JPH059654A - Wear and shock resistant tool steel having excellent grindability - Google Patents

Abstract

PURPOSE:To produce wear and shock resistant tool steel having excellent grindability and fit to produce a veneer lacing knife used for cutting a veneer board from material wood. CONSTITUTION:This wear and shock resistant tool steel having excellent grindability consists of by weight, 0.60-0.70% C, 0.8-1.7% Si, 0.4-1.0% Mn, 0.3-1.0% Cr, 0.4-1.0% Mo, 0.6-1.2% W, 0.1-0.5% V, 0.05-0.3% Nb and the balance of Fe with inevitable impurities or further contains 1.0-3.0% Co, has hardness and toughness necessary for a veneer lacing knife and can reduce the rate of occurrence of grinding cracks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant and impact-resistant tool steel suitable for a veneer knife used for producing veneer boards from wood in the woodworking industry and having excellent grindability.

[0002]

2. Description of the Related Art A veneer knife is composed of a blade and a base metal, and after forging and welding each material, it is processed by heat treatment and then processed into a lathe mounting portion and a blade portion to be a product. Also, when a veneer plate is processed using a veneer knife, when the blade edge wears to a certain extent, regrinding is performed, thereby restoring the initial blade edge shape and then reusing. Typical examples of the material of the conventional blade portion include alloy tool steel for cutting tools and alloy tool steel for impact resistance shown in JIS, and alloys disclosed in Japanese Patent Publication No. 54-4322.

[0003]

Generally, a veneer knife has a sharp cutting edge, but when cutting due to factors such as hardness and softness of raw wood, knots, gravel intervening during logging and transportation, and unstable external shape of wood. Strong impact, machined plywood and blades
The blade is pressed by the blade. Therefore, the blade material quality is
The sharpness is of course required, but it must have excellent cutting durability. In addition, grindability must be good for re-polishing after use. In order to meet these conditions, the blade must have the necessary hardness, wear resistance, and toughness, as well as the property that grinding cracks do not easily occur. For example, the alloying tool steel for cutting specified in JIS G4404 is effective in that it can form a sharp cutting edge and obtain high hardness, but its toughness is low, so if the blade part receives a strong impact, There was a drawback that it caused chipping. Also JI
When the impact resistant alloy tool steel specified in S G4404 is used, the ultimate hardness after machining heat treatment such as osforming and forging quenching is low, so that the problem of blade bending and early wear during use I got it. In addition, Japanese Examined Japanese Patent Publication No. 54-4322
Although the alloy disclosed in US Pat. No. 5,968,961 has been found to be suitable for thermomechanical treatment and to improve the cutting edge strength, it suffers from the drawback that grinding cracks often occur depending on the re-grinding conditions of the cutting edge.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to solve the drawbacks found in conventional steels and to provide a wear and impact resistant tool steel excellent in grindability suitable as a veneer knife. . The inventors of the present invention have found that the matrix strength of the blade material, that is, reduction of retained austenite after heat treatment, martensite roughness and It was judged that the refinement of the grain size and the appropriate amount of fine carbide distribution were effective. As a means, Si, Cr,
After Mo, W, V, Co, etc. were added and forged and quenched, the total amount was dissolved into the matrix and the composition balance was obtained by adding Nb to distribute hard fine carbides.
In particular, W, Mo, Cr, and V have a strong tendency to form carbides, and the residue thereof has a negative effect on the fine chipping of the cutting edge and the grindability, so the component balance as a suppressing means is an important point of the present invention.

That is, the steel of the present invention is
C: 0.60 to 0.75%, Si: 0.8 to 1.7%,
Mn: 0.4 to 1.0%, Cr: 0.3 to 1.0%, M
o: 0.4 to 1.0%, W: 0.6 to 1.2%, V:
0.1 to 0.5%, Nb: 0.05 to 0.3%, balance iron and unavoidable impurities, and Co: 1.
It is a wear-resistant and impact-resistant tool steel with excellent grindability containing 0 to 3.0%.

