Chromium Recycling

Chromium Recycling

Chromium is an indispensable element in a variety of strategic and critical applications. It is used to produce steels, superalloys, refractory brick, and a variety of chemicals. There is no substitute for chromite ore in the production of chromium ferroalloys, chromium chemicals, or chromium refractories. There is no substitute for chromium in stainless and heat-resistant (SHR) steels—the major end use of chromium—nor for chromium in superalloys— the major strategic end use of chromium. The United States currently is dependent on foreign supplies of virgin chromium, imported primarily as chromite ore or as chromium ferroalloys. Most of the U.S. chromium demand has been filled by the Republic of South Africa, along with Turkey, Zimbabwe, Yugoslavia, the Philippines, China, and several other nations (1-2) (see table 1). In the future, most new production of chromium is expected to come from the Republic of South Africa, where 95 pct of these resources are located.

World resources of chromium are ample for the foreseeable future (i), as are the resources of cobalt, manganese, and the platinum-group metals (PGM). However, past political and economic events have raised concern about the uninterrupted availability and reliability of supplies of these commodities. For this reason, and because of the essential nature of these commodities, the metals are considered strategic and critical materials. The risk of cobalt supply disruption was considered high around the time of the 1978 Katangese rebellion in Zaire. The price of cobalt rose from $11/kg in 1977 to $51 /kg in 1979. Even though some of this price increase was due to sharply increased demand, the rapid changes in the cobalt market generated significant concern about future disruptions to the supply of cobalt, and also chromium, manganese, and PGM. For chromium, the lack of domestic supply, geographically concentrated foreign supply, and foreign supply from unfriendly sources (U.S.S.R at that time) or potentially politically unstable sources (Republic of South Africa) were the major causes of concern. This concern led to studies on the strategic importance, availability, and supply vulnerability of chromium and a number of other commodities. Most of these studies either are now out of date or do not supply information on losses of the strategic and critical commodities due to waste disposal, downgrading, and/or export. The lack of knowledge on these unknown losses makes conservation efforts difficult.

Industry officials in the production, manufacturing, and recycling of strategic and critical commodities are reluctant to discuss the quantities of materials that go to disposal, downgrading, and export. This information is often considered to be proprietary in nature.

Even when data are available, there is confusion between disposition of materials and recycling. For example, in a survey of seven scrap recyclers in 1987, the following estimates were obtained for disposition of scrap from the superalloy industry:

chromium-consumption-disposition-of-scrap

These estimates are typical of the data on processing, manufacturing, disposal, downgrading, and recycling of strategic and critical materials. Therein lies the difficulty in determining the amounts of critical and strategic commodities that are discarded, downgraded, or exported. This study was conducted to ascertain how the United States is using and losing its strategic and critical materials.

In 1980, the U.S. Bureau of Mines (USBM) reported the results of contract studies by Inco Research and Development Center, Suffern, NY, and Arthur D. Little, Inc., Cambridge, MA, to assess the domestic availability of chromium in scrap metal and the amount of scrap being recycled. These reports contain data up to 1976 and 1978, respectively; no updates of these studies were conducted following their publication. In the 1970’s and the early 1980’s, the National Materials Advisory Board (NMAB) conducted a number of studies on the consumption of chromium, its strategic importance, and contingency plans for the future.

In May 1985, the U.S. Congress, Office of Technology Assessment (OTA), produced a study entitled “Strategic Materials: Technologies To Reduce U.S. Import Vulnerability”. Included in the study was a set of recommendations to the USBM to conduct a survey of recycling- related activities. OTA recommended a scrap recycling study to update the chromium scrap metal information contained in two USBM publications and to expand the scope of the previous studies to include information on scrap generated by the cobalt, manganese, and PGM industries, as well as the wastes generated by all the various industrial and Department of Defense (DOD) users of these four commodities.

Acting on this recommendation, in 1987 the USBM initiated a study of the four commodities. The main objective of this study is to produce a commodity-oriented structural model tracing flow, recycling, and final disposition of the four identified commodities, which can be updated in subsequent years. A second objective of the study is to provide, in an understandable manner, an overview of the commodity flow that can be used by Congress and industry associations as a tool to help in the study of that commodity’s vulnerability to political and availability factors outside the control of the United States. Another objective of the study is to highlight significant commodity loss areas where further research is required.

A hierarchical model for the commodity cobalt was developed. The model is generic and can be applied to other strategic and critical commodities. The model previously has been applied to PGM, as well as to cobalt. To meet the stated objectives of this study, the model was applied to chromium with slight modification. (Note: The described flow model is a “snapshot” of a dynamically changing view of chromium consumption. Thus, the flow model is based on the best available data at the time of the snapshot. Recent data (obtained after 1990) show that consumption data for SHR steel scrap contain both the obsolete scrap and the prompt scrap. However, this will not be shown in the snapshot.)

