When valve body and valve cover need 100% RT inspection, casting pass rate is about 85%-90%, rework cost is high;
Forging internal is dense, RT pass rate ≥ 98%.
If single valve price > 500 US dollars or pressure ≥ PN100, suggest changing to forging, can lower comprehensive cost about 10%-15%.
Table of Contents
Togglert inspection expense
Ray flaw detection (RT)
According to ASTM E446 industrial specification, once film on appears 2 grade above shrinkage looseness shadow, quality inspector’s red pen will heavily at drawing on draw circle. A caliber 24 inches, pressure grade 900 pounds carbon steel valve body, merely is flange to middle cavity’s transition section, steel wall thickness just reaches 85 millimeters.
Want to penetrate 85 millimeters thick solid steel plate, conventional Iridium-192 isotope source completely hits not through, ray exposure time will be forcefully delayed to 40 minutes above. Workshop only can push out containing heavy Cobalt-60 radioactive source’s lead canister, buying one grain high energy isotope needs to spend dropping 3500 US dollars, its half-life period only has 5.27 years.
According to specification’s grid dividing method, this two tons heavy giant metal shell is by chalk drawn into dozens small squares, front front back back needs to shoot 72 different angles’ perspective areas.
- Imported D7 industrial film single piece consumable 4.5 US dollars
- Washing 72 pieces films consumed’s developing liquid fixing liquid 15 US dollars
- Lead wire image quality indicator loss sharing roughly 3 US dollars
- Dark room inside washing adding strong wind blowing dry consumes dropping 2.5 hours
At North America’s industrial zone, hiring a holding high-level certificate’s technician, every hour labor fee is 115 US dollars starting step. He needs at strong light under naked eye staring at 72 pieces films, finding those width only has 0.5 millimeters’ gray thin lines.
As long as at drawing C area’s film on measures out a long 15 millimeters’ slag inclusion, whole machining assembly line just has to immediately stop work. Carbon arc air gouging machine dragged into field, accompanying 100 decibels’ ear-piercing noise, electric arc instantly takes that piece area burns to 3000 degrees Celsius. Compressed air flow takes iron water deadly life blows away, exposes pure metal base.
Welder holding E7018 low hydrogen welding rod, with every hour melting 1.5 kilograms metal’s slow action, a little bit takes that 30 millimeters deep’s elliptical big pit fills full. Hiring a hand inside has 6G special welding certificate’s senior master, factory one day needs to dig out 280 US dollars.
Thick heavy metal piece is by overhead crane hung stuffed into bogie type resistance furnace, several rows heating tubes all open, furnace inside temperature every hour honestly climbs 50 degrees Celsius. Arrived 620 degrees Celsius still needs to hard stand heat preservation 4 hours, one set eliminating stress heat treatment done finished, electricity meter on runs dropping 800 degrees industrial electricity.
Whole set repair process consumes entering 5 days time, technician again dragging heavy lead canister runs back work station. They need at original that manual dug repaired area, newly stick on new film, arrange good lead letter marks, again comes one time high intensity’s ray irradiation.
- Machine tool newly finding flat clamping delays 4 hours
- Large workshop occupying land stopping machine one day loses 500 US dollars
- Foreign party stationed’s inspector travel fee every day 200 US dollars
- Delivering not goods causes container pressing port every day 150 US dollars fine
Lens cuts to forging workshop, 12000 tons’ hydraulic press exactly facing burned to 1150 degrees Celsius’s solid steel bar towards down smashes, metal grain size is hard rawly squeezed to extremely fine’s 6 grade above. Originally hiding at liquid steel water inside’s tiny bubbles, at several ten thousands tons’ violent rolling pressing under even zero point several millimeters’ survival space all gone.
Iron lump cools through after pushed onto ultrasonic flaw detector, probe smeared on industrial syrup same’s coupling agent at blank surface scrapes passed. Screen on’s waveform flat flat steady steady, finds not any representing empty hole clutter wave’s jumping. Checking finished one whole thick wall equipment only spent not arriving 45 minutes.
Defect & rework
One piece carrying red circle’s film sent back workshop, that 15 millimeters long’s dark gray crack hides at 85 millimeters thick’s steel wall internal, distance surface fully has 40 millimeters deep. Angle grinder deals not with that thick’s metal layer, must take whole heavy reaching 2.4 tons’s valve body newly use iron chain tie good, lift to dedicated’s rework station.
