JP2017155310A - Handsaw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a handsaw good in abrasion resistance and toughness.SOLUTION: A handsaw is formed by a steel sheet containing 0.60 mass% to 1.25 mass% of C, 0.50 mass% or less of Si, 0.30 mass% to 1.20 mass% of Mn, 0.03 mass% or less of P, 0.03 mass% or less of S, 0.30 mass% to 1.50 mass% of Cr and 0.10 mass% to 0.50 mass% of Nb and the balance Fe with inevitable impurities and Nb-containing carbide with particle diameter of 0.5 μm or more exists in a matrix with a density of 3000/mmto 9000/mm.SELECTED DRAWING: None

Description

  The present invention relates to a hand saw having excellent wear resistance and toughness.

  Hand saws used for processing wood, polyvinyl chloride resin, metal, etc. require wear resistance to improve work and prevent chipping or breakage of the blade due to strong impact during work. Therefore, toughness is required.

  Abrasion resistance can be improved by hardening the material of the hand saw. However, since wear resistance and toughness are contradictory, in order to improve toughness, the current situation is that the hardness and the amount of C are reduced at the expense of wear resistance. Often used. In addition, some of the cutting edges are increased in hardness by impact quenching (ultra-frequency quenching).

  As a material for blades such as this type of hand saw, the abrasion and impact resistant tool steel of Patent Document 1 is known.

  In Patent Document 1, the wear resistance and toughness are improved by adjusting the contents of W, Mo, Cr, V, and the like.

JP-A-5-9654

  In the above-mentioned patent document 1, since it is necessary to add W, Mo, and V, which are relatively expensive elements, to generate a special carbide, there is a problem that it cannot be efficiently manufactured.

  In addition, hand saws are required to have both wear resistance and toughness, but it is difficult to achieve both of these conflicting wear resistances and toughness, and there is a need for hand saws with good wear resistance and toughness. .

  The present invention has been made in view of these points, and an object thereof is to provide a hand saw having good wear resistance and toughness.

The hand saw described in claim 1 is C: 0.60 mass% or more and 1.25 mass% or less, Si: 0.50 mass% or less, Mn: 0.30 mass% or more and 1.20 mass% or less, P: 0.03% by mass or less, S: 0.03% by mass or less, Cr: 0.30% by mass to 1.50% by mass and Nb: 0.10% by mass to 0.50% by mass The balance is Fe and inevitable impurities, and Nb-containing carbide having a particle diameter of 0.5 μm or more is present in the matrix at a density of 3000 / mm ² or more and 9000 / mm ² or less.

  The hand saw described in claim 2 is the hand saw according to claim 1, wherein Ti: 0% by mass (including no additive) and 0.50% by mass or less and B: 0% by mass (including no additive). .) Containing 0.005% by mass or less.

  The hand saw described in claim 3 is the hand saw according to claim 1 or 2, wherein Mo: 0% by mass (including no additive) and 0.50% by mass or less, V: 0% by mass (no additive) And at least one of Ni: 0% by mass (including no addition) and 2.0% by mass or less.

According to the present invention, in the component range, Nb-containing carbide having a particle size of 0.5 μm or more is present in the matrix at a density of 3000 / mm ² or more and 9000 / mm ² or less, so wear resistance and toughness Can be improved.

It is a schematic diagram which shows the shape of the impact test piece used for an impact test.

  Hereinafter, the configuration of an embodiment of the present invention will be described in detail.

  The hand saw according to an embodiment includes C (carbon) of 0.60% by mass or more and 1.25% by mass or less, Si (silicon) of 0.50% by mass or less, 0.30% by mass or more and 1.20% by mass. % Mn (manganese), 0.03% by mass P (phosphorus), 0.03% by mass S (sulfur), 0.30% by mass to 1.50% by mass Cr (chromium), And it is formed with the steel plate which contains 0.10 mass% or more and 0.50 mass% or less Nb (niobium), and the remainder consists of Fe and an unavoidable impurity.

  Moreover, 0 mass% (including no addition) or more and 0.50 mass% or less of Ti (titanium), and 0 mass% (including no addition) or more and 0.005 mass% or less as necessary. It is preferable to contain B (boron).

  Furthermore, 0% by mass (including no addition) to 0.50% by mass Mo (molybdenum), 0% by mass (including no addition) to 0.50% by mass or less V (as required). It is preferable to contain at least one of vanadium) and 0 mass% (including no addition) or more and 2.0 mass% or less of Ni (nickel).