Description of Flow Model

As stated in the introduction, the chromium flow model is based on the generic flow model developed for the commodities cobalt and PGM, with some minor modifications.

Definitions

Consumption

Apparent consumption.—Production plus net trade plus stock changes. Production is domestic mine production plus recycle. Net trade is imports minus exports. Stock change is beginning minus ending stocks. (Note that neither reported nor apparent consumption is actual consumption. However, apparent consumption is very close to actual consumption.) A more detailed definition and calculation of apparent consumption is in the appendix.

Consumption.—Apparent consumption, except where it is listed as reported consumption.

Reported consumption.—Those data reported to the USBM in response to the Bureau’s industry consumption survey questionnaires. In addition, estimated data from nonrespondents often is included in USBM reported consumption tables.

Scrap

Home scrap.—Scrap generated during processing that is internally recycled within the generating company and that can be considered as being endlessly recirculated. It is some times referred to as “run-around scrap.” It is not counted as part of consumption.

Obsolete scrap.—Scrap generated by users and recyclers when used products are overhauled or when the product has reached the end of its productive life cycle.

Prompt scrap.—Also called prompt industrial scrap or new scrap; consists of solids, turnings, grindings, sludges, and liquors generated during the manufacturing process when the primary product is fabricated into a finished product.

Run-around scrap—Home scrap.

Downgraded scrap.—Scrap that is used for a lower grade alloy, such as superalloy scrap used for stainless steel or alloy steel scrap used for cast iron.

Recovery and Recycle

Recovery—The practices of acquiring metals from obsolete material for recycle back into new products.

Recycle.—The processes of collecting, cleaning, assaying, and sorting materials for reuse in industry.

Losses.—Materials such as fume, spilled contaminated metal, scale, metal trapped in slag, material removed in pickling, plating wastes, grindings, etc.

Recovery loss—Those obsolete materials that are never collected for recycling. An example is obsolete material that is used as landfill.

Recycling loss.—Those losses that occur in the recycling process. For example, a major loss area is downgraded scrap material that is recycled to lower quality metals, particularly where the metal in question is not needed but is acceptable.

Ferroalloys

Chromium ferroalloy and metal.—Ferrochromium plus ferrochromium-silicon plus chromium metal.

Chromium ferroalloy.—Ferrochromium plus ferro-chromium-silicon.

Ferrochromium.—High- plus low-carbon ferro-chromium.

Ferroalloys.—All ferroalloys, including ferrochromium, ferrochromium-silicon, ferromanganese, ferrosilicon, ferronickel, ferroboron, ferrovanadium, ferrotitanium, ferrotungsten, etc.

General Configuration

A typical chromium flow model is shown in figure 1. (Mathematical relationships in the chromium model are discussed in the appendix.) The supplies of chromium come from imports of chromite ore, chromium ferroalloys, chromium chemicals, and chromium metal, and secondary production (scrap). In any given year, fractions of this material go to exports, stocks, domestic processing, and manufacturing. During processing, about 28 pct of input reports as home scrap and is internally recycled. About 5 pct of input reports to processing losses, about 2.6 pct of input reports to downgraded material, and most of the chromium reports to manufacturing. Note that home scrap is not counted, as it is endlessly recycled, and counting it would be double counting. However, it is part of the recycling of the commodity. The processed material then goes to product manufacturing. During manufacturing, a small amount of chromium (about 4 pct) reports as losses and some as downgraded material (about 12 pct). The remainder goes to final products. Prompt scrap amounts to about 13 pct, of which 0.3 pct goes to export and the remainder to processing. After a normal use life, each product that is not in a dissipative end use winds up as obsolete scrap and waste. The estimated amount recycled, based on data reported to the USBM, was 99,221 mt of chromium. Much of this material (97,098 mt of chromium) was SHR steel and superalloy. Some additional material, nearly all metallurgical material, is

chromium-consumption typical flow model

recycled, but act for its chromium content. There are currently no available published data on the percentages of contained chromium in these scrap materials.

Properties of Flow Model

The flow model described in IC 9252 and IC 9303 is generic in nature and thus capable of being used for a wide variety of commodities with only minor modifications. The model is easily updated, is generally understood by the public, and highlights areas where recycling research is needed. The model is hierarchical, with three levels: the entire chromium industry, the individual industry level, and the individual plant level. The data in this report cover the entire chromium industry and the individual industry level.

