Looking forward: ductile iron's 'roar' into the 21st century.

An analysis of the marketplace examines ductile iron's increasing applications and how a surge in demand is expected in the new millennium.

Economic and technological developments are expected to propel ductile iron into the new millennium. Following growth at a rate of 4%/year since the recession of 1991, ductile iron shipments are likely to sputter slightly in the next few years and then roar into the 21st century, reaching peak levels from 2002-2008.

In the 50 years since the announcement of the discovery, ductile iron has grown through technology and has been able to withstand the economic troughs that slowed the growth of other ferrous metals.

It all started with a Ford crankshaft and a housing cast at Cooper-Bessemer, followed by the development of ductile iron pipe applications in Virginia and Alabama, along with other automotive applications. Analysis of the marketplace in those early years indicates that most of the initial ductile iron applications came at the expense of forgings and fabrications. This was followed by increasing conversions of malleable iron and steel applications to ductile iron, a trend that accelerated in the early 1980s.

The key to the early growth was the writing of new American Society for Testing and Materials (ASTM) specifications that assured casting buyers that the casting was "ductile" and the graphite had achieved a spheroidal shape throughout. The first ASTM material specification was in 1949, followed by other new specs in the 1950s. Ductile iron now offers grades and specifications covering all the matrix structures including ferritic, pearlitic, martensitic, austenitic, bainitic and intermediate structures.

Tracing Shipments

The '50s were a development period, with shipments finally reaching 100,000 tons in 1958. Then things started to happen in the early 1960s as John Deere and International Harvester replaced malleable iron applications with ductile, Chevrolet opened a new foundry to make ductile iron crankshafts, and pipe began to be produced in large tonnages at ACIPCO, McWane, Clew, U.S. Pipe and other plants. Total ductile iron production reached 1 million tons for the first time in 1968.

Ductile iron exploded in the early 1970s with a gain of 500,000 tons in 1971 due to new automotive parts and conversions from malleable iron. Applications such as calipers, knuckles and differential carriers became major applications as shipments hit 2 million tons for the first time in 1972 and reached 3 million in 1978.

Gray iron shipments dropped 6 million tons in the recession of 1982, malleable iron slipped to below 300,000 tons and steel castings dropped 500,000 tons. Ductile iron slipped slightly in 1982 but immediately bounced back to 3 million tons of shipments in 1985 as new applications in construction, refrigeration, gears, diesel engines and special machinery were developed, and a new material specification spurred valve and pump production. A big surge to 4 million tons of shipments occurred in 1994 as ductile iron usage per light automotive vehicle reached 175 lb/vehicle.

Ductile iron shipments in the U.S. reached their peak in 1998 with 4.19 million tons, including 1.8 million tons of centrifugally cast pipe and 1 million tons consumed by the automotive light vehicle industry. Ductile iron casting sales reached $5 billion for the first time, equalling 86% of gray iron sales. As of 1998, 506 foundries in the U.S. employ ductile iron, according to the most recent Casting Source Directory.

Ductile iron casting shipments are expected to grow at an annual rate of 2.9% through 2008, when they are expected to peak at 5.57 million tons. Sales are expected to increase to $8 billion in the same period and exceed gray iron sales by $600 million in 2008. Ductile iron sales will likely lead all of the cast ferrous metals in casting sales.

Table 1 illustrates the major individual growth markets for ductile iron castings along with their forecast annual growth rates.

Valves & Fittings

U.S. shipments to this market are forecast to grow 3.2%/year to 312,000 tons in 2008, with sales growing to $574 million.

Grade 60-40-18 valves are accepted by the American Society for Mechanical Engineers (ASME) Boiler Code for use in petroleum, gas and pipeline applications. Ductile iron's low melting point has restricted growth in refinery applications, and its weldability problems have prevented extensive use in pipelines. However, it has grown with pressure pipe in water and wastewater valve applications. Ductile iron valves have replaced gray iron where impact resistance and resistance to shock is required. The low-silicon annealed grade has excellent mechanical and thermal shock properties and is used in cold climates where a low transition temperature is required.

Most threaded pipe fitting applications are still specified in malleable iron by the American National Standards Institute (ANSI), thus limiting applications in the near future. Specification changes are likely to take place in the future and ductile iron may be offered as an alternative material, replacing some malleable iron applications.

Captive capacity is estimated at 90,000 tons, thus limiting sales from non-captive foundries to 171,000 tons in 1999. Imports will continue to exceed exports at 35,000 tons.

Supply presently exceeds demand; however the 50-150-lb valve casting category, produced on cope and drag machines, could offer shortage possibilities in future peak years.

