1. History of wire
   
   
2. Stainless Steel : history & production
   
   
3. Stainless Steel Wire manufacturing
   
   
4. Stainless Steel Wire Mesh
   
   
5. Stainless Steel Wire in household uses
   
   
6. Stainless Steel Wire in interior decoration
   
   
7. Stainless Steel Wire in food processing
   
   
8. Stainless Steel  Wire in automobile applications
   
   
9. Stainless Steel Wire in aerospace applications
   
   
10. Stainless Steel Wire in medical applications

Wire is one of the generic types of metallurgical products, together with plates, sheets, bars, tubes. Encyclopaediae generally define metallic wire as a “ single strand or rod of metal, usually cylindrical “. The history of wire making goes way back in Antiquity .

The first known writing relating to wire appears in the Bible (Ex.39:3): “ And they did beat the gold into thin plates, and cut it into wires...) However, archeological discoveries date the art of wire making to much earlier times, probably as far back as 4000 BC : a necklace containing gold wire was found in the tomb of an Egyptian Pharaoh who reigned about 2750 BC and there are wire-containing jewelry and ornaments made by Assyrians  in the 1700's BC.

The manufacturing of wire was for a long time limited to jewelry and similar decorative items using “soft” materials such as gold or bronze. Utilitarian uses started to appear in the latter years of BC, as shown by 3 bronze wires twisted into a cable  found in Pompei. For many centuries, wire was manufactured by hammering the ductile metals gold & bronze into thin sheets. Then hammers and files were used to transform the thin strips into short round pieces , which could  eventually be brazed into  longer wires . There is however evidence that even in the antique Egypt some wire were actually drawn through tapered holes , the crude predecessors of  “dies”.

Modern wire manufacturing done by drawing through dies can be traced to the 300 AD   to 700 AD period. Wire manufacturing by drawing through dies became common in the 12th to 14th centuries, in France, England and Germany: in those times, wire was drawn by hand. German wire manufacturers started to use waterpower to replace hand operation in the Middle Age. Also, German manufacturers of the Düsseldorf area discovered about 1650 the advantage of using lubricants (such as stale beer!) to draw hard steel.

Thus, the basic method of wire manufacturing, i.e. drawing a soft metal through a hard, incompressible die has remained unchanged for centuries. Obviously, modern industrial wire manufacturing has developed for productivity and quality a number of sophisticated technologies pertaining to:

- Wire rod  (feed material coming from the hot rolling mill) quality and special coatings

- Drawing  lubricants  (Na or Ca based soap–type compounds)

- Diamond (oil drawing) or carbide dies (dry drawing) of increasing high technology

- Very productive highly automated multi-hole drawing machines

- Continuous processes combining cleaning, annealing, coating and skin pass sizing

The above narrative obviously only pertains  to the “metallic wire” and not  to the increasingly important glass wire involved in the  “fiber optics” industry.

Stainless Steel (also commonly referred to as “inox” or “rostfrei”) is now a very common feature of 21st Century living. However, this material is the most modern type of steels:  basically, its invention dates only to the early days of the 20th Century when it was discovered that a certain amount of Chromium as alloying element (minimum about 11%) added to ordinary steel made it shiny and highly resistant to tarnishing and rusting. This rust-resisting property translates into “corrosion resistance “which sets stainless steel apart from all other steels. Though the true “discovery” of stainless steel occurred in the 1900 to 1915 time period, several earlier contributions can be traced back to:

- 1821: Frenchman Berthier found that iron alloyed with Chromium was acid resistant

- 1872: English engineers Wood & Clark applied for a patent on a 30% Chromium iron alloy

The actual discovery credit is now widely recognized to be shared between both:

Frenchman Léon Guillet, who published in 1904 research on steels with close to current grades 410, 420 compositions and 1906 a detailed study of an alloy iron-nickel-chromium with the basic metallurgical structure of the 300 series stainless steel. These findings were completed by Frenchman Portevin who published in 1909 studies on an alloy close to current 430 stainless steel

At the same time, Englishman Harry Brearley, Chief of the research lab of Thomas Firth & Sons in Sheffield conducted research which led to the first industrial cast of a stainless steel in 1912. Beardley called the new material “rustless steel”. Shortly therafter, the manufacturer Ernest Stuart coined the name “stainless steel”.

Later on, W. Hatfield, successor of H. Brearley at Thomas Firth patented the 18% Chromium and 8% Ni austenitic stainless steel which became the most widespread used stainless steel known as grade 304. On a parallel time frame, Société d’Electrométallurgie d’Ugine has to be credited for the metallurgical research and industrialization of the ferritic grades such as 430, with 17% Chromium and no Nickel. Also, German metallurgists of Krupp Research Institute have to be recognized for their work in the 1915 to 1930 time frame.