Assumptions in Model

In the development of the model, a number of assumptions had to be made. These are as follows:

  1. Where data were found, the percentages reporting in each category were used. Where no current data were available, the data from NMAB-335 and NMAB-406 were used and assumed to be still valid.
  2. The use lives of various products vary over a wide range. NMAB estimated the lifetimes of a number of products. Its estimation for the lifetimes of superalloys, welding and hardfacing materials, SHR steels, high-strength low-alloy (HSLA) steels, and tool steels was 5 years, and its estimation for other alloys (based on the high content of magnetic alloys in the “other alloys” category) was 10 years. The lifetimes of carbon steels and cast irons are based on the current life cycles of automobiles and light trucks because these items are high in consumption of carbon steels and cast irons. Currently, the life cycle of motor vehicles is about 10 years. The lifetimes of miscellaneous and unspecified materials is assumed to be 5 years, based on the most frequent lifetimes of metal products. Nearly all refractory materials, with the exception of glass furnace refractories, have lifetimes of less than 1 year. Chemical products are nearly all used in dissipative end uses and are not recycled.
  3. Thus, it is assumed that obsolete scrap available for recycle in 1989 would come from 1979 consumption of carbon steels, cast irons, and other alloys; from 1984 consumption of superalloys, welding and hardfacing materials, SHR steels, alloy steels, HSLA steels, tool steels, and miscellaneous and unspecified metal products; and from 1989 refractory products.
  4. Unless otherwise stated, all chromium quantities are metric tons of contained chromium. All values reported are the best estimates possible with currently available data.

Chromium Industry

Chromium is consumed by three major industries in the United States. In 1989, the metallurgical industry consumed about 84 pct, the chemical industry about 13 pct, and the refractory industry about 3 pct. The major overall end use is for SHR steels, which account for about 78 pct of metallurgical consumption, or about 65 pct of apparent consumption of chromium. In 1989, the United States imported about 78 pct of the chromium that it consumed. There has been a trend in chromite-producing countries to vertically integrate their chromium industries by developing their own ferrochromium production facilities. This has led to a significant change in the percentages of chromium imported as chromite ore versus chromium imported as ferrochromium. The data from 1973 to 1989 are shown in table 2. Ore imports have fallen from 72.9 pct of imports in 1973 to 44.1 pct in 1989, and ferrochromium imports have risen from 27.1 pct in 1973 to 55.9 pct in 1989. The trend in U.S. imports is shown in figure 2. This trend of producer nations toward their own production of chromium ferroalloys has caused a decline in U.S. chromium ferroalloy production.

chromium-consumption production of ferroalloy

chromium-consumption ore imports

The breakdown of chromium consumption in the United States by end use industries in 1989 is shown in table 3, and an overview of the U.S. chromium industry is shown in figure 3. The flow model does not include domestic ferrochromium production losses (1,028 mt). In 1989, chromium input to the U.S. economy amounted to 428,376 mt distributed among various input materials as follows: chromite ore contained 162,113 mt of chromium; chromium ferroalloy, 208,152 mt; chromium metal, 4,202 mt; chromium chemicals, 4,688 mt; and recycled scrap, 99,221 mt. The distribution of this input material was as follows: exports of chromite ore and chromium ferroalloys, metal, and chemicals contained 24,801 mt of chromium; additions to industry stocks, 1,806 mt; materials consumed directly by industry, 360,668 mt; and chromite ore for chromium ferroalloy production, 91,101 mt. During processing to chromium ferroalloys, slag and particulates containing 1,028 mt of chromium reported as losses while chromium ferroalloys containing 90,073 mt of chromium reported to U.S. chromium-consuming industries.

The metallurgical industries consumed materials containing 378,974 mt of chromium. The chromium chemical industries consumed material (mostly ore) containing 60,210 mt of chromium, and the refractory industry consumed ore containing 11,832 mt of chromium.

The only current domestic supply of chromium is recycled scrap. SHR steels and superalloys are recycled primarily for their nickel and chromium content. An electric furnace charge for SHR steels may consist of as much as 50 pct prompt and purchased SHR steel scrap. In many cases, mixed turnings and borings from superalloy product manufacturing are downgraded to stainless steel scrap. While this does not waste the nickel and chromium content, a higher value scrap is then sold as a lower value scrap, and valuable supplies of superalloys are lost to a lesser product. Most of the other steel and other alloys containing chromium may be recycled, but not specifically for their chromium content. Chromium chemicals generally are consumed in dissipative end uses and thus are not recycled. There is some recycling of chromium refractories, particularly foundry sands. However, there may be some recycling of chromium from waste materials in the future because of increasingly strict environmental standards and increasing disposal costs for wastes.

Carbon Steels

Carbon steels are consumed in the manufacture of automobiles, appliances, structural steels, and a wide variety of other products. During 1989, the carbon steel industry consumed 7,776 mt of chromium, mostly in the form of chromium ferroalloys. The flow model for chromium in carbon steels is shown in figure 4. An additional 357 mt of chromium in prompt scrap and 1,005 mt of

chromium-consumption overview chromium industry

chromium-consumption carbon steel flow model

chromium in home scrap were also consumed during processing. A quantity of material containing 392 ml of chromium reported to processing losses (slags, dusts, etc.). A quantity of material containing 392 mt of chromium was downgraded to lesser materials. The remaining material, containing 7,350 mt of chromium, reported to product manufacturing.

