It’s a Changing World

It’s a Changing World

While the types of scrap used by ferrous foundries have varied over the years, the importance of scrap--and scrap processors--to these operations hasn’t diminished one bit.

By Robert H. Wilson

The general consumption process at foundries has changed little over the years: They melt purchased scrap, occasionally adjust the melt chemistry for certain specifications, and pour the molten metal into molds. What has changed--and changed significantly--are the types of scrap employed at foundries.

The old foundry that used pig iron, mixed cast, clean motor blocks, and stove plate is currently about as viable as the Model "A." The big tonnage foundry buyers of steel scrap today are ductile iron producers, which make ductile pipes for water and sewage transmission and product movement from close to 100-percent purchased scrap. These foundries are large consumers of plate and structural scrap, No. 2 foundry steel, unstripped motor blocks, and shredded scrap.

These and other production foundries reportedly have found that ductile and alloyed castings made from such scrap are stronger and lighter than castings made from pig iron and cast scrap. Employing steel scrap also has allowed these foundries to increase production significantly

Furnace Factors

Years ago, the furnaces in most ferrous foundries were small refractory-lined cupolas, which were powered by fossil fuels and produced 30 to 40 tons of molten metal per hour. While electric induction furnaces employ a significant amount of scrap today, cupola furnaces are still popular. However, these furnaces are quite different from yesterday's counterparts. The cupolas are high-production, water-cooled units that range m diameter from 84 to 150 inches and have melt rates of 60 to 100 tons per hour. These water-cooled, hot-blast cupolas allow much more flexibility in scrap usage-they can make gray iron and ductile iron from the same furnace.

In the old refractory-lined cupolas, which used mixed and other cast grades, the inclusion of improperly stripped auto blocks was a sure reason for rejection, since aluminum, die-cast, and babbitt (an alloy of tin, copper, and antimony) scrap in the mix ruined pipe and castings. Today, many foundries use whole, unstripped motor blocks to their advantage. The aluminum pistons, housings, and other parts aid the exothermics in melting. However, the aluminum must be controlled through oxidation and burned off.

Making the Most of What's Available

One of the biggest factors affecting the types of scrap used in foundries is the change in makeup of manufactured products, which dictate what becomes scrap and, thus, what may be available to melt. At one time, many products that found their way to scrap processors were made of gray iron castings, which became No. 1 cupola cast, mixed cast, stove plate, and similar grades. Many of these scrap types no longer exist, so, obviously, consumers have had to change their buying practices to reflect what is available.

The popularity of the automobile shredder has all but done away with auto blocks, transmission housings, and castings, which are now usually contained in shredded scrap. This, coupled with the availability of large tonnages of shredded scrap, has encouraged foundries to use such scrap. In fact, today, many foundries use almost straight melts of shredded scrap. Others mix it with plate and structural, foundry steel, or other grades.

Analyzing the Problems

Cupolas do have their limitations. Size becomes a problem with scrap that is particularly small or large. Too many punchings or small stampings in scrap can choke down the air flow in a cupola furnace by blocking the air blast's movement through the charge materials, thus causing cold spots that slow down melting and can cause analysis problems. Most foundries cover this in their specifications.

Large scrap may not fit through the charge door of many cupolas and, in some cases, may be too large to be contained inside a furnace. This causes hang-ups that can result in expensive downtime in production. And if scrap cannot enter the furnace without problems, it is of little or no value to the foundry.

Improper analyses and contamination, no matter how minor, have always been problems for scrap consumers and their suppliers. A vital step toward eliminating such concerns is for scrap processors to know exactly what their consumers make, how they make it, and why they can or cannot use a particular scrap grade.

Naturally, foundries want their scrap free of obvious contaminants, such as dirt, wood, bricks, and rubber hoses, which can cause severe problems in foundries' air cleaning systems. Therefore, many foundries inspect purchased scrap with this potential problem in mind.