Worker connects 800 amperes’ DC power supply, takes a 5/8 inches thick’s carbon air gouging rod clamps at welding handle on. Piercing eyes’ electric arc light at steel plate on explodes open, 3000 degrees Celsius’s high temperature takes solid metal hard rawly burns into iron water, beside 0.6 megapascals’ high pressure air following trend takes red through’s iron water all blows to ground on.
In order to dig out that 15 millimeters’ tiny defect, operator has to follow funnel shape towards down gouge, eventually at flat’s metal surface opens out a top end wide reaching 60 millimeters, deep 45 millimeters’ U shape big pit. Been destroyed and dug dropping’s high quality metal volume, fully is that defect itself size’s 20 times above.
Towards ice cold’s steel pit inside filling weld seam will trigger severe’s cold crack. Two workers holding high power propane baking gun, facing that piece area burned whole 45 minutes. Until temperature measuring pen at distance groove 50 millimeters’ place draws down a red line, confirming metal base temperature already reaches 150 degrees Celsius, welding just can start.
Holding certificate’s senior welder wearing mask, hand inside pinching 4 millimeters thick’s E7018 low hydrogen welding rod. A long 350 millimeters’ welding rod, at electric arc under burning 90 seconds just only leaves a head. He maintains every hour depositing 1.2 kilograms metal’s slow action, one layer one layer takes that deep pit fills full, middle still needs continuously use cleaning hammer knocks dropping waste welding slag.
| Maintenance action item | Estimated time consuming | Labor/material unit price | Single rework bill expense |
|---|---|---|---|
| Carbon arc air gouging digging groove | 2.5 hours | 45 US dollars/hour | 112.5 US dollars |
| Propane preheating and grinding | 1.5 hours | 30 US dollars/hour | 45.0 US dollars |
| Senior welder filling operation | 4.0 hours | 65 US dollars/hour | 260.0 US dollars |
| 15 kilograms flaw detection grade welding material | – | 8.5 US dollars/kilogram | 127.5 US dollars |
| Newly shooting film re-inspecting | 3.0 hours | 120 US dollars/time | 360.0 US dollars |
Very not easy takes pit fills flat, that 2.4 tons’s iron guy again is stuffed into bogie type heating furnace. Furnace temperature every hour slow swallowingly climbs, burned to 620 degrees Celsius after maintains 12 hours. Industrial electricity meter crazily rotates, one whole night just can eat dropping 900 degrees electricity, exiting furnace after still needs to spend two days time waits it naturally cools through.
Local passed 3000 degrees’ high temperature baking, thick heavy metal block at cooling time happened not arriving 0.8 millimeters’ distortion. Originally at large CNC machine tool on turned flat flat neat neat’s flange sealing face, now uses feeler gauge one measures, tilts up a naked eye looking not seeing yet can let high pressure gas instantly leak empty’s gap.
In order to repair this 0.8 millimeters’ deformation, behind follows a series let person headache’s machining trouble.
- Valve body needs newly moved onto five-axis vertical lathe goes scrapes flat that layer skin
- Scraped dropping 1 millimeter after, flange thickness from standard’s 85 millimeters shrinks becomes 84 millimeters
- Ring-shaped distributed’s 24 bolt hole positions, connecting bringing happened 0.5 millimeters’ deviation
- Lathe tool walking tool’s labor time fee again needs extra adding on 200 plus US dollars
If that pit dug too deep, lathe scraping skin after remaining’s metal thickness reaches not ASME B16.34 standard regulated’s 68.5 millimeters lowest wall thickness, this piece order just thoroughly scrapped. Factory only can open eyes watching spent 20 days time, invested near ten thousand US dollars cost’s semi-finished product, according to every kilogram 0.3 US dollars’ price serves as scrap iron sells dropping.
Originally contract on writing’s 45 days delivery period, because this one set digging repairing, heat treatment, machining restoring’s continuous action, was deadly dragged to 75th day. Salesperson every day needs at telephone inside deal with foreign party urging goods’ buyer, port booked good’s special bulk cargo space passed time, in vain lost 1500 US dollars’ deposit.
Buyer at drawing on knocks down 100% flaw detection’s requirement time, whole casting assembly line just started tossing coin same’s probability game. Pressure grade at Class 900 above’s heavy shell body, appearing shrinkage looseness being pulled to air gouging rework’s proportion year round hovers at 15% to 30% between.
