JPH0418974B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a shearing blade for hot steel pieces such as continuous casting slabs and blooming slabs, and more particularly to a shearing blade that can withstand cutting of a large amount of hot steel pieces. [Prior Art] Various types of cutting devices have been proposed for cutting hot steel slabs such as continuous casting slabs and blooming slabs. Most of these cut the steel pieces by applying shearing force to them using upper and lower blades. The upper and lower blades used for this cutting have the structure shown in FIG. 2a, for example. In Fig. 2a, the reference numeral 1 indicates a fixed upper blade, and the reference numeral 2 indicates a lower blade that can be raised and lowered, and the two are designed so that they can pass each other in order to apply shearing force to the material 3 to be cut. arranged in parallel.
When the material to be cut 3 is cut using the upper and lower cutters, the cut surface has a sloping shape 4 as shown in FIG. 2b.
A sheared surface 5, a fractured surface 6, and a burr 8 are generated. When the material to be cut 3, which is a hot steel piece, is repeatedly cut using such shearing tools 1 and 2, the cutter may be worn out or damaged, resulting in cuts caused by segregation in the center of the steel material on the fracture surface. The burrs 7 and burrs 8 increase and cause surface flaws in the next steel plate rolling process, so they must be cut and removed after the steel plate is rolled, leading to a significant reduction in steel plate yield. Several documents have been published regarding conventional shearing knife techniques to prevent this. For example, as shown in ``Recent Advances in Blooming Technology in Japan'', published by the Iron and Steel Institute of Japan, August 1, 1961, pp. 152-161, forged steel is usually used to harden the cutting edge.
It is often used by welding with Cr-Mn steel welding material with a hardness of 25 to 35Hs, and sometimes alloy tool steel with a hardness of 45Hs or more is used. Also, as a build-up method, under-filling is used to prevent the weld metal from cracking and to increase the amount of build-up at low cost.
The replacement cycle of shearing blades for hot-cutting machines for steel slabs, the so-called shearing blade casting life, is normally between 20,000 tons and 80,000 tons of steel slabs to be cut, and at most 120,000 tons. It was hot. [Problems to be solved by the invention] However, in a continuous casting process or a direct connection process aiming at energy saving in which a blooming process and a hot rolling process are directly connected, cutting capacity that matches the capacity of the preceding and succeeding processes cannot be adjusted. is necessary. Furthermore, since hot steel pieces are handled in the direct coupling process, it is difficult to remove the cutting burrs and burrs generated on the cut surface while hot, and it is necessary to replace the shearing blades more frequently. On the other hand, the shearing blades presented in the document ``Recent Advances in Blooming Technology in Japan'', published by the Iron and Steel Institute of Japan, August 1, 1960, have excessive or insufficient Hs hardness, and are not suitable for replacement intervals. maximum
The capacity is approximately 120,000 tons, and the replacement cycle is short under the direct-coupling process, which is a major impediment to production, and there was a strong desire to extend the replacement cycle of the shearing blade. An object of the present invention is to provide a shearing blade for a hot cutting machine for steel billets, which solves the above-mentioned problems. [Means for Solving the Problems] In order to achieve the purpose of the shearing blade for hot cutting steel billets of the present invention, a pair of rectangular shear blades whose cutting edges are offset above and below the billet and opposed to each other are used to cut the billet. In a steel billet hot cutting machine that applies shearing force to the steel billet and cuts it by passing the steel billet from a direction perpendicular to the steel billet, the cutting edge of the rectangular shearing blade is square in cross section and has a heat resistant hardness of 36 to 44 HS mechanical properties.・Made of wear-resistant steel, an intermediate reinforcing layer is formed on the two sides of the shearing blade base material side of this cutting edge section via a heat/shock buffer layer with a hardness of 25HS or less, and the shearing blade base material side of this intermediate reinforcing layer is This shearing blade for a steel billet hot cutting machine is characterized in that it has a stepped slope and a shearing blade base material is formed on the slope side with a heat/shock buffer layer having a hardness of 25HS or less interposed therebetween. In other words, with this configuration, the blade edge portion 1
The shear reaction force and thermal stress received on the upper surface (lower blade) or lower surface (upper blade) of 4, the plastic flow and thermal stress received on the passing surfaces, and the bending moment generated from these are transferred to the heat/shock buffer layer 15 and the intermediate layer. The reinforcing layer 16 and the heat/shock buffer layer 17 on its stepped slope gradually reduce the heat and impact and propagate it to the shearing blade base material 18 to prevent cracking of the cutting edge portion 14 and the shearing blade base material 18 due to bending moment, This also prevents the progression of peeling between the cutting edge portion 14, each of the cushioning material layers 15 and 17, and the intermediate reinforcing layer 16. [Function] The inventors of the present invention have investigated the effects of various materials for shearing blades and overlay methods on the casting life of shearing blades, and have obtained the following knowledge. For example, as shown in the lower blade of Fig. 3a, the cutting edge of the shearing blade produces a sag 9 and a burr 10 due to the plastic flow stress σ _p caused by the sliding contact phenomenon between the cutting edge of the shearing blade and the material to be cut during cutting. , the burr 10 is worn away by the cutting action with the material to be cut.
As this cutting phenomenon process is repeated, the cutting edge portion wears out. If a material having mechanical properties with a hardness of 45Hs or more is used for the cutting edge of the shearing blade, the wear of the burrs 10 will not progress due to the high hardness, and the burrs of the upper and lower blades will interfere during shearing, resulting in damage to the cutting edge. In addition, it has been found that when the hardness is less than 35Hs, the amount of sagging and wear of the burrs progresses rapidly, shortening the life of the shearing blade. Further, as shown in the lower blade of Fig. 3b, the stress generated in the shearing blade during cutting is caused by the shearing bending moment M, which generates a tensile stress _σt inside the shearing blade, and the crack 11 Occurs in the longitudinal direction. It was found that this crack 11 was further enlarged by the tensile stress, and seizure, etc. occurred from this position, which progressed to damage of the shearing blade. Therefore, it has been found that if this crack 11 is suppressed, even if the bending moment increases, it will not progress to the point of shearing blade breakage. On the other hand, in the conventional build-up method, since both the shear blade base material 13 and the blade edge build-up layer 12 have high yield strength, shear stress and thermal stress are not alleviated, and At the same time, the shear blade is work hardened, the yield strength increases, and the elongation decreases, which are the main factors, resulting in peeling from the fused portion of the shear blade base material 13 and the blade edge build-up layer 12, which have the weakest strength. Therefore, if a material with a hardness of 25Hs or less and low yield strength is used as a heat/shock buffer, and a heat-resistant and wear-resistant steel with a hardness of 25 to 35Hs is used as an intermediate reinforcing material, crack resistance can be further increased and the shear life can be significantly extended. I found out that. [Example] Next, an example of the present invention will be described. The cutting conditions are as shown in Table 1, and the continuous casting slab is 280×
Roll from 1800 mm to a finished rolling size of (120-275) x (750-1750) mm using a large-width reduction rolling mill, and after rolling, use a cutting device to remove irregularly shaped parts at the front and rear ends of the rolled material and the next process, hot steel plate rolling. I cut it to the required length.