The large development of industrial production of stainless steels is only fairly recent: It has exhibited a spectacular growth from 2 Million Tons in 1950 to 48 million Tons in 2017, with 3 modern metallurgical processes playing a key role in this development:

• Successive developments since the early 1900 of Electro Metallurgy
• The Argon-Oxygen (AOD) refining convertor allowing to reach low Carbon content
• Since the late 1970’s, widespread use of the continuous casting technology

Like every type of steel wire, stainless steel wire is an established and widely used basic metallurgical product. Made of a modern specialty steel “discovered “in the 1910’s, it is also manufactured by the “drawing process” dating back to Antiquity and extensively developed in Europe in the 12th to 16th Centuries. The wire drawing process is simple in concept: it reduces the cross-section of the wire by pulling it through a single or a series of drawing dies typically made of Tungsten carbide or polycrystalline diamond (in the case of fine stainless-steel wire sizes).

The raw material/ feedwire for drawing stainless steel wire is stainless steel “wire rod” produced on modern hot rolling mills from billets issued of the “Electric furnace + AOD converter + continuous casting” process. The wire rod comes in sizes 5.5 to 30 mm with   5.5 mm (0.218”) being the prevalent size; the wire rod is annealed + pickled or simply pickled if the rod is controlled-cooled.

For wire sizes > 0.8mm, the drawing process   is known as “dry drawing”. In this case, the wire rod is subjected to a phosphate pre-coat which will provide a suitable substrate for wire drawing lubricants, typically Na or Ca-containing soaps. The stainless steel wire is then drawn through a series of dies boxes containing the lubricant in powder form + the tungsten carbide die, often on so-called multi-holes or multiple-die machines (up to 12 in some of the most modern machines). Depending on the finish size and the grade, it may be necessary to do intermediate operations of in-line cleaning followed by in-line annealing in N2/H2 reducing atmosphere and eventual re-coating for finish drawing. Depending on the range of tensile strength and the surface condition specified, a final anneal and a “skin-pass” light draw might be performed. Also, single block drawing is sometimes used with grease as lubricant, to obtain bright surface finish.

For fine stainless steel wire production, typically < 0.80mm, the process is quite different and known as “wet drawing”. The feed wire is a so-called “redraw wire” in sizes smaller   than 1.2mm and fully annealed. The drawing process is performed through a series of diamond dies (up to 30 in some machines) fully immersed in an oil-type lubricant. This delicate process is followed, for soft wire, by in-line cleaning, annealing in N2/H2 atmosphere and precision spooling on special take-ups adapted to the various types of spools.   Ultra fine stainless steel wires, down to about  0.010 mm, are thus produced by   a few highly specialized stainless steel wire producers.

Stainless Steel Wire Mesh is one of the most widespread uses of stainless steel wire. Over the years, the terminology in the industry has evolved concerning the three following terms “wire mesh”, “wire cloth” and “wire fabric”.  In today’s market place, these three wordings are used interchangeably and refer to the same product, with “wire mesh” or even “mesh” as the most prevalent from the purchasing and usage standpoints. Meshs made of stainless steel wire may be woven, knitted, welded depending on the applications and the wire size. Woven stainless steel is the most prevalent mesh. Woven wire products cover a wide variety of weaving patterns depending on the final end-use. Main patterns:

• Plain weave, where each warp is going over and under successive weft wires, ensuring maximum weaving stability and thus more accurate mesh openings
• “Dutch” weave, similar to plain weave, with warp wires thicker and closer to each other: this type of mesh is used in industrial filters and separation apparatus
• Twill Dutch weave: a combination of twill and dutch weave, for a stronger wire cloth ideal for fine filtration
• Weaving after crimping the wire, for screening in mines, construction, etc.…

 Thus woven stainless steel wire mesh encompasses a large range of wire sizes from 0.04 mm for the finest woven “wire cloth” to 3 to 4 mm for the industrial meshs. End uses cover a very large array from separation, sizing, conveyors, very diverse types of filtration, fencings, screenings, interior/exterior architectural decoration, etc.…

Knitted stainless steel wire mesh is another very common type of mesh, obviously mostly with finer wire sizes. The loop structure gives knitted mesh springiness or two-dimensional flexibility, allowing it to be crimped or compressed to alter characteristics for specific applications, for instance using the high mechanical damping properties of such mesh. Stainless steel knitted mesh can be processed into compressed, pleated or pad forms to allow liquid or gas flowing through. Knitted stainless wire mesh are widely used in auto parts and engineering applications such as filters, mufflers, catalytic converters blanket mesh. Another large area is the field of demisters and separation engineering.