During manufacturing, material containing 357 mt of chromium was recycled to processing as prompt scrap, material containing 1,149 mt of chromium was downgraded to lesser metals, and material containing 1,149 mt of chromium reported to manufacturing losses (dusts, contaminated metal, grindings, etc.). Final products using carbon steels contained 4,696 mt of chromium.

Because carbon steel products are used heavily in automobiles and appliances, these products are estimated to have a 10-year life cycle. Material containing 5,859 mt of chromium from 1979 carbon steel industry consumption potentially was available for recycling. While considerable amounts of this material were recycled to various steel melts as part of the scrap charges to the furnaces, essentially none is recycled specifically for its chromium content. In many instances, the chromium-containing carbon steels are not identified as such and are, thus, recycled to other steels. There are no data available to indicate the success of recovering chromium-bearing carbon steels as such and recycling them back to chromium-containing carbon steels.

Stainless and Heat-Resistant Steels

SHR steels are used in many environments where resistance to corrosion or heat is required. They also have end uses as varied as kitchen sinks or other sinks, counter tops, decorative components of automobiles and marine vessels, and jet engine parts. SHR steels are the largest consumers of chromium, accounting for 65 pct of 1989 apparent consumption of chromium. SHR steels also accounted for most of secondary or recycled chromium- bearing scrap by consuming 97,098 mt of this scrap. The flow model for SHR steels is shown in figure 5. The total feed to SHR steels included obsolete scrap containing 97,098 mt of chromium, prompt scrap containing 49,071 mt of chromium, home scrap containing 174,947 mt of chromium, and new material containing 197,325 mt of chromium. During processing, in addition to home scrap, 32,003 mt of chromium reported to processing losses, while 14,721 mt of chromium reported to downgraded scrap, and material containing 296,770 mt of chromium went as feed to manufacturing.

chromium-consumption stainless and heat resistant

During manufacturing, material containing 46,164 mt of chromium reported to downgraded scrap, material containing 4,614 mt of chromium reported to manufacturing losses, and material containing 49,071 mt of chromium returned to processing as prompt scrap. The final products contained 196,922 mt of chromium.

Obsolete scrap for 1989 consumption of chromium in SHR steels came from 1984 production of these materials. From 1984 apparent consumption of chromium in SHR steels, material containing 231,463 mt of chromium potentially would be available for recycle. Available data indicate that SHR steel obsolete scrap containing 43,443 mt of chromium was exported in 1989. This left scrap containing 188,020 mt of chromium available for recovery. Of this amount, scrap containing 80,133 mt of chromium was lost to unknown and unrecovered losses. The remaining scrap, containing 107,887 mt of chromium, was processed for recycling. During recycling, material containing 10,789 mt of chromium reported to recycling losses, and scrap containing 97,098 mt of chromium reported to 1989 SHR steel consumption. The recycling loss material probably includes major amounts of downgraded scrap.

These export, unknown, unrecovered, and recycling losses of SHR steel scrap account for the largest losses of scrap that contains chromium. This amounts to a loss of material containing 134,365 mt of chromium. This lost material would amount to about 30 pct of 1989 total apparent consumption of chromium.

Alloy Steels

Special alloying constituents give alloy steels the strength necessary for their many end uses. These alloys are most frequently used in structural steel applications such as in bridges and buildings. These alloys may contain from 0.4 to 4.0 pct chromium. The flow model for alloy steels is shown in figure 6. New chromium material feed to processing contains 33,453 mt of chromium. Additional feed to processing is home scrap containing 4,325 mt of chromium and prompt scrap containing 1,537 mt of chromium. During processing, loss material containing 1,685 mt of chromium and downgraded material containing 1,685 mt of chromium are generated. Processing material feed to manufacturing contains 31,620 mt of chromium.

During manufacturing, in addition to prompt scrap, loss material containing 4,941 mt of chromium and downgraded material containing 4,941 mt of chromium are produced. Final products contain 20,201 mt of chromium.

chromium-consumption alloys steels flow model

Potentially available material for recycling was provided by 1984 apparent consumption of chromium for alloy steels. This material contained 28,720 mt of chromium. Essentially none of this material was recycled for its chromium content, and thus, obsolete scrap containing 28,720 mt of chromium was lost in unknown and unrecovered materials. While almost all steel melts contain between 30 and 50 pct scrap material, none is known to be specifically recycled for its chromium content. Thus, there are no data on the amounts of chromium in this recycled steel that arrive in the new products. Any chromium that remains in the melted scrap is augmented by additions of chromium, mostly from ferrochromium.

High-Strength Low-Alloy Steels

These alloys were originally developed for the Alaska Pipeline, where environmental conditions required unusually high strength materials. These steels are now used extensively as structural steels in automobiles, buildings, and bridges, and also have some uses where the properties of these steels provide protection against atmospheric corrosion. The flow model for HSLA steels is shown in figure 7. Feed to processing included new material containing 13,049 mt of chromium, prompt scrap containing 600 mt of chromium, and home scrap containing 1,687 mt of chromium. During processing, loss material containing 657 mt of chromium and downgraded material containing 657 mt of chromium were generated. The remaining material, containing 12,334 mt of chromium, went as feed to manufacturing.