Next door forging plant sent coming’s 3 tons heavy A105 solid forging blank, body on finds not to even 0.1 millimeters’ sand hole. Machine tool blade at water flow washing under cuts open dense’s metal layer, cutting down coming’s iron shavings present out beautiful’s continuous spiral shape.
Delivery period delay
That piece delayed to 75th day’s shipping order, placed at Middle East oil refinery engineering general contractor’s office desk on, became a sky price dunning bill. A daily producing crude oil 200 thousand barrels’s catalytic cracking device, absolutely not tolerates lacking a 24 inches’ metal shell body just stops down whole construction progress schedule.
According to plan, this heavy reaching 2.4 tons’s thick wall equipment originally should at October 15th noon before, hang onto Persian Gulf coastline No. 2 berth’s crawler crane. Film on’s that 15 millimeters crack triggered workshop inside’s continuous repair welding operation, ocean freight bill of lading on’s date was hard rawly changed to November 20th.
Purchasing contract annex C inside’s delay penalty clause writes extremely clear: every overdue one day, deducts order total amount’s 0.5%, delaying exceeding 30 days not issuing goods, owner party has right unilaterally terminates contract and claims full amount advance payment.
Port that side messy into a pot of porridge. Originally for this out-of-gauge equipment pre-booked’s 40 feet special frame container, at dock empty waited three days after was by shipping company forcefully pulled away. Ocean freight department needs newly goes spot market grabs space, one trip 4500 US dollars’ freight fee meets year end peak season, quotation sheet on’s number soars to 8200 US dollars.
A 24 inches equipment’s absence, lets construction site’s pipeline connecting progress just like falling down’s dominoes:
- 30 meters high’s heavy scaffolding at wind sand inside in vain built 20 days, every day rent 120 US dollars
- Hired coming doing large caliber flange connecting’s special welder team, 8 people every day’s waiting work fee as high as 1600 US dollars
- Used to give pipeline doing high pressure blowing sweeping test’s 15 large power air compressors, all forced turning off fire stopping rotating
- External hired’s third party non-destructive testing supervising engineer, visa extension spent 500 US dollars processing fee
At pipeline welding work area, that section leaving blank’s pipeline two ends was by wind sand eroded half a month. Workers took 4 pieces waterproof tarpaulin takes diameter 600 millimeters’ pipe mouth deadly wraps holding, preventing sand dust blows into internal. Safety supervisor every day needs at form on deducts dropping 50 points’ construction progress points.
Container at 80th day very not easy floats ocean crosses sea arrives site. Large crane entering field’s schedule missed, that 750 tons grade’s Demag crawler crane early was dispatched goes 5 kilometers outside’s next door factory area doing work. Only waiting crane newly queuing drives coming, wooden packing box just at customs supervision warehouse inside ate a week’s sand.
Waiting that 2.4 tons’s repair welded goods hoisted to mid air inside, responsible for locking tight bolts’s fitter discovers flange face not too right. Passed several thousand degrees high temperature repairing and long distance ocean freight bumping, metal face produced 0.2 millimeters’ tiny warping.
- Renting flange end face repairing machine one day’s fee is 850 US dollars
- Two operators laying at 30 meters high air newly finding flat spent 6 hours
- Original matching’s metal spiral wound gasket thickness not enough, running goes warehouse received 3 pieces thickened custom made style
- Pipeline full line pressure testing node was hard dragged to December 28th’s early morning
Finance room desk on places two portions comparison bills: buying casting blank time saved down’s 3000 US dollars price difference, finally handed’s a sum overdue default money adding empty space fee is 18500 US dollars. Fine number enough buys two same size’s solid forging pieces.
Changed into ten thousand tons hydraulic press inside coming out’s forging blank, production schedule table on’s progress bar walks like quartz clock same accurate. December 1st solid steel bar cutting material, December 5th vertical lathe rough machining, ultrasonic flaw detector sweeping passes one breath finishes, December 15th pushed into assembly area.
