The reason why the quenching process is complicated is that in order to obtain martensitic in the process, the cooling rate must be greater than the critical cooling rate, and the rapid cooling will inevitably cause large internal stress, which often causes the deformation or cracking of the cutter body, or reduces the toughness of the cutter, and the cutting edge is easy to crack in the process of use.

If the cooling rate is less than the critical speed, the horse low body will not be obtained after quenching, and the hardness, wear resistance and sharpness of the blade are insufficient.

Therefore, the cooling rate must be just right, not only to ensure the martensite, but also to reduce deformation, prevent cracking, and maintain toughness, which is the main problem in the quenching process.

Su Yuan stared at the meteoric iron, only to see that the originally dim golden light was accompanied by blows again and again, slowly recovering, and even becoming more and more intense, as if he had undergone rebirth, been tempered, and broke out of the cocoon into a butterfly.

"Tempering!"

Su Yuan put the meteorite into the furnace again, and ordered Emi Yanagi to reduce the wind speed so that the meteorite gradually warmed up and regained his strength.

Emi Yanagi stared at the furnace, quenching and tempering are closely related, and they are often used together, and both are indispensable. After strong forging, a special quenching agent is used for softening treatment, so that the sword body can be rigid and soft, and can be bent and stretched. It is a high-precision process, which is not handy for ordinary craftsmen.

"Prepare for oil quenching!"

Xu Kui hurriedly put down the hammer, picked up the wooden stick, and vigorously stirred the beef and mutton fat and yellow mud in the cauldron, so that the two were fully integrated, which was the long-lost secret recipe for oil quenching.

Su Yuan looked at the meteorite that was slowly recovering its vitality, in fact, the ideal quenching and cooling speed of steel in theory is: from more than 650 degrees slower to 650-500 degrees faster and then to less than 300 degrees slower.

But meteorites are different, after all, they are visitors from outside the sky, and after high-speed friction against the atmosphere, the temperature may reach several thousand degrees, so the greater the temperature difference, the more it can stimulate the potential and increase the limit.

"Get out of the way!"

Su Yuan quickly picked up the meteoric iron, took a few steps to the cauldron, asked Xu Kui to get out of the way, and directly inserted the red sword embryo into the oil pot, and in an instant, the light smoke was faint, and a smell of oil emanated.

"Running water!"

"Both sides of the sword!"

It was another new round of thrashing, the two cooperated more and more tacitly, and the sense of rhythm was stronger, Xu Kui was a master after all, and he quickly adapted to Su Yuan and found his own feeling.

In industry, it is usually a quenching agent made of aqueous solutions prepared from salt, alkali, water glass, polyvinyl alcohol, zinc chloride-alkali, etc. Although these quenching agents can meet the requirements of ordinary quenching process, they have the disadvantages of strong corrosiveness and difficult to clean.

Su Yuan looked at the golden light that was getting richer and richer, and the sword embryo had been quenched with oil, as if he had eaten the Ten Perfection Tonic Pills, and in an instant, the dragon spirit was fierce and his demeanor was flying. I was relieved, and it seemed that my analysis was not wrong, and it was so.

There are two benefits of oil quenching: the first sword embryo is first slowly cooled in the air, and then quenched in the muddy water, and when it reaches the low temperature zone, the yellow mud condenses on the surface of the knife, hindering the contact of the oil and reducing the cooling rate in the low temperature zone.

The second is that yellow mud is rich in various trace elements, which is a tonic for swords, which is fully absorbed in the two heavens of ice and fire, improving quality, and increasing strength and toughness.

It's like a person practicing martial arts, not only practicing hard day and night, but also cooperating with diet and supplementation, so that the progress can be rapid and the skill can improve by leaps and bounds.

"Rainbow!" "Emi Yanagi stared at the sword embryo in the oil quenching, and suddenly looked excited, exclaiming: "It's actually a rainbow!"

Xu Kui's face also showed a look of shock, and he watched Su Yuan quickly lift the sword embryo from the oil, and the boundary between the cold and hot areas of the sword body actually appeared at this time!

Under the moonlight,

colorful,

In a flash of inspiration,

Amazing!

Su Yuan stared at the blade with all his attention, under the effect of the remaining temperature, the rainbow quickly moved towards the blade, and when the rainbow approached the edge, it quickly dipped into the oil again, and then quickly lifted it up, repeating it three times, and the rainbow finally disappeared.

"Awesome, damn awesome!"

Xu Kui couldn't help it, and directly burst into foul language, watching the rainbow just disappear at the tip of the sword, and said excitedly: "Colorful at a glance, three in one!"

Putong knelt down, kowtowed to Su Yuan three times in a row, and said loudly: "It's really the method of oil quenching, thank you master, thank you master!"

"This is the legendary ancient method of oil quenching?"

Emi Yanagi next to him looked at Su Yuan blankly, suddenly came back to his senses, quickly knelt down, and said respectfully: "The master really deserves his reputation, such a stunt makes Emi stunned, and her five bodies fall to the ground." ”

Su Yuan was stunned for a moment, looked at Xu Kui who was kneeling on the ground, couldn't cry or laugh, and scolded: "Now is not the time to kowtow, hurry up and continue to fight!"

After hearing this, the stupid big man also knew that he was too excited, so he quickly stood up, and his originally somewhat tired body instantly seemed to have been beaten with chicken blood, screaming strangely, picking up a sledgehammer and beating desperately.

"Don't stand stupidly, increase the wind, and add more charcoal. ”

Yanagi Emi blushed, ran to pick up the pine charcoal, and added it to the stove, Su Yuan put the sword embryo into the flames, and the fire broke out in an instant, and he breathed a sigh of relief.

"The double quenching is finally complete!"

Suddenly his mouth was dry, he drank two bowls of water in a row, looked at the dazzling golden light in the fire, and completely completed the first round of folding, four forgings, four fires, three oils and one water, and four or four to one.

"Hurry up and rest, start the second round in twenty minutes!"

Seeing Xu Kui's excitement, Su Yuan scolded with a smile: "It's too early to be excited, it's not too late to wait for the sword embryo to come out!"

"The method of oil quenching...... Rainbow...... Finally see it with your own eyes!" Xu Kui kept muttering to himself, and when he heard Su Yuan's words, he suddenly came back to his senses, slapped his chest hard, and laughed: "It's okay, it's worth it to see the oil quenched to death!"

Su Yuan threw the towel over, the stupid big one is a treasure, such a strong animal is rare in a hundred years, where can I find another one if I am tired?

"Go on!"

Twenty minutes later, the workshop remembered the continuous sound of striking iron, spread all over the streets and alleys of Longquan, not only them, many people like to work late at night, this is the charm of Longquan!

Again, the group, the water,

cold spring quenching,

tertiary oil quenching,

tempering, annealing,

Ice and fire,

Every time the sword embryo is like experiencing the cycle of life and death,

Broken again and again and then standing,

Nirvana reborn,

After three lives and three lives,

Breaking out of the cocoon into a butterfly,

Three-foot Qingfengcheng!