How Sulfur Affects 1.2312 Plastic Mold Steel | Tool Life & Wear

Sulfur in 1.2312 pre-hardened plastic mold steel can improve cutting performance, generally controlled at 0.05%~0.10%.

Appropriate amount of sulfur forms MnS inclusions, reducing tool wear by about 15%~25%, extending tool life.

But excessively high will reduce polishability and toughness. During processing, it is recommended to select carbide tools, cutting speed controlled at 120–180m/min.

Extended Cutting Tool Life

Natural "Solid Lubricant"

CNC machine tool spindle carrying 10mm end mill presses down at full speed, the moment the blade cuts through 1.2312 mold steel, the cutting area generates intense physical collision. Steel internal pre-hardened to 28-32 HRC, ordinary alloy tools under this hardness dry cutting, tool tip temperature will rush to 800 degrees Celsius within 0.1 seconds.

Smelting furnace before tapping accurately injected 0.08% mass fraction sulfur, with manganese element coordination, generating countless 5 to 10 micron diameter manganese sulfide particles. These particles are like extremely tiny capsules, uniformly distributed in the ferrite matrix. When the tool sweeps over at a linear speed of 150 meters per minute, the cutting edge bears more than 2000 Newtons of squeezing pressure per square millimeter.

400 degrees Celsius cutting heat makes the originally hard sulfides become as soft as plasticine, adhering to the higher temperature carbide insert surface. A layer invisible to the naked eye, only 2 microns thick solid lubricant film rapidly spreads on the friction surface, blocking molecular-level contact between the steel matrix and tool material.

· Dry cutting friction coefficient dropped off a cliff from 0.60 to 0.22

· Rake face friction heat generation reduced by 35%

· 3 micron thick AlTiN coating avoided high temperature oxidation peeling

· Tool edge radius maintenance kept within 10 microns

Without sulfur involvement, 1.2311 steel during processing, chips will because of high temperature deathly stick to the tool edge forming built-up edge, like a thick layer of chewing gum stuck on a sharp kitchen knife. 1.2312 steel relies on the manganese sulfide film layer, letting chips along the 15-degree rake angle slippery discharge.

Measuring machine tool spindle ammeter, processing the same volume of metal, 1.2312 material lets motor load from 35% steadily drop to 28%. This power drop feedback on tool consumption, manifests as the wear curve slope becoming extremely flat. Technician under 40x stereo microscope compares, after cutting for 60 minutes, tool flank wear width (VB) is only 0.11 mm.

Thermal imager aimed at the cutting zone, 1.2312 generated spark color is more towards dark red, rather than bright white caused by excessive high temperature. Cutting heat conduction path occurred change, 80% of heat energy along with chips is instantly flung away. Tool shank flange face actual measured temperature maintains at around 42 degrees Celsius, this temperature control capability protects precision spindle bearing accuracy from not producing displacement due to thermal expansion.

· Per hour metal removal amount increased by 22%

· Tool change frequency from 4 times per shift reduced to 1 time

· Processed surface roughness fluctuation controlled within Ra 0.2 microns

When 8mm alloy drill bit goes deep into steel blank 120mm place, internal space is extremely closed. Although 50 Bar pressure high pressure coolant continuously sprays, drill bit chisel edge still bears huge rotational friction. 1.2312 steel discharged fine "C" shaped chips will not block chip grooves, reducing torque load.

Drill bit margin and hole wall repeatedly friction, manganese sulfide film on the hole wall surface forms a temporary isolation layer. Taken out drill bit surface has no obvious silver-white metal adhesion traces, originally fragile chisel edge after continuously drilling 100 deep holes, still retains factory geometric angles. In contrast, ordinary sulfur-free P20 steel often at the 30th hole will trigger torque alarm.

On the production cost accounting sheet, tool procurement expenditure occupies more than 15% of mold processing costs. 1.2312 material through internal self-contained manganese sulfide particles, disguisedly in the cutting zone established a set of dynamic supply system. As long as cutting action is ongoing, lubricant thin film will continuously at wear positions restack, until the whole template processing completes.

