T E C H N I C A L B U L L E T I NVolume I • Number 4

Extreme Resistance To Breakage AndAbrasion – In One High-Performance AlloyHistorically, choosing the right refinerplate alloy for low consistencyapplications has been a matter ofcompromise. It was not possible tohave both abrasion-resistance andbreakage-resistance.

In the ideal refining situation, theprimary concern would be tominimize plate wear by selecting anabrasion-resistant plate material,such as the high carbon nihards,white irons, or the medium carboncast 440 grade stainless steels.However, virtually no mill operatesunder “ideal” conditions. Suchproblems as process upsets, trampmaterials and plate-to-plate contactcan – and routinely do – cause refiner plates made from thesematerials to fracture.

The results: disruption of the refiningoperation and the risk of damage torefiners and downstream equipmentcaused by bar fragments.

Plate fracture can be eliminated withthe virtually unbreakable 17-4PH

alloy, a low-carbon stainless steel.However, it is also the least effectiveof all the alloys when it comes towear-resistance.

So what to do? Opt for maximumwear and risk damaging breakage?Or the reverse? Until now, there hasnot been a satisfactory answer.

Fortunately, compromise is no longernecessary with the introduction ofthe revolutionary J&L C90 alloy. Notonly does it match the fracture-resistance of the 17-4PH alloy, it also offers much more wear-resistance, comparing favorably with cast 440 grade stainless steel(which, however, providessignificantly lower breakageresistance). Only the high carbonalloys are more wear-resistant.

C90 also exhibits superior perfor-mance in two other areas of concern:corrosion- and cavitation-resistance.

The following are test resultscomparing the C90 alloy with themost commonly used alloys (nihards,high chromium white irons, cast 440grade stainless steels and 17-4PH):

OVERVIEW

• In the past, norefiner plate alloyfor low consistencyapplications offeredboth abrasion-resistance andbreakage-resistance.

• The C90 alloymatches thefracture resistanceof the 17-4PH alloy,and also offersmore wearresistance.

• C90 also providessuperior corrosionresistance andcavitationresistance.

• C90 cansignificantlydiminish majorcauses of platefailure.

Revolutionary C90 Alloyfor Low ConsistencyRefiner Plates – In a Class by Itself.Developed by the Technical Group, J&L Fiber Services

Fracture ToughnessSpecimens of all five alloys weresubjected to the impact of a gravity-driven weight in an instrumented droptower. Because of the intrinsicresistance to crack propagation of theC90 alloy, testing was performed onspecimens without pre-crack condi-tioning. This permitted direct testingand comparison of the brittleness ofeach alloy. Computer monitoringmeasured the energyabsorbed prior to thefracture of eachmaterial, thus providingdata on their relative“fracture toughness.”As Fig. 1 shows, theC90 alloy demon-strated a fracture-toughness ratio nearlythree times that of 440grade cast stainlessand almost six timesthat of the nihard alloy.

Abrasive WearResistanceSamples of eachmaterial, taken directlyfrom refiner plates,were abraded undercontrolled load on acontinuously renewedgarnet-clad abrasivecloth. (Garnet mostclosely simulatesabrasive conditions in arefining operation.)Weight loss was usedto measure abrasionresistance.

CorrosionResistanceA polarization test wasconducted on samplesof each material takenfrom refiner plates.Each sample was used

as an electrode immersed in an elec-trolyte solution of chlorides with a pHof three (similar to an actual refinerenvironment). A potential was passedthrough the wetted surface of thesample to stimulate corrosion. Thecorrosion rate was then measured.

Cavitation ResistanceTest samples of each material wereextracted from refiner plates and

mounted to the base of an acousticsystem. Oscillation of the acoustic tipcaused liquid displacement, resultingin cavitation and subsequent weightloss of each sample. This method oftesting closely simulates the actualrefining conditions that causecavitation. The weight loss was usedto measure and compare thecavitation-resistance of the alloys.

T E C H N I C A L B U L L E T I N

Results: J&L’s C90 alloy matched 17-4PH incorrosion resistance and was vastly superior to allother alloys tested.

Fig. 3

Fig. 4

Results: J&L’s C90 alloy exceeded the cavitation-resistance of 17-4PH alloy and was far superior tothe nihards and 28% chromium white irons. Itclosely matched cast 440 grade stainless steel,the alloy most commonly used to combat thisfailure mode.

Results: J&L’s C90 alloy has a fracture toughnessequivalent to the unbreakable 17-4PH alloy andfar superior to all other alloys tested.

Fig. 1

Results: J&L’s C90 alloy has much greaterabrasion-resistance than 17-4PH and comparesclosely with the cast 440 grade stainless steels.As expected it was lower than the ultra high car-bon nihards and the 28% chromium white irons.

Fig. 2

Innovative MetallurgicalTechniques Used toDevelop New C90 AlloyThe C90 alloy offers the best of allworlds: an extreme toughness toresist brittle failure and a self-sharpening cutting edge for optimumfiber development. These remarkableperformance characteristics are theresult of an innovative processdeveloped by J&L metallurgists.

The matrix of the highly corrosion-resistant alloy CB-7CU was modifiedextensively to create a duplex micro-structure that afforded an extraordin-ary resistance to premature failure:

• Careful control of the austenite andferrite-forming elements, based ona Schaeffler diagram, to produce ahard, wear-resistant martensiticstructure and to avoid theformation of brittle sigma phase.

• Careful control of the martensite’scarbon content toward the upperlimit of its alloy class. (There is adirect, positive relationshipbetween martensite’s abrasion-resistance and toughness and itscarbon content.)