  C is an element necessary for improving the strength of the steel sheet and needs to be added in an amount of 0.60% by mass or more in order to be used for a hand saw. However, if the C content exceeds 1.25% by mass, coarse undissolved carbides increase, which may cause deterioration factors such as impact characteristics. Therefore, the C content is set to 0.60 mass% or more and 1.25 mass% or less.

  Si is added as a deoxidizing material in the steelmaking stage, but no deoxidation failure occurs even if it is not added. Further, if the Si content increases, the toughness deteriorates, and if it exceeds 0.50 mass%, the toughness for use in a hand saw may not be ensured. Therefore, the Si content is 0.50 mass% or less (including no addition), and preferably 0.30 mass% or less.

  Mn is an element effective for improving the hardenability of steel, and if the content is less than 0.30% by mass, the hardenability cannot be sufficiently improved. However, if Mn is added in a large amount exceeding 1.20% by mass, it will be hardened, resulting in a loss of manufacturability and toughness. Therefore, the content of Mn is set to 0.30% by mass or more and 1.20% by mass or less.

  Since P and S both adversely affect toughness, it is preferable that the content be as small as possible. Accordingly, the P content and the S content are both 0.03% by mass or less.

  Cr is an element that has the effect of improving the hardenability of steel, the effect of improving the strength of the steel sheet, the action of improving the wear resistance of the steel sheet, and the action of suppressing the coarsening of cementite during annealing. . And in order to show said each effect | action by Cr, it is necessary to make content of Cr 0.30 mass% or more. However, Cr may adversely affect the solution of cementite in the heat treatment during the quenching treatment. If the Cr content exceeds 1.50% by mass, the amount of undissolved cementite during the quenching treatment is reduced. It can be a factor to increase. Therefore, the Cr content is set to 0.30 mass% or more and 1.50 mass% or less.

  Nb forms a very hard Nb-containing carbide in the steel in the cooling process after casting, and contributes to improvement of wear resistance, particularly abrasive wear resistance. Further, Nb contributes to improvement of toughness by refining crystal grains during quenching. In order to exhibit these actions by Nb, the Nb content needs to be 0.10% by mass or more. However, when Nb is added in a large amount, Nb-containing carbide is excessively generated, and this Nb-containing carbide becomes a starting point of fracture and a crack propagation path, which causes deterioration of toughness. Also, in order to ensure good toughness after tempering heat treatment in applications where the C content level is relatively high, it is important to suppress the Nb content to 0.50 mass% or less. Therefore, the Nb content is set to 0.10% by mass or more and 0.50% by mass or less.

  Ti, like Nb, forms a very hard Ti-containing carbide in the steel in the cooling process after casting, and contributes to wear resistance. In addition, TiC that is re-dissolved during hot rolling or the like and precipitated during hot rolling or cooling contributes to improving toughness by refining crystal grains during quenching. Further, since the bonding force between Ti and N is strong, when B is added, the formation of BN is prevented, and it is effective in extracting the effect of improving the hardenability of B. Therefore, it is preferable to add Ti as needed, and it is effective to make the Ti content 0.01% by mass or more in order to achieve the above-described effects of Ti. However, if the Ti content exceeds 0.50% by mass, a large amount of Ti-based carbides are present in the steel sheet, which tends to cause toughness deterioration. Therefore, when Ti is contained, the content of Ti is 0% by mass (including no addition) or more and 0.50% by mass or less.

  B is an element effective for improving hardenability, and is preferably added as necessary. In order to achieve this hardenability improving effect, it is effective that the B content is 0.0003 mass% or more. The effect of improving hardenability by B is saturated when the B content is 0.005% by mass. Therefore, when B is contained, the content of B is set to 0% by mass (including no addition) or more and 0.005% by mass or less.

  Mo and V are both effective elements for improving toughness, and it is preferable to add them as necessary. In order to achieve the toughness improving action by Mo and V, it is effective to set the content to 0.10% by mass or more. However, since Mo and V are relatively expensive elements, and excessive addition causes an increase in cost, the content of Mo when Mo is contained is 0 mass% (including no addition) or more and 0. When V is contained, the V content is 0 mass% (including no addition) or more and 0.50 mass% or less.

  Ni is an element effective for improving hardenability and low temperature toughness, and is preferably added as necessary. In order to achieve the effect of improving the hardenability and the low temperature toughness by Ni, it is effective to make the Ni content 0.10% by mass or more. However, excessive addition of Ni is a factor that impairs economic efficiency. Therefore, when Ni is added, the Ni content is set to 0 mass% (including no addition) or more and 2.0 mass% or less.