Perfect "Chip Breaker"

Inside the CNC machine tool closed processing chamber, 1.2312 pre-hardened mold steel is at 180 meters per minute linear speed passing through milling cutter edge.

In every square millimeter of steel matrix, scattered thousands of long-strip manganese sulfide inclusions. These particles about 5 to 15 microns long, at the moment the tool plows through the metal surface, become weak points inside the material.

Ordinary sulfur-free P20 steel during cutting, metal plasticity is extremely strong, chips like long snakes flying and tightly wrapping on the spindle. 1.2312 steel is completely different, when tool tip cut-in depth reaches 2 mm, manganese sulfide stress concentration points inside chips will produce micro-cracks.

Metal flow layer when passing through tool rake face, due to sulfide existence, cannot form continuous coiled chips as long as 500 mm. Force balance is broken, chips at length reaching 3 to 8 mm will occur physical brittle fracture.

· Chip morphology presents regular "C" type or "6" character type

· Single chip weight maintains between 0.02 grams to 0.05 grams

· Chip groove internal filling rate always below 40% safety threshold

· Chips leaving workpiece surface initial speed reaches 15 meters per second

"In processing mold cavities as deep as 150 mm, debris can be easily carried away by 0.6 MPa pressure air blow. This material property eliminated the risk of long chips scratching mold already processed surface, Ra 1.6 roughness can be stably maintained."

If chips cannot timely break, above 700°C high temperature heat will through long chips continuously conduct to tool body. 1.2312 steel's chip fragmentation tendency, lets 80% of cutting heat in 0.01 seconds fly away with debris.

Tool head part infrared sensor temperature shows, processing 1.2312 tool tip peak temperature is about 120°C lower than processing 1.2311. Lower temperature rise speed slowed down carbide insert thermal fatigue loss.

Carbide coating in 300°C to 500°C violent temperature difference fluctuation extremely easily peels. Due to chip breaking effect being excellent, coolant can more accurately spray to the edge center, temperature control accuracy increased more than 15%.

Operator adjusted feed per tooth from 0.12 mm up to 0.18 mm, machine tool spindle vibration frequency still maintains at low position below 2000 Hz.

· Cutting resistance torque decreased by 12% to 18%

· Spindle motor current fluctuation range controlled within 0.5 Ampere

· Tool overhang length reaching 5 times diameter, cutting howl sound reduced 10 decibels

· Rough processing stage metal removal rate increased to 450 cubic centimeters per hour

"When deep hole drill bit in 1.2312 steel blank internal excavates, spiral groove will not occur chip jamming drill-burst accident. Actual measured data shows, 8 mm diameter drill bit continuous drilling depth can reach 160 mm, during process no need multiple tool retracting for chip removal."

Internal manganese sulfide particles are not only lubricants, but more efficient physical barriers. It stops super strong bonding between metal atoms, letting chips in early stage of plastic deformation prematurely enter failure state.

Even under dry cutting conditions lacking external cooling, 1.2312 generated fine chips also can avoid heat accumulation at cavity bottom. Dark blue debris piled on workshop floor, is the best physical evidence of cutting heat being successfully carried away.

Under 28-32 HRC hardness background, this chip breaking characteristic let single tool effective cutting path increase 3500 meters. Comparing sulfur-free similar steel, cleaning machine tool bottom debris time shortened by more than 50%.

Finish processing stage, tool operates with 0.05 mm tiny depth of cut. Manganese sulfide particles still can induce chips to produce fine fracture, avoiding long chips scratching cavity corners leading to grinding rework, single set mold benchworker polishing duration reduced about 4 hours.

· Carbide insert tool change cycle from 90 minutes extended to 140 minutes

· Precision run-out error controlled within 0.005 mm

· Machine tool filtering system filter element cleaning frequency reduced 30%

· Cutting fluid chemical stability life extended by 200 processing hours

Mold Wear Resistance and Longevity

Microstructure and Micro-faults

Inside steelmaking furnace 1600°C molten steel tumbles, 0.08% sulfur atoms and manganese atoms at this moment completed combination, generating fine manganese sulfide crystals. These crystals during cooling are tightly surrounded by lattices composed of iron atoms.