Next, the reasons for limiting the components of the present invention will be described. C: C is a matrix-strengthening element, which forms a solid solution in the matrix in the austenite region above the Ac1 transformation point, and increases the hardness by the martensite transformation after quenching and tempering to improve the cutting durability of the veneer lace knife. Increase. Further, some of them form carbides with Nb to improve wear resistance. If it is less than 0.60%, the required hardness cannot be obtained and the blade bends, causing wear. If the content is 0.75% or more, the forgeability and impact resistance are lowered, the retained austenite after quenching and tempering is increased, and the blade chipping and the grindability are deteriorated. Therefore, the range is set to 0.60 to 0.75%. To do.

Si: Si acts as a deoxidizer on steelmaking. At the same time, it forms a solid solution in the matrix to increase the resistance to temper softening and improve the yield ratio of steel. If 0.8% or less, the effect is not obtained, and if it is 1.7% or more, the hot workability is impaired, so the range is set to 0.8 to 1.7%.

Mn: Mn acts as a deoxidizing agent on steelmaking like Si and improves the hardenability of steel. 0.4%
The effect is not obtained below, and the residual amount is 1.0% or more.
The range is 0.4-1.0 because it increases the austenite
%.

Cr: Cr enhances hardenability and
Improves the yield strength of steel by forming a solid solution in stenite. If it is less than 0.3%, the effect cannot be expected.
The range is 0.3 to 1.0% because the remaining blade bend and grindability are affected even if a part of carbide is added to the amount of stenite.
And

Mo: Mo improves not only hardenability but also tempering softening resistance and stress level against heat distortion during grinding. It also has the effect of widening the quenching temperature range and preventing the coarsening of crystal grains. If it is less than 0.4%, there is no effect, and if it is more than 1.0%, no remarkable improvement is seen.
The range is 0.4 to 1.0%.

W: W improves the edge strength by refining the martensitic structure and increasing the resistance to temper softening. If it is less than 0.6%, there is no effect, and if it is more than 1.2%, a large amount of undissolved WC carbide is distributed, which has a negative effect on the improvement of grindability which is one of the objects of the present invention.
The range is limited to 0.6 to 1.2%.

V: V has the effect of adjusting the crystal grains and suppressing the growth, and imparts impact resistance. It also improves wear resistance.
V of the present invention is added in order to form a solid solution in austenite to adjust the structure of the steel, and if a large amount of V is added, stable (V, W) C is likely to be formed, and its residual tendency is increased. This reduces the strength and grindability by absorbing C in the matrix, so the range is limited to 0.1 to 0.5%.

Nb: Nb contributes to wear resistance by forming stable NbC. Further, by the action of suppressing the production of (V, W) C, C in austenite is fixed and cutting durability is increased. If the Nb content is 0.05% or less, no wear resistance effect is observed, and if the NbC content is 0.3% or more, coarsening of NbC is caused, and chipping of the cutting edge and grindability are impaired.
Limited to ~ 0.3%.

Co: Co is added as required in the steel of the present invention. All of Co is solid-solved in the matrix and raises the transformation point of the steel to increase the softening resistance against the thermal strain generated during grinding. As a result, the deterioration of the structure of the veneer knife is prevented and the grindability is improved. C to austenite
It has an action of promoting solid solution of r, Mo, W, V, etc., and is effective in strengthening the matrix. If it is 1% or less, the effect is small, and if it is 3% or more, the toughness of the steel is impaired and the economical efficiency is also impaired. Therefore, the range is limited to 1.0 to 3.0%.