During manufacturing, prompt scrap containing 600 mt of chromium, loss material containing 1,927 mt of chromium, and downgraded material containing 1,927 mt of chromium were produced. Final products contained 7,880 mt of chromium. From 1984 apparent consumption of chromium in HSLA steels, obsolete material containing 7,150 mt of chromium potentially was available for recycling. Essentially all of this material reported as unknown and unrecovered losses. As with alloy steels, almost all this material is not recycled for its chromium content. Thus, the entire 7,150 mt of contained chromium is lost to efficient recycle.

Tool Steels

Tool steels arc designed for cutting, forming, or otherwise shaping a material. Typically these steels may contain

chromium-consumption high strength low-alloys steels flow model

from 0.25 to 13.5 pct chromium. The flow model for tool steels is shown in figure 8. New material containing 4,370 mt of chromium, prompt scrap containing 201 mt of chromium, and home scrap containing 565 mt of chromium were the feed to processing. Loss material containing 220 mt of chromium and downgraded scrap containing 220 mt of chromium were produced during processing. Processed material containing 4,131 mt of chromium was sent as feed to manufacturing,

During manufacturing, prompt scrap containing 201 mt of chromium, downgraded scrap containing 645 mt of chromium, and loss material containing 645 mt of chromium were produced. The final products contained 2,639 mt of chromium.

Material containing 3,680 mt of chromium from 1984 apparent consumption of chromium in tool steels potentially was available for recovery and recycling. Virtually all this material reported to unknown and unrecovered losses. The reason none is shown to be recycled is that obsolete scrap from these types of end uses is not recycled for its chromium content. Thus, the fate of material containing this 3,680 mt of chromium is unknown.

Cast Irons

Cast irons have a variety of end uses. Some of the major ones are as engine blocks, some types of gears, and large pieces of many different types of machinery. Typically these cast irons may contain from 0.03 to 0.45 pct chromium. The flow model for cast irons is shown in figure 9. New feed material containing 7,454 mt of chromium went to processing. Prompt scrap containing 1,357 mt of chromium and home scrap containing 359 mt of chromium also were part of the feed to processing. During processing, material containing 373 mt of chromium reported to processing losses. Material containing 8,438 mt of chromium was feed to manufacturing.

During manufacturing, material containing 132 mt of chromium reported as manufacturing losses, and prompt scrap containing 1,357 mt of chromium was produced and recycled back to processing. Final products contained 6,949 mt of chromium.

Typically, today’s automobiles last an average of 10 years. Because automobile engine parts are the heaviest users of cast irons, a lifetime of 10 years is assumed.

chromium-consumption cast irons flow model

Thus, potentially available obsolete scrap for 1989 production would come from 1979 apparent consumption of chromium in cast irons. Thus, obsolete scrap containing 11,304 mt of chromium potentially would be available for consumption in 1989. This material is not recycled for its chromium content, but for its iron content, A large percentage of cast iron scrap is recycled and rcmelted; however, because there were no data on amounts recycled for their chromium content, it is assumed that 1979 obsolete scrap reports to unknown and unrecovered losses.

Superalloys

Superalloys are metals that have very high strengths and that are resistant to corrosion and oxidation at high temperatures. Because of their high values (up to $31/kg), much care is taken in recycling these materials. Typical uses are in jet aircraft engine components, both moving and stationary parts. A number of these alloys also are used for applications in highly corrosive environments. Typically, superalloys are nickel- or cobalt-based alloys; however, there are also some iron-based superalloys. Superalloys may contain from 8 to 30 pct chromium. The flow model for superalloys is shown in figure 10.

Processing feed materials included new material containing 10,128 mt of chromium, 2,123 mt of chromium in obsolete scrap, 4,154 mt of chromium in prompt scrap, and 11,488 mt of chromium in home scrap. During processing, material containing 221 mt of chromium reported as processing losses, and scrap containing 377 mt of chromium reported to downgraded scrap. Processing metal feed to manufacturing contained 15,808 mt of chromium.

During manufacturing, material containing 1,312 mt of chromium reported to manufacturing losses, and scrap containing 1,678 mt of chromium reported to downgraded scrap. Prompt scrap containing 5,685 mt of chromium also was produced. Part of this prompt scrap, containing 1,531 mt of chromium, was exported. The remaining prompt scrap, containing 4,154 mt of chromium, was recycled to processing. Final products contain 7,132 mt of chromium.