Large hydraulic press performs repeated forging on several tons of steel ingot, originally spherical manganese sulfide particles are stretched into long fibers up to 50 microns.

1.2312 steel through pre-hardening treatment, hardness stable between 28 to 32 HRC. Internally inlaid manganese sulfide hardness is extremely low, Mohs hardness level only 3, texture close to human fingernails.

· Manganese sulfide inclusion average length 35 microns

· Cross-section width controlled at around 3 microns

· Mohs hardness only one-tenth of metal matrix

· Per square millimeter section distributed with hundreds of such weak points

CNC machine tool alloy insert at 150 meters per minute speed cuts into steel, tool tip every time meeting a manganese sulfide particle will occur one tiny vibration.

Chips along these "soft spots" with hardness only one-tenth of matrix automatically break, presenting fine C-type length less than 5 mm. Tool tip and metal friction generated heat is rapidly carried away, cutting zone temperature dropped about 40°C.

Processing efficiency in the factory thus increased 35%, originally needing 3 days to complete rough processing man-hours was compressed to within 2 days. Three-axis machining center spindle load meter reading from 60% dropped to 45%, tool durability doubled.

· Machine tool cutting speed increased to 120-180 meters/minute

· Insert edge wear amount per hour reduced 0.05 mm

· Deep hole processing chip removal success rate reaches above 98%

· Rough processing man-hour reduction amount about 30%

Injection molding machine mold clamping pressure reaches 150 tons, 240°C liquid polypropylene plastic at 50 meters per second high speed rushes into mold cavity. Plastic fluid under high pressure like a grinding wheel frictioning metal atoms on cavity surface.

Those manganese sulfide cigar-shaped fibers distributed on the surface, become the cavity's first lost position. High temperature melt continuously pulls soft inclusions, making them detach from matrix, leaving micro holes depth about 5 microns.

Originally polished into Ra 0.2 micron smooth mold surface, after experiencing 50,000 shots, filled with dense tiny pits. These pits difficult to distinguish by naked eye will capture plastic molecules, leading to obvious drag marks during demolding.

· Injection pressure maintains at 80 to 120 MPa

· Cavity surface roughness from Ra 0.2 climbed to Ra 1.2

· Mold surface per square centimeter produces about 50 micro pits

· Demolding required ejection force increased more than 15%

If plastic mixed with 30% hard glass fiber, micro-fault collapse speed will accelerate. 10 micron diameter glass fiber like a micro chisel, accurately cuts into manganese sulfide left pit edges.

Every injection cycle, glass fiber particles will pry pit edges of martensite structure. Tiny cracks along manganese sulfide fiber direction extend to internal, eventually leading to a whole piece metal grain occurring spalling.

Originally 0.02 mm dimension accuracy after 100,000 cycles completely lost. Injection molded part edges start appearing 0.1 mm wide flash, production line has to stop, taking down mold weighing hundreds of kilograms for repair.

· Glass fiber diameter about 8 to 12 microns

· Most severely worn area located within 10 mm near gate

· Cavity edge dimension out of tolerance reaches above 0.05 mm

· Mold maintenance cycle shortened to one-third of original

Experienced old masters will suggest performing 0.1 mm depth gas nitriding on cavity surface. Nitrogen atoms permeate steel surface layer, pulling surface hardness forcibly to around 1000 HV, putting on a layer of armor for weak manganese sulfide.

Nitriding layer filled micro hardness gap, glass fiber no longer can easily cut metal surface. Treated 1.2312 mold, even if producing high-wear plastic, also can safely pass 300,000 times service cycle.

Injection Molding Material & Life

In injection molding workshop, hopper filled with white ABS resin particles. Injection molding machine heating cylinder stabilizes temperature at 220°C, screw pushes melted liquid ABS into 1.2312 steel made mold cavity. ABS fluid like thick honey, has extremely small friction against steel surface pre-hardened to 30 HRC.

A set of 1.2312 mold producing TV back shell, operated at 2 shots per minute rhythm for 280 days. Counter shows total shots break through 500,000 mark, taking down mold using CMM to detect, cavity main dimension wear amount only 0.015 mm.