Assembly line on has no at dark room inside washing film delaying’s 24 hours, has no bogie type resistance furnace rising temperature dropping temperature grinding dropping’s 5 working days. Assembly group no need prevents sudden coming’s air gouging digging repairing rework. Workshop director closing eyes also can calculate out, 35th day afternoon 2 o’clock, flatbed truck will on time stop at loading platform.
forging material cost
Ex-factory price & loss
Cylindrical shape’s A105 carbon steel solid iron lump is sent into natural gas heating furnace. Furnace chamber inside’s temperature set at 1220 degrees Celsius, one time can load entering 5 tons’ material. Takes a diameter 300 millimeters’ steel ingot thoroughly burns through through, needs to spend on 4.5 hours. Month end once pulls bill, every burning one ton steel material just needs to burn dropping 180 cubic meters’ natural gas.
Steel material at this high’s temperature under, surface with air touching at together reacts extremely fast. Exiting furnace’s that moment, red thoroughly’s steel ingot outer layer will rustlingly towards down drop a layer thick thick’s black skin. Single time heating burned dropping’s this layer oxide skin, can occupy reaching steel ingot original weight’s 2.5% to 3.0%. Bought entering 1000 kilograms’ steel material, even forging machine’s edge all not touched, just already burned gone approaching 30 kilograms.
Clamping machine like a big pliers, takes 800 kilograms turning red turning hot’s steel ingot steadily places at 8000 tons grade hydraulic press’s anvil on. Workshop top on’s overhead crane hanging heavy mold, aimed accurate towards down ruthlessly presses. This giant monster every starting one hour, electricity meter just needs to run dropping 450 degrees industrial using electricity. Merely is this equipment’s monthly depreciation fee, year round calculated down all at 150 thousand RMB up down swaying.
Operating console front sitting three workers, eyes staring at flipping steel machine, coordinating taking turning red’s iron block flips coming flips going. Hard rawly smashes out a 4 inches 900 pounds grade valve’s rough rectangular cuboid outline, skilled’s team also has to work on 25 minutes. A day shift 8 hours, pinching dropping eating meal and handing over shift’s gap, at most also just knocks out coming 16 pieces blanks.
Leaving forging plant before, iron lump body on already carried not few scattered’s expenses:
- Cutting dropping steel ingot two ends 15% easy having shrinkage hole’s waste material
- Ultrasonic flaw detection smeared’s chemical water and worn out’s probe
- Thrown into 900 degrees Celsius furnace inside heat preservation 3 hours’ electricity fee
- Using 12 kilograms cast steel shot beating dropping surface layer black skin’s shot blasting fee
Drawing requirement extremely strict, iron block single side extra left 25 millimeters’ thickness waiting lathe goes scraping. Take a 8 inches’ gate valve for saying, forging plant sent coming’s blank on scale one weighing fully 680 kilograms. But drawing on draws clear clear, this valve done finished after’s net weight only can have 290 kilograms.
Takes this 680 kilograms’ heavy guy mounts to horizontal CNC lathe on clamps tight. Master takes main spindle rotating speed tunes to every minute 120 revolutions, eating tool amount set at 8 millimeters. Lathe tool cuts down going, blue purple color’s iron shavings like curling’s spring same from tool edge continuously towards outside bursts. Machining finished such one piece big valve body, at least has to scrap two pieces unit price 85 yuan’s hard alloy coated blades.
390 kilograms’ high price steel material, at lathe on rotating coming rotating going, all became ground on’s broken iron pieces. Initially purchasing blank was according to every kilogram 35 yuan paid to forging plant, calculating down has 13650 yuan’s material fee became ground on’s scrap. Scrap recycling station’s big truck drives into factory area takes iron shavings pulls away, given out’s scrap iron recycling price only has every kilogram 2.2 yuan.
Buying entering and selling exiting one compares, single valve merely is acting as scrap iron sold dropping’s price difference loss just reaches 12792 yuan. Factory hard rawly swallowed down 60%’s metal loss rate. Horizontal lathe slow work produces fine work, cutting finished this one piece has to endure on 14 hours, according to machine shift fee calculating every hour again needs towards inside smashes 120 yuan.
As long as lathe one rotates, four around’s consuming just not stopped passed:
- Every day splashing to ground on and evaporating dropping’s 5 liters emulsified cooling liquid
- Turning thread’s blade cuts full 300 buckles forcefully scrapped changing new
- Dedicated person driving small forklift every 4 hours shovels one time receiving material tray iron shavings
- Fiercely eating tool lets machine tool main spindle bearing lost one third life span
Boring machine only can stretch entering a long rod, takes solid’s metal a little bit digs out coming. Facing diameter 150 millimeters’ deep hole, tool head every hour only can difficultly towards inside pushes forwards 40 millimeters. Digging empty internal channel scrapped’s blade money, compared to cutting outside one circle higher out whole 3 times.
