Studying at Western University starts with a knife-forging competition

The forged Chinese dagger blank lay quietly on the anvil, the dark red residual heat slowly fading from the blade. The curve from the tip to the hilt was clean and crisp, and the double edges were symmetrical like a mirror image.

Lin Yuan used pliers to pick up the knife blank, examined it twice, and confirmed that the forging marks were even and dense, with no obvious hammer marks misalignment or cracks at the edges.

The forging process is complete.

But he knew that the real test was just beginning.

The quenching process for Damascus steel is much more complex than that for high-carbon steel alone. 1084 and 15N20 steels have different carbon contents, different coefficients of thermal expansion, and different temperature ranges for the transformation of austenite to martensite.

If the quenching and cooling rate is too fast, the difference in shrinkage rates between the two types of steel will generate huge thermal stress between the layers, which can lead to warping or even cracking. If the cooling rate is too slow, the hardness will not be achieved, and the edge retention will be meaningless.

This knife has a nearly three thousand-layer cloud-patterned steel structure. The interfaces between the layers are thinner and denser than those of ordinary Damascus steel. If a micro-crack appears on any interface, the entire knife will be ruined.

Lin Yuan clamped the blade blank back into the forging furnace and began the final preparation before quenching—normalizing.

The purpose of normalizing before quenching is to refine the grains, eliminate residual stress accumulated during forging, and prepare for the upcoming severe thermal shock.

He precisely controlled the furnace temperature above the critical temperature, ensuring the steel billet was heated evenly and then allowed to cool naturally in the air. He repeated this step twice.

After two normalizing processes, the oxide scale on the surface of the blade blank exhibits a uniform grayish-blue color, a color that only a good steel that has undergone thorough forging and standardized heat treatment would have.

The time for quenching had come. Lin Yuan walked to the quenching tank.

The production team prepared two quenching media for each workstation: rapid quenching oil and a tank of clean water.

Most competitors choose rapid quenching oil—its cooling rate is moderate, the risk of deformation is low, making it the safest choice in competitions. The textbooks at the American Bladesmith School clearly state that water quenching of high-carbon steel is too risky and not recommended for competitions.

Lin Yuan glanced at the tank of oil, then walked toward the water tank.

Without hesitation, he moved the water tank directly to his workstation.

This action was immediately noticed by the judges. J. Nelson lowered his arms from his chest, took two steps forward from behind the judges' panel, and stood in a position where he could see Lin Yuan's quenching operation more clearly.

He didn't speak, but his brows were furrowed. David Baker also stood up.

In the entire workshop, almost no one used water for quenching. The quenching tanks of the other three contestants were full of oil, while Lin Yuan's tank was filled with clear water. Quenching high-carbon Damascus steel with water is one of the riskiest choices in any forging competition.

Water quenching cools much faster than oil quenching, provides a stronger driving force for martensitic transformation, results in higher hardness, finer grain size at the cutting edge, and better cut retention—but at the cost of any operational error being penalized by dramatically amplified thermal stress.

If the water temperature difference is one degree, the angle of entry into the water is one degree off, or the blade stays in the water for even half a second longer, the blade blank may crack on the spot.

But Lin Yuan knew what he was doing. Water quenching wasn't simply about plunging a red-hot knife into water. That kind of practice is called "ruining the knife," not quenching. True water quenching is a process precise to the second and degree.

He had been observing this process at his father's sword-making factory since he was nine, and began practicing it himself at twelve. By the time he was seventeen, he was able to independently complete the water quenching of traditional Longquan sword blades. Water quenching is the core technology in Longquan sword-making.

The blade edge needs to be locally hardened, while the body needs to maintain its toughness. During quenching, it is essential to achieve "hard blade and tough body"—these four words seem simple, but behind them lies generations of experience in judging the heat and the techniques for immersing the blade in water. The first thing his father taught him was not how to swing a hammer, but how to judge the heat.

What color should the steel billet be when it's heated in the furnace before it's taken out? How many seconds should it be pre-cooled in the air after being taken out? When it's put into water, should the blade edge or the back of the blade touch the water first? How fast should it slice across the water? How many times should it be repeated? — These things are not written in textbooks. You can only learn them by standing in front of the forging furnace for ten years.

Lin Yuan reheated the blade blank to the quenching temperature.

