JPH08225886A - Steel sheet for metal slitting saw substrate excellent in weldability and its production - Google Patents

Abstract

PURPOSE: To produce a steel sheet suitable for producing a metal slitting saw substrate having high strength and toughness and moreover having good weldability and to provide a method for producing the same. CONSTITUTION: This steel sheet for a metal slitting saw substrate excellent in weldability is the one having a compsn. contg., by weight, 0.20 to 0.29S C, <=0.40%, preferably 0.05 to 0.40% Si, <=0.50%, preferably 0.10 to 0.50% Mn, 1.00 to 3.O0% Cr, 0.40 to 1.00% Mo, 0.20 to 0.40% V, <=0.010% P, <=0.006% S and 0.010 to 0.10% Al as acid soluble Al, furthermore contg. one or two kinds of 0.01 to 0.10% Ti and 0.01 to 0.20% Nb according to necessary, and the balance Fe with inevitable impurities and in which the average grain size of carbides before hardening and tempering is regulated to <=1μm. A hot rolled steel sheet with a bainitic structure having the same componental compsn. is produced, and this steel sheet with a bainitic structure is annealed, by which the average grain size of carbides can be regulated to <=1μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate for a metal saw substrate having high strength and toughness and good weldability, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Circular saws and band saws formed by joining chips (swords) such as cemented carbide and diamond to a metal plate for a blade (metal saw substrate) used in wet type and those used in dry type There is. The one used in the wet type may prevent excessive temperature rise during use, so the chip and the metal saw substrate may be joined by brazing, but the one used in the dry type may increase the chip temperature during use. There is a problem that the strength of the brazed joint decreases as the temperature rises and the chip easily falls off. For this reason, especially in a dry saw, the tip is joined to the base metal (metal saw substrate) by laser welding to increase the joining strength.

The material used as the metal saw substrate is SK5, SKS5, SKS when it is used in a wet type.
High carbon alloy tool steel such as 51 is used. On the other hand, in the case of being used in a dry type, as a material of the metal saw substrate, an alloy steel having a low or medium carbon content of about SCM430 is used to secure weldability. Then, these steel sheets are formed into a predetermined shape by press punching or laser cutting, and then subjected to heat treatment such as quenching and tempering to increase strength, and further subjected to polishing and straightening to manufacture a metal saw substrate. Chips such as cemented carbide and diamond are brazed to this metal saw substrate or joined by laser welding to obtain a product.

[0004]

Thus, the metal saw substrate used in the dry method is required to have weldability, but at the same time, high strength and toughness are required in order to obtain durability as the blade itself. Of course. However, in order to secure the toughness of the metal saw substrate, the above-mentioned tempering performed after the forming process is usually performed at 400 ° C. by avoiding a low temperature.
Processed at ~ 500 ° C. Therefore, in alloy steel with a low or medium carbon content such as SCM430, the hardness after refining is about HRC35, and the hardness of the brazing substrate (metal saw substrate used in wet) is HRC4 after refining.
Compared with about 3, the hardness of the metal saw substrate used in the dry method is low. Therefore, it has been desired to develop a steel plate for a metal saw substrate, which has a hardness of about HRC43 after heat treatment and is excellent in weldability that enables laser welding with a chip.

An object of the present invention is to provide a steel plate suitable for manufacturing a metal saw substrate having high strength and toughness and also having good weldability, and a manufacturing method thereof.

[0007]

According to the present invention, the weight percent is
C: 0.20 to 0.29%, Si: 0.40% or less, preferably 0.05 to 0.40%, Mn: 0.50% or less, preferably 0.10 to 0.50% , Cr: 1.00 to 3.00
%, Mo: 0.40 to 1.00%, V: 0.20 to 0.40
%, P: 0.010% or less, S: 0.006% or less, A
1: 0.01 to 0.10% as acid-soluble Al, and optionally Ti: 0.01 to 0.10% or Nb: 0.01 to 0.20
% Of 1 type or 2 type, the balance of which is Fe and unavoidable impurities, and the average grain size of carbide is 1 μm or less before quenching and tempering treatment, and a steel plate for metal saw substrate having excellent weldability is provided. It

Further, according to the present invention, a hot-rolled steel sheet having a bainite structure having the above-described composition is manufactured, and the steel sheet having a bainite structure is annealed to have an average carbide grain size of 1 μm.
Provided is a method for producing a steel plate for a metal saw substrate, which is excellent in weldability and is set to m or less.

