KR101170248B1 - Material for projecting material for shot-peening, finished wire, production process, and projecting material for shot-peening - Google Patents

Abstract

In the step of obtaining a finish line by drawing a fresh line, the material and finishing line of the shot peening projection material which can prevent a disconnection and improve productivity, and the manufacturing method of the shot peening projection material which can improve productivity, and the projection material by the manufacturing method are provided. do. For short peening, the area occupied by carbide having a particle diameter of 2 µm or less in the finishing line is 80% or more of the total area of the finishing line by the step of drawing the wire rod and the step of repeatedly annealing and cold drawing the wire rod. Finishing line of the projection material. Mass%, contains 0.95 ~ 1.10% carbon, 0.15 ~ 0.30% silicon, 0.40% or less manganese, 0.020% or less phosphorus, 0.010% or less sulfur, 1.40 ~ 1.60% chromium, 0.0015% or less oxygen. The material of the shot peening projection material whose remainder consists of iron and an unavoidable impurity. The manufacturing method of the shot peening projection material using this, and the projection material by the manufacturing method.

Description

MATERIAL FOR PROJECTING MATERIAL FOR SHOT-PEENING, FINISHED WIRE, PRODUCTION PROCESS, AND PROJECTING MATERIAL FOR SHOT-PEENING}

TECHNICAL FIELD This invention relates to the material of a shot peening projection material, a finishing line, a manufacturing method, and a shot peening projection material.

Conventionally, in the production of shot peening projection materials, the so-called bearing steel is drawn and processed to be drawn, and the drawn wire is cut into lengths equal to its diameter, and then the steel wall is It is known to make a predetermined Vickers hardness by projecting and rounding an edge and grinding it to obtain a predetermined sphericity, and then quenching and tempering to obtain a predetermined Vickers hardness ( See, for example, Japanese Patent Laid-Open No. 2001-79766.

However, when the so-called bearing steel is used as the material of the shot peening projection material (for example, high-carbon chromium bearing steel SUJ2 specified in Japanese Industrial Standard JIS G4805, the composition is shown in Table 2), There was a problem that a breakage occurred in the process of obtaining a finished wire and the improvement of productivity was not obtained. That is, when disconnection occurs in the wire drawing process, the line which is drawn at a high speed of about 100 m / min is stopped, which greatly affects the production efficiency. As a result, productivity of a projection material will also fall. In particular, when the diameter of the fresh wire becomes thinner than 0.7 mm (for example, about 0.3 mm), the tendency is remarkable, and disconnection occurs frequently in the drawing process. That is, the manufacturing method of the shot peening projection material for obtaining the optimal shot peening projection material from a thin finish line is not established.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a shot peening projection material in which production of shot peening projection material is prevented from breaking in the process of obtaining a fresh finish line. The present invention provides a method for producing a shot peening projection material from which a material, a finish line, and an improvement in productivity can be obtained, and a projection material by the production method.

That is, the manufacturing method of the shot peening projection material of this invention uses the material of the specific shot peening projection material, in order to prevent disconnection and ensure the cleanliness, and secures an appropriate finishing line from this material, and makes the carbide fine before quenching The state is maintained to secure an appropriate structure after quenching and tempering. Moreover, this invention provides the shot peening projection material which can provide the lifetime of a shot peening projection material, and an appropriate compressive residual stress. Moreover, this invention provides the manufacturing method of the shot peening projection material excellent in hardenability and suitable for shot peening.

The present inventors have studied closely to solve the above problems, and as a first aspect of the present invention, in the material of the shot peening projection material, the mass is 0.95 to 1.10% carbon, 0.15 to 0.30% silicon, Achieving the desired purpose is achieved by containing 0.40% or less of manganese, 0.020% or less of phosphorus, 0.010% or less of sulfur, 1.40-1.60% of chromium, 0.0015% or less of oxygen, and making the remainder iron and inevitable impurities. The present invention has been completed based on these findings.