[Table] The steel type used for the base material 18 of shearing blades has high tensile strength and yield strength, as well as counter-sinking strength, and is ductile to prevent breakage and cracking, and the cutting edge is overlaid. It must also have good weldability, and nickel chrome steel (SNC), nickel chrome molybdenum steel (SNCM), chrome molybdenum steel (SCM), carbon steel (S30C to S45C), etc. are suitable, but the inventors et al. used SNCM due to the risk of shear blade breakage and cracking as a result of long-term use. Figure 1 shows the configuration of a shearing blade for a hot billet cutting machine. Comparative Examples 1 and 2, which show comparative examples of shearing blade materials in Table 2, use 16Cr-16Mn alloy steel (CRM) with heat resistance and wear resistance and a hardness of 25 to 35 Hs as the cutting edge member 14. 4 has a hardness that is approximately the same as the heat-resistant and wear-resistant 20Ni-20Cr-20Co alloy steel (NCC) used in the present invention, but has mechanical properties such as yield point, tensile stress, and elongation. 30Mn-60Co alloy steel (STL) with 45Hs or more
20Ni-20Cr- with a hardness of 36 to 44Hs was used in Examples 1 to 6, which show examples of shearing cutter materials in Table 3.
20Co alloy steel (NCC) was used. Furthermore, 12Ni-25Cr stainless steel (NCF), which is one of the austenitic stainless steels with a hardness of 25Hs or less and a low yield strength, was used as a thermal/shock buffering material 15 and 17 to prevent cracks and peeling. Comparative example 4, implementation