Certain types of scrap have the potential to cause problems in foundries' wastewater monitoring operations. The inclusion of too much zinc-coated, galvanized, or lead-containing scrap, for example, can result in those materials entering the wastewater or settling ponds at foundries and may cause the residuals to be considered hazardous.

Analysis of scrap for use in electric furnaces is particularly important. An induction furnace works much like a saucepan on a stove: You put a stick of butter in it, melt it, and you have melted butter. If you include unwanted alloys or contaminants, you get contaminated, melted steel--bad butter! Although induction foundries can accomplish some alloying, they can accomplish very little refining.

Watching Out for Alloys

One of the primary concerns of foundries today is fear of a shortage of the type of quality scrap they've become accustomed to using. Therefore, they're exploring ways to handle scrap not traditionally used in foundries. For instance, the increasing use of coated and alloyed steels in products likely will result in changes in the way foundries inspect and use scrap.

Because alloys pose a potential problem, scrap processors that supply foundries must watch carefully what they buy or be certain they sort their scrap meticulously during production. Knowledge of a scrap item's original use is very important. For example, corrosion- or wear-resistant castings usually contain high levels of chrome, nickel, and/or manganese, which can cause castings to fail, improperly anneal, or improperly machine.

Foundries continue to look to scrap processors to work with them on a cooperative basis to sort, inspect, and prepare scrap to their satisfaction and specifications. The scrap processor that is attentive to a foundry's needs can eliminate many potential scrap problems before the materials get to the foundry, and perhaps become a preferred supplier.

The foundry business, through its dramatic changes in the last 15 to 20 years, has become a better consumer for the scrap industry. Larger tonnages of more readily available scrap are purchased and consumed today than in the past.

Most foundries welcome their scrap suppliers' input and interest. Therefore, it behooves scrap processors to visit their foundry consumers and have their consumers visit their plants to understand each others' scrap concerns. Teamwork in solving these problems should significantly reduce the possibility of rejections after scrap arrives.

It’s a Changing World

While the types of scrap used by ferrous foundries have varied over the years, the importance of scrap--and scrap processors--to these operations hasn’t diminished one bit.

By Robert H. Wilson

The general consumption process at foundries has changed little over the years: They melt purchased scrap, occasionally adjust the melt chemistry for certain specifications, and pour the molten metal into molds. What has changed--and changed significantly--are the types of scrap employed at foundries.

The old foundry that used pig iron, mixed cast, clean motor blocks, and stove plate is currently about as viable as the Model "A." The big tonnage foundry buyers of steel scrap today are ductile iron producers, which make ductile pipes for water and sewage transmission and product movement from close to 100-percent purchased scrap. These foundries are large consumers of plate and structural scrap, No. 2 foundry steel, unstripped motor blocks, and shredded scrap.

These and other production foundries reportedly have found that ductile and alloyed castings made from such scrap are stronger and lighter than castings made from pig iron and cast scrap. Employing steel scrap also has allowed these foundries to increase production significantly

Furnace Factors

Years ago, the furnaces in most ferrous foundries were small refractory-lined cupolas, which were powered by fossil fuels and produced 30 to 40 tons of molten metal per hour. While electric induction furnaces employ a significant amount of scrap today, cupola furnaces are still popular. However, these furnaces are quite different from yesterday's counterparts. The cupolas are high-production, water-cooled units that range m diameter from 84 to 150 inches and have melt rates of 60 to 100 tons per hour. These water-cooled, hot-blast cupolas allow much more flexibility in scrap usage-they can make gray iron and ductile iron from the same furnace.

In the old refractory-lined cupolas, which used mixed and other cast grades, the inclusion of improperly stripped auto blocks was a sure reason for rejection, since aluminum, die-cast, and babbitt (an alloy of tin, copper, and antimony) scrap in the mix ruined pipe and castings. Today, many foundries use whole, unstripped motor blocks to their advantage. The aluminum pistons, housings, and other parts aid the exothermics in melting. However, the aluminum must be controlled through oxidation and burned off.

