Some educational knowledge: The function of a knife is absolutely not to cut iron! If you really need to cut iron frequently, it is advisable to use a steel saw instead of a knife, as a knife that can cut iron without damaging its edge is not necessarily a good knife! Because a knife that can cut iron without damaging its edge must be dull. To make a knife sharp, the edge needs to be thin, but to cut iron, the edge needs to be thick, which is contradictory. A knife that can both "cut like a razor" and "cut iron and copper" does not actually exist; A knife without an edge has a U-shaped blade, with a thicker edge. When cutting iron, since the hardness of the knife steel is much higher than that of iron, it can be cut freely. However, after sharpening the edge, the blade has a V shape, and the edge is very thin. The sharper the knife, the thinner the edge. If a thin-edged knife is used to cut iron, regardless of how hard the knife is, the result of a single strike is self-evident.

Sharpness is primarily related to the purpose and craftsmanship of the knife rather than the material. Even with 45 steel, a knife can be sharpened to be extremely sharp. Whether a knife is sharp depends on its intended use and craftsmanship. Different blade angles and thicknesses serve different purposes.

Blade thinness, sharpness, and delicate cutting.

The quality of a knife mainly depends on three aspects: 1. Blade shape 2. Material 3. Heat treatment. A one-sided pursuit of sharpness or hardness alone is superficial knowledge. As the saying goes, "A truly rare and excellent knife is one that is sharp but without edge." Regarding the existence of blade chipping, there are several factors to consider. Generally speaking, in the traditional knife world, there is a rule that "we repair rolled edges but not chipped edges," meaning that knife edges with rolled parts can be repaired, but not those with chipped edges. However, as a responsible knife maker or seller, no one wants to encounter such problems but may have to deal with them.

The toughness of a knife is mainly determined by several factors: material, forging process, heat treatment, blade geometry (including grinding and edge angle), the user's cutting technique, etc. For example, for general medium carbon steel knives, if they are quenched to be slightly harder, their impact toughness will be relatively poorer. Modern steel mills determine the service range of such materials during design and production. Additionally, the same type of steel from different countries or different steel mills domestically, or even different batches from the same mill, may exhibit significantly different performance, possibly varying by ten times or more. This underscores the importance of careful material selection and testing.

Since both can be sharpened, what are the advantages of better steel?

The main advantage lies in edge retention. Steel A may lose its edge after 3 cuts, while steel B can withstand 30 cuts before losing its edge or may not lose it at all. This is the advantage of better steel.

Below is a brief discussion of the performance differences that arise from different forging techniques:

For example, differential heat treatment, such as opening and inserting steel, tends to produce slightly softer blades compared to full steel blades. This is because the higher heating temperature and longer heating time increase the likelihood of decarburization and oxidation. Some blades also undergo folding forging or twisting, which further impacts their properties. Moreover, the physical condition, mood, and skill level of the maker also play a significant role.

As for heat treatment, its importance cannot be overstated. When customers encounter chipping issues during knife usage, they often blame the blade maker or seller, highlighting the critical importance of proper heat treatment techniques. Heat treatment processes vary according to different materials and performance requirements, and there are no fixed rules.

Regarding blade geometry, an illustrative example is the grinding and edge formation of a machete. The edge typically starts from the middle to lower part of the blade, making the back of the blade thick and suitable for heavy chopping tasks. Some blades are ground flat with a small angle edge, making them sharp and suitable for light cutting tasks. Others are ground with a curved edge, less sharp but suitable for chopping tasks.

The choice of blade usage is influenced by individual preferences. For example, a sharp blade might be used for shaving or paper cutting, while a thick-edged blade might be suitable for chopping bamboo or even steel pipes. However, those unfamiliar with knives may misuse them and expect them to be indestructible weapons. Personal cutting techniques also play a role; individuals with weak grips or unstable cutting motions, or those who forcefully draw the blade or use incorrect cutting angles, are more likely to encounter issues such as chipping.