[0015]

EXAMPLES Table 1 shows the chemical composition of the steel of the present invention and a comparative steel, which are made into a flat steel of 25 × 110 × 720 mm by smelting a steel ingot of 400 kg in a high frequency furnace, forging and rolling. Table 2 shows the hardness, mechanical properties, and grindability of the sample steel and base metal after forged and welded to a workability of 70%, then allowed to cool to the prescribed quenching temperature and then quenched and tempered. The results of comparison are shown. The transverse rupture strength was obtained by taking a 5 × 10 × 80 mm test piece from the forged and quenched product and performing a 3-point bending test. Impact value is 5 × 10
A 55 mm non-grooved test piece was sampled and determined by a Charpy impact test. Rotor SCM43 using Ogoshi type abrasion tester
5, friction distance 400m, friction speed 0.94m / sec,
The specific wear amount when the test was performed under the condition of a load of 6.3 Kg was shown. Test piece 6 x 40 x 60 mm using a surface grinder
Was set in a rotary table, and was ground for 10 minutes with a WA grindstone having a grain size of 60 and a bond degree of J with a cutting depth of 2/100 mm. Then, the presence or absence of abrasive cracks on the surface was observed with a microscope of 50 times. The test was repeated and the occurrence rate was used to express the evaluation of grindability.

[0016]

[Table 1]

[0017]

[Table 2]

According to the steel of the present invention, a hardness of HRC 60 or more required for a veneer knife is obtained, and both wear resistance and toughness are high. The grindability was also superior to that of the comparative steel in the evaluation of grindability, and was the most balanced in the comprehensive evaluation. Table 3 shows the No. of the steel of the present invention. 1 and comparison steel N
o. 4 shows a veneer lace knife manufactured from No. 4 and cutting was performed for 2 hours using this veneer lace knife, and the cutting edge wear amount after cutting out a veneer plate from wood is shown. In determining the amount of wear of the cutting edge, as shown in FIG. 1, the cutting edge is determined by the width a and the thickness b of the cutting edge wear area W of the cutting edge portion T surrounded by the tip of the cutting edge 1 and the cutting edge 2 after 2 hours from the start of cutting. The amount of wear was determined. According to Table 3, the wear amount of the cutting edge of the steel of the present invention is about 1/2 or less as compared with the comparative steel, which is extremely small, and the cutting durability life is greatly improved.

[0019]

[Table 3]

[0020]

As described above, the tool steel according to the present invention has a weight ratio of C: 0.60 to 0.75%, S
i: 0.8 to 1.7%, Mn: 0.4 to 1.0%, C
r: 0.3 to 1.0%, Mo: 0.4 to 1.0%, W:
0.6-1.2%, V: 0.1-0.5%, Nb: 0.
05-0.3%, balance iron and unavoidable impurities, and Co: 1.0-3.0%, if necessary, so that a hardness of HRC 60 or more required for a veneer knife can be obtained. Was given. Further, the amount of wear of the cutting edge is extremely small, the cutting durability life is greatly improved, and the toughness is also very good. In addition, the rate of occurrence of grinding cracks can be suppressed to a low level, resulting in excellent grindability. Therefore, regardless of whether the wood is soft or soft,
In addition to improving the cutting performance of the knife,
It can be applied to other woodworking tools, cutlery, etc. and has many excellent effects.

[Brief description of drawings]

FIG. 1 is a sectional view of a blade edge showing a blade edge wear amount measuring position of a veneer knife.

Claims (2)

[Claims] 1. A weight ratio of C: 0.60 to 0.
75%, Si: 0.8 to 1.7%, Mn: 0.4 to 1.
0%, Cr: 0.3 to 1.0%, Mo: 0.4 to 1.
0%, W: 0.6 to 1.2%, V: 0.1 to 0.5%,
Nb: 0.05 to 0.3%, wear-resistant and impact-resistant tool steel excellent in grindability and composed of balance iron and unavoidable impurities. 2. A weight ratio of C: 0.60 to 0.
75%, Si: 0.8 to 1.7%, Mn: 0.4 to 1.
0%, Cr: 0.3 to 1.0%, Mo: 0.4 to 1.
0%, W: 0.6 to 1.2%, V: 0.1 to 0.5%,
Nb: 0.05 to 0.3%, Co: 1.0 to 3.0%,
Abrasion and shock resistant tool steel with excellent grindability, consisting of balance iron and inevitable impurities.