Of course, the stainless steel wire meshs of all types capitalize on the corrosion resistance of stainless steel. Main grades are austenitic 304/304L and 316/316L depending on the corrosion specificities of the usage; also occasionally ferritic 430 (demisters, decoration).

Stainless  steel is now the most commonly used material of choice for household appliances and utensils due to its “food compatibility” and more generally to its resistance to various types of corrosion. Leaving aside the important segment of interior decoration, stainless steel wire finds its place in a very wide array of household  applications, either in straightened cut lengths, formed or shaped parts or as wire mesh. We will segment here the household uses as follows:

Kitchen & cookware utensils:

There are many kitchen utensils which use stainless steel  wire at the various stages of home food preparation and cooking . Noteworthy: 

- wire whips, wire mixers, wire mashers made of formed, assembled wires

- strainers , large and small, combining wire mesh and single wire handles

- butter, cheese, cake slicers/cutters

Cooking & storage:

In this broadly defined  category , most applications involve single wire or coarse weaves.

- frying baskets either made of  formed and electropolished wire or  wire mesh

- anti-splatter covers for frying pans made of tight wire mesh

- oven and barbecue grids  and related woven meshs

- storage, refrigerator  or strainer racks, sometimes with mesh wire

Electrical appliances:

Stainless steel wires are present in every  modern electrical appliances in a wide variety   of applications.

Just to mention a few well known or sometimes overlooked  uses :

- welding wire of stainless formed sheets in dishwashers, washing machines, dryers

- wire mesh filters in dishwashers

- spring wire in “on/off” switches, closing clamps in  drum washing machines, etc.

Miscellaneous other domestic uses:

- upscale bathrooms: soap holders, flexible metal hoses made of fine braided wire

- springs in a large variety of aerosol spray systems used in cleaning with bleach,…

- springs in beauty or luxury sprayers : hair spray, perfumes/fragrances

In view of the very diverse household uses, a wide variety of stainless steel grades are encountered : austenitic grades  304, sometimes 316  are the most used, but a substantial proportion of simple utensils use ferritic grade 430  (mixer whips, mesh strainers, etc.. ), all the more so in view of the cost difference with Ni-containing grades. Aerosol spray spring wires  sometimes require high corrosion resistance necessitating the use of super-stainless grades such as 904L

The use of stainless steel in interior decoration is a fairly recent phenomenon, quite coherent with the modernity of this material and its  widespread production increasing at a yearly rate of over 5% since the 1950’s. Not surprisingly, stainless steel wire has found a broad array of such uses due to its good formability and also its ability to be put in mesh form (via weaving, knitting, crimping) and wire rope/cable form through stranding. The many applications of stainless wire in interior decoration are usually segmented as follows:

- General decoration of interiors of buildings: these applications  cover interior decoration of office buildings, shopping malls, museums, theaters, etc. They are a natural component of decorative uses of stainless steels in overall architecture . Stainless steel wire is thus found  as wire ropes connecting posts in  stairways to complement hand rails made of stainless tubes, in balustrade applications of similar type : such applications combine decorative and structural functionalities. Stainless steel wire in a wide variety of meshes can be found as metallic fabric and drapery for wall cladding decoration. Ring mesh curtains  with single wire or wire ropes are often found in shopping malls as dividers. Modern designers can propose and realize very elegant combinations of stainless steel tubes, wire ropes and wood  in staircases for building interiors.

- Restaurants and upscale shops: there too, stainless steel wire is in demand for purely decorative reasons as well as functional, in keeping with the luster and cleanliness image of stainless steel . Thus stainless steel wire meshes can be found as: functional partitions, mesh drapery curtains and intercrimp wire meshs for decorative purposes. Also, certain lounge seats and bar stools of “trendy” designs can combine elegantly stainless steel wire mesh and cushions.

- Home decoration & furnishing: mixing functionality and beauty, stainless steel wire mesh was recently used in the renovation of a large luxury apartment complex in Chicago: elegant wall panels offered distinctive decoration while concealing mechanical equipment  and complex home control systems. Stainless steel as a modern trendsetter is often combined with glass in dining room and sitting room  furniture  such as dining room table and chairs, coffee tables, bar stools, lamp stands with intertwined wire, modern design chandeliers, etc. Stainless steel wire is also widely used for art work either in free standing structures or framed with a background of velvet for wall hanging. Finally, stainless steel wire mesh are found in partition screens and also draperies in bathrooms.