Making the Most of What's Available

One of the biggest factors affecting the types of scrap used in foundries is the change in makeup of manufactured products, which dictate what becomes scrap and, thus, what may be available to melt. At one time, many products that found their way to scrap processors were made of gray iron castings, which became No. 1 cupola cast, mixed cast, stove plate, and similar grades. Many of these scrap types no longer exist, so, obviously, consumers have had to change their buying practices to reflect what is available.

The popularity of the automobile shredder has all but done away with auto blocks, transmission housings, and castings, which are now usually contained in shredded scrap. This, coupled with the availability of large tonnages of shredded scrap, has encouraged foundries to use such scrap. In fact, today, many foundries use almost straight melts of shredded scrap. Others mix it with plate and structural, foundry steel, or other grades.

Analyzing the Problems

Cupolas do have their limitations. Size becomes a problem with scrap that is particularly small or large. Too many punchings or small stampings in scrap can choke down the air flow in a cupola furnace by blocking the air blast's movement through the charge materials, thus causing cold spots that slow down melting and can cause analysis problems. Most foundries cover this in their specifications.

Large scrap may not fit through the charge door of many cupolas and, in some cases, may be too large to be contained inside a furnace. This causes hang-ups that can result in expensive downtime in production. And if scrap cannot enter the furnace without problems, it is of little or no value to the foundry.

Improper analyses and contamination, no matter how minor, have always been problems for scrap consumers and their suppliers. A vital step toward eliminating such concerns is for scrap processors to know exactly what their consumers make, how they make it, and why they can or cannot use a particular scrap grade.

Naturally, foundries want their scrap free of obvious contaminants, such as dirt, wood, bricks, and rubber hoses, which can cause severe problems in foundries' air cleaning systems. Therefore, many foundries inspect purchased scrap with this potential problem in mind.

Certain types of scrap have the potential to cause problems in foundries' wastewater monitoring operations. The inclusion of too much zinc-coated, galvanized, or lead-containing scrap, for example, can result in those materials entering the wastewater or settling ponds at foundries and may cause the residuals to be considered hazardous.

Analysis of scrap for use in electric furnaces is particularly important. An induction furnace works much like a saucepan on a stove: You put a stick of butter in it, melt it, and you have melted butter. If you include unwanted alloys or contaminants, you get contaminated, melted steel--bad butter! Although induction foundries can accomplish some alloying, they can accomplish very little refining.

Watching Out for Alloys

One of the primary concerns of foundries today is fear of a shortage of the type of quality scrap they've become accustomed to using. Therefore, they're exploring ways to handle scrap not traditionally used in foundries. For instance, the increasing use of coated and alloyed steels in products likely will result in changes in the way foundries inspect and use scrap.

Because alloys pose a potential problem, scrap processors that supply foundries must watch carefully what they buy or be certain they sort their scrap meticulously during production. Knowledge of a scrap item's original use is very important. For example, corrosion- or wear-resistant castings usually contain high levels of chrome, nickel, and/or manganese, which can cause castings to fail, improperly anneal, or improperly machine.

Foundries continue to look to scrap processors to work with them on a cooperative basis to sort, inspect, and prepare scrap to their satisfaction and specifications. The scrap processor that is attentive to a foundry's needs can eliminate many potential scrap problems before the materials get to the foundry, and perhaps become a preferred supplier.

The foundry business, through its dramatic changes in the last 15 to 20 years, has become a better consumer for the scrap industry. Larger tonnages of more readily available scrap are purchased and consumed today than in the past.

Most foundries welcome their scrap suppliers' input and interest. Therefore, it behooves scrap processors to visit their foundry consumers and have their consumers visit their plants to understand each others' scrap concerns. Teamwork in solving these problems should significantly reduce the possibility of rejections after scrap arrives.