  In order to improve the wear resistance using a steel plate whose components are adjusted in the above range as a hand saw, the action of carbide containing Nb is used. When Ti is contained, Ti carbide is also effective in improving the wear resistance. However, in order to ensure toughness for use in a hand saw, it is necessary to control the particle size of the carbide.

Specifically, the hand saw, which is the final member after the tempering heat treatment, has Nb or Nb-containing carbide containing Nb and Nb and Ti having a particle diameter of 0.5 μm or more of 3000 / mm ² or more / 9000 / When the metal structure is present in the matrix with a density of mm ² or less, the wear resistance is improved and the adverse effect of impairing toughness can be avoided.

  The carbide containing Nb is a hard carbide containing NbC as a main component, and the carbide containing Nb and Ti is a hard carbide containing (Nb, Ti) C as a main component (hereinafter referred to as “Nb, Ti) C”). These carbides containing Nb and carbides containing Nb and Ti are hard carbides.)

  Whether or not the precipitated particles contained in the steel correspond to hard carbides can be confirmed by microscopic analysis using EDX or the like. Moreover, about the hard carbide confirmed in this way, each area is measured, the diameter of the perfect circle which has the same area is calculated, and this diameter is made into the particle diameter of a hard carbide.

If the hard carbide in steel has a particle size of 0.5 μm or more and less than 3000 pieces / mm ² , the effect of improving the wear resistance by the hard carbide is insufficient, and sufficient wear resistance as a hand saw cannot be secured. there is a possibility. On the other hand, if the number of hard carbide particles having a particle size of 0.5 μm or more is more than 9000 / mm ² , these hard carbides become the starting point of fracture and crack propagation path, leading to deterioration of toughness. Therefore, in the hand saw, hard carbide (Nb-containing carbide) having a particle diameter of 0.5 μm or more is present in the matrix at a density of 3000 / mm ² or more and 9000 / mm ² or less.

  Next, an example of a method for manufacturing the hand saw will be described.

  Steel sheets used for hand saws are manufactured through casting, hot rolling and cold rolling, and tempering heat treatment.

  In the casting process, hard carbides are precipitated in the steel during the cooling process. In order to adjust the particle size and density of the precipitated hard carbide, it is important to strictly limit the C content, the Nb content, and the cooling rate during casting.

  The steel plate thus produced is heated at 830 ° C. for 5 to 10 minutes and cooled with oil, and then subjected to press tempering at around 300 to 350 ° C. to obtain a hardened steel strip.

  Further, the hardened steel strip is processed into a predetermined shape by laser cutting or punching, and distortion is removed by waist insertion.

  Then, the shape of the cutting edge is formed with a grinder or the like, Cr plated, and a hand saw is obtained.

  Next, the effect of the one embodiment will be described.

According to the hand saw according to the above-described embodiment, in the range of the above components, the hard carbide having a particle diameter of 0.5 μm or more containing Nb is a matrix with a density of 3000 / mm ² or more and 9000 / mm ² or less. Since it exists in it, while being able to ensure the abrasion-resistant improvement effect by the hard carbide containing Nb, the deterioration of toughness by the excessive production | generation of a hard carbide can be prevented. Therefore, the wear resistance and toughness are good.

  Moreover, by including Ti as required, the wear resistance and toughness can be improved by the wear resistance improving action and the toughness improving action of the hard carbide containing Ti.

  Furthermore, hardenability can be improved by containing B as needed. In addition, when B is contained, the generation of BN due to the combination of B and N can be prevented by containing Ti, and the effect of improving hardenability by B can be easily achieved.

  Moreover, toughness, hardenability, and low temperature toughness can be improved by containing at least 1 sort (s) of Mo, V, and Ni as needed.

  Hereinafter, this example and a comparative example will be described.

  Table 1 shows the chemical composition of the steel sheet that is the base material of the hand saw.

  Each steel slab shown in Table 1 was melted, and 30 kg steel ingots for melting and solidification experiments were cut out. Moreover, the steel ingot was melted in a crucible furnace to obtain molten steel, and a solidified ingot (simulated slab) simulating a slab was obtained.

  Each simulated slab was processed in the order of hot rolling, annealing, cold rolling, and annealing to produce a wear test piece and an impact test piece having a plate thickness of 2.2 mm.

  Furthermore, the wear test piece and the impact test piece were tempered to a temper hardness of 50 to 53 HRC by tempering heat treatment.

