JPH0349976B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a clad steel plate for a high-speed rotating blade used for mowing grass, woodworking, etc., that is, a circular saw, and provides a three-layer clad steel plate that has particularly excellent toughness, good cutting ability, and good abrasion resistance. It is. Generally, high carbon steel containing 0.5% by weight or more of C is used for cutlery, and this is usually quenched to obtain a predetermined hardness and ensure sharpness. However, if the material is hardened, it is extremely brittle and is prone to chipping and cracking, making it impractical. For this reason, the actual situation is that tempering treatment is performed after quenching, even though the hardness decreases to some extent and the sharpness decreases. In particular, with circular saws for mowing grass and circular saws for woodworking that require high-speed rotation, if the blade spills or breaks during cutting, it poses a great danger to the operator, so the purpose is to improve the toughness after quenching and tempering. However, even with such materials, it is difficult to achieve both sharpness (hardness) and toughness, so it is difficult to satisfy such requirements. There was a strong demand for the development of a new rotary blade material that could be used. Therefore, in recent years, clad steel plates have been used as rotary blade materials, with low carbon steel (hereinafter referred to as core material) with a content of 0.15% or less placed in the center of the plate thickness, and high carbon steel (hereinafter referred to as coating materials) placed on the front and back surfaces. It has attracted attention and has been put into practical use in some cases. In this clad steel plate, high toughness is ensured by the low carbon steel core material, so compared to conventional circular sawn material made of a single high carbon steel material, less tempering is required, which increases the Since the hardness of the high carbon steel part is ensured, the cutting quality is also excellent, and therefore toughness and cutting quality can be satisfied at the same time. However, the rotary blade made of a clad steel plate as described above has the disadvantage that it is more easily worn than a rotary blade made of a single material having the same hardness. This invention was made in view of the above circumstances, and aims to provide a clad steel plate for circular saws that improves the conventional clad steel plate for circular saws and has not only sharpness and toughness but also wear resistance. This is the purpose. In order to achieve the above-mentioned object, the present inventors first observed the state of wear of the cutting edge of a rotary blade made of a conventional material after long-term use, and found the following fact. In other words, in the case of a conventional rotary blade made of a single material, the entire cutting edge 1 gradually wears out as shown in Fig. 1A, whereas in the case of a rotary blade made of a clad steel plate, As shown in Figure 1B, the core material 2 made of low carbon steel wears out preferentially.
It has been found that the coating material 3 made of high carbon steel wears out accordingly. As a result, the core material selectively wears rapidly at the cutting edge of the cladding material, and as a result, the relative pressure on the dressing material increases, and as a result, the wear of the dressing material rapidly follows the wear of the core material. Therefore, it is thought that the overall wear rate of the cladding material cutting edge is faster than the wear rate of the single material cutting edge. Therefore, in order to reduce the wear on the cutting edge of the cladding material, it is necessary to suppress the wear on the core material, and for this purpose it is necessary to increase the hardness of the core material. However, if the hardness of the core material becomes too high, the toughness will deteriorate and the properties as a clad steel will be lost. Therefore, as a result of further experiments and studies regarding the material of the core material, the inventor decided to make the material of the core material a medium carbon steel with a specific C content range, and to combine the core material with high carbon steel or high carbon steel. It has been discovered that a clad steel plate for circular saws that has both sharpness, toughness, and wear resistance can be obtained by adjusting the ratio of the cladding material made of alloy steel to the coating material within an appropriate range, and has accomplished this invention. I've reached it. That is, the clad steel plate for circular saws of this invention has C
High carbon steel or C containing 0.50% or more (weight %; all components below are weight %)
The coating material is high carbon alloy steel containing 0.50% or more and one or more of Ni 2.5% or less, Cr 0.70% or less, and Mo 0.30% or less, and the coating material is arranged on the front and back surfaces of the core material. In the clad steel plate for circular saws, the core material is medium carbon steel containing 0.20 to 0.30% C,
Moreover, the core material thickness is 30 to 70% of the total thickness of the steel plate. The clad steel plate for circular saws of the present invention will be explained in more detail below. The coating material for the clad steel sheet of this invention is high carbon steel containing 0.50% or more of C, or a high carbon steel containing 0.50% or more of C and 2.5% or less of Ni.
High carbon low alloy steel containing one or more of 0.70% or less Cr and 0.30% or less Mo is used. The reason why the clothing material was made of a high carbon material with C0.50% or more is because C is
If it is less than 0.50%, the hardness due to quenching and tempering will be low;
This is because it lacks sharpness, making it unsuitable as a knife. In addition, Ni, Cr, and Co are sometimes added to improve the hardenability and wear resistance of the coating material itself, and to impart toughness after tempering, but clad steel originally has good toughness added to it by the core material. Even if it is added in a large amount, it will only increase the manufacturing cost and no significant improvement in toughness can be expected.
Ni was limited to 2.5% or less, Cr 0.70% or less, and Mo 0.30% or less. On the other hand, medium carbon steel with a C content in the range of 0.2 to 0.3% is used as the core material. By setting the C content within such a range, a core material having both wear resistance and toughness can be obtained. That is, as shown in FIG. 3 of the example described later, the C content is 0.2%.
If the C content is less than 0.3%, the amount of wear will increase significantly, while if the C content exceeds 0.3%, the toughness will decrease rapidly.
To achieve both wear resistance and toughness, C0.2~
It must be within the range of 0.3%. Further, in the clad steel sheet of the present invention, the ratio of the core material thickness to the total thickness must be 30 to 70%. In other words, the thickness of each coating material placed on the front and back surfaces of the core material in the center (thickness of the coating material on one side) needs to be 15 to 35% of the total thickness of the steel plate. The reason for this decision is as follows. In other words, the thinner the coating material, the easier the cutting process, but if the coating material is thinner, the core material ratio will inevitably increase, making it easier to wear out.
Additionally, the blade itself becomes weak and may bend during operation. On the other hand, if the coating material is too thick, the core material ratio will be small, the toughness will deteriorate and it will be easy to break. According to the experiments conducted by the present inventors, as shown in FIG. 4 of Examples described later, if the core material ratio exceeds 70%, the amount of wear increases, while if the core material ratio becomes less than 30%, the toughness decreases. It was found that there was a sharp decline. Therefore, in order to have both wear resistance and toughness, the core material ratio must be within the range of 30 to 70%. When actually applying the clad steel plate of this invention to a circular saw, it goes without saying that it must be quenched and tempered, and by applying the specified quenching and tempering, it can achieve the desired sharpness (hardness), toughness, and durability. Abrasion resistance can be ensured. Examples of the present invention will be described below along with comparative examples. SK4 steel type as coating material, specifically C0.95%,
Using high carbon steel of 0.21% Si, 0.42% Mn, 0.018% P, and 0.007% S, the core material composition and cladding ratio were varied to create three layers shown in sample symbols A to K in Table 1. A clad steel plate was created. Each clad steel plate was quenched and tempered to create a rotary blade with a coating hardness of Hv580 to 680, and each rotary blade was examined for its impact characteristics at 20°C, and a wear resistance test was conducted in which the cutting edge came into contact with sand. The wear of the cutting edge was investigated when the machine was rotated at 2000 rpm for 50 hours. However, as shown in FIG.
The amount of wear p was investigated.