This material is intended to reduce the amount of nonmetallic inclusions that degrade the bondability of the matrix in order to prevent disconnection due to cracking in the fresh wire. That is, compared with the manufacturing method of Unexamined-Japanese-Patent No. 2001-79766, in order to reduce oxide stably, the amount of oxidation needs to be low and oxygen was made very low (0.0015% or less). In addition, the upper limit of the amount of silicon is lowered by 17%. In addition, to reduce the amount of sulfides, especially MnS, manganese and sulfur were reduced. In general, the upper limit of the content of components other than iron is generally limited. In order to make a basic amount of carbide constant, the amount of carbon was made the same.

In addition, the finished wire of the shot peening projection material of the present invention is a step of drawing the material of the shot peening projection material according to the first aspect of the present invention with a wire rod, and annealing the wire material. ) And cold drawing are repeated to form a finish line, whereby the area occupied by carbide having a particle diameter of 2 μm or less in the finish line is 80% or more of the total finish line area. .

In other words, in the present invention, the wire is "drawn" by drawing from an ingot, and the wire is manufactured. Next, the wire is repeatedly drawn by "annealing" and "cold drawing." In the carbide state at the finish line at this time, the area occupied by carbide having a particle diameter of 2 μm or less is 80% or more of the total finish line area.

In the second aspect of the present invention, the wire reduction obtained by drawing the material of the shot peening projection material according to the first aspect of the present invention to a step of repeating annealing and cold drawing to form a finish line is a drawing reduction ratio. Iv) If the wire rod is high, the wire rod loses its ability to elongate and breaks easily, and at least, the wire rod is annealed in a state in which the elongation is slowed down to a constant level, the work hardening is removed, and the elongation is restored again. It is because it is preferable to perform drawing.

The cold drawing was made cold in which work hardening and refinement of crystal grains are accompanied, because the extension of crystal grains occurs in the hot state and the miniaturization effect is not obtained.

The recovery of annealing is preferably three to five times. The fresh reduction ratio is preferably 10% to 40%.

In the finishing line, the area occupied by carbides having a particle diameter of 2 μm or less was 80% or more of the total area of the finishing line, thereby obtaining an appropriate structure in the thin finishing line, thereby securing an optimum structure for subsequent shot peening materials. Because. In addition, by confirming the properties at the finishing line, it leads to the improvement of the quality of the final product, so that no waste of material occurs.

Here, a finishing line is a thin line which is finished, and is a thing before cutting, and is obtained by repeating annealing and cold drawing of the wire rod of the material obtained by rolling and drawing.

In addition, by finishing annealing at 720 degrees C or less, a finishing line prevents the coarsening of the carbide of the finishing line of the shot peening projection material, and maintains the fine state of the carbide before quenching. As a result, since fracture strength increases by refinement | miniaturization of a grain, it can ensure that a larger load is added to a shot short peening material. Moreover, it is preferable to perform annealing at 700 degreeC heating using the bright annealing furnace. By using the bright annealing furnace, oxidized scales are not produced on the surface of the wire rod, and an acid cleaning process is unnecessary.

Moreover, the manufacturing method of the shot peening projection material of this invention is a process which cut | disconnects and cuts the finishing line of the shot peening projection material which concerns on the 2nd aspect of this invention to produce a shot peening material, and the said shot peening It characterized in that it comprises a step of quenching and tempering the material (tempering).

According to the present invention, since the finish line having excellent properties and using the confirmed properties is used, it is possible to provide a shot peening projection material having high productivity and excellent quality.

The tempering is defined by tempering parameter = T ((21.3-5.8 x [C]) + logt), and C is set as T whose value is 6200 to 7300. Here, T: tempering temperature (K), t: tempering time (h), and C: carbon amount (%). If the tempering parameter is set to a tempering temperature T, a carbon amount C, and a tempering time t of 6200 to 7300, coarsening of grains is prevented, and work stress is relaxed to increase toughness. It is preferable to have a feature.

Moreover, you may further include the process of plastic working. According to the present invention, since the corners of the projection material are rounded, there is an advantage that the origin of breakage during pinning is difficult to occur. Here, the plastic working to form the short peening material means that the cut finish line having a short wire rod shape is formed into a round short peening material by plastic working. That is, the shot peening material is not rounded by cutting, polishing, or the like.