[0009]

The steel sheet obtained according to the present invention has high strength and toughness by being formed into a predetermined shape by press punching or laser cutting, and is quenched and tempered. It will be possible to manufacture excellent metal saw substrates.

The meanings of the steel components, their contents, and the manufacturing conditions specified in the present invention will be individually described below together with their actions.

[Composition of Steel] C: A basic element that determines the strength and toughness of steel. In order to secure the strength required as a metal saw substrate material, C
The amount must be 0.20% or more. Although the strength of steel increases as the C content increases, on the other hand, if the C content exceeds 0.29%, the weld portion of the tip becomes brittle. Therefore, the amount of C is 0.
It was set to 20 to 0.29%.

Si: an element which is necessary and effective as a deoxidizing element for steel, enhances the hardenability, and acts effectively as a solid solution strengthening element for ferrite, but also causes the weldability to be impaired. Since it is an element, its upper limit was set to 0.40%. A preferable Si amount is 0.05 to 0.40%. The deoxidation of steel can be supplemented by other elements such as Mn and Al, but in this case Si may be added without addition.

Mn: an element which is necessary and effective as a deoxidizing element for steel and which enhances the hardenability of austenite,
It is also an element that forms Mn-based non-metallic inclusions and develops a striped structure to reduce toughness. Since Mn impedes weldability more than Si, its upper limit is 0.50.
%. The preferable amount of Mn is 0.10 to 0.50%. Note that deoxidation of steel can be supplemented with other elements such as Si and Al, but in this case, Mn may not be added.

Cr: Indispensable as an element for improving the hardenability, strength and toughness of steel and an element for suppressing the diffusion of C. In order to prevent decarburization on the substrate side of the welded portion between the metal saw substrate and the chip, and to maintain sufficient strength and toughness even with the same high temperature quenching and tempering heat treatment as the chip, Cr is used.
The amount should be 1.00% or more. But Cr 3.00
%, The effect of preventing decarburization of the welded part and the effect of increasing strength and toughness are both saturated, and the manufacturability of the intermediate product is markedly reduced, resulting in a sufficient weldability. Since it will not be obtained, the upper limit is 3.00
%.

Mo: C as an element for improving the hardenability, strength and toughness of steel and an element for suppressing the diffusion of C
It is essential like r. Also, in order to prevent decarburization on the substrate side at the welded part with the chip and to maintain sufficient strength and toughness even with the same high temperature quenching and tempering heat treatment as the chip, the Mo content must be 0.40% or more. is there. However, M
When the amount of o exceeds 1.00%, the effect of preventing decarburization of the substrate at the weld with the chip and the effect of increasing strength and toughness are both saturated, and the manufacturability of the intermediate product is significantly reduced. Further, sufficient weldability cannot be obtained, so the upper limit was made 1.00%.

V: Effectively acts as an element for improving the strength and toughness of steel by the action of making the austenite crystal grain size fine and as an element for suppressing the diffusion of C. In order to prevent decarburization of the substrate at the welded part with the chip and to secure sufficient strength and toughness even with the same high temperature quenching and tempering heat treatment as the chip, the V content must be 0.20% or more. . However, even if the V content exceeds 0.40%, the effect of preventing decarburization of the substrate material at the weld part with the chip and the effect of increasing strength and toughness are both saturated, and the manufacturability of the intermediate product is remarkably high. Since it deteriorates and sufficient weldability cannot be obtained, the upper limit was set to 0.40%.

P: The lower the amount of P is, the more preferable since it segregates at the crystal grain boundaries and reduces the toughness after quenching and tempering. Since the toughness required as a metal saw substrate material can be achieved by setting the P content to be 0.010% or less, its upper limit is 0.010.
%.