Table 1. Growth Markets for Ductile Iron Castings (1998-2008)

Industry                                     Expected Annual
                                             Growth Rate (%)

Internal Combustion Engine                          +4
Special Industry Machinery                        +3.7
Construction Equipment                            +3.5
Electrical Machinery & Equipment                  +3.5
Medium-to-Heavy Truck                             +3.4
Pumps and Compressors                             +3.3
Passenger Car & Light Truck                       +3.2
Valves & Fittings                                 +3.2
Farm Equipment                                      +3
Power Transmission                                  +3
Refrigeration & AC                                  +3
Pressure Pipe                                     +2.6
Machine Tool                                        +2
Oil Field Equipment                                 +2

Pressure Pipe

Centrifugally cast ductile iron pipe has replaced practically all the gray iron pressure pipe for water and gas applications. PVC pipe, however, is very competitive in the smaller diameter sizes for water distribution systems and has replaced ductile iron, especially in some southern states. Pre-stressed concrete is competitive in the larger sizes. Ductile iron is mainly used in commercial areas and where resistance to shock and ground movement can cause fractures.

Shipments of ductile iron are forecast to grow 2.6%/year from 1.85 million tons in 1998 to 2.39 million tons in 2008 and continue to consume 43% of the total U.S. ductile iron shipments.

Exports of pipe to Third World countries continue to increase, though pipe from France and Japan may offer stiff competition in the future as the dollar strengthens.

Internal Combustion Engines

Shipments of ductile iron castings consumed in non-automotive gasoline and diesel engines are forecast to grow at a rate of 4%/year from 101,000 tons in 1998 to 140,000 tons in 2008.

Most of the tonnage in small gasoline engines continues to be in crankshaft applications, while growth in diesel engine exhaust manifolds, flywheels, bearing caps and other parts is increasing. Austempered ductile iron (ADI) is being considered as a replacement to forgings for shafts, timing gears and other applications.

Captive capacity has now been reduced to zero, resulting in 103,000 tons of available demand for non-captive foundries.

Farm Machinery & Equipment

All manufacturers of farm machinery have closed or sold their ductile iron casting facilities, leaving 145,000 tons of demand for non-captive shops. Shipments in the U.S. are forecast to increase to 180,000 tons by 2008, a 3% annual growth rate, with 29% in the 0-50-lb and 26% in the 50-150-lb casting weight range categories.

Ductile iron has replaced almost all of the malleable iron and steel applications in farm machinery, with most being cast in grade 80-55-06 ductile iron.

Construction Machinery & Equipment

Shipments of ductile iron castings are forecast to increase at a rate of 3.5%/year to 240,000 tons in 2008. About 51% of the usage is in the medium casting weight range of 50-700 lb. Ductile iron is expected to continue to replace steel in rear-end housings and suspension castings. Increased usage of low-silicon ferritic annealed ductile iron is expected where low temperature impact properties are required. Specific applications are: covers, plates, pump housings, differential cases and carriers, shaft brackets, bearing cages, trucks, planet carriers, flywheels, wheels, and other brackets.

ADI is expected to contribute greatly to growth, replacing forgings.

Oil Field Equipment

Demand for ductile iron in oil field equipment is 27% captive and is heavily concentrated in gears and related equipment for oil pumping rigs such a drive units, mud pumps, valves, swivels and fittings.

Shipments are expected to grow at 2%/year to 62,000 tons, based on the rise in oil prices required to increase demand.

Table 2. Forecast for Ductile Iron in the Motor Vehicle Industry
(in thousands)

Year   U.S. Produced    Ductile Iron    U.S. Produced   Ductile Iron
       Light Vehicles    Shipments     Med/Hvy Trucks    Shipments
          (units)         (tons)           (units)        (tons)

1998      11,600            1,044             320           213
1999      11,300            1,035             310           203
2000      10,900            1,025             300           198
2001      10,520              990             290           192
2002      11,700            1,129             320           210
2003      12,100            1,168             360           261
2004      13,500            1,303             380           275
2005      14,000            1,351             380           275
2006      14,500            1,400             400           290
2007      14,550            1,405             400           290
2008      14,700            1,419             410           300

Metalworking Machinery

Machine tools and dies are expected to see growth rates of 2% and 1.7% respectively, while rolls will decline 0.9%. Demand for rolls continues to decrease based on increased usage of continuous casting equipment. Double pour rolls will be mostly centrifugally cast.

Special Industry Machinery

Ductile iron shipments from U.S. foundries are forecast to grow 3.7%/year to 146,000 tons in 2008 from 102,000 tons in 1998. A continued replacement of gray iron and steel for applications in printing, paper mill and plastic machinery is expected.

Supply is expected to exceed demand, though closings of foundries could cause a shortage of capacity in future years in large cope and drag and nobake floor shops.