Moreover, the manufacturing method of the shot peening projection material of this invention is a process of drawing the material of the shot peening projection material of 1st aspect of this invention with a wire rod, repeating annealing and cold drawing, and making it a finishing line; And cutting the finish line and performing plastic working to form a shot peening material, and quenching and tempering the shot peening material.

According to the present invention, there is an advantage that the crystal grains are refined and the toughness is recovered after the heat treatment.

Moreover, the manufacturing method of the shot peening projection material of this invention is a manufacturing method of the said shot peening projection material, It is characterized by the quenching temperature being 820-850 degreeC.

According to the present invention, there is an advantage that it is difficult to produce residual austenite, and a uniform martensite structure is obtained for the whole material.

The shot peening projection material of the present invention is a shot peening projection material produced by the above-described manufacturing method, which is martensite whose structure is substantially tempered, and fine carbide is deposited. In addition, the area ratio of the carbide is preferably 70% to 95%. When the metal part, which is the bonding layer, decreases, the known bondability is weakened because when the carbide part exceeds 95% and the metal part becomes very small, the carbides are in close contact with each other. In addition, when the area ratio of carbide is less than 70%, Vickers hardness Hv 950, which is a hardness suitable as a shot peening projection material such as JIS SUJ2 material, may not be satisfied. According to this invention, it can be set as the projection material which is optimal for shot peening.

On the other hand, the particle size of the carbide is preferably smaller than 2㎛. More preferably, it is 1 to 0.1 micrometer. This is because, when the particle size is 2 µm or more, the influence as a starting point of the crack in the shot of the shot peening projection material is increased. A particle size of 1 to 0.1 mu m is preferable because the exposure from the matrix is less, and the influence of carbide is less.

In addition, the shot peening projection material of the present invention has a mass% of 0.95 to 1.10% of carbon, 0.15 to 0.30% of silicon, 0.40% or less of manganese, 0.020% or less of phosphorus, 0.010% or less of sulfur, and 1.40 of chromium. The material of the shot peening projection material which contains -1.60% and oxygen or less and 0.0015% or less, and remainder consists of iron and an unavoidable impurity is drawn as a wire rod, and the said wire is annealed and cold drawn repeatedly, and a finish line is finished. A short peening material produced by quenching and plasticizing a wire and quenching and tempering the short peening material, the structure being composed of fine carbide and tempered martensite, and the area ratio of carbide is 70% It is preferable that the Vickers hardness is Hv 950 to Hv 1050 by adjusting the hardness by firing at 95% and by plastic working. If the Vickers hardness is Hv 950-Hv 1050, the peening treatment suitable for a high hardness product can be performed.

Since the material of this invention is a composition material with few disconnections, productivity improves. Moreover, it can process at high speed even a thin line. The finish line of this invention is suitable for manufacture of the projection material for shot peening. The production method of the present invention is excellent in productivity and quality, and can produce a projection material suitable for shot peening. The projection material of this invention is suitable for shot peening.

This application is based on a patent application No. 2008-046967 filed on February 28, 2008 in Japan and a patent application No. 2008-169971, filed on June 30, 2008, the contents of which are incorporated herein by reference. It forms part of the content.

In addition, the present invention will be more fully understood by the following detailed description. However, detailed description and specific Example are preferred embodiment of this invention, and are described only for the purpose of description. This is because various changes and modifications are apparent to those skilled in the art from this detailed description.

Applicants have no intention of offering any of the described embodiments to the public, and any of the disclosed modifications and alternatives, which may not be included in the language of the claims, are part of the invention under the equal theory.

In the description of the present specification or claims, the use of nouns and identical directives should be construed to include both the singular and the plural unless specifically indicated otherwise or unless clearly indicated by the context. The use of all illustrative or exemplary terms (eg, "etc.") provided herein is only intended to facilitate describing the present invention, and the scope of the present invention unless specifically stated in the claims. It does not impose any restrictions on.