In view of the low level of corrosion resistance required for interior decoration, stainless steel grades used are mostly austenitic 304 with its elegant gray luster and also ferritic 430 where bright and shiny appearance is needed.

Stainless Steel Wires , as one of the generic stainless steel products, find numerous applications in food processing . Indeed, stainless steels have long ago established themselves as the materials of choice for almost all food processing  and storage equipment. What attributes make stainless steels so eminently suitable ? First and foremost, it is their corrosion resistance which makes them ideal for food contact, provided that the proper grades are used in view of the possible aggressive content of some foods, mostly salt presence. If home cooking is included,  food processing  is estimated to encompass close to 50 % of all stainless steel wire usages.

“Industrial” food processing : this large domain of applications goes from the upstream crop processing to the booming industrial areas of meat, dairy, cheese and cooked edible products, whether for animal feeds or, more or less extensively processed , food products for human consumption. On the upstream , wire mesh grids are used to screen agricultural raw products from grain to vegetables and fruit where calibration is a must and finer wire  mesh are used for filtering primary juices such as olive oil, fruit juices. In the downstream, many uses of stainless wire baskets, trays, racks are found in meat and cheese processing, as well as hooks made of formed stainless steel wire. Also, wires  woven, crimped  or straight & cut , are the choice in many conveyor belt systems used for food processing and transfer. Grade selection is obviously a must with  prevalence of the austenitic grades 304, 316 (if presence of salty mixtures or brine, etc.) and sometimes 314 (heat resistant grade).  Cable trays made of  stainless wire baskets are also a common use  all through the “food chain” of industrial processing.

“Professional" food processing: though the limit between industrial and professional is not clear cut, “ professional” correspond to food processors in direct contact with end consumers, such as bakeries, butcheries, delicatessen shops , fish markets, restaurants (regular , fast food ). As to be expected, one will find there the same types of usages as in industrial, but on smaller scale and different product mix: for instance, prevalence of racks for display to customers and cold storage, formed wire in mid-size mixers, cooking racks for ovens, wire baskets for strainers and also  specific applications such as formed wire for transfer trolleys. Fast food outlets have generated a large use of frying baskets for French fries, most often electropolished 304 formed wire of so-called “EPQ” quality. Also, the wineries use routinely stainless wire mesh for filtering purpose, all through the wine making process.

In summary, food processing is a key area of use of stainless wire or mesh.     Beyond  the prime aspect of resistance to corrosion and well established “food compatibility”, austenitic stainless steel wire also brings its unique mechanical properties : easy conformation and strain induced  high strength.

Stainless  Steel , a modern material in view of its attractive combination of mechanical and corrosion resistance properties, has found a large array of usages in the Automobile Industry, as to be expected in spite of its cost higher than regular steels.  Stainless steel wire  is used in very diverse applications, notably as follows:

--Automobile fasteners:  fasteners is a generic wording for a range of parts used to link or fasten in place several components of a vehicle: this covers bolts, nuts,washers and rivets usually cold headed from stainless steel wire rod or drawn wire. There is a large variety of grades used in automotive fasteners generally per ASTM A193 . Most prevalent are 302HQ, 304L, 316L, 410, 409Cb . Also 17-4 (grade 630) for restraint systems and for brakes. Noteworthy the substantial use of high temperature “super stainless” A286 (grade 660)  for exhaust manifold safety bolts : this very same grade is a common use in Aerospace applications. Also  409Cb bolts in exhaust line.

--Exhaust line: the development of use of stainless steel  in car exhaust systems started in the USA and Germany in the 1980's with the catalytic converters, then spread out in all the Automotive Industries , with also usage in all components of the exhaust line from manifolds to tail pipes. The prevalent grade for pipes and converters shell is the low-grade 409 Ti; this has brought a large usage of grade 409Cb welding wire for the components of the exhaust line, as well as use of 409Cb large size wire for exhaust systems hangers. Some exhaust lines use ferritic grade 439  and  hence the welding wire 439 Cb. There are significant other usages such as:

--- knitted mesh in exhaust line spacers, support matts, muffler packing

--- “ silencer steel wool “ : peeled from drawn wire in ferritic grade 434

--Miscellaneous other automobile applications, as follows:

--- Air bag safety systems: knitted fine wire pads are used as filters to prevent damage of the air bag by residues of the explosive cartridge

--- fine stainless wire braids as reinforcment/protection of fuel or brake hoses

--- various stainless steel cables used in very diverse operative functions

--- flat stainless steel wire for windshield wipers         

Thus, stainless steel wire is indeed a widely used  material essential to Automobile safety, durability and performance.

