JPH04310371A - Manufacture of high-strength long-life shot ball - Google Patents

Abstract

PURPOSE:To provide the manufacturing method of a shot ball of high Vickers hardness and long life suitable for high strength material shot. CONSTITUTION:A shot ball, obtained by cutting a high carbon steel wire to form a cut wire and further rounding it, is provided with a TiN coating layer. The shot ball of high strength and long life can be obtained by using this shot ball manufacturing method.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing shot balls used in shot blasting or shot peening, and more particularly to a method for manufacturing shot balls with high strength and long life.

0002

2. Description of the Related Art Shot balls are used for shot blasting to introduce compressive residual stress into the surface of a material. Shot balls include shot balls manufactured by cutting steel wire as in the present invention and Japanese Patent Application Laid-Open No. 2-190266, shot balls made of ceramic, and shot balls produced by an atomization method. Ceramic shot balls break easily, so if the material being shot is strong, there is a problem that the broken shot ball may damage the shot material.

[0003] It is difficult to adjust the strength of shot balls produced by the atomization method, and even if a high-strength shot ball can be obtained, it will only have a Vickers hardness of about 500. When producing shot balls with increased strength using the atomization method, there was a problem in that it was difficult to achieve high strength because the life of the shot particles was significantly reduced. On the other hand, even in shot balls made from steel wire, there has been a problem in that when shot balls have been manufactured with increased strength, the life of the shot balls is significantly shortened.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a shot ball having a high Vickers hardness and a long life, which is suitable for shot from high-strength materials.

[0005]

[Means for Solving the Problems] The present invention provides a method for producing a shot ball, which comprises cutting a high carbon steel wire to obtain a cut wire, and further rounding the resulting shot ball to provide a coating layer of TiN on the shot ball. It is.

Furthermore, the present invention has a C:0.90 to 1.0% by weight.
10%, Si: 0.4% or less, Mn: 0.5% or less, C
r: 0.10 to 0.30%, Al: 0.050% or less,
Using high carbon steel wire consisting of residual iron and unavoidable impurities,
Strength after final patenting is 135 or more 145kgf
/mm2, and then drawn to a true strain of 3.0 to 3.10 to a diameter of 0.4 mm.
φ or more and less than 0.8mmφ and Vickers hardness Hv=75
It is characterized by using a cut wire wire with a diameter of 0 or more and 800 or less, with a strength after final patenting of 145 or more and 155 kgf/mm2 or less, and then drawing processing with a true strain of 3.10 to 3.30. ,
Diameter 0.4 or more and less than 0.8 mmφ and Vickers hardness H
It is characterized by using a cut wire wire with v=800 or more and 850 or less, and the strength after final patenting is 1.
For cut wires with a diameter of 0.8 or more and 1.0 mmφ or less and a Vickers hardness Hv of 750 or more and 800 or less. It is characterized by using wire.

[0007]

[Operation] While the shot ball is being shot at an object, the shot particles collide with each other or between the shot particles and the shot material, so the surfaces rub against each other and generate heat. For this reason, the strength near the surface of the shot ball decreases. In particular, when the strength of the shot ball is increased and shots are made with greater force, the wear and tear of the shot ball due to heat generation increases. Therefore, by coating the surface of the shot ball with TiN, it was possible to reduce the heat generated during the collision.

The above effects are particularly effective for shot balls manufactured from high-strength shot ball wire.

The reasons for limiting the steel composition of the present invention are as follows. C: 0.8 in normal patenting processing
The present inventors have found that pro-eutectoid ferrite precipitates along the prior austenite grain boundaries even when the eutectoid component is around %, and that this pro-eutectoid ferrite causes a decrease in ductility after wire drawing. C is an economical and effective reinforcing element, but it is also an effective element in reducing the amount of precipitated cementite.

[0010] Therefore, the diameter is 0.4mmφ or more and 0.8mm
In the case of manufacturing a cut wire with less than φ and a Vickers hardness of 750 or more and less than 800, if the C amount is less than 0.90, it is impossible to obtain a Vickers hardness of Hv=750 or more, so the C amount should be 0.90% or more. shall be. Furthermore, if the amount of C exceeds 1.10%, it is difficult to suppress the precipitation of pro-eutectoid cementite, and the life of the cut wire is significantly reduced, so the amount of C is set to 1.10% or less.