• Control of the nitrogen content to astrict maximum to obtain desired

wear resistance and fracture tough-ness. (This is extremely importantsince nitrogen causes brittleness.)

• Careful selection of secondaryhardening techniques to developthe critical size and distribution ofthe precipitation phase. The resultis a hard precipitate which greatlyenhances edge retention.

• Development of new testtechniques to assure optimumperformance for refiner plateapplications.

Fig. 5

Schaeffler Diagram showing the optimum balance of alloys, trace elements and gases that is necessary toprovide the C90 alloy’s unique microstructure.

The C90 Alloy: Created For The Real World of Low Consistency Disc RefiningAs mentioned earlier, low consistencyrefining does not occur in a closedenvironment, where undesirableevents leading to plate failure can be100% avoided. Every mill must facethese realities:

• Plate gaps on the order of two tothree fiber diameters

• Floating rotor disks on refiners

• Fluctuations in stock pressure,consistency, flow rate and specific energy

• Tramp material

With the new C90 alloy and platedesigns tailored to the precise andunique refining needs of each mill,these major causes of plate failurecan be diminished significantly.

The C90 alloy offers the highestpossible level of toughness andresistance to abrasion, corrosion and cavitation available in a singlelow consistency refiner plate alloytoday. It has now established new,higher standards for optimum fiberprocessing performance.

T E C H N I C A L B U L L E T I N

J&L Fiber Services, Inc. • 809 Philip Drive • Waukesha, WI 53186 USA • Phone 414-544-1890 • Fax 414-547-8166

Refiner plate made of 17-4PH showing accelerated bar wear resulting in smearing anddeformation of the bar surface.

Refiner plate made of J&L’s C90 alloy showing flat, even wear while maintaining a sharpleading bar edge.

Refiner plate made of nihard, showing extensive bar breakage, allowing pieces of the broken bars to pass through the system.

Fig. 1 C90 17-4PH

Figure one shows the entire refining surfaces of the C90 plate (left) and the 17-4PH plate (right).

T E C H N I C A L B U L L E T I NU P D A T E

Volume I • Number 4

OVERVIEW

• C90 has becomethe premium alloyfor low consistencyrefining operations.

• Recent fieldstudies, comparingC90 to 17-4PH,support thisassessment.

C90 Versus 17-4PH: A Case StudyDeveloped by the Technical Group, J&L Fiber Services

In 1989, J&L Fiber Servicesintroduced the revolutionary C90alloy to the pulp and paper industry.Since then, C90 has gained wide-spread acceptance as the premiumalloy for low consistency refiningapplications, where breakage andabrasive bar wear are the majorcauses of refiner plate failure.

The benefits of C90 have becomeeven more evident through theindustry’s increased utilization of the alloy. The following case studydescribes C90 applications in thefield and the results obtained. Thisstudy demonstrates the typicalbenefits of using C90 and is just one of many examples of the alloy’s success.

Case Study DetailsThis study provides a visual compari-son between a C90 plate and a 17-4PH plate in a 42" double disc refinerrunning top sheet at a mill producinglinerboard at a rate of 450 tons perday, a consistency of 4.0%, and apH of 7.5. Both plates described inthis study had a bar code of 2.7-2.7-4.8, and performed under virtuallyidentical conditions. Theseconditions included plate-to-platecontact, tramp materials, as well asthe abrasive forces of stock flow.

Life expectancy. The normal lifeexpectancy of the 17-4PH alloy wasfour months, while the C90 alloy ranfor over nine months.

Abrasive wear resistance. Thefollowing four graphic examplescompare the C90 alloy to the 17-4PH.

ConclusionThis case study clearlyshows that the C90 alloy livesup to its reputation underhigh-stress conditions in thefield. C90 stands up to thereal-life situations of lowconsistency refining; itprovides the highest possibleresistance to abrasive wear,breakage and bar deforma-tion available in single refinerplate alloy; and hasestablished new and higherstandards for optimal fiber-processing performance.

T E C H N I C A L B U L L E T I N

U P D A T E

J&L Fiber Services, Inc. • 809 Philip Drive • Waukesha, WI 53186 USA • Phone 414-544-1890 • Fax 414-547-8166

Fig. 2 C90 17-4PH

Figure two is a close-up of the ID section of each plate. It is clear that plate clashing and abrasion hasoccurred; however, the response of the C90 plate (left) to these common refining conditions is quite differ-ent from that of the 17-4PH plate (right). The bar surfaces and bar edges of the 17-4PH plate are deformedand smeared, resulting in blockage or complete closing of the groove area and limited throughput. TheC90 material, under the same conditions, remains open at the ID (and OD, as seen in figure one) of theplate because bar deformation has been eliminated. Bar height is also maintained for greater flow capacity.

Fig. 3 C90 17-4PH

Figure three shows an even closer view of the ID of each plate. The amount of deformation and pluggingof the grooves occurring in the 17-4PH material (right) is quite obvious. A 4mm groove width has beencompletely blocked, causing restricted stock flow. It is evident that plate clashing did occur with the C90plate (left), but the grooves remain clear even after nine months.

Fig. 4 C90 50X 17-4PH 50X

Figure four depicts the edge wear of both materials. The leading edge of the 17-4PH plate (right) hasblunted, even though the top of the bar is flat from plate clashing. The trailing edge has developed burrsfrom material deformation. On the other hand, the C90 plate (left) maintains a sharp leading edge, creating a 90° angle, and a distinct trailing edge to provide optimum refining conditions.