Pumps & Compressors

Ductile iron casting consumption in pumps and compressors is forecast to grow from 90,000 tons in 1998 to 124,000 tons in 2008, an annual growth rate of 3.3%. The major growth is expected in applications in irrigation and mud pumps and in replacement of gray iron and conversion of copper alloyed applications to ductile Ni-Resist.

Refrigeration & Air Conditioning

Shipments of ductile iron are forecast to increase from 42,000 tons in 1998 to 56,000 tons in 2008, an annual growth of 3%. Ductile iron crank-shafts in as-cast pearlitic ductile iron have become a standard in the industry and new opportunities are being opened for ADI applications.

Electrical Machinery & Equipment

In the past, this industry had few ductile iron applications except in the area of explosion-proof annealed ductile iron motor frames/covers and some electrical fittings. The expected future growth is expected to be in the fitting sector as ductile iron begins to replace malleable iron in the early 21st century.

Shipments are forecast to increase from 18,000 tons in 1998 to 25,000 tons in 2008, a 3.5%/year rise.

Motor Vehicles

In 1998, consumption of ductile iron castings in all cars and trucks reached 30% of the total U.S. shipments of ductile iron castings as weight per light vehicle reached 180 lb and 980 lb per medium-to-heavy track. Ductile iron castings are being used for crankshafts, differential carriers and cases, calipers, camshafts, knuckles, exhaust manifolds, brackets, suspension parts, and other automotive applications to replace forgings, fabrications and other cast metals.

Shipments of ductile iron for consumption in light vehicles are forecast to increase 3.2%/year and gain 400,000 tons by 2008 to reach 1.4 million tons, or 195 lb/vehicle, based on the following contributing factors:

* increased sales of light trucks, sports utility vehicles and vans;

* continued replacement of malleable iron yokes, steering gear housings and other applications at GM;

* redesign of brake and steering safety applications to reduce weight and improve strength-to-weight ratios in the vehicle;

* development of new ADI as a replacement for forgings;

* use of new high-silicon molybdenum, ductile Ni-Resist and other high-temperature ductile iron alloys for use in new hot engine applications.

Some declining factors include the possible replacement of suspension and brake castings with aluminum and the loss of exhaust manifold applications to stainless steel. Up to 15% of the safety part applications could be lost to aluminum and aluminum composites to reduce vehicle weight in compliance with corporate average fuel economy (CAFE) regulations.

Ductile iron casting demand in medium-to-heavy trucks is growing, and shipments are expected to increase at a long-term annual rate of 3.4% to 300,000 tons in 2008 as weight per truck and trailer reaches 1000 lb.

Domestic shortage of supply is forecast in the future unless new capacity is installed. Captive capacity in 1999 will fall to 170,000 tons and is expected to decline to almost zero by 2003 as OEMs outsource their entire ductile iron requirements.

The ductile iron forecast for cars and trucks is based on a motor vehicle forecast of vehicles produced (not sales) in the U.S. (Table 2).

Table 3. Forecast of 1999 Supply/Demand Conditions of Medium-to-High
Production Engineered Ductile Iron Castings (in thousands)

Weight            Demand        Domestic        Demand/
Range                            Supply         Supply
(lb)              (tons)         (tons)

0-50               1,333          1,520           0.88
50-150               344            400           0.86
150-300              163            200           0.82
300-700              108            150           0.72

Domestic demand supply conditions have been tight in recent years in specific weight ranges and are forecast to be tight in the peak years. Table 3 is a forecast of 1999 supply/ demand conditions of medium-to-high production engineered ductile iron castings with pipe excluded.

Twenty More Years

Based on the overall forecast of 2.5%/year of economic growth in the U.S. and the expected loss of automotive applications to aluminum and other light metals, a continued growth of 2%/year is forecast for ductile iron castings, bringing shipment levels to 8 million tons in 2028.

ADI is expected to occupy a significant part of the ductile iron picture as forgings and other manufactured parts in motor vehicles and machinery will be converted to the heat-treated iron.

The continuing 20 years from 2008-2028 will be enhanced by the development of new ferrous metal alloys that will bring ductile iron to new levels of heat resistance and physical properties. New alloys will allow the metal to be cast to final shape and final dimension by new molding methods. Productivity levels of 1-1.5 man-hours/ton will be necessary with the new ferrous alloy to assure that ductile iron can be cast in light sections with high strength-to-weight ratios to be competitive with nonferrous light metals.

New high-temperature alloys will be required to meet new engine temperatures and be cast into thin sections in high-production molding operations. New pouring methods will allow thin sections to be cast and meet high ductility requirements without heat treatment.