71: Chapter 71 Lost-wax casting method: The admirable wisdom of our ancestors!

The steam rotary tiller was the easiest to produce.

Elder Mo's research team was also the first to create molds for the parts of the steam rotary tiller.

To speed up the process, every member of Elder Mo's research team was responsible for making the mold of a single component.

They used the lost-wax method to create the molds.

They first used beeswax to make a model of the casting, then used refractory materials to fill the mud core and apply the outer mold. After heating and baking, the wax model would melt and drain away completely, leaving the entire casting model as a hollow shell. Molten liquid was then poured inside to cast the required parts.

Zhao Fusu also admired the wisdom of the ancestors; they had actually been able to invent the lost-wax method!

This lost-wax method invented by the ancestors could not only cast parts with complex shapes, but raw materials like wax could be reused, which also reduced costs.

However, during the demolding process, the outer mold had to be broken.

The next time, the mold would have to be hand-crafted again, which was not suitable for the large-scale production of components.

Zhao Fusu frowned, not very satisfied with the production efficiency of these parts.

He needed to produce a large number of steam tractors and steam threshers in a short period of time.

In terms of component production, he needed a high-efficiency method.

The outer mold of a painstakingly manufactured mold had to be smashed just to take out the cast component, which meant the mold could only be used once.

This method of producing parts was too inefficient.

It would be best if the molds were reusable.

After the cast component was removed from the mold, the mold could be reused to cast a new one.

That would make the production of parts truly fast!

Zhao Fusu knew there must be a reason why Elder Mo and the others weren't doing it that way.

The problem lay in the demolding process.

If the mold was made of metal, the components would stick tightly to the mold under high-temperature casting; how would one then remove the component from the mold?

A metal mold could not be smashed apart.

This was also the reason why Elder Mo and the others did not use metal for their molds.

Zhao Fusu grew curious; for the sake of efficiency, modern factories definitely used reusable molds.

So how did they solve the demolding problem?

Unfortunately, he didn't have a phone; otherwise, he could have just searched on Douyin.

With so many vloggers, there would surely be someone who knew this information.

Fortunately, Zhao Fusu had previously obtained the book 'industrial encyclopedia' through a check-in.

While Elder Mo and the others were making the steam rotary tiller parts, Zhao Fusu had nothing to do, so he flipped through the 'industrial encyclopedia' he had obtained.

While flipping through it, he actually found the answer.

The book stated that when modern factories produced metal components, they mainly used cast iron to make molds.

Cast iron molds and hot-forged metal often bonded severely, making demolding difficult, and they could not be smashed like the ceramic outer molds.

To make demolding easier, hexagonal boron nitride lubricating mold release agent was applied to the mold.

hexagonal boron nitride has excellent lubricity, heat resistance, and chemical corrosion resistance.

It is relatively stable against almost all molten metals and does not undergo chemical reactions.

In hot extrusion molds, after evenly applying the hexagonal boron nitride release agent, the lubricity between the hot-forged metal and the mold can be increased, friction reduced, and sticking avoided. This makes the demolding of the product smoother, reduces the generation of ripples, and improves the smoothness of the product.

It is recommended to use hexagonal boron nitride with a particle size of four to twelve microns; its primary particle size is smaller while its agglomerated particle size is larger. Therefore, it is more suitable as a release agent for hot forming.

As Zhao Fusu looked at the knowledge points in the book, his expression turned sour.

He had no place to buy hexagonal boron nitride release agent, which meant he needed to make it himself!

Zhao Fusu's face turned into a look of bitter frustration.

Maybe he should just let Elder Mo and the others hand-mold a new mold for every part.

But he still felt that such efficiency was far too low.

If cast iron molds were used, and then hexagonal boron nitride release agent was evenly applied inside, the required parts could be easily demolded.

Then, by pouring in more hot-forged metal, the next required part could be obtained.

This speed would be much faster than having to hand-mold a new mold for every single part.

"Phew!"

Zhao Fusu let out a heavy breath.

"Let's do it!"

After gritting his teeth, Zhao Fusu decided to see how to produce the hexagonal boron nitride release agent.

Zhao Fusu continued reading the 'industrial encyclopedia'; perhaps the system wanted him to create the hexagonal boron nitride release agent, as the book contained records on how to produce it.

"The production principle of hexagonal boron nitride involves borax and urea at high temperatures. The borax first dehydrates and decomposes, while the urea decomposes to produce nitrogen-containing gases such as ammonia. Boron oxides then react with the ammonia gas to generate hexagonal boron nitride."

"borax?"

"Oh!"

Zhao Fusu remembered what borax was.

borax was also known as Pengsha or Pensha.

It could be used as medicine.

Its properties were bitter, pungent, warming, and non-toxic.

It was mainly used to treat phlegm, stop coughing, and break up throat obstructions.

Many medicine halls carried borax.

With borax found, urea was even simpler.

Human urine contained urea.

Zhao Fusu immediately had people look for borax and extract urea from urine.

It was quite simple to say: solid urea is produced by evaporating, concentrating, and crystallizing a urea solution.

Zhao Fusu looked at the specific production steps for hexagonal boron nitride.

"First, mix borax and urea in a certain proportion and grind them evenly to ensure full contact between the raw materials."

"Then, place the mixture in a high-temperature resistant crucible and put it inside a high-temperature furnace. Raise the temperature to 1000 to 1200°C and maintain it for a period of time to allow the reaction to proceed fully."

"After the reaction is over, let it cool with the furnace."

"Finally, perform post-processing on the product, such as washing with acid or alkali solutions to remove unreacted raw materials, impurities, and sodium salts generated during the reaction process, then filter and dry to obtain the hexagonal boron nitride product."

"I see!"

Now that Zhao Fusu knew how hexagonal boron nitride was made, he immediately organized manpower to produce it.

The labor was selected from the million corvée labor workers.

Over a million corvée laborers had been digging up silt, and the silt around Xianyang City had been completely turned over by them.

Under the leadership of the Field Attendants, they had also produced a large amount of local-method fertilizer.

That fertile silt and the produced local fertilizer would be used as fertilizer for wheat, millet, and soybeans when crop rotation began after the summer harvest.

These million corvée laborers were gradually running out of things to do, and since Zhao Fusu happened to need a lot of manpower, he selected suitable people from among them.