[Table] Among these measurement results, the core material ratio is 33 to 39%.
FIG. 3 shows the relationship between the C content of the core material, the impact value, and the amount of wear for samples A to G, which have approximately constant values. From Figure 3, the C content of the core material is 0.2
It is clear that excellent wear resistance and good impact properties are obtained within the range of ~0.3%. Also, among the above measurement results, the C content of the core material
FIG. 4 shows the relationship between the core material ratio, impact value, and amount of wear for samples E, H to K containing 0.25%. From FIG. 4, it is clear that good wear resistance and excellent impact properties are obtained when the core material ratio is 30 to 70%. As described above, according to the clad steel plate of the present invention, sharpness is ensured by using high carbon steel or high carbon alloy steel, and at the same time, the core material is made of medium carbon steel with C0.2 to 0.3% and the core material ratio is By setting the content to 30 to 70%, it is possible to obtain good toughness and excellent wear resistance at the same time, making it ideal for circular saws with high-speed rotating blades for woodworking or grass cutting. .

[Brief explanation of drawings]

Figures 1A and B are cross-sectional views showing the state of wear on the cutting edge of high-speed rotating blades made of conventional materials, Figure 2 is a front view of the high-speed rotating blade to show the definition of the amount of wear on the cutting edge, and Figure 3 is a three-layer A correlation diagram showing the relationship between the C content of the core material of a high-speed rotating blade using a clad steel plate, impact value, and amount of wear. Figure 4 shows the relationship between the core material ratio, impact value, and amount of wear of the same high-speed rotating blade as above. FIG. 2... Core material, 3... Clothing material, p... Cutting edge wear amount.

Claims (1)

[Scope of Claims] 1. High carbon steel containing 0.50% by weight or more of C or 0.50% by weight or more of C and 2.5% by weight or less of Ni, 0.70% by weight or less of Cr, and A clad steel plate for a circular saw on which a coating material made of high carbon alloy steel containing one or more selected from 0.30% by weight or less of Mo is arranged, wherein the core material contains 0.20 to 0.30% by weight of C. It is considered to be a medium carbon steel, and the core material thickness is 30 to 70 of the total thickness of the steel plate.
A clad steel plate for a circular saw, characterized by being within the range of %.