Two ends connecting pipe’s flange plate, thickness mostly at 50 millimeters up down. Middle that section valve body belly on’s pipe wall only has 20 millimeters thick. In order to keep holding two ends 50 millimeters’ flange shape, lathe only can takes middle that section 30 millimeters thick, fully 400 millimeters long’s extra iron skin a little bit hard scrapes down coming.
Changing one kind called precision mold pressing’s playing method, account book on’s numbers greatly changes appearance. Up down two pieces molds one close together. Turning red turning soft’s iron block at inside one time nature was squeezed out two ends thick, middle thin’s appearance. Left to lathe goes scraping’s thickness, instantly from 25 millimeters shrinks reduces to single side 5 millimeters. Blank on scale one weighing, weight from 680 kilograms drops to 350 kilograms.
Finding mold factory opens one set 8 inches valve using’s high temperature resistant mold, other party quotes price 180 thousand RMB. Material quality using is H13 hot work mold steel, can resist holding 1200 degrees Celsius’ iron block repeatedly scalding baking.
RT flaw detection bill comparison
A 300 millimeters times 80 millimeters’ high photosensitivity industrial X ray film, single piece getting goods price at 12 yuan up down. A 10 inches’ casting valve body wants whole body up down shoots a whole time, outer skin needs tightly seamlessly sticking on 24 pieces to 30 pieces films. Holding certificate taking post’s flaw detection worker chest front hanging radiation dose pen, according to every shooting one piece film 25 yuan piece-rate settles account. Dark room inside washing film using’s developing liquid and fixing liquid, every changing one pool new chemical water just has to dig out 400 yuan.
Film appraiser takes out a carrying scale’s ten times magnifying glass, face sticks going up one inch one inch finding black spots. According to ASME B16.34’s inspection industry rule, film on as long as pops out exceeding 2 millimeters’ dense pores, or length exceeding 5 millimeters’ stripe shape black shadow, this piece film just counts scrapped. Ordinary sand casting process made out coming’s valve body, first time shot finished’s returning goods rate year round stuck at 18% to 25% between.
Following not qualified film on’s position at iron lump on makes mark. Grinding worker carrying a thick heavy’s carbon arc air gouging gun starts work digging meat. Several thousand degrees high temperature’s electric arc instantly takes has pores’s metal melts, high pressure air flow immediately takes iron water blows flying, hard rawly at valve body on gouges out a deep 40 millimeters’ deep pit. Finished matter after still has to holding angle grinder takes scorched black’s edge grinds out metal base color, merely this one set action just needs to consumes 2 plus hours.
Full head big sweat’s welder takes over relay baton, holding E7018 low hydrogen welding rod towards pit inside a little bit fills meat. Moving hand before has to first use liquefied gas baking gun takes surroundings iron skin preheats to 150 degrees Celsius. In order to fill full a also just is pigeon egg size’s shrinkage hole, needs to burn dropping 1.5 kilograms’ welding rod, spend dropping almost 40 minutes. Welding rod at hardware warehouse’s unit price is 18 yuan one kilogram, senior welder’s hourly wage every hour needs 50 yuan.
Repaired finished weld’s area internal holding a burst of strength, just like this placing not caring, passes not 5 days surely will crack open a crack. Heavy’s valve body needs newly to be by forklift sent into heat treatment big furnace, heated to 620 degrees Celsius heat preservation two and half hours. Opening one trip furnace’s starting price set at 800 yuan. If workshop inside exactly only has this one piece rework part waiting eliminating stress annealing, this 800 yuan’s electricity fee only can all smash at its head on.
Original digging pit repairing welding’s place, in order to insurance seeing, needs towards outside extra expands out a segment distance extra sticks several pieces films. Rework shooting film’s fee one cent not less, single piece film’s shooting adding washing film cost calculating down still has to dig out 37 yuan.
Engineering specification white paper black words writing entirely without accommodating room, same one position’s rework times at most allows three times. If arrived third time shooting film, light box on still is can faintly seeing black spots, quality inspector just will holding red paint at iron lump on draws a big cross. Front buying blank paid’s money, lathe cutting consumed dropping’s electricity fee, shooting film repairing welding given out’s labor fee, instantly all hit water skipping.