BRIEF DESCRIPTION OF THE DRAWINGS The flow of the manufacturing method of the shot peening projection material of this invention.
Fig. 2A is a microstructure (× 1000) using SEM of the finish line for the shot peening projection material of the present invention.
Fig. 2B is a microstructure (× 5000) using SEM of the finish line for the shot peening projection material of the present invention.
Fig. 3A is a microstructure (× 1000) using SEM of the shot peening projection material of the present invention.
3B is a microstructure (× 3000) using SEM of the shot peening projection material of the present invention.
4A is a microstructure (× 1000) using SEM of the shot peening projection material of the present invention.
4B is a microstructure (× 3000) using SEM of the shot peening projection material of the present invention.
It is a graph which shows the particle size distribution of the carbide of the shot peening projection material of this invention.
Fig. 6A is a graph showing the relationship between the carbide area ratio and the hardness (compound hardness) of the shot peening projection material of the present invention.
Fig. 6B is a graph showing the relationship between the carbide area ratio and hardness (composite hardness) of the shot peening projection material of the present invention (when the composition is low hardness).

The inventors of the present application, for the composition of JIS G4805-SUJ bearing steel, adjust the bearing steel to a composition excellent in the thin line for the shot peening projection material, and draw out the properties of the composition, thereby achieving excellent shot peening from the thin line. Provide ash. Table 1 shows the material of the shot peening projection material of the present invention. As a comparative example, the material (JIS standard) of the conventional SUJ2 is shown in Table 2.

As compared with Table 1 and Table 2, the material of the present invention restricts sulfur to 0.010% or less and oxygen to 0.0015% or less, as compared to the composition of JIS G4805-SUJ bearing steel, and therefore inclusions such as sulfides and oxides. There is little precipitation, and the cleanliness of the material can be secured, and the occurrence of uneven structure that causes disconnection can be prevented, so that disconnection can be prevented or minimized. For this reason, even if a wire becomes thin, the disconnection in a wire drawing process can be prevented as much as possible.

Moreover, compared with the composition of JIS G4805-SUJ bearing steel, manganese and phosphorus are restrict | limited low. This restriction is preferable in that the production of residual austenite and the production of intercrystalline grain tertiary compounds are suppressed.

Moreover, when copper is limited to 0.15% or less, it is preferable at the point that carburizing property does not fall.

Moreover, when nickel is limited to 0.15% or less, it is preferable at the point that carburism property does not fall.

Example 1

Hereinafter, the flowchart of the method which manufactured the shot peening projection material using the material of the shot peening projection material of this invention is shown. Hereinafter, it demonstrates in detail according to FIG. In a flowchart, first, the material of the composition specified in Table 1 is prepared in a 1st process. Fresh with wire rod in the second process. Annealing and cold drawing are repeated in the third process. It cuts in a 4th process.

Plastic working is performed in the fifth step. Quench and temper in the sixth process. In the seventh step, they are vacant in some cases.

Table 3 shows a comparison between the composition of JIS G4805-SUJ bearing steel of Table 2 and Example 1 from the first step to the third step. The wire diameter of the drawn material after being fresh with the wire rod in the second step was 1.6 mm, and the hardness was Hv 320.

Example Comparative example 0.95 to 1.10% carbon, 0.15 to 0.30% silicon, 0.40% or less manganese, 0.020% or less phosphorus, 0.010% or less sulfur, 1.40 to 1.60% chromium, 0.0015% or less oxygen, 0.15% or less copper , 0.15% or less nickel, 0.06% or less molybdenum, and the balance of iron and unavoidable impurities By weight, it contains 0.95 to 1.10% of carbon, 0.15 to 0.35% of silicon, 0.50% or less of manganese, 0.025% or less of phosphorus, 0.025% or less of sulfur, 1.30-1.60% of chromium, and the balance of iron and inevitable impurities In the production of shot peening projection materials, disconnection does not occur in the process of drawing fresh and finishing lines. In the production of shot peening projection materials, disconnection occurs in the process of obtaining fresh and finished lines.

In Table 3, in Example 1, in manufacture of the shot peening projection material, disconnection does not generate | occur | produce in the process of drawing fresh and finishing line. On the other hand, in the comparative example, in manufacture of the shot peening projection material, disconnection generate | occur | produces in the process of drawing fresh and finishing line.