  In the hot rolling, the heating temperature is 1250 to 1350 ° C. and held for 60 minutes, the finishing temperature is 850 ° C., the winding temperature is 590 ° C., the hot rolled sheet thickness is 3.5 mm (3.0 mm by grinding). ) Was obtained. In annealing, it heated to 690 degreeC and hold | maintained for 18 hours.

  The tempering heat treatment was performed under general conditions except that the solution temperature was 1000 ° C. or less so that the distribution state of the already adjusted hard carbide was not destroyed. Specifically, after heat treatment at 830 ° C. for 15 minutes, oil cooling was performed to 60 ° C. to obtain a tempered material having a tempered hardness of 50 to 53 HRC.

  Here, the steel plate before the tempering heat treatment was mirror-polished on a cross section (L cross section) parallel to the rolling direction and the plate thickness direction, and then etched with Murakami reagent (alkaline solution of red blood salt). Observed. Moreover, the image was processed, the number of Nb containing carbide | carbonized_material (hard carbide | carbonized_material) which exists in a visual field area was measured, and the existence density was computed.

For the hard carbide containing Nb, the number of particles having an observation area of 90 × 60 μm and a particle diameter of 0.5 μm or more existing in 20 fields was counted and converted to the number per 1 mm ² . Table 2 shows the measurement results of the number of Nb-containing carbides (pieces / mm ² ).

  The particle diameter is a value corresponding to the equivalent circle diameter of the particle area, and particles having a particle diameter of 0.5 μm or more were picked up by image processing.

  The wear test was performed with a pin-on-disk wear tester using a wear test piece with an oxide scale removed of φ5 mm.

  In the wear test, # 400 emery paper (silicon carbide) was used as the wear material, the test load was 20 N, the friction speed was 0.66 m / sec, and the friction distance was 300 mm.

Then, based on the plate thickness difference between the wear test pieces before and after the wear test, the volume of the material that disappeared due to wear was calculated and used as a wear loss W (mm ³ ).

Further, the specific wear amount calculated from the formula: specific wear amount (mm ³ / N · m) = wear loss W / (test load F × friction distance L) is 1.5 × 10 ⁻⁴ mm ³ / N · m or less. Were evaluated as having good wear resistance as a hand saw (pass). The results of this abrasion resistance test are shown in Table 2.

Toughness was evaluated by a Charpy impact test method (JIS Z 2242) for metal materials. The impact test piece was provided with an R U-notch having a plate thickness of 2.2 mm, a length in the width direction of 10 mm, a length in the longitudinal direction of 55 mm, a depth of 2 mm at the center in the longitudinal direction, and a tip of 1 mm. . FIG. 1 shows a schematic diagram of the shape of a test piece. And using such a test piece, a Charpy impact test was carried out, and those having an impact value of 30 J · cm ⁻² or more were evaluated as having good toughness (impact characteristics) as a hand saw (pass). . The results of this impact test are shown in Table 2.

As shown in Table 2, all of the present examples in which the number of hard carbides (Nb-containing carbides) having a particle diameter of 0.5 μm or more was adjusted to 3000 to 9000 pieces / mm ² within a predetermined component range, In addition to excellent wear, it had excellent toughness and high impact characteristics.

  No. which is a comparative example. 21, no. 22, no. Since Nos. 26 to 32 did not contain Nb, there was no Nb-containing carbide, and the wear resistance was extremely low.

No. which is a comparative example. In No. 23, since the Nb content was small, the number of Nb-containing carbides was less than 3000 / mm ² , and the wear resistance was insufficient.

  No. which is a comparative example. 24 and no. In No. 25, since the Nb content was excessive, the Nb-containing carbide remained excessively and the impact characteristics were remarkably low.

Claims (3)

C: 0.60 mass% or more and 1.25 mass% or less, Si: 0.50 mass% or less, Mn: 0.30 mass% or more and 1.20 mass% or less, P: 0.03 mass% or less, S: 0.03% by mass or less, Cr: 0.30% by mass or more and 1.50% by mass or less and Nb: 0.10% by mass or more and 0.50% by mass or less, with the balance being Fe and inevitable impurities,
A hand saw having a Nb-containing carbide having a particle size of 0.5 μm or more in a matrix at a density of 3000 / mm ² or more and 9000 / mm ² or less. Ti: 0% by mass (including no addition) to 0.50% by mass or less and B: 0% by mass (including no addition) to 0.005% by mass or less. The described hand saw. Mo: 0% by mass (including no addition) to 0.50% by mass or less, V: 0% by mass (including no addition) to 0.50% by mass or less, and Ni: 0% by mass (including no addition) .) The hand-drawn saw according to claim 1, comprising at least one of 2.0% by mass or less.

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