Taking gaze turning towards hydraulic press smashed out coming’s forging piece, internal’s metal grain is by several thousand tons’ strength squeezed entirely without gap. Taking forging piece shot out’s film hangs onto flaw detection room’s light box, clean just like a piece semi-transparent’s frosted glass. One thousand forging pieces sent entering accepting ray irradiation, can check out internal cracks or pores’ quantity breaking fingers all can count over coming.
Taking two kinds material processes at flaw detection link’s bill pulls out places at desk surface on, one stroke one stroke calculates a clear. A 8 inches 1500 pounds grade’s base, two kinds origin’s metals at this room filled full of ray’s room inside, needs to face completely different’s expense accounts.
| Fee flow direction table | Casting piece single machine average shared expense | Forging piece single machine average shared expense |
|---|---|---|
| First round film and shooting labor | 750 yuan (according to 30 pieces calculates) | 750 yuan (according to 30 pieces calculates) |
| Defect air gouging and grinding consumables | 120 yuan (calculates into rework probability) | 0 yuan (probability extremely low) |
| Welding rod loss and repairing welding hourly wage | 85 yuan | 0 yuan |
| Entering furnace eliminating stress electricity fee sharing | 150 yuan | 0 yuan |
| Second time re-inspection shooting film miscellaneous fee | 120 yuan (extra shooting 3 pieces calculates) | 0 yuan |
Flaw detection bill on looking not seeing’s hidden accounts, exactly at workshop outside real gold white silver towards outside flowing water:
- Queuing occupying line: rework parts and normal parts squeezing at one flaw detection window grabbing time, whole batch goods’s delivery period forced towards back delays 3 to 5 days.
- Travel expense: client stationed’s third party inspector comes factory inside looking at film, extra staying one day’s eating living adding labor time fee as high as 2500 yuan.
- Default compensation money: delivery period exceeded according to every day contract total amount’s five thousandths deducts penalizing, forced urgently only can spend four five ten thousands chartering flight air freight.
Front end less paid several tens bucks one kilogram’s material fee, meeting 100% flaw detection requirement’s drawing, several pieces fingernail size’s black spot films just can take account face’s profit strips clean clean.
Quantity changes process
Purchaser takes a 20 pieces’ order throws to forging factory quoting price. Factory director swept one eye drawing bottom’s quantity, without hesitation at process confirmation sheet on ticked selected free forging. If drawing on marks 2000 pieces, he will immediately dig out mobile phone finding mold factory inquiring H13 hot work mold steel’s current price.
Doing 15 pieces 6 inches’ valve body, not worth spending ten plus ten thousands goes opening one set dedicated’s metal mold. Furnace inside burned to 1200 degrees’ cylindrical steel material is by clamping machine dragged out coming, bare body thrown at several tons heavy’s air hammer anvil on.
Accompanying air hammer clank clank smashing down going, round steel is stiffly knocked into a rectangular cuboid. A finished product net weight 45 kilograms’ 6 inches valve body, using free forging process knocked out coming’s blank weighing weight as high as 120 kilograms. According to every kilogram A105 carbon steel 15 yuan’s buying price calculating, merely buying blank’s money just has to dig out 1800 yuan. Extra coming out’s 75 kilograms meat, all left to behind’s lathe goes gnawing.
Factory inside’s cost accountant calculated passed a detailed account, 100 pieces below’s scattered orders all rely on air hammer hard smashing. Buying several tens kilograms extra steel material paid out’s money, far far compares not to finding person drawing drawing, going CNC milling machine slowly digging out one set steel mold’s expense big.
A piece unit price 85 yuan’s hard alloy blade, needs to at turning black’s iron block on scrapes dropping larger half’s thickness. Machining one piece consumes 6.5 hours not stopping machine, according to 80 yuan one hour calculating, merely machine shift fee just needs to give machine tool reverse subsidizes 520 yuan. Scraped down coming’s waste iron shavings swept into iron bucket, scrap station given’s recycling price only has pitiful’s 2.2 yuan.
Quantity fiercely increases to 1500 pieces, abacus’s playing method all changed. Forging factory’s purchasing will pull coming one whole piece heavy reaching 600 kilograms’ alloy steel, sent onto slow wire cutting machine tool, a little bit cuts out valve body uneven’s internal cavity shape. One side upper mold adding one side lower mold, connecting labor bringing material done out coming’s quotation exactly stops at 85000 yuan.