Obsolete products from 1984 apparent consumption of chromium in superalloys contain 8,524 mt of chromium and potentially are available for recycling. During recovery, scrap containing 6,165 mt of chromium reported as unknown and unrecovered losses. Of the obsolete scrap going on to processing, material containing 236 mt of chromium reported to recycling losses, and scrap containing

chromium-consumption superalloys flow model

2,123 mt of chromium was recycled. Thus, scrap containing about 6,401 mt of chromium, and also cobalt and nickel, is lost to efficient recycle. This would amount to about 52 pct of 1989 apparent consumption of chromium in superalloys.

Data shown by Papp give an estimated breakdown of the various scrap and loss components in the flow model for chromium in superalloys (see table 4). Note that the prompt scrap that is exported contains mostly grindings and turnings (69 pct), which frequently are not suitable for recycle back to vacuum-melted superalloys because of possible contamination. All 1,531 mt of chromium in the exported prompt scrap is lost to domestic production of superalloys, which contain chromium, cobalt, and manganese—strategic and critical materials. Total losses of superalloys to wastes, downgraded scrap, and export (5,119 mt contained chromium) amounted to about 42 pct of 1989 apparent consumption of chromium in superalloys.

Welding and Hardfacing Materials

These materials are used for joining steels and other alloys and for putting wear-resistant coatings on items such as teeth on digging equipment. These alloys are also used for automotive engine valves, fluid valves, knives, cutters, erosion shields, hot-working dies, and bearing surfaces that cannot be lubricated. These cobalt-base alloys may contain up to 31 pct chromium. The flow model for welding and hardfacing materials is shown in figure 11. In 1989, materials containing 1,208 mt of chromium were consumed for these alloys. Feed to processing also included prompt scrap containing 556 mt of chromium and home scrap containing 306 mt of chromium. During processing, material containing 259 mt of chromium reported to processing losses. An additional amount of material containing 145 mt of chromium reported to downgraded scrap. Processed material going to feed for manufacturing contained 1,360 mt of chromium.

During manufacturing, prompt scrap containing 556 mt of chromium was produced. Materials reporting as manufacturing losses contained 44 mt of chromium. Final products contained 760 mt of chromium.

Material from 1984 apparent consumption for welding and hardfacing applications contained 996 mt of chromium that potentially would be available for recovery and recycling. Significant amounts of this material are lost during their use life, and most of the rest, while it may be recycled, is not recycled back to this end use and, thus, is in unknown and unrecovered losses.

chromium-consumption composition of superalloy scrap

Other Alloys

Materials in this industry are cutting materials, magnetic alloys, aluminum alloys, copper alloys, nickel alloys, and various other alloys. The chromium content of these alloys varies widely: magnetic alloys, 0.5 to 5.75 pct chromium; aluminum alloys, 0.04 to 0.4 pct chromium; copper alloys, 0.4 to 3.2 pct chromium; nickel alloys, 0.25 to 27 pct chromium; cobalt alloys, 20 to 30 pct chromium; and thermocouple and electrical resistance alloys, 4 to 30 pct chromium. These materials are used in a wide variety of applications: aluminum alloys for marine, automobile, and aircraft parts, drilling rigs, TV towers, and armorplate; copper alloys for switches, circuit breakers, continuous

chromium-consumption welding and hardfacing materials flow model

casting molds, heat exchanger tubes, and pipe; nickel alloys for seawatcr corrosion resistance, high-temperature applications, and heating elements; cobalt alloys for bearings and valve seats; magnet alloys for permanent magnets; and other alloys for thermocouples, resistance heating elements, and cutting materials.

The flow model for other alloys is shown in figure 12. Processing feed consisted of new materials containing 4,105 mt of chromium, prompt scrap containing 684 mt of chromium, and home scrap containing 832 mt of chromium. During processing, material containing 703 mt of chromium reported to processing losses, and the remaining materials, containing 4,087 mt of chromium, reported to feed for manufacturing.

During manufacturing, prompt scrap containing 684 mt of chromium and manufacturing loss material containing 64 mt of chromium were produced. The remaining material was final products containing 3,339 mt of chromium.
These products are assumed to have a 10-year use life. Thus, the 1979 apparent consumption of chromium in other alloys potentially is available for recycling; this material contains 4,535 mt of chromium. However, none of this material is known to be recycled for its chromium content, and thus, it reports as unknown and unrecovered losses, leaving no material for recycling.

Miscellaneous and Unspecified Materials

This category contains small metallurgical end uses of chromium, including the consumption of an unknown quantity of material in which ferrochromium silicon is used to produce tool steels. (Thus use of ferrochromium silicon in tool steels is withheld to avoid disclosing company proprietary data.) The assumed flow model for this category of material is shown in figure 13. Processing feed included new material containing 611 mt of chromium, prompt scrap containing 102 mt of chromium, and home scrap containing 124 mt of chromium. During processing, material containing 105 mt of chromium reported to processing losses and material containing 30 mt of chromium reported to downgraded scrap. Processing material feed to manufacturing contained 578 mt of chromium.