[0011] In the case of manufacturing a wire for cut wire with a diameter of 0.4 or more and less than 0.8 mmφ and a Vickers hardness of 800 or more and 850 or less, if the C content is less than 0.95%, the Vickers hardness is Hv = 800. Since the above cannot be obtained, the amount of C is set to 0.95% or more. Also, the amount of C is 1
．． When added in an amount exceeding 10%, it is difficult to suppress the precipitation of pro-eutectoid cementite and the life of the cut wire is significantly reduced, so the amount of C is set to 1.10% or less.

[0012] When producing a wire for cut wire with a diameter of 0.8 to 1.0 mmφ and a Vickers hardness of 750 to 800, if the C content is less than 0.95%, the Vickers hardness is Hv = 800. Since the above cannot be obtained, the amount of C is set to 0.95% or more. Also, the amount of C is 1
．． If it is added in an amount exceeding 10%, it is difficult to suppress the precipitation of pro-eutectoid cementite and the life of the cut wire is significantly reduced, so the amount of C is set to 1.10% or less.

[0013]Si is an element necessary for deoxidizing steel, and therefore, when its content is too low, the deoxidizing effect becomes insufficient. In addition, Si dissolves in the ferrite phase in pearlite formed after heat treatment and increases the strength after patenting, but on the other hand, it reduces the ductility of the ferrite and the ductility of the ultra-fine wire after wire drawing, so 0.4% The following shall apply. It is desirable to add a small amount of Mn to ensure the hardenability of the steel. However, addition of a large amount of Mn causes segregation and generates supercooled structures such as bainite and martensite during patenting, impairing subsequent wire drawability, so the Mn content is limited to 0.5% or less.

In the case of the hypereutectoid steel of the present invention, a cementite network tends to occur in the structure after patenting, and thick cementite tends to precipitate. In order to achieve high strength and high ductility in this steel, it is necessary to make the pearlite fine and eliminate the cementite network and thick cementite as described above. Cr has the effect of suppressing the appearance of such abnormal parts of cementite and further making pearlite fine. However, addition of a large amount increases the dislocation density in the ferrite after heat treatment, which significantly impairs the ductility of the ultrafine wire after drawing. Therefore, the amount of Cr added should be 0.10% or more, which is expected to have the effect, and 0.30%, which does not increase the dislocation density in ferrite and impair ductility.
The following shall apply.

[0015] As with conventional ultra-fine steel wires, the S content is set to 0.020% or less in order to ensure ductility, and since P also impairs the ductility of the wire rod, the content is set to 0.020% or less. It is desirable to do so.

[0016] Al is a cause of decreasing the ductility of ultrafine wires.
2 O3 , MgO-Al2 O3 etc.
There are non-ductile inclusions mainly composed of Therefore, in the present invention, the Al content is set to 0.050% or less in order to avoid a decrease in ductility due to non-ductile inclusions.

The reasons for the limitations of the manufacturing method of the present invention are as follows. Diameter 0.4mmφ or more according to the method of the present invention
．． In the case of manufacturing a cut wire with a diameter of less than 8 mm and a Vickers hardness of 750 to 800, it is difficult to achieve a Vickers hardness of 750 or more if the strength is 135 kgf/mm 2 or less during final LP. In addition, if the tensile strength is set to 145 kgf/mm2 or more, the Vickers hardness will exceed Hv=800, so the tensile strength should be set to 135 kgf/mm2 or more and 145 kgf/mm2.
2 or less.

By repeatedly drawing the wire adjusted to a certain strength range, the wire has a diameter of 0.4 mm.
It is processed to a diameter of 0.8 mm or less. At this time, if the machining amount is less than 3.0 in true strain, Vickers hardness H
It is not possible to obtain wires with v=750 or more. Also,
If processing is performed with a true strain of 3.10 or more, the Vickers hardness will exceed 800, so the amount of drawing processing is set to a true strain of 3.0 or more and 3.10 or less. A shot ball manufactured from the wire for cut wire manufactured in this way is coated with TiN by CVD (vapor phase reactive vapor deposition method) or the like.
A coating layer is provided to make a shot ball.

[0019] Diameter of 0.4 or more and 0.8 mm as shown in the method of the present invention
In the case of manufacturing a cut wire wire having a Vickers hardness of less than φ and a Vickers hardness of 800 to 850, it is difficult to achieve a Vickers hardness of 800 or more if the final LP strength is 145 kgf/mm 2 or less. In addition, if the tensile strength is set to 150 kgf/mm2 or more, the Vickers hardness will exceed Hv=850, so the tensile strength should be set to 145 kgf/mm2 or more and 150 kgf/mm.
2 or less.