The [Focus] skill pushed his visual acuity to its limit—the steel billet in the furnace changed from dark red to cherry red, and from cherry red to bright orange; every change in the color of the flame seemed to be slowed down by half a beat.

He knew that the quenching temperature of high-carbon damascus steel had to be more conservative than that of single high-carbon steel because the interlayer interface is more prone to oxidation at high temperatures. If the temperature is slightly higher, carbon migration at the interface will be accelerated, and the contrast of the pattern will decrease.

When the billet reaches a bright orange color and the surface oxide scale begins to show a slight flow, he uses pliers to remove the billet.

Then, he did not immediately head towards the quenching tank.

He gripped the pliers and let the blank of the knife dart remain suspended in the air for a few seconds.

This step is called "pre-cooling". The purpose of pre-cooling is to reduce the surface temperature of the blank slightly from the peak of the quenching temperature, so that the heat can be evenly conducted from the center of the blade to the surface, avoiding excessive temperature difference between the surface and the core, which would lead to thermal stress concentration during quenching.

The pre-cooling time can be judged by sight – when the oxide scale on the surface of the blade blank changes from bright orange to dark orange, and the edge of the blade begins to darken slightly, it is the perfect time to put it into the water.

These few seconds of pre-cooling are the dividing line between a knife maker who knows how to water quench a knife and someone who just throws the knife into the water.

He moved.

The pliers gripped the blade blank and carried it towards the quenching tank. The water in the tank was as calm as a mirror, reflecting the photography lights on the workshop ceiling. Lin Yuan took a deep breath, twisted his wrist, and positioned the blade blank with the blade pointing downwards, forming a precise angle between the blank and the water surface—not a vertical insertion, but rather allowing the blade edge to glide across the water at an extremely shallow angle.

The 【Quenched Water Blade】 skill is activated the instant the blade touches the water's surface.

It is integrated with his quenching action—the moment the cutting edge comes into contact with the quenching medium, his perception extends along every inch of the blade blank, and he can clearly judge whether the cooling rate is uniform, where the thermal stress begins to concentrate, and from which point the martensitic transformation begins and in which direction.

"laugh--"

The blade sliced ​​through the water, producing a short, sharp hiss of steam. The water boiled the instant it touched the scorching blade, forming a vapor sheath that enveloped the edge.

Instead of immersing the entire knife in the water, he made the blade trace an arc across the surface at an extremely fast speed, the tip entering the water, tracing a path, and exiting the water—the whole process taking less than a second.

Localized quenching. This is one of the core principles of the Longquan water quenching method. The blade is the thinnest part of the knife, the part that needs the most hardness, and also the part that is most prone to cracking during quenching.

If the entire knife is submerged directly in water, the difference in cooling rate at the junction of the thick and thin blades will generate enormous thermal stress. This stress will concentrate in the transition zone between the blade root and the back of the blade, which is where cracks begin.

The method of partial quenching involves first quenching the blade edge, allowing it to undergo martensitic transformation in a very short time, while the back and blade remain at high temperatures. The effect of this is that the blade edge achieves high hardness, while the back and blade retain their toughness due to the slower cooling rate.

A hard blade and a tough body – that’s what “hard blade and tough body” means.

Without pausing after the first stroke, he immediately flipped the blade over and sliced ​​the other side of the blade across the water at the same angle.

The alternating cooling rates on both sides of the blade edge are consistent, and the thermal stresses cancel each other out along the center line of the blade, avoiding the side bending deformation that can easily be caused by single-sided quenching.

Then came the second stroke. This time, the blade was sliced ​​across the middle section of the blank, alternating between both sides with fluid, seamless movements. The third stroke targeted the tip of the blade.

He performed four localized quenchings, controlling the contact time between the blade and the water surface to be less than one second each time. After each stroke, he would glance at the color change of the oxide scale on the surface of the blade blank out of the corner of his eye to judge the degree of temperature drop.

The [Internal Vision] skill played a crucial role at this moment. This passive skill allowed him to perceive the changes in the internal structure of the steel during the quenching process—where the starting point of the transformation from austenite to martensite was, whether the transformation was progressing at a uniform rate, and which areas cooled faster or slower.

This perception is not visual, but an instinct closer to touch, like the heat conduction you can feel when your fingers touch the surface of a steel billet, but its depth extends to the grain level.

He could sense that the martensitic transformation of the blade on both sides had been almost completed during the alternating strokes across the water—the goal of edge hardening had been achieved.