During manufacturing, material containing 102 ml of chromium reported as prompt scrap, material containing 91 mt of chromium reported to downgraded scrap, and material containing 9 mt of chromium reported to manufacturing losses. The final products contain 376 mt of chromium.

As with most other end uses of chromium, little or no material is recycled for its chromium content. Thus, the

chromium-consumption miscellaneous and unspecified materials

material from 1984 apparent consumption of chromium in miscellaneous and unspecified materials potentially available for recycle (containing 1,734 mt of chromium) reports to unknown and unrecovered losses.

Chemicals

Chromium chemicals are used for electroplating, pigments and paint, leather tanning, drilling muds, water treatment, and wood treatment. The flow model for chromium chemicals is shown in figure 14. Chemical processing consumed mostly chromite ore containing 60,210 mt of chromium in 1989. During processing, material containing 1,806 mt of chromium reported to processing losses. The remaining material, nearly entirely sodium dichromate, reported to chemical manufacturing and contained 58,404 mt of chromium. During manufacturing of chromium chemicals, material containing 2,920 mt of chromium reported to manufacturing losses. The final chemical products contained 55,484 mt of chromium.

Chromium chemicals, like most chemicals, are used in dissipative end uses. Thus, the chromium content is not readily available for recycle. However, ever stricter environmental controls on chromium will make recycling of chromium-bearing wastes a necessity. While most recycling processes suggested to date are not economically feasible at this time, the continuously escalating costs of disposal of chromium-containing wastes will eventually make recycling a necessity. For example, it soon may be prohibitively expensive to use plating waste as landfill. Thus, a process to reclaim the chromium content of these wastes may become economically feasible. Some end uses, such as pigments and paints, will continue to remain unavailable for recycling for the foreseeable future. This might make the use of alternative materials a necessity.

Refractories

Chrome refractories include chrome bricks, chrome-magnesite bricks, chrome-containing gunning mixes, and chromite foundry sands. There is a decreasing demand for chrome-containing bricks and gunning mixes because of the replacement of these materials with substitutes. Chromite refractory sands are still in high demand. The flow model for chromium refractories is shown in figure 15. New material containing 8,070 mt of chromium, recycled obsolete foundry sands containing 3,762 mt of chromium, prompt scrap containing 947 mt of chromium, and home scrap containing 592 mt of chromium were processing feeds. During processing, material containing 401 mt of chromium reported to processing losses, and material containing 12,377 mt of chromium reported as processing feed to manufacturing.

During manufacturing, prompt scrap containing 947 mt of chromium and manufacturing loss material containing 371 mt of chromium were produced. Final products contained 11,060 mt of chromium.

Because nearly all uses of chromium-containing refractories, except glass furnace linings, have life cycles of less than 1 year, material available for recycle would come from 1989 final products, which contained 11,060 mt of chromium. During recovery, only foundry sands are being processed, thus unknown and unrecovered losses account for a small fraction of foundry sands and essentially all chrome bricks and gunning mixes. This material contained 5,253 mt of chromium. During recycle, an additional amount of material reported as recycle losses containing

chromium-consumption chemicals flow model

chromium-consumption refractories flow model

2,044 mt of chromium. The final amount of recycled material, virtually all foundry sand, contained 3,762 mt of chromium.

Overall Chromium Industry

A composite flow model summed from the values in all chromium industry flow models described previously is shown in figure 16. Processing feed consisted of new chromium material containing 347,759 mt of chromium, recycled obsolete scrap containing 102,983 mt of chromium, prompt scrap containing 59,566 mt of chromium, and home scrap containing 196,230 mt of chromium. Material reporting to processing losses contained 38,825 mt of chromium, and material reporting to downgraded processing scrap contained 18,227 mt of chromium. The remaining material, containing 453,257 mt of chromium, reported as processing feed to manufacturing.

During manufacturing, prompt scrap containing 61,097 mt of chromium was produced. Superalloy prompt scrap containing 1,531 mt of chromium was exported, and the remaining prompt scrap, containing 59,566 mt of chromium, went to processing. In addition, downgraded manufacturing scrap containing 56,595 mt of chromium and manufacturing loss material containing 18,128 mt of chromium were produced. Final products contained 317,438 mt of chromium.

Potentially available obsolete materials for recovery and recycle contained 315,025 mt of chromium, an amount equal to about 70 pct of 1989 apparent consumption of chromium. Of this potentially available material, material containing 43,443 mt of chromium was exported, unknown loss and unrecovered material containing 155,529 mt of chromium reported as recovery losses, and waste material containing 13,069 mt of chromium reported as recycling losses. Recycled SHR steels, superalloys, and foundry sands (the only materials being efficiently recycled) contained 102,983 mt of chromium. This was about 33 pct of the material potentially available for recycle and accounted for 23 pct of 1989 apparent consumption.