[0020] By repeatedly drawing the wire whose strength has been adjusted to a certain range,
Process to a diameter of φ or more and 0.8 mm or less. At this time, if the processing amount is 3.10 or less in terms of true strain, it is not possible to obtain a wire with a Vickers hardness of Hv=800 or more. In addition, if processing is performed at a true strain of 3.30 or more, the Vickers hardness will exceed 850 and the life of the shot grains will be significantly reduced, so the amount of drawing processing is reduced to a true strain of 3.30 or more.
10 or more and 3.30 or less. A shot ball manufactured from the wire for cut wire thus manufactured is provided with a coating layer of TiN by CVD or the like to form a shot ball. Diameter 0.8 or more according to the method of the present invention 1
．． In the case of a cut wire wire having a diameter of less than 0 mmφ and a Vickers hardness of 750 to 800, it is difficult to achieve a Vickers hardness of 750 or more if the final LP strength is 140 kgf/mm 2 or less. Furthermore, if the tensile strength is 150 kgf/mm2 or more, the life of the shot grains will be significantly reduced, so the tensile strength is set to 140 kgf/mm2 or more and 150 kgf/mm2 or less.

[0021] By repeatedly drawing the wire whose strength has been adjusted to a certain range, it is possible to
Process to a diameter of φ or more and 0.8 mm or less. At this time, if the processing amount is 3.00 or less in terms of true strain, it is not possible to obtain a wire with a Vickers hardness of Hv=750 or more. In addition, if processing is performed at a true strain of 3.20 or more, the Vickers hardness will exceed 800, and the life of the shot grain will be significantly reduced.
0 or more and 3.20 or less. A shot ball manufactured from the wire for cut wire thus manufactured is provided with a coating layer of TiN by CVD or the like to form a shot ball.

[0022]

EXAMPLE A shot ball was manufactured according to the present invention. Sample numbers 1 to 6 in Table 1 are shot balls manufactured according to the method of the present invention, in which hot-rolled wire rods with the components shown in Table 1 are drawn to a predetermined wire diameter, and then subjected to patenting treatment as shown in Table 1. Adjusted the intensity. Thereafter, wire drawing was performed with the area reduction ratio shown in Table 1 to obtain steel wires with the wire diameters shown in Table 1. The hardness at this time is shown in Table 1. The comparative steel was adjusted to have a hardness within the range of the present invention. Thereafter, rounding was performed, and the steel of the present invention was coated with TiN by CVD.

[0023] Sample numbers 7 and 8 are at a level prepared for comparison, and in sample numbers 7 and 8, the wire for the cut wire used for manufacturing shot balls is the same as the second method of the present invention, and after rounding. , which was not coated with TiN.

[0024] In order to examine the life of the cut wire using these shot balls, shots were continuously performed for 1000 hours, and the amount of wear on the shot grains was calculated by subtracting the weight of shot grains of a predetermined size or larger after shot from the initial shot grain weight. It was determined in weight percent.

Shot balls coated with TiN have a lower wear rate over their lifetime than shot balls without TiN coating according to the present invention.

[0026]

[Table 1]

[0027]

[Effects of the Invention] When a shot ball is manufactured according to the present invention, a shot ball with high strength and long life can be obtained.

Claims (4)

[Claims] 1. A method for producing a shot ball, comprising: cutting a high carbon steel wire into a cut wire, and further rounding the resulting shot ball, and providing a coating layer of TiN on the shot ball. [Claim 2] C in weight%: 0.90 to 1.10
%, Si: 0.4% or less, Mn: 0.5% or less, Cr:
Using high carbon steel wire consisting of 0.10 to 0.30%, Al: 0.050% or less, balance iron and unavoidable impurities, the strength after final patenting is 135 to 145 kgf/m
m2, then perform drawing processing to a true strain of 3.0 to 3.10, and use a cut wire wire with a diameter of 0.4 mmφ or more and less than 0.8 mmφ and a Vickers hardness Hv of 750 or more and 800 or less. The method of manufacturing a high strength, long life shot ball according to claim 1, characterized in that: Claim 3: Strength after final patenting is 145
155 kgf/mm2 or less, and then processed by drawing to a true strain of 3.10 to 3.30, with a diameter of 0.4 or more and less than 0.8 mmφ and a Vickers hardness Hv of 800 or more and 850 or less. 2. The method of manufacturing a high-strength, long-life shot ball according to claim 1, characterized in that: Claim 4: The strength after final patenting is 140.
150 kgf/mm2 or less, and then the wire is drawn to a true strain of 3.00 to 3.20, and the wire has a diameter of 0.8 or more and 1.0 mmφ or less and a Vickers hardness Hv of 750 or more and 800 or less. 2. The method of manufacturing a high-strength, long-life shot ball according to claim 1, characterized in that: