Walking beside the railway tracks, those dark brown sleepers seem ordinary, but they bear the weight of thousands of tons of trains. They can persist for decades in the wind and rain without rotting. The key is that high temperature and high pressure technology is used in the production process. What is so special about this technology? Let's start with the metamorphosis of an ordinary pine.

Why doesn't the old method work?

More than 100 years ago, when Europeans first tried to treat sleepers with coal tar, they simply soaked the wood in an oil pool. Although the surface is covered with oil stains, the anti-corrosion oil cannot penetrate into the wood. It's like coating an apple with sugar. The surface looks bright, but the pulp inside will still rot. The rainwater flows into the wood along the gravel seam under the rail, and the fungi grow madly under the damp oil film. What is more troublesome is that the oil film will crack in summer and winter, and the new crack will become a water inlet instead. Sleepers treated in this way often have to be replaced every three to five years.

How to solve the problem of high temperature and high pressure?

There is a large iron can with a diameter of twoorthree meters in the modern factory, which is the key equipment to make pine "reborn". The workers dry the wood first, and then put it into the pressure tank to vacuumize - just like sucking air out of the tank when drinking a drink with a straw, and the tank becomes negative pressure. Then inject anti-corrosion oil heated to about 90 ℃ and pressurize it to more than ten atmospheres at the same time, which is equivalent to throwing wood into the deep sea to bear huge water pressure.

In these six hours, magical changes took place: high temperature opened the wood fibers, and high pressure forced the anti-corrosion oil into the depths of the wood. The anticorrosive oil, which could only penetrate 2-3mm, can now be drilled to more than 13mm, and even the resin pipe in the center of the wood is filled. The pine resin that comes with the pine wood reacts with the anticorrosive oil at high temperature to form a waterproof layer that is stronger than glue.

Tangible benefits

After high temperature and high pressure treatment, the service life of sleepers is directly extended to more than ten years or even decades. In the south where there is plenty of rain, they can carry termites to eat; In extremely cold weather in the north, it will not crack due to repeated freezing and thawing. The sleeper will only make a slight squeak when the train is rolled dozens of times every day, which is due to the internal buffer structure of the wood. For the railway department, the period of sleeper replacement has changed from a few years to decades, which not only saves the maintenance cost, but also reduces the impact of construction on train operation.

At present, the world consumes tens of millions of railway sleepers every year, and more than 70% of them adopt this high temperature and high pressure treatment process. Pine trees cut from the Northeast Forest Farm have turned into dark brown "iron bones" after this process, silently guarding the crisscross railway network. This seemingly simple technology embodies the wisdom of human beings to resist natural corrosion for a century, and also enables the steel torrent of modern transportation to run safely on wood.