S: Mainly forms non-metallic inclusions consisting of MnS, which adversely affects the workability, strength and toughness of steel. In particular, in the rolled material, MnS expands in the rolling direction, so that the in-plane anisotropy of the workability, strength, and toughness of the steel largely appears. In order to prevent such an adverse effect of S,
Since the amount of S needs to be 0.006% or less, the upper limit was made 0.006%.

Al: An element necessary and effective as a deoxidizing element of steel, and is also effective as an element that combines with N in steel to form AlN and suppresses abnormal growth of austenite crystal grains during heat treatment. Since the action of Al is exhibited by containing 0.010% or more as acid-soluble Al, its lower limit was made 0.010%. The action of these Al is 0.10 as acid-soluble Al.
% Is sufficient, and addition of more Al not only unnecessarily increases the manufacturing cost but also increases Al.
It is not a good idea to increase surface defects due to
The upper limit was 0.10%.

Ti: Ti is contained as a selective component.
Ti forms a carbonitride that is difficult to form a solid solution during heat treatment, suppresses coarsening of crystal grains during quenching and heating, and has an effect of preventing deterioration of toughness. To obtain this effect, Ti is 0.0
It is necessary to contain 1% or more. But 0.1
If Ti is contained in excess of 0%, coarse nitrides are formed and the toughness is deteriorated, so the upper limit was made 0.10%.

Nb: Nb is also contained as a selective component like Ti. Nb forms stable carbonitrides, and V,
Similar to Ti, it has an effective effect of suppressing coarsening of crystal grains during quenching and heating and preventing deterioration of toughness. In order to obtain such an effect, it is necessary to contain 0.01% or more of Nb. However, if Nb is contained in an amount exceeding 0.20%, the solid solution of carbide in the matrix is reduced and the strength is lowered, so the upper limit was made 0.20%.

[Manufacturing Conditions] When manufacturing a metal saw substrate of special steel having the above composition, in the present invention, the steel is melted in a converter or an electric furnace, and then the composition is adjusted through a vacuum degassing device. A continuous cast slab is made by continuous steel casting equipment, and this slab is hot-rolled to produce hot rolled steel sheet with bainite structure. Then, this hot-rolled steel sheet having a bainite structure is annealed, and if necessary, cold rolling and annealing are repeatedly performed to obtain a steel sheet having a desired sheet thickness. According to the present invention, by using bainite as the structure of the hot-rolled steel sheet having the above-mentioned composition, the decomposition and spheroidization of the carbides progress finely and uniformly during subsequent annealing, and the carbides in the steel sheet after annealing Can have an average particle size of 1 μm or less.

If the average grain size of the carbide in the steel sheet exceeds 1 μm, the solid solution of the carbide will be insufficient during heat treatment such as quenching and tempering, and the strength of the matrix will not be uniform, and the shape of the metal saw substrate may be deteriorated. . This deterioration of the shape makes the work of polishing and straightening the metal saw substrate difficult and also deteriorates the material properties of the product. On the other hand, if the distribution of the carbide in the steel plate is fine and uniform so that the average grain size is 1 μm or less, the properties of the punched surface during punching of the steel plate are excellent, the wear of the tool is reduced, and the tool life is extended. There are advantages such as. According to the present invention, a hot-rolled steel sheet having a bainite structure is annealed so that the average grain size of carbides in the steel sheet is 1 μm or less, so that the punchability is excellent as described above, and shape deterioration does not occur after quenching and tempering treatment. It becomes possible to obtain a steel plate.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples. Steel with the components and compositions shown in Table 1 was melted in a converter and continuously cast into slabs.

[0025]

[Table 1]

This slab was hot-rolled by a normal hot strip mill and then wound in the range of 500 to 600 ° C. to produce a hot rolled steel sheet having a plate thickness of 3.2 mm. The obtained hot-rolled steel sheet was pickled, then spheroidized in the range of 670 to 720 ° C,
A quenching and tempering process was added. Table 2 summarizes the quenching temperature and tempering temperature, the hardness of the steel sheet after quenching and tempering, the impact value, the former austenite grain size number, and the carbon equivalent (C _eq ).

[0027]

[Table 2]

Steel C, which is a comparative steel having a chemical composition outside the scope of the present invention, has a low carbon content and a good weldability because of its low C content, but has a low hardness after quenching and tempering and is required as a metal saw substrate. The strength is not obtained. Also,
Steel D, which is a comparative steel, has high strength because it has a high C content, but has low toughness and also has a high carbon equivalent and poor weldability. Further, E steel, which is a comparative steel, has a high content of carbide forming elements such as Cr, Mo, and V, so that hardness and toughness are secured, but no significant improvement in properties is recognized as compared with the steel of the present invention. Excessive addition of these elements not only impairs manufacturability but also is economically disadvantageous. In addition, Si, Mn
Since the content of such as is high, the carbon equivalent becomes high and welding is not possible. Similarly, the comparative steel F steel has a low hardness after quenching and tempering because it contains a small amount of carbide forming elements such as Cr, Mo and V.

On the other hand, steels A and B, which are examples of the present invention,
Both steel and G steel ensure the strength, toughness, and weldability required as a metal saw substrate after quenching and tempering. Since B steel and G steel contain a small amount of Ti and Nb, the former austenite grain size becomes finer and the toughness tends to be improved.

Table 3 shows the metallographic structure of the hot rolled steel sheet and the average carbide grain size after annealing.

[0031]

[Table 3]

The metallographic structure of the hot-rolled steel sheet of F steel, which is a comparative steel having a chemical composition outside the scope of the present invention, contains ferrite and pearlite in addition to bainite. The average carbide grain size after annealing is over 1 μm. On the other hand, the steel of the present invention has a bainite structure in hot rolling, and the average carbide grain size after annealing is 1 μm or less. The steel of the present invention is excellent in the properties of the punched surface when punching a steel plate, lessens the wear of the tool, and can prolong the tool life. Further, the steel of the present invention can suppress the occurrence of problems such as uneven strength and defective shape during quenching and tempering. Therefore, it is understood that the present invention can provide a steel plate for a metal saw substrate having strength, toughness, and weldability.

[0033]

As described above, according to the present invention, a metal saw substrate having both high strength and toughness and excellent weldability can be manufactured.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C22C 38/28 C22C 38/28

Claims (3)

[Claims] 1. By weight%, C: 0.20 to 0.29%, Si: 0.40% or less, preferably 0.05 to 0.40%, Mn: 0.50% or less, preferably 0. .10 to 0.50%, Cr: 1.00 to 3.00
%, Mo: 0.40 to 1.00%, V: 0.20 to 0.40
%, P: 0.010% or less, S: 0.006% or less, A
1: 0.01 to 0.10% as acid-soluble Al, balance F
A steel plate for a metal saw substrate, which comprises e and unavoidable impurities and has an average grain size of carbides of 1 μm or less before quenching and tempering treatment and which has excellent weldability. 2. In weight%, C: 0.20 to 0.29%, Si: 0.40% or less, preferably 0.05 to 0.40%, Mn: 0.50% or less, preferably 0. .10 to 0.50%, Cr: 1.00 to 3.00
%, Mo: 0.40 to 1.00%, V: 0.20 to 0.40
%, P: 0.010% or less, S: 0.006% or less, A
1: 0.01 to 0.10% as acid-soluble Al, Ti:
0.01 to 0.10% or Nb: 0.01 to 0.20% of 1
A steel plate for a metal saw substrate, which is excellent in weldability, in which the average grain size of carbides is 1 μm or less before quenching and tempering treatment, which is composed of two or more kinds, the balance being Fe and unavoidable impurities. 3. In% by weight, C: 0.20 to 0.29%, Si: 0.40% or less, preferably 0.05 to 0.40%, Mn: 0.50% or less, preferably 0. .10 to 0.50%, Cr: 1.00 to 3.00
%, Mo: 0.40 to 1.00%, V: 0.20 to 0.40
%, P: 0.010% or less, S: 0.006% or less, A
l: 0.010 to 0.10% as acid-soluble Al, and optionally Ti: 0.01 to 0.10%
Or Nb: 0.01 to 0.20% of one or two kinds, and the balance is Fe and unavoidable impurities to produce a hot-rolled steel sheet having a bainite structure, which is annealed to obtain a carbide. A method for producing a steel plate for a metal saw substrate, which has an average grain size of 1 μm or less and is excellent in weldability.