 are cases where the area reduction rate is 0, the annealing hardness is hard, and the cold workability is inferior. On the other hand, No. which is steel of the present invention. It can be seen that 1 to 11 are excellent in any of the characteristics.

As described above, high C and high Cr steels are annealed after coil rolling, and then are pulled and annealed at the optimum area reduction rate, thereby generating moderate strain inside the steel and promoting carbide spheroidization. In addition, by performing annealing several times, more stable softening hardness can be obtained, and steel for cold forging with good workability and wear resistance can be obtained at low cost. It is possible to obtain an excellent effect that can promote the sales of the developed steel to production materials such as parts.


Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina

Claims (3)

Cold forging, characterized in that high-carbon alloy tool steel is continuously annealed after coil rolling, then drawn at a reduction in area of 10 to 20%, and subsequently annealed once or twice at 850 to 900 ° C. Manufacturing method for wear-resistant materials. The method of claim 1, wherein
C: 1.40 to 1.60%
Cr: 11-13%,
Mo + 1 / 2W: 0.5-1.5%
V + 1 / 2Nb: A method for producing a wear-resistant material excellent in cold forgeability, characterized in that a steel material containing 0.2 to 1.0% and the balance being Fe and inevitable impurities is processed. . The method of claim 1, wherein
C: 0.70 to 1.10%,
Cr: 7.0 to 9.0%,
Mo + 1 / 2W: 1.5-3.0%,
V + 1 / 2Nb: A method for producing a wear-resistant material excellent in cold forgeability, characterized in that a steel material comprising 0.2 to 2.0% and the balance being Fe and inevitable impurities is processed. .