It is no surprise that Stainless Steel, a modern material with an attractive combination of  mechanical and corrosion resistance properties, would indeed find many usages in Aeronautics/Aerospace domains. Stainless steel in wire  form is understandably on the forefront of these usages, in view of the weight savings considerations, in spite of the increasing competition from the more expensive Titanium alloys. Thus stainless steel wire, wire rope and wire mesh are found in many critical parts of aircrafts and  primarily in the areas of fasteners (via cold heading) and aircraft cables, as follows:

-- Aerospace fasteners: fasteners is a generic wording for a wide range of parts  used to link together several  components together such as stringers, flanges, skins,ribs, stiffners in the aircraft airframe and the engine mostly. Such fasteners are cold headed from wire rod or drawn wire into screws, bolts,washers,nuts and rivets. In view of the stringency of the applications, the wire rod or wire is frequently “shaved” to minimize the occurrence of surface cracks. Though regular grades such as 302HQ and 316L are used, specific grades are prevalent in Aerospace, primarily A286 – grade 660 / ASTM A453. This high end austenitic Ni/25-Cr/15 is age hardenable and combines good corrosion resistance with excellent creep resistance up to 700°C. It is therefore widely used, particularly for jet engine components. Another set of precipitation hardening grades 13-8Mo and 15-7Mo, have found a large use as stems of blind rivets (Allfast technology).

-- Aircraft cables: aircraft cables are obviously of primary importance to safely provide the essential functions of controls in aircrafts for wing flaps, landing gear, as well as adjustable head-back on passenger seats, etc. Note also other applications such as helicopter hoists for cargo loads or rescue .These cables are made of  wire ropes stranded  from 304 and preferably 316 wires.

-- Miscellaneous applications: a specific application of particular relevance to safety of aircraft assemblies is the “safety lock wire”. This wire is a physical locking device which holds nuts, bolts or other fasteners in place to counteract  forces due to vibrations. Safety lock wire  is often an annealed 316 stainless wire, size ranging from 0.5 to 1mm packed in small canisters. Also more traditional uses of stainless wires : springs for switches, flexible metal hoses,  emphasizing the large use of stainless wire in Aerospace applications.

Stainless steel wires are increasingly present in medical applications which rely on their attractive combination of corrosion resistance, durability and mechanical properties. The main domains of applications are primarily the increasingly sophisticated field of “medical devices" used in diagnosis, investigations and innovative surgical techniques such as laparoscopy, and   the more traditional areas of implants as well as surgical miscellaneous parts. Stainless steel wire can be in various presentations (round, flat or shaped wire) and forms (mesh, braided, straightened cut lengths, cables). Main grades used are 302, 304, 316L most often as the ESR-remelted  grades  302 V, 304V, 316 LVM. Also used are grades 630 (17-4 PH) and 440C . Wire sizes are mostly  in the smaller dimensions.

Hereafter a short summary of key modern uses in medical applications:

-- Vascular therapy: continuous improvements of medicine allow minimally invasive intervention through arteries and veins. Stainless steel wires are found in intra-arteria stents, angioplasty catheters, guide wires and diagnostic catheters, aneurysm clips, etc.

-- Orthopaedics applications: this broad field  covers trauma,reconstructive, spinal & sports medicine. Stainless wires can be found in fracture fixations, spinal devices, nails, bone pins and screws, cerclage cables, suture wire.

-- Endoscopic medical devices: this fast growing field targets efficiency, comfort through minimally invasive procedures. Strands and cables made of fine stainless steel wires are used for : biopsies, gallstone removal, support of colonoscopy, retrieval of foreign objects in airways, laparoscopic surgery...

-- Orthodontics: this specific field of applications often uses shaped stainless steel wires for arch wire, self-litigating brackets , springs. Both the aesthetic and the mechanical properties of stainless steel are at work there. Related field of “implant dentistry” also makes use of stainless steel wire.

– Surgical and diverse applications: Stainless steel wire is often used for post-surgery staples, suture wire and needles , stylets. Another important field of use of stainless steel spring wire are the spring mechanisms of syringes , medical or self-injection systems for diabetes, allergic reactions.

Stainless steel wire is thus an important item in the increasingly diversified and fast growing medical field, in surgery, implants and sophisticated devices.