Chromium Losses

Overall, 345,347 mt of contained chromium was lost in 1989 (see table 5). This overall loss amounts to 76 pct of 1989 apparent consumption of chromium. Of this amount, 131,775 mt of chromium, representing 29 pct of 1989 apparent consumption, was lost during processing and manufacturing operations, and 213,572 mt of chromium, equaling 47 pct of 1989 apparent consumption, was lost

chromium-consumption overall industry flow model

from recovery and recycling operations on obsolete scrap material. The major loss of materials was in the SHR steels industry, where the total loss of chromium during processing and manufacturing in 1989 was 97,502 mt of contained chromium, while recovery and recycling operations on chromium-containing SHR steel obsolete scrap showed a loss of 134,365 mt of chromium, or about 30 pct of 1989 apparent consumption. At the same time, all other industries had a recovery and recycling loss of 79,207 mt of chromium, equal to 18 pct of 1989 apparent consumption.

If 90 pct of all chromium-containing obsolete scrap could be recycled efficiently (283,523 mt contained chromium), then the net import reliance would fall from the 1989 level of 78 pct to a value near 37 pct (see table 6). Thus, our national reliance on imported chromium would be very significantly diminished. However, the materials potentially available for recycle would first have had losses to processing and manufacturing equal to about 42 pct during the years the materials were produced. Thus, the maximum possible recycle would be about 58 pct, which would equal a 60-pct net import reliance. This level of recycle would be the best level possible unless technology to process and manufacture could be developed that would lead to lower levels of losses and downgraded materials.

 

chromium-consumption loss

chromium-consumption-net-imports

Summary

A commodity flow model was developed for the industries that consume chromium. Based on available data, the model follows chromium through its processing, manufacturing, and recycling operations, showing estimated values for material lost through these operations. The model was developed using certain estimates and assumptions and the best data available at the time. The model can be easily updated as new data become available. The multiplication factors will all change with time. New factors can replace older ones as data are acquired.

An industry flowchart was presented for each of the industries that consume chromium. The overall flow of the chromium commodity also was presented. The apparent consumption of chromium in 1989 was 451,769 mt. The estimated amounts consumed by the various industries are shown in table 3. The metallurgical industries consumed materials containing 379,728 mt of chromium, or about 84 pet of 1989 apparent consumption; the chemical industry, materials containing 60,210 mt of chromium, or about 13 pct; and the refractory industry, material containing 11,832 mt of chromium, or about 3 pct. Of the 84 pct of 1989 apparent consumption of chromium by the metallurgical industries, 294,423 mt of chromium or 65 pct of 1989 apparent consumption of chromium was in SHR steels. The next three highest metallurgical industry consumers of chromium were the alloy steel industry, 33,453 mt or 7 pct of the 1989 apparent consumption of chromium; HSLA steel industry, 13,049 mt or 3 pct; and the superalloy industry, 12,251 mt or 3 pct. All other metallurgical industries combined accounted for 26,552 mt or 6 pct of 1989 apparent consumption of chromium.

Based on the estimated lifetimes of the various products and the estimated amounts consumed in 1979 (10 years), 1984 (5 years), and 1989 (1 year), there were potentially recyclable products containing 315,025 mt of chromium (figure 16). From literature data, material containing an estimated 102,983 mt of chromium that can be traced was recycled in 1989 for consumption. Papp shows a total of 99,221 mt of contained secondary chromium. The difference between the reported 99,221 mt of chromium from secondary sources and the 102,983 mt of recycled chromium estimated from literature data is due to data concerning the recycling of chromium-bearing foundry sands. There currently is no means of tracing how much chromium-bearing steel scrap is actually recycled to the same end use or to another chromium-consuming end use.

During 1989, 345,347 mt of chromium was lost as processing waste and downgraded material, manufacturing waste and downgraded material, recovery and recycling loss material, and scrap exports. The major loss area was in the SHR steels industry, where losses amounted to 231,867 mt of chromium.

Conclusions

A chromium flow model was developed. The mathematical relationships in the model are discussed in the appendix. The model estimates the distribution of 451,769 mt of chromium consumed in the 12 chromium-consuming industries. The best available data estimate that about 131,775 mt of chromium was lost during processing and manufacturing operations, 56,953 mt of chromium to waste, and 74,822 mt of chromium to downgraded scrap. The 59,566 mt of chromium in prompt scrap that was produced during manufacturing and the 196,230 mt of chromium in home scrap that was generated during processing were efficiently recycled. Of the material potentially available for recycling, estimated with current available data, only the disposition of about 102,983 mt of chromium to recycling can be followed. Material, mostly SHR steel scrap and superalloy scrap, containing 44,974 mt of chromium was exported. The remaining material, containing 168,598 mt of chromium as unknown, unrecovered, use life, or dissipative losses, cannot be traced with current data. There is a need to obtain data that trace where this material goes. Thus, it is recommended that the USBM make changes in its data-gathering survey sheets to obtain the required information on a continuing basis. This would provide a continuously up-to-date flow model that can be supplied to those requiring the information in developing national policy regarding chromium.