Pig iron

People make pig iron in a hot furnace.

This iron has a lot of carbon in it. This makes the metal break easily. It is not good for making tools yet.

Long ago, people made it in China. They poured the hot metal into sand. It made shapes that looked like baby pigs. Workers broke the small pieces off. These pieces are called piglets. We melt this iron to make steel. It is a very important step.

Pig iron is a middle step in making steel.

Workers make it by smelting iron ore in a blast furnace. This is a very hot furnace. The iron has a lot of carbon in it. It also has silica and other bits of waste. Because of this, the metal is brittle. This means it can break easily.

People used to pour the hot metal into sand molds. These molds had a shape like a family of pigs. The main channel was called the sow. The smaller pieces were called piglets. Workers broke the piglets off the sow once they cooled.

Chinese people made pig iron a long time ago. They made it during the Zhou ruling family. In Europe, people used different furnaces. One way to use pig iron is to make gray iron. This happens by melting the pig iron again. You can also add steel or scrap iron to it. Modern mills often move the hot metal right to the steel mill. They use big furnaces to burn off the extra carbon. This turns the pig iron into strong steel.

Pig iron is a very important middle step in making steel.

It is an intermediate good used by the iron industry. Workers create it by smelting iron ore inside a blast furnace. This metal has a high carbon content of 3.8% to 4.7%. It also contains silica and other bits of waste called dross. These things make the metal brittle. Because it is brittle, it cannot be used directly for most jobs. It must be changed into something stronger first.

Making pig iron is a big technical leap from older ways.

In the past, people used a bloomery to make iron. A blast furnace is much larger and needs more power. It requires high-quality refractory material to hold the heat. The furnace must reach temperatures above 1538°C to melt the iron. This is the melting point of iron. Once liquid, the metal is often called hot metal.

The name pig iron comes from the shape of its molds.

Workers used sand to make molds with a branching shape. A central channel was called the sow. Many smaller ingots sat at right angles to that channel. These smaller pieces looked like piglets being nursed by a sow. When the metal cooled, workers broke the piglets from the sow. The uneven size of these pieces does not matter much. This is because the iron is meant to be melted again.

History shows that people have made pig iron for a long time. The Chinese made it during the later Zhou dynasty. This era ended in 256 BC. In Europe, some furnaces like Lapphyttan in Sweden are very old. They may date back to the 12th century. Other furnaces in the County of Mark date to the 13th century. This area is now part of Westphalia, Germany. It is not clear if Europe learned this from China. Some think the ideas traveled along the Silk Road.

Today, pig iron is used to create many different metals.

It can be remelted to make gray iron. Workers add steel or scrap iron to the mix. They also add alloys and change the carbon content. Some high purity grades are used to make ductile iron. In modern mills, the hot metal often goes straight to a steel mill. It might enter an electric arc furnace or a basic oxygen furnace. There, the extra carbon is burned off to make strong steel.

Pig iron is a vital intermediate good in the iron industry. It serves as a primary step in the production of steel.

This metal is created by smelting iron ore inside a blast furnace. Because of its chemical makeup, it is not a finished material for most uses. It contains a high carbon content, typically between 3.8% and 4.7%. It also contains silica and other waste materials known as dross. These impurities make the iron very brittle. Because it is brittle, it cannot be used directly for most construction or tools.

The process of making pig iron requires intense heat and specific equipment. To create it, the furnace must reach temperatures above 1538°C. This temperature is necessary because it is the melting point of iron.

Moving from an older method called a bloomery to a blast furnace is a massive technical leap. A blast furnace requires much larger structures and more powerful blowers. It also needs high-quality refractory material to withstand the heat. Finally, a crucible is needed to hold the molten metal. In a bloomery, workers had to avoid melting the iron completely. If the iron turned to liquid in a bloomery, it became too brittle to hammer into shape.

The name "pig iron" comes from the traditional way the metal was cast.

Workers used sand to create branching molds for the liquid metal. These molds featured a central channel known as a "sow." Many individual ingots were placed at right angles to this central runner. This shape resembled a litter of piglets being nursed by a sow. Once the metal cooled and hardened, workers broke the small ingots, or "pigs," away from the sow. The uneven size of these pieces is not a problem. This is because pig iron is intended to be remelted later.

History shows that pig iron production has existed for many centuries. The Chinese were making pig iron during the later Zhou dynasty. This dynasty ended in 256 BC. In Europe, some furnace sites are quite old as well. For example, the Lapphyttan furnace in Sweden may date back to the 12th century. Some furnaces in the County of Mark, now in Westphalia, Germany, date to the 13th century. It is not certain if Europeans learned these techniques from China. Some researchers suggest a link through the Silk Road and Viking contacts with Persia.

There are several ways to transform pig iron into useful metals. Traditionally, it was worked into wrought iron using finery forges or puddling furnaces. In a puddling furnace, the iron is melted and stirred with a strong current of air. This process causes impurities like silicon to oxidize. The resulting product is often called refined pig iron or finers metal. Pig iron can also be used to make gray iron. To do this, workers remelt the pig iron and add steel or scrap iron. They also add alloys and adjust the carbon content to reach the right balance.

High purity grades of pig iron are used for specialized tasks. These grades are used to create ductile iron. To make ductile iron, workers must control certain elements. They may choose pig iron that is low in manganese, sulfur, phosphorus, or silicon. High purity pig iron helps dilute harmful elements in the ductile iron charge.

This ensures the final metal has the correct properties for its specific job.

In modern industry, the handling of pig iron has changed significantly. Historically, the molten metal was poured from the bottom of the furnace. It traveled through a channel into a ladle car to be sent to a steel mill. In this liquid state, it was called "hot metal." Today, many modern steel mills transfer hot metal immediately to steelmaking vessels. These vessels include electric arc furnaces, induction furnaces, or basic oxygen furnaces. In these machines, the excess carbon is burned off to create steel. Some plants still use pig-casting machines to create "stick pigs" for later use.