Routine soft resin raw materials cooling shrinkage rate mostly around 0.5%. Mold temperature machine set circulation water temperature at 60°C, 1.2312 mold internal 8 mm diameter cooling water channel distance from cavity surface 15 mm, every minute stably carries away 2000 kcal of heat.

· Polypropylene (PP) fluid injection pressure only needs 60 MPa

· ABS demolding friction coefficient low as 0.3

· Running half year cavity surface roughness still maintains at Ra 0.8 microns

· Rust prevention maintenance cycle long as wiping once every 100,000 shots

Changing to produce car headlight transparent mask, raw material became polycarbonate (PC). PC melt viscosity is extremely high, injection machine must raise heating cylinder to 280°C, applying 120 MPa high pressure to press it into every corner of the mold.

PC fluid under high pressure will deathly bite mold metal surface, demolding pull force sharply surges. Manganese sulfide inclusions under huge mechanical pulling start peeling, mold at hitting 200,000 shots, surface produces naked eye visible 0.02 mm deep drag marks.

Challenging physical limit is electric tool shell production line, raw material bag printed with PA66+30%GF. Formula ratio marked every 100 grams molten nylon, mixed with 30 grams length of 3 mm hard glass fiber.

Melt with glass fiber rushes through gate at 600 mm per second extreme speed. 1.2312 steel 30 HRC hardness is completely vulnerable before glass fiber with Mohs hardness reaching 6.5, cavity surface sulfur-containing areas instantly gouged with countless micro grooves.

Operated for only 50,000 shots, water baffle wall facing the gate was washed away 0.05 mm metal thickness. Injection molded electric drill shell edges grew prickly flash, 0.05 mm thick feeler gauge in inspector's hand can already easily insert into mold closing gap.

· Glass fiber and steel surface friction instantaneous temperature can reach 320°C

· Steel at runner corners every 10,000 shots wears 0.01 mm

· Polished surface within 3 days roughness rises to Ra 2.0 microns

· Mold must every two weeks go offline for weld-repair dimension restoration

Mechanic used argon arc welder to repair wear parts, stack-welded a layer of 1.2344 high hardness welding wire at 0.05 mm deep groove. Heat affected zone produced around welding area, hardness mutation extremely easy to produce 0.1 mm stress micro-cracks under next injection high pressure.

Meeting polyvinyl chloride (PVC) raw material, physical wear evolved into chemical reaction. PVC material in 190°C barrel stays slightly long, heat decomposition releases pungent hydrogen chloride (HCl) gas, gas meets condensation water becomes extremely destructive hydrochloric acid micro-droplets.

1.2312 steel chemical composition table, chromium (Cr) element content only 1.8% to 2.1%. Metal resisting acid corrosion needs at least 12% above chromium element involvement in rust prevention, hydrochloric acid micro-droplets without obstacle permeate steel surface.

Manganese sulfide micro-pores on bare steel surface became best micro storage tanks for acid liquid. Newly opened mold after injecting PVC merely 3 days, surface grew red-brown rust blocks, after 20,000 shots cavity all covered with 0.02 mm deep pits corroded out.

Production supervisor issued surface treatment order, mold sent into electroplating tank, soaked and energized in 60°C chromic acid solution for 48 hours. A layer of thickness accurately controlled at 0.015 mm hard chrome plating tightly adhered to 1.2312 steel surface.

Plating hardness high as 900 HV, completely isolated internal steel from external hydrochloric acid gas contact. Electroplated mold after re-mounting, in one breath hit 150,000 PVC pipe joints, spent surface treatment cost only 450 yuan per square meter.

Flame retardant additives in fire-resistant plastic similarly not friendly to metal cavity. Fire-rated ABS material contains 15% bromide, at 240°C precipitates acid corrosive substances, unprotected steel surface polishing layer within two weeks will completely lose specular reflection luster.

Manufacturing Benefit Analysis

On procurement department desk lie two mold steel quote sheets. Left is conventional 1.2311 material, per kg selling price 18.5 yuan; right is 1.2312 with trace sulfur added, per kg selling 19.2 yuan. Buying an 800 kg heavy car door panel mold blank, choosing 1.2312 needs to pay 560 yuan more material fee.

