JP6671772B2 - High hardness and toughness powder - Google Patents

Description

  The present invention relates to a shot material for shot peening, a raw material powder for high hardness powder metallurgy having excellent corrosion resistance to hydrochloric acid, a hard friction powder, a high hardness and high toughness powder used for hard particles for sintering, and the like.

  Conventionally, Co-Mo and Co-W alloys produce various intermetallic compounds as can be seen from their respective binary phase diagrams. These intermetallic compounds have high hardness and are suitable for various high-hardness materials and wear-resistant materials. Mo and W also have an effect of improving corrosion resistance by being dissolved in Co, and have a particularly large effect of improving corrosion resistance against reducing acids such as hydrochloric acid. In addition, Co itself has high corrosion resistance to various acids as a base metal. Therefore, powders of these alloy compositions can be used as shot peening shot materials, raw material powders for high hardness powder metallurgy having excellent hydrochloric acid corrosion resistance, hard friction powders, hard particles for sintering, and the like.

  For example, a CoMoCrSi-based alloy powder [Trivalloy (registered trademark)] disclosed in WO2012 / 0635512A1 (Patent Document 1) is often used. On the other hand, Si is added in the alloy to increase the hardness, and forms a hard but brittle silicide, which reduces the bending strength of the alloy. Was sometimes a problem. From these facts, Mo and W have to be kept low in consideration of bending strength and toughness, even if it is desired to add Mo and W as much as possible in order to improve hardness and corrosion resistance. there were.

WO2012 / 0635512A1

  Therefore, the present inventors have studied in detail the amount of Si to be added to a powder based on Co and containing Mo and W in total of 25% or more, and found a range having high toughness (deflection strength), and have reached the present invention. . In addition, in the composition range of the alloy of the present invention, hard and brittle silicide is not generated, and on the other hand, it has been found that it has age-hardening property due to generation of Co-Mo-based or Co-W-based intermetallic compound. Since it is possible to change the hardness by heat treatment after solidification and molding by, for example, the HIP method or the like, it is also possible to machine with a low hardness state and then increase the hardness by aging treatment before use. . Therefore, it is possible to work in a state of low hardness, which is easy to machine, and use it in a state of high hardness with excellent wear resistance.

The gist of the invention is that
(1) High content, in which Mo or / and W are contained in a total amount of 25 to 50%, Cr is 5 to 15%, and Si is 0.3% or less, and the balance is Co and inevitable impurities. Hardness and high toughness powder.
(2) In addition to the above (1), the composition contains one or more selected from among 35% or less of Mn, 20% or less of V, and 15% or less of Fe in mass%. High hardness and high toughness powder.

  As described above, according to the present invention, a shot material for shot peening, a raw material powder for a high hardness powder metallurgy having excellent hydrochloric acid corrosion resistance, a hard friction powder, and a high hardness and high toughness powder used for a sintering hard particle can be provided. .

Hereinafter, the present invention will be described in detail.
The most significant feature of the present invention is that both the high hardness and the high toughness are achieved by reducing the amount of Si added compared to the conventional CoMoCrSi alloy. In addition, it has been found that in this component range, it has age hardening properties. Further, one or more of Mn, V, and Fe may be added as a range of the additive element that does not affect these characteristics.

  As a method for producing the powder, gas atomization, water atomization, disk atomization, quenching of a rapidly quenched foil strip or a casting material, which are conventionally known, can be used. A method of obtaining a spherical shape such as a gas atomizing method or a disk atomizing method (for example, a circularity of 0.85 to 0.75 or more by image analysis) or a method of obtaining a substantially spherical shape such as a water atomizing method (for example, a circularity of 0.80) When the powder is used as a shot peening blast material, the surface roughness of the material to be projected is suppressed, and when used as a raw material powder for sintering, the filling rate at the time of molding is increased and the near net This is advantageous for molding.

  On the other hand, powder obtained by a method of obtaining an irregular shape (for example, a circularity of less than 0.80 to 0.70), such as various pulverization methods, was used as a shot peening shot material as a pretreatment for a film forming process such as thermal spraying. In this case, the surface roughness of the material to be projected is increased to improve the adhesion of the film, and when used as a raw material powder for sintering, there is an effect of improving the shape retention during molding.

Hereinafter, the reason for regulating the component composition according to the present invention will be described.
Mo or / and W: 25 to 50%
In the alloy of the present invention, Mo and W are elements that increase the hardness of the alloy but decrease the bending strength and toughness. However, if the total amount is less than 25%, sufficient hardness cannot be obtained. On the other hand, if it exceeds 50%, the bending strength decreases. Preferably it is more than 30% and less than 50%, more preferably more than 35% and less than 45%.

Cr: 5 to 15%
In the alloy of the present invention, Cr is an element that increases the hardness together with Mo and W, and also has an effect of improving corrosion resistance. However, if it is less than 5%, the hardness and corrosion resistance are insufficient, and if it exceeds 15%, the hardness before aging becomes high and the age hardening width becomes small. Preferably it is 6 to 14%, more preferably 7 to 13%.

Si: 0.3% or less In the alloy of the present invention, Si is an element which lowers the transverse rupture strength due to silicide formation and reduces the age hardening width, so it is necessary to define an upper limit. When the content exceeds 0.3%, the bending strength is significantly reduced, and the age hardening width is reduced. Preferably it is 0.19% or less, more preferably less than 0.15%.

One or more of Mn: 35% or less, V: 20% or less, Fe: 15% or less In the alloy of the present invention, Mn, V, and Fe are elements that do not impair the features of the present invention as long as they are not excessively added. And can be added as needed. When the addition amount of each element exceeds 35%, 20%, and 15%, the transverse rupture strength decreases. On the other hand, Mn and Fe are elements that contribute to a reduction in raw material costs. Therefore, it is preferable that Mn is added in excess of 20% and Fe is added in excess of 5%. V is preferably less than 15% in order to suppress a decrease in bending strength.