Example Comparative example It contains 0.010% or less of sulfur and 0.0015% or less of oxygen. It contains 0.025% or less of sulfur. In the production of shot peening projection materials, disconnection does not occur in the process of drawing fresh and finishing lines. In the production of shot peening projection materials, disconnection occurs in the process of obtaining fresh and finished lines.

Annealing and cold drawing were repeated in a 3rd process, and the finishing line of the shot material for shot peening was produced. At this time, the wire diameter of the drawing material used as a material of a finishing line was 1.6 mm, and the hardness was Hv320. Since this material is Hv320 and is not work hardened, cold drawing can be made easy. In the process of repeating annealing and cold drawing in a 3rd process, the method of specifically, heating 4m at 700 degreeC and cooling 4m using 8m bright BA annealing furnace was used.

The size change, for example,

Diameter 1.6mm-1.5mm-1.4mm → (BA annealing) → 1.3mm-1.2mm-1.1mm-1.0mm → (BA annealing) → 0.9mm-0.8mm-0.75mm-0.7mm → (BA annealing) → 0.6 Mm-0.55 mm-0.5 mm-0.45 mm-0.4 mm → (BA annealing) → 0.35 mm-0.3 mm (finish), and a total of four annealing is included.

Comparative Example 1 Example Comparative Example 2 Annealing and cold drawing were repeated to make the final diameter larger than 0.6 mm. Annealing and cold drawing were repeated, so that the final diameter might be 0.6 mm or less and 0.25 mm or more.
The annealing is performed at 720 ° C or lower. Annealing and cold drawing were repeated to make the final diameter thinner than 0.25 mm. The annealing is performed higher than 720 ° C. When larger than 1.0 mm, it is too large as a shot peening projection material. In the production of shot peening projection materials, disconnection occurs in the process of obtaining fresh and finished lines. The internal residual stress is removed by annealing, the steel is softened, and the cold drawing process is appropriately performed. If the wire diameter is less than 0.25 mm, cutting is impossible. If the annealing is performed higher than 720 占 폚, there is a problem that the possibility of changing the base structure due to exceeding the transformation point increases.

The structure of this finish line was confirmed, but the area occupied by carbide having a particle diameter of 2 µm or less was 80% or more of the total area of the finish line.

The microstructure using SEM of the finishing line (after nitrile corrosion of 0.3 mm in diameter) for the shot peening projection material of this invention is shown in FIG.

As a result, it was confirmed that the structure of the excellent finish line was obtained with the shot peening projection material.

The diameter of the finish line at this time is repeated so that annealing and cold drawing may be carried out so that a final diameter may be 0.6 mm or less and 0.25 mm or more. When the final diameter was 0.3 mm, the Vickers hardness was Hv 350. Even if the Vickers hardness is Hv 350, since the material is hardly hardened, the cutting can be easily performed even in a thin line.

In Example 1, an example in which a diameter of 0.3 mm to 0.6 mm was produced as the shot peening projection material was given. However, those up to about 1.0 mm in diameter are used for short peening. However, even if Example 1 of the present invention is not used, that is, even if cold drawing and annealing are not repeated, 1.0 mm can be manufactured relatively easily. In this sense, the drawing process becomes more difficult as the wire diameter becomes smaller, so the present invention is suitable for shot peening projection materials (finish lines of wire diameter of 0.6 mm or less) having a diameter of 0.6 mm or less. In addition, the particle size of the shot peening projection material is measured using the particle size test method prescribed | regulated to Japanese Industrial Standard JIS G5904, for example.

Example Comparative Example 1 Comparative Example 2 80% or more of carbides having a particle diameter of 2 μm or less. Less than 80% of carbides having a particle diameter of 2 μm or less. 80% or more of carbides having a particle diameter larger than 2 μm. Easy to cut The hardness was Hv 350. Since work hardening is advanced, cutting is not easy. Difficult to cut, brittle

Next, the finishing wire rod was cut in the fourth step. It was pressurized with a material stopper, fixed with a buckling prevention wire grip device, and cold sheared by a cutting die in order to suppress non-uniformity of the material and to have a certain dimension. As a cold cutting device, the mechanical press by the cam drive of a crankshaft, or hydraulic or electric press is used. You may use a dieing machine. This cutting length was made into 1.5 times the range of equivalent to the diameter of a finishing line.

Plastic working is performed in the fifth step. For example, the shape is made close to a spherical shape by a pressure vessel. Alternatively, the corner of the cylinder is rounded by colliding with the wall at high speed.

Quench and temper in the sixth process. In Example 1, the structure and the hardness are adjusted to be suitable for quenching and tempering. The tempering parameter at this time is set to 6200 to 7300. The effect at that time is shown in Table 7.

Comparative example Example Comparative example Less than 6200 Tempering parameter (= T ((21.3-5.8 × [% C]) + logt)) is set between 6200 and 7300 Greater than 7300 The toughness of the projection material is insufficient, and the life of the shot peening projection material is reduced. Toughness is sufficient and hardness is ensured to impart the life of the pinning projection material and residual compressive stress on the workpiece. The hardness of the projection material decreases, and residual compressive stress cannot be imparted to the workpiece.

As shown in Table 7, the life of the projection material is improved by appropriately managing the tempering parameters. In addition, the life of the projection material is also affected by the nonuniform composition caused by the deposition of inclusions. However, in the present invention, an area occupied by carbides having a particle diameter of 2 μm or less is 80% or more of the total finish line area. Therefore, also in this respect, it has a good influence on the lifetime of a projection material. In addition, as described later, proper shot peening conditions (such as hardness of the projection material equal to or greater than the workpiece) also have a good effect on the life of the projection material. In the present invention, the Vickers hardness of the projection material was Hv 940 at 0.6 mm in diameter and Hv 960 at 0.3 mm in diameter. Here, FIG. 2A shows the micro structure using SEM (* 1000) of the finishing line of diameter 0.3mm. 2B shows a microstructure using SEM (× 5000) of a finish line having a diameter of 0.3 mm.

The result of having observed the structure of the projection material obtained by Example 1 and a comparative example is demonstrated below. In the examples, the tissues are fine carbide and tempered martensite tissues (Table 8). For this reason, there is an effect that there is little destruction of the projection material which causes the inclusion to be destroyed by projection. This was evident by comparing the structure of the projection material before and after use. Microstructure using SEM of the shot peening projection material of this invention after nitrile corrosion of 0.6 mm in diameter (before use) and 0.3 mm in diameter (after use) is shown to FIG. 3, FIG. Here, FIG. 3A is the micro structure which used SEM of 0.6 mm diameter projection material, and before use (x1000). 3B is a microstructure using SEM of 0.6 mm diameter projection material and before use (× 3000). 4A is the micro structure which used SEM of 0.3 mm diameter projection material, and after use (x1000). 4B is a microstructure using SEM of 0.3 mm diameter projection material and after use (× 3000).

Example Comparative example It is a fine carbide of less than 2㎛ and tempered martensite structure. Carbides larger than 2 μm and incomplete tempered martensite structure. There is little destruction of the projection material which causes the inclusion to be destroyed by the projection. Incorporation of broken projection material can damage the workpiece and create a new starting point for failure.

Comparative Example 1 Example Comparative Example 2 Quenching temperature is lower than 820 ℃ Quenching temperature is 820 ℃ ~ 850 ℃ Quenching temperature higher than 850 ℃ The solid solution of carbide is so small that it does not turn into fine carbide. The employment of carbides is appropriate. Too much carbide is employed.

Example 1 and a comparative example of the projection material obtained by the manufacturing method of this invention are demonstrated below (Table 9). Thus, in this invention, when the hardening temperature was set to 820 degreeC-850 degreeC, the solid solution of carbide was appropriate.

FIG. 5 is a graph showing a particle size distribution of carbides of the shot peening projection material of FIG. 3B according to the present invention. FIG. As for the ratio of carbide, the area | region of each carbide was calculated | required and the distribution was calculated | required by making the area | region calculated | required the square area | region using the grid paper after the projection of each carbide. As average particle diameter, it was 0.8 micrometer. The particle diameter was 2.0 µm or less and 0.5 µm or more. Further, carbides having a particle diameter of less than 0.5 µm are difficult to measure substantially and are excluded from the measurement. In addition, the average particle diameter was calculated | required by the number average (numeric mean).

Example 2

Table 10 shows the conditions and results when the projection material of the present invention is actually projected onto the workpiece and subjected to the shot peening treatment.

According to the second embodiment, the projection material (Vickers hardness of Hv 950) of the present invention has a small amount of cutting with respect to a workpiece of high hardness, and it is easy to work harden the workpiece, and a large residual stress It was possible to introduce (Experiment Nos. 11 to 17).

In Experiment Nos. 11 to 17, although the Vickers hardness of the projection material was originally Hv 950, there was some curing to Hv 1050 by use.

Here, the amount of cut was measured as follows.

<Method of measuring the amount being scraped off>

The diameter of the to-be-processed material before and after the shot peening treatment was measured using the laser dimension measuring apparatus, and the cut amount used the value computed by following Formula. In addition, the cut amount used the average value measured n = 10 times, and the measurement site | part was made into the shot peening objective position center (maximum cut amount generation part).

Cut quantity = (D1-D2) / 2

Dl = diameter before shot peening

D2 = diameter after shot peening

In addition, the compressive residual stress was measured as follows.

<Method of Measuring Compressive Residual Stress>

As a non-destructive method, the X-ray stress measurement method using the X-ray diffraction prescribed | regulated to general "JIS B2711" was used for the non-destructive method. Since the sample of this time is steel of a martensite structure, the measurement was performed using the characteristic X-ray type = CrKalpha ray and X-ray stress coefficient k = -318 [MPa / degree].

In addition, the measurement site | part was made into the shot peening objective position center.

In addition, the peak value (= maximum value) of compressive residual stress was calculated | required by measuring the residual stress distribution after removing almost twice the range of the cross-sectional dimension of incident X-ray flux to predetermined depth by electropolishing.

In addition, the cross-sectional hardness of the processed goods was measured as follows.

<Method of measuring cross section hardness>

Hv 0.3 in a table | surface shows the value of the Vickers hardness of the cross section when the 50 micrometer position is measured by the load of 300g from the surface of a cross section.

Generally, the carburizing abnormal layer has a depth of about 25 μm on the surface of the gas carburized product, and the hardness is very low. Even if the part in such a state is measured, the material and the heat treatment cannot be evaluated. Therefore, the cross-sectional hardness is measured.

<Method of relative hardness measurement>

The relative hardness in a table | surface shows the value of the relative hardness which is the value which subtracted the hardness of the projection material from the surface hardness measured from the surface of the processed article. Compared with the cross-sectional hardness for evaluating the material and the heat treatment, the hardness of the surface is important for selecting the projection material hardness, so that the indenter is dropped directly on the surface and measured. In addition, the measurement of hardness used the Micro Vickers hardness tester (load 500g).

Therefore, in the case of a gas carburized product, it becomes the value containing the hardness of a surface abnormality layer. The vacuum carburized product is characterized in that no surface abnormality layer is formed, but the hardness of the surface may be lowered depending on the characteristics of the quenching.

Moreover, as for the area ratio of carbide, 70%-95% are preferable. More preferably, it is 80% to 95%. Fig. 6A is a graph showing the relationship between the carbide area ratio and the hardness (composite hardness) of the shot peening projection material of the present invention (when the composition is of high hardness). 6B is a graph showing the relationship between the carbide area ratio and the hardness (composite hardness) of the shot peening projection material of the present invention (when the composition is of low hardness).

From these graphs, it can be seen that when the area ratio of carbides is 70% to 95%, the Vickers hardness is Hv 920 to Hv 1030. In the case of Hv 950, the area ratio of carbide is 70% to 78%.

That is, hardness Hv (m) of the shot peening projection material is given by following formula (1)-(3).

Then, if equation (2) and equation (3) are substituted into equation (1),

Carbon amount was 0.75%.

This value is used as a value near the carbon tolerance limit of the matrix (martensite). Since it is the formula which calculates | requires a matrix hardness, the carbon amount at this time is made into 0.75%, and the carbide | crystallization exceeding an allowable limit is excluded.

In addition, residual austenite (γ _R ) remaining during the heat treatment was considered as follows.

From these, the composite hardness of the hardness of the shot peening projection material was calculated | required, and it described in FIG. 6A and 6B.

On the other hand, in the comparative example 1, the projection material which rounded the ridgeline after cutting the steel wire (hardness is Hv 700, material is, for example, mass%, carbon 0.81%, manganese 0.48%, Silicon 0.23%, phosphorus 0.012%, sulfur 0.004%, and unavoidable impurities, abbreviated in the CCW formula, are highly carburized steels (steels suitable for carbide dispersed carburizing, with Vickers hardness ranging from Hv 880 to 990). Large residual stress could not be introduced into the hardened workpiece of (experimental number 8). In addition, experiment number 15 corresponds to this invention.

The super economic projection material (Vickers hardness of Hv 1380) of Comparative Example 2 is excessively hard, and has a drawback in that a large amount of the workpiece (SCM420H: quenched steel) is cut. (Experiment number 10). In addition, experiment number 11 corresponds to this invention.

As described above, according to the present invention, in the production of the shot peening projection material, the material, the finishing line, and the improvement of the productivity of the shot peening projection material can be prevented from disconnection in the step of drawing fresh and obtaining the finish line. The manufacturing method of the shot peening projection material obtained, and the projection material by the manufacturing method can be provided.

In addition, according to the present invention, it is possible to provide a shot peening projection material capable of imparting the life of the shot peening projection material and appropriate compressive residual stress. Moreover, according to this invention, the manufacturing method of the shot peening projection material suitable for the shot peening excellent in hardenability can be provided.

Claims (11)

Mass%, contains 0.95 ~ 1.10% carbon, 0.15 ~ 0.30% silicon, 0.40% or less manganese, 0.020% or less phosphorus, 0.010% or less sulfur, 1.40 ~ 1.60% chromium, 0.0015% or less oxygen. The material of the shot peening projection material, in which the remainder is made of iron and unavoidable impurities,
The process of drawing with wire rod,
The area occupied by carbides having a particle diameter of 2 μm or less in the finish line is finished by a step of annealing and cold drawing the wire to form a finished wire. A finishing line of shot peening projection material, characterized in that it is 80% or more of the total area of the line. The method of claim 1,
Finishing line of the shot peening projection material, characterized in that the annealing is carried out at 720 ℃ or less. The finish line of the shot peening projection material according to claim 1,
Cutting, plasticizing and short peening material,
And a step of quenching and tempering the short peening material. The method of claim 3, wherein
The tempering parameter (= T ((21.3-5.8 × [C]) + logt)) in the tempering is 6200 to 7300, where T is the tempering temperature (K), t is the tempering time (h), and C is It is carbon amount (%), The manufacturing method of the shot peening projection material. The manufacturing method of the shot peening projection material characterized by further having the process of carrying out the plastic working of the shot peening projection material manufactured by the manufacturing method of Claim 3 or 4. It is manufactured by the manufacturing method of the shot peening projection material of Claim 3, a base of a structure is tempered martensite, fine carbide is precipitated, and the area ratio of carbide is 70 to 95%. Projection material for short peening, characterized in that the. In mass%, it contains 0.95 ~ 1.10% carbon, 0.15 ~ 0.30% silicon, 0.40% or less manganese, 0.020% or less phosphorus, 0.010% or less sulfur, 1.40 ~ 1.60% chromium, 0.0015% or less oxygen. , The material of the shot peening projection material consisting of iron and unavoidable impurities is drawn into the wire rod, and the wire is repeatedly annealed and cold drawn to form a finishing line, and the cutting line is cut and plasticized to form a short peening material. As a shot peening projection material manufactured by quenching and tempering the shot peening material,
Fine carbides are deposited at the base where the tissue is tempered martensite,
Short peening projection material, characterized in that the area ratio of carbide is 70% to 95%. The method of claim 7, wherein
Vickers hardness Hv 950 to Hv 1050, the shot peening projection material. delete delete delete

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