Thick steel ingot hoisted by overhead crane to five-axis machining center worktable. Milling cutter disk equipped with 6 carbide inserts cuts into metal at 6000 rpm speed. Feed rate pointer on operation screen steadily stops at 2800 mm/min scale line, machine emits heavy rhythmic cutting sound.

· Cutter disk depth of cut maintained at 1.5 mm

· Metal material removal rate reaches 320 cubic centimeters per minute

· Spindle load meter pointer stops in 45% safety interval

· Coolant splash amount nearly one-third less than processing conventional steel

Operator puts same hardness but sulfur-free steel on machine, feed rate forced to drop to 1800 mm/min. Tool tip in hard and continuous metal matrix difficultly gnaws, spindle load surges to 70% red warning line. High speed friction produces nearly 600°C high temperature, insert edge within two hours blackened and chipped.

Changing new inserts once needs downtime 15 minutes. A 63 mm diameter milling cutter disk equipped with 6 imported alloy inserts, each procurement price 45 yuan. Processing one 800 kg mold cavity, 1.2312 steel consumes 2 sets of inserts, spending 540 yuan; sulfur-free steel hard-gnawed through 5 sets of inserts, tool fee high as 1350 yuan.

Large CNC machine tool hourly rate calculated by hour, workshop assigned cost for this machine is 150 yuan per hour. 1.2312 steel took 28 hours to run all rough processing programs. Un-sulfurized tough steel processing time lengthened to 42 hours, hourly rate alone more spent 2100 yuan.

Workshop director drew a circle on production schedule: material fee indeed paid several hundred more, machine processing fee and tool wear saved nearly three thousand. Machine vacate one day early, new jobs waiting in line behind can earlier go on machine to earn processing fee.

Mold internal to drill through hundreds of 8 mm diameter, 300 mm deep cooling water holes. Gun drill bit deep into metal internal, chip removal space extremely narrow. Chips once connected into dozens of centimeters long coil, will jam dead in hole, within seconds twisting off imported drill bit worth 300 yuan.

Cut down metal debris automatically breaks into less than 5 mm short fine C-type, along with high pressure oil flow discharged from deep hole. 120 cooling water holes needing two days to drill, benchworker master finishes all in one 8-hour day shift.

Polisher uses 400 mesh sandpaper to push flat tool marks left by machining, 1.2312 hardness distribution uniform, one worker per day grinds out 2 square meters pre-polished surface. Customer pushing for plastic samples, a set of TV back cover mold, from drawing issuance to first test mold, period compressed to short 18 days.

· Rough processing man-hours compressed from 42 hours to 28 hours

· Deep hole drilling broken bit accident rate decreased above 80%

· Single set medium mold delivery cycle advanced full 5 days

· Mold factory single month capacity from 12 sets increased to 15 sets

1.2312's reparability under pre-hardened state came in handy, machine EDM only used 3 hours to erode away 0.5 mm steel at buckle position, mold went on injection machine for second test mold verification that night.

Polishability and Surface Finish

Physical Limitations

When old masters polish 1.2312 steel blocks with oilstone, sandpaper changing to 600 mesh makes it very hard to go further up. Forcing use of 1 micron particle size diamond grinding paste to rub repeatedly, touching by hand feels quite smooth, instrument measuring surface roughness always stops around Ra 0.63 micron jumping up and down. Making transparent parts needs Ra 0.01 micron optical mirror effect, using it simply cannot be ground out.

Looking at steel cross-section with magnifying glass, inside mixed one by one 80 to 120 microns long manganese sulfide. Sulfur and manganese added in smelting furnace hugged into clumps. Surrounding steel originally has 330 HV hardness, that strip of manganese sulfide soft-downed only has around 160 HV.

Wool polishing wheel at 2000 rpm speed high speed wipes across surface, soft manganese sulfide cannot bear pulling, hard-detached from steel plate. Polishing for 30 minutes, original 5 micron deep small pits can be pulled large to 25 microns. Surface all filled with dense pits, light shining on it occurs diffuse reflection, looking gray and dark.

· Surface roughness value oscillating back and forth between Ra 0.8 to 1.2 microns.

· Under microscope every square millimeter can count 15 to 30 pinholes.

· Inclusions along the steel plate rolling direction arranged in a line.

· Sandpaper changing above 2000 mesh, naked eye sees no change in brightness.

Neighbor sibling model 1.2311 death-presses sulfur content below 0.03%, master slowly grinding can produce SPI B1 grade bright surface. Using 1.2312 death-clash polishing time, surface metal will under uneven force squeeze into orange peel texture like waves. Taking to hit transparent PP plastic particles, molded out shell like covered with a layer of water mist blurry.

Making mold for car intake grille, drawing requires VDI 30 spark texture, using it is very comfortable. CNC machine doing deep hole drilling job, tool head advance efficiency 25% faster than 1.2311. Tool wear less, master no need frequently stop machine for insert change, period can save several days.

· Spindle running to 3500 rpm machine bears 18% less resistance.

· One 12 mm deep hole drill bit service life can last 35% more.

· After sparking, surface deteriorated hardened layer thickness about 0.02 mm.

· Thermal conductivity at room temp 20 degrees maintains at 33 W/m·K.

Drawing wrote roughness below Ra 0.2 micron, procurement department must go buy 1.2083 ESR or NAK80. 1.2083 ESR passed electroslag remelting furnace, sulfur content washed below 0.005%, impurity particles not even 5 microns. Fewer impurities, then can grind out SPI A1 grade surface that serves as a mirror.

Steel plate factory pre-hardened to around 30 HRC, along the texture and across the texture smashing down reaction completely different. Smashing across impact energy only 15 Joules, along can have 35 Joules. Material brittle, benchworker fitting mold trimming corners, file slightly forceful will chip off meat-eye invisible micro-nicks.

When doing injection molding, mold must bear 1000 MPa squeezing. Injection machine hits melted plastic in with 120 MPa pressure, pits on mold face very easily jam plastic residue. Demolding ejector pin pushes out, residue on plastic part surface scratches out one by one drag lines, one day down scrap a pile of defectives.

· Carbon content ratio stuck at around 0.40% to guarantee basic hardness.

· Manganese added to 1.50% to neutralize hot shortness trouble brought by sulfur.

· Put 1.90% chromium to bring a little bit rust prevention base.

· Milling machine rough processing single side must leave 3.0 mm allowance to handle deformation.

Large iron blocks thicker than 100 mm, outside and inside hardness difference can be controlled within 30 HB. Making that kind of 65-inch TV back shell very suitable. Back shell back does frosted texture, drawing specified Ra values all above 1.6 microns. Those pits where manganese sulfide fell off, are sprayed once by sandblasting gun with diamond sand, all covered inside and cannot be seen.

Put into salt spray box spray two weeks, places growing manganese sulfide first sprout red rust. Workshop humidity up to 90% in back-to-south days, its polished surface rust speed 15% faster than 1.2311. Oxide layer can pierce into meat 0.05 mm, after Chinese New Year back to work finding rust, master only can use coarse sandpaper to grind surface off one layer again.

Retaining Sulfur Element

1.2312 steel sulfur content artificially controlled between 0.05% to 0.10%. This layer of ratio lets it during machine processing behave like self-contained lubricant. Tool tip cuts into steel surface, meeting manganese sulfide (MnS) distributed in matrix, chips will automatically break into short fragmented coiled shape.

In workshop actual measurement, processing same volume mold frame, 1.2312 feed rate can open to 150-200 meters/minute. Comparing sulfur-free P20 or 1.2311, its comprehensive cutting efficiency increased 25% to 30%.

Using 12mm diameter coated carbide end mill processing, cutting 1.2312 generated heat is about 50-80 degrees Celsius lower than ordinary steel. Lower heat load prevented tool tip from generating crater wear. Same insert, cutting 1.2311 only lasts 4 hours, cutting 1.2312 can steadily run 6 hours or even longer.

1.2312 steel block internal manganese sulfide particles broke metal lattice continuity, making drilled iron chips length mostly maintain within 5 mm. Debris under 40 MPa high pressure coolant flushing, can along drill chip groove rapidly discharge, not to the point of jamming drill bit dead at 300 mm deep hole bottom.

Doing car bumper this kind of giant mold weighing 5 tons, corner clearing and face flying tasks are extremely heavy. Selecting 1.2312 can let machine spindle load drop 15%, whole machine power consumption subsequently decrease.

In order to offset hot shortness brought by sulfur, steel mills pulled manganese (Mn) ratio high to 1.40% to 1.60%. MnS inclusions formed by sulfur and manganese combination present long-strip shape. These strip objects in front of cutting edge act as solid lubricant, reducing built-up edge generation probability, workpiece side wall left textures are more neat.

During EDM rough processing, 1.2312 discharge gap maintains at around 0.15 mm. Although sulfur element will slightly interfere with discharge stability, but because its material matrix consistency is good, overall electrode wear rate controlled within 0.3%.

· 1.2312 common in appliance shells, home appliance bases etc. non-decorative part molds.

· Car dashboard skeleton molds, injection shots usually set above 300,000 times.

· Steel pre-hardened hardness stable at 280-325 HB, no need subsequent heat treatment deformation risk is low.

· Module four-side bright processing, parallelism error can be controlled within 0.05 mm per meter.

Manganese sulfide existence has negligible effect on heat conduction, 1.2312 at 20 degrees Celsius thermal conductivity is 33 W/(m·K). In injection cycle, cooling water path carrying away heat speed is almost same as 1.2311. Using 1.2312 will not lengthen production cycle, molding cooling time still maintains in 25 to 45 seconds interval.

Sulfur element in 1.2312 internal formed micro defect points, instead became buffer rooms for processing stress. After large-cutting-amount rough processing, module internal residual stress about 150 MPa, through simple aging treatment can be reduced to 50 MPa, preventing mold from cracking in use.

Compared to 1.2083 this kind of stainless mold steel, 1.2312 price cheaper nearly 40%. It although not resistant to acid gas corrosion, but for ordinary ABS, PP, PS plastic processing more than enough. Under single set mold manufacturing fee 200,000 budget, choosing 1.2312 often can save around 15,000 material and processing comprehensive cost.

Steel mills use above 50 tons electric arc furnace to refine 1.2312, then perform vacuum degassing treatment. Even if sulfur content is high, its internal hydrogen content is also controlled below 2ppm.

In tapping operation, 1.2312 performance is superior to most medium carbon steels. Due to sulfides reducing metal surface shear strength, taps when processing M16 above large threaded holes, required torque decreased by 22%. This reduced tap snapping risk in hole, especially advantage obvious when handling heavy template lifting holes.

During mold storage, 1.2312 polished surface rust prevention period roughly only 3 to 5 days. Manganese sulfide particles easily occur electrochemical reaction with moisture in air. Experienced warehouse keepers will apply thickness above 0.2 mm rust prevention oil, and cooperate with dehumidifier to press warehouse humidity below 50%, preventing needle-like rust spots from permeating matrix.

In mold life end stage, 1.2312 still possesses extremely high recycling value. Due to its alloy ratio clear, scrap steel recycling price usually higher than ordinary carbon steel by 35%. For large OEM factories consuming hundreds of tons of mold steel annually, this scrap residual value is also a data item not to be ignored in cost control.

Extreme Processing Efficiency

Machine tool spindle speed pulled up to 2500 rpm, fly cutter disk sweeps over 1.2312 steel plate surface, chips burst open like popcorn. Comparing 1.2311 steel, its feed rate can from 800 mm per minute directly adjust up to 1100 mm.

Due to manganese sulfide acting as "chip breaker", cut down iron chips length usually maintains between 2 to 8 mm. Short fragmented chips will not wrap on tool shank to form "bird nest", reducing machine operator master stop-cleaning times. CNC machining center full load running 8 hours, 1.2312 effective cutting time nearly 50 minutes more than ordinary P20 type steel.

Same carbide insert, processing 1.2312 generated friction heat lets tool tip temperature control below 650 degrees Celsius, avoiding coating occurring thermal softening too early.

In rough processing stage, per cubic centimeter metal removal amount consumes lower power. Ammeter shows spindle load long-term maintains in 45% stable interval, rather than violently fluctuating above 60%. Low load operation extended machine lead screw and bearing geometric accuracy life, large mold frame after processing finished flatness error often can be controlled within 0.03 mm.

· Side milling operation feed per tooth can reach 0.15 to 0.25 mm.

· 100 mm diameter face milling cutter depth of cut supports 3 to 5 mm continuous eating.

· Carbide drill bit on 1.2312 cutting speed Vc reaches 120 meters per minute.

· Tool durability compared to 1.2311 under same hardness increased about 40%.

· Machine spindle vibration frequency monitoring value 12 decibels lower than processing conventional mold steel.

Drilling deep holes is heavy task of mold water path processing, sulfur element lubrication effect at this time is magnified. Deep-diameter ratio reaching 20 times drilling process, 1.2312 no need frequent tool retracting for chip removal, high pressure internal cooling system can easily carry away debris. Drill bit at hole bottom torque resistance constant, snapping risk reduced 35%, this is huge safety guarantee for large modules worth tens of thousands of yuan.

Masters often say 1.2312 is like "cutting tofu", this describes the crispness when its cutting edge separates from material, completely no sticking knife leading to dragging feel.

In tapping operation, M24 large diameter threaded holes one-time forming rate is extremely high. Manganese sulfide particles induce micro-cracks at chip root, tap bears squeezing stress lightened more than 20%. Even in workshop environment above 30 degrees Celsius continuously working, built-up edge generation speed on tap surface is significantly slower than other pre-hardened mold steels.

· Deep hole drill per minute feed rate stable above 280 mm.

· Tap service life without applying lubricant can reach 150 holes.

· Module six-side processing man-hours from traditional 12 hours shortened to 8.5 hours.

· Surface roughness after finish milling can maintain around Ra 1.6 without polishing.

Aiming at large car molds, single body weight often exceeds 3 tons. Using 1.2312 to manufacture mold base, whole set mold manufacturing cycle can from 45 days compress to 38 days. Saved 7 days period for car part manufacturers anxious for production, can produce tens of thousands more sets of plastic injection parts.

Laboratory data indicates, 1.2312 shear strength during cutting process is about 150 MPa lower than 1.2311, machine tool does work easier.

In EDM rough processing, because sulfur element changed local conductivity of arc discharge channel, discharge removal rate increased about 10%. Although this will slightly increase electrode loss, but in handling complex deep cavities, faster corner clearing speed compensated electrode loss cost. For home appliance shell molds not needing mirror polishing, this efficiency advantage is extremely competitive.

· Fly cutter disk spindle speed recommended in 800 to 1200 rpm interval.

· Under same cutting conditions, tool tip wear amount VB value only 0.12 mm.

· Rough milling per hour metal removal rate highest can reach 1800 cubic centimeters.

· Material internal stress release uniform, deformation after finish processing less than 0.02 mm.

Material factory hardness distribution extremely even, 300 mm thick plate from surface to core hardness difference fluctuation less than 3 HRC. This hardness consistency ensured CNC program when running at different depths, tool force situation always same. Will not appear due to hitting internal hard points leading to insert fracture, guaranteed machine tool can 24 hours unattended automated operation.

This steel performance in processing efficiency, is essentially converting part of steel mill smelting cost into later processing plant profit space.

For medium mold factories with annual demand exceeding 500 tons, after switching to 1.2312, tool warehouse requisition amount decreased 22%. Average every three-axis milling machine annual output value increased more than 150,000 yuan. Although material surface not suitable for optical grade polishing, but in 85% of conventional industrial mold applications, its shown processing throughput is difficult for other grades to reach.

· Single edge cutting force actual measured data about 1200 Newtons.

· Cutting heat affected layer thickness remaining at side finish milling less than 15 microns.

· Module four corner positioning hole processing accuracy repeatability maintains at 0.01 mm.

· Thermal expansion coefficient at 100 degrees Celsius stable at 12.1.

Adopting ultrasonic assisted drilling, 1.2312 internal sulfides can rapidly respond to high frequency vibration, further reducing cutting resistance. In electronic product structural part molds with extremely short production cycle requirements, it can guarantee mold base completes transformation from blank to quasi-finished product within 48 hours.