Hereinafter, the present invention will be described specifically with reference to examples.
First, as powders, test powders were prepared by a gas atomizing method, a water atomizing method, a quenched ribbon pulverizing method, and a casting pulverizing method. In the atomization method, a melted raw material weighed to 25 kg is induction-melted to 1750 ° C. in a refractory crucible under reduced pressure Ar, and hot water is discharged from a nozzle having a diameter of 7 mm below the crucible, and atomized using nitrogen gas or water as a spray medium. Done.

  In the quenching ribbon pulverization method, a molten raw material weighed to 30 g is induction-dissolved in a quartz tube under reduced pressure Ar, and hot water is supplied from a 1 mm nozzle at the bottom of the quartz tube to a copper roll having a diameter of 300 mm and a rotation speed of 500 rpm to obtain a quenched ribbon. Was. This was pulverized in an Ar-substituted planetary ball mill. This was vacuum-sealed in a quartz tube, kept in a heating furnace at 1200 ° C. for 1 hour, and then subjected to a solution treatment of air cooling.

  In the casting and pulverization method, the melted raw material weighed to 200 g was arc-melted under reduced pressure Ar in a water-cooled copper mold having a diameter of 50 mm, and the solidified ingot was roughly pulverized with a stamp mill, and then replaced with an Ar-substituted planetary ball mill. And crushed. This was vacuum-sealed in a quartz tube, kept in a heating furnace at 1200 ° C. for 1 hour, and then subjected to a solution treatment of air cooling. The average circularity measured by PITA-1 manufactured by Seishin Enterprise Co., Ltd. was 0.80 or more for gas atomized powder, 0.75 or more for water atomized powder, and less than 0.75 for pulverized powder.

  Regarding the hardness of the powder, the powder classified into 150 μm or less was embedded in a resin, polished, and evaluated for Vickers hardness. The test load was evaluated at 2.94 N (300 gf), n = 5 average. In addition, Vickers hardness was similarly measured for powders aged at 800 ° C. for 3 hours in Ar.

  Regarding the hardness and bending strength of the powder metallurgy body, the powder classified into 150 μm was filled in a stainless steel capsule having an inner diameter of 30 mm and a height of 30 mm, degassed and sealed, and held at a temperature of 1150 ° C., a holding time of 3 h, and a molding pressure. HIP molding was performed at 147 MPa, followed by slow cooling. This molded article was evaluated for Vickers hardness (the same method as for powder) and bending strength (a three-point bending test with a fulcrum distance of 10 mm).

  For evaluation of each item, a powder having a composition shown in Table 1 was prepared and evaluated. The hardness of the powder was A when the Vickers hardness of the powder after aging treatment was 700 HV or more, B when it was less than 700 HV and 500 HV or more, and C when it was less than 500 HV.

  As the age hardening width of the powder, "hardness of powder metallurgy-hardness of powder before aging treatment" was 200 A or more for A, B for less than 200 HV and 100 HV or more, and C for less than 100 HV. .

  The bending strength of the powder metallurgy body was A when the bending strength of the powder metallurgy body was 800 MPa or more, B when it was less than 800 MPa and 400 MPa or more, and C when it was less than 400 MPa.

As shown in Table 1, Nos. 1 to 12 are examples of the present invention. 13 to 23 are comparative examples.

  Comparative Example No. 1 shown in Table 1. Sample No. 13 is inferior in hardness in the test powder because the total amount of Mo element and W element in the powder composition is small. Comparative Example No. No. 14 is inferior in transverse rupture strength because the total amount of the Mo element and the W element in the powder composition is large. Comparative Example No. No. 15 is inferior in hardness and corrosion resistance of the test powder because Cr is not contained in the powder composition. Comparative Example No. In No. 16, since the content of Cr, which is a powder composition, is large, the hardness before aging of the test powder increases, and the age hardening width decreases.

  Comparative Example No. In Nos. 17 to 20, since the content of Si, which is a powder composition, is large, the drop in bending strength becomes remarkable, and the age hardening width of the test powder becomes small. Comparative Example No. In Nos. 21 to 23, since the contents of Mn, V, and Fe, which are powder compositions, are all large, the bending strength is inferior. On the other hand, in the case of No. 1 of the present invention. All of Nos. 1 to 12 satisfy the conditions of the present invention, indicating that the hardness of the test powder, the age hardening width of the test powder, and the bending strength are excellent.

As described above, in particular, by containing Mo and W in a total amount of 25 to 50%, sufficient hardness is obtained, and at the same time, the corrosion resistance by Cr is increased, and the upper limit of Si is regulated, so that the transverse rupture strength and large Achieves both age hardening width and is used for shot peening shot material with excellent age hardening and bending strength, raw material powder for high hardness powder metallurgy with excellent hydrochloric acid corrosion resistance, hard friction powder, hard particles for sintering, etc. High hardness and high toughness powder can be provided.


Patent applicant Sanyo Special Steel Co., Ltd.
Attorney Patent Attorney Shiina Jin

Claims (2)

By mass%, Mo or / and W are contained in a total of 25 to less than 50%, Cr is contained in a content of 5 to 15%, Si is contained in a content of 0.05 to 0.3%, and the balance is made of Co and inevitable impurities. High hardness and toughness powder. 2. The high hardness according to claim 1, further comprising at least one selected from the group consisting of Mn of 35% or less, V of 20% or less, and Fe of 15% or less in mass%. High toughness powder.