Pig Iron vs Scrap Iron
When it comes to quality soil pipe and fittings, scrap beats pig every time.
There is a notion being propagated by importers of Chinese-made cast iron soil pipe and fittings that the use of “virgin” pig iron as a raw material for manufacturing these products is preferable to recycling scrap iron into new products. While pig iron may be the more economical input, technically and ecologically speaking, scrap iron is a far superior raw material.
Products produced in modern foundries in developed countries never contain 100 percent pig iron, an intermediate product of the smelting of iron ore, and in fact they are normally produced with no pig iron at all. Grey iron castings for automotive, agricultural, construction, power, plumbing and waterworks are almost universally produced using 100 percent recycled iron and steel scrap as feedstock but because it is a better raw material.
The use of recycled materials allows skilled manufacturers to blend the correct ratios of different types of scrap and other inputs to produce the most uniform chemistries and metallurgical properties. U.S. domestic foundries use spectrometers for metallurgical analysis to ensure the physical and chemical properties of grey iron castings meet all the required specifications.
Foreign foundries in less developed countries use pig iron because it is cheap. An oversupply of iron ore, combined with declining global industrial demand and Chinese steel-making overcapacity, resulted in a slump in iron ore prices over the past two years. As a result, Chinese pig iron has become an attractive raw material.
But the use of 100 percent pig iron restricts the melting process to the chemistry of the pig iron, which can vary wildly. What goes in must come out, and the foundry using 100 percent pig iron has little control over the metallurgy of the iron that goes into its products. The use of 100 percent pig iron is generally restricted to the foundries that do not possess the equipment, resources or knowledge to properly utilize scrap as a raw material.
Scrap is also far better for the environment. U.S. foundries and steel mills are some of the largest recyclers in the country, melting hundreds of thousands of tons of scrap iron and steel each year. Charlotte Pipe and Foundry cast iron soil pipe products are certified to contain 98 percent post-consumer recycled material and can be recycled again at the end of their useful life.
Iron ore, on the other hand, must be mined, processed, reduced to molten iron in a blast furnace, cast into solid “pigs”, and then re-melted to produce iron suitable for casting into pipe or fittings, putting an unnecessary strain on the environment.
China is the largest producer of iron ore in the world and ore mining in that country is a dirty, and often unregulated, industry. Most iron ore in China is extracted through opencast, or open-pit, mines – a surface mining technique of extracting rock or minerals from the earth. Open-pit mining can be an extremely destructive practice that often has very negative impacts on the surrounding environment. Open-pit mining creates large amounts of mineral waste in the form of waste rock and tailings. Tailings are the waste material from the ore processing phase, and it often contains toxins left over from the ore separating process along with heavy metals that were not fully removed.
Waste rock and tailings contain lead, minerals and other materials that can lead to dangerous runoff and water contamination when stored improperly. Some mine waste and tailing dump sites in China are structurally unsound and can overflow or break, allowing contaminants to spill out over the surrounding environment, as was the case at the Tashan mine in Linfen city, China (the most polluted city in the world).
In 2008, a devastating mud and rock slide caused by the collapse of a waste reservoir at Tashan buried more than 300 people. The subsequent Chinese government investigation found that the accident at the unlicensed ore mine was caused by illegally discharging waste sand into the mine’s tailings dam on a mountain above a village. When the dam reached its capacity amid heavy rains, it burst, inundating a crowded marketplace and killing 277 people.
But it’s not just the mining process that is dangerous and bad for the environment. Many large-scale mines have ore processing facilities on site where extracted ore is sent for crushing, washing and various physical or chemical separation processes and these processes also create pollution.
The most common processing practice is the use of a blast furnace. Coke (made from coal), ore, sinter (a mixture of iron ore and other materials prepared for smelting) and limestone are fed, or ‘charged’, into the top of a blast furnace. A hot air blast, from which the furnace gets its name, is injected through nozzles in the base of the furnace. The blast fans the heat in the furnace to white-hot intensity, and the iron in the ore and sinter is melted out to form a pool of molten metal in the bottom, or hearth, of the furnace. The limestone combines with impurities and molten rock from the iron ore and sinter, forming a liquid ‘slag' which, being lighter than the metal, floats on top of it. The molten iron from the bottom of the furnace can then be formed into solid “pigs”, which are subsequently re-melted to produce iron for casting.
Neither the coke ovens nor the blast furnaces nor the foundries in less developed countries utilize modern environmental controls that are common in the developed world. These facilities produce huge amounts of hazardous pollutants and are often unregulated. The unfortunate workers at the coal mines, coke ovens, blast furnaces and foundries in China work for near slave wages and are subjected to unsafe working conditions that would not have passed muster in developed countries in the 1920s.
Domestic cast iron soil pipe products are made in accordance with strict U.S. environmental and safety regulations by American workers, keeping middle class manufacturing jobs right here at home. Do something good for the environment and your fellow Americans – specify, buy and install American-made cast iron soil pipe and fittings.
Bill Morris is vice president/technical services for Charlotte Pipe and Foundry. He has more than 20 years of experience in the plumbing industry.