【table】

【table】

[Table] - Numbers in the part column indicate the symbols in Figure 1.
In Examples 4 to 6, CRM with a hardness of 25 to 35 Hs was used as the intermediate reinforcing material 16 with heat/shock buffering material on both sides of the base material and the cutting edge as the underlay of the cutting edge of the shearing blade. It is. In addition, 18 in the figure is a shearing blade base material. Furthermore, when using NCF as a heat/impact material, the cutting edge of the shearing tool is the part that is subjected to a huge load.
If the wall thickness of NCF is too large, the material is soft, which may cause the shearing cutting edge to collapse or sag, and the high coefficient of thermal expansion may cause bulges, creating wavy bumps on the cutting edge, making the shearing blade unusable. , the wall thickness is 5
Must be less than mm. SNCM, NCF, used in this comparative example and examples,
Table 4 shows the composition of CRM, STL, and NCC materials.
Table 5 shows the mechanical properties of each material.

【table】

〔Effect of the invention〕

As explained above, the shearing blade of the present invention is
Compared to conventional shearing blades, the shear life has been significantly improved, and it can now be used industrially in cutting equipment installed in wide reduction rolling processes in direct-coupling processes. As a result, the production process has great effects, such as fewer production failures due to replacement of shearing blades and a significant reduction in consumption of shearing blades, greatly improving productivity and economic efficiency.

[Brief explanation of drawings]

Figure 1 is a diagram explaining the material composition of the shearing blade (lower blade) used in the examples of the present invention, Figure 2a is the state of cutting of the material to be cut by the shearing blade, and Figure 2b is the shearing of the material to be cut. Figure 3a shows the condition of the cutting edge of the shearing blade (lower blade), and Figure 3b explains the force acting on the cutting edge (lower blade) of the shearing blade. . 14...Blade edge member, 15...Thermal shock buffer material, 16...
Intermediate reinforcing material, 17... Thermal shock buffer material, 18... Shearing blade material.

Claims (1)

[Claims] 1. In a steel billet hot cutting machine that cuts a steel billet by applying shearing force to the steel billet by advancing a pair of rectangular shearing blades that are opposed to each other with their cutting edges shifted above and below the steel billet from a direction perpendicular to the steel billet so as to pass each other, The cutting edge of the rectangular shearing blade has a square cross section and is made of heat-resistant and wear-resistant steel with mechanical properties of hardness 36 to 44HS, and heat and shock buffering material with hardness of 25HS or less is placed on two sides of the cutting edge on the shearing blade base material side. An intermediate reinforcing layer is formed through the layers, and the shearing blade base material side of this intermediate reinforcing layer is a stepped slope, and the shearing blade base material is attached to this slope side via a heat/shock buffer layer with a hardness of 25HS or less. A shearing blade for a steel billet hot cutting machine, characterized in that