Eight thousand tons’ hydraulic press pushing upper mold bringing wind sound ruthlessly presses down coming. High temperature state under like dough same’s iron water is deadly held at closed’s mold cavity inside, only can follow gap fills full every one designed good’s corner.
Cooling after taken out coming weighing, single blank’s weight cliff style dropped to 52 kilograms. With before that 120 kilograms’ silly big black thick comparing rising, outer shape already extremely close to drawing on required’s appearance.
- Material fee plummeting: every piece less buys 68 kilograms high price steel material, according to 15 yuan unit price multiplying entering, one piece saves down 1020 yuan.
- Mold fee amortizing: 85000 yuan’s mold opening fee divided by 1500 pieces’ quantity, every piece account face on only shares 56.6 yuan.
- Machining fee halved: outer periphery left to turning’s allowance remains thin thin’s 4 millimeters, lathe runs 2 hours surely can get off line.
Lathe main spindle’s load all of a sudden relaxed. Eating tool depth from fierce’s 8 millimeters reduces to gentle’s 2 millimeters. Originally turning two pieces valves just has to chipped edge scrapping’s CNC blade, now can smoothly one breath cuts finished twelve pieces. Cooling water pump pumped up coming’s emulsion consuming amount, also follows less dropping one half still more.
Hardware purchasing circle inside has a not randomly said’s word, 300 pieces is a dead stuck’s watershed. Passed 300 pieces big gate’s batch orders, whoever again goes letting workers take air hammer one by one smashes iron blocks, purely is taking company’s account book at fire on bakes.
Calling a load bearing 10 tons’ nine meters six high fence truck comes factory inside pulling goods. Loaded full 120 kilograms one piece’s free forging big iron blocks, truck box inside full calculating full counting only can stuff down 80 pieces, again extra loading traffic police just needs to according to overloading opens fine ticket.
Changed into 52 kilograms’ precision mold forging pieces loading truck, one trip can light light easy easy pull away 190 pieces. Paid to driver’s 2800 yuan single trip freight fee dividing a bit, single piece’s shared freight fee from 35 yuan dropped to not reaching 15 yuan. Logistics cost at quantity’s stacking under, quietly soundlessly thinned a big circle.
Forging workshop inside that natural gas heating furnace burning one full furnace, exactly can stuff entering 5 tons’ raw material. Doing several tens pieces scattered orders, worker hand inside knocks slow, furnace door frequently opening opening closing closing runs dropping large amount hot air, every burning one ton material needs to in vain wastes dropping 40 cubic meters’ natural gas.
rejection rate reduction
Film not qualified
Inspection room’s strong light light box lighting piercing eyes’ white light, brightness at 30000 candela/square meter up down. Worker takes just washed out coming’s industrial X ray film inserts going up, gray color’s film on reveals out several not reaching 2 millimeters’ deep black small round dots. Responsible for looking at film’s master takes red oil pen heavily at black spot outside drew a circle.
Drawing on plain text writing 50 millimeters wall thickness’s steel material internal cannot have exceeding 1.5 millimeters’ sand hole. This piece drawing red circle’s film along with a piece not qualified report sheet, was by an iron wire deadly tied at heavy reaching 300 kilograms’ valve body outer shell on. Forklift takes it all the way pulls back full is dust’s cleaning workshop.
Workers carrying up carbon arc air gouging gun aiming red circle position starts digging pit. High pressure air pairing on several thousand degrees’ electric arc, at originally flat’s metal surface hard rawly cuts out a U shape deep groove.
- Air gouging depth often exceeds black spot depth’s 20%
- Digging eliminating scope compared to film spot big one circle, wide out 15 millimeters
- Flaw detector holding flashlight leaning close confirming pit bottom clean clean
- Absolutely not allows remaining half point naked eye can seeing’s fine crack
Wearing thick heavy mask’s electric welder changes on a E7018 model’s welding rod, takes ammeter knob twists to 140 amperes. One drop drop totally red’s iron water follows welding rod tip drops into deep pit, one layer continuing one layer towards up paving.
Local welding repairing produced’s high temperature will let surrounding’s pig iron sharply expands, very easy tears out hair strand thickness’s new crack. A 12 inches 600 pounds grade’s heavy gate valve blank, repaired finished pit even one minute all cannot stop, must hurriedly sent into several hundreds meters outside’s heat treatment furnace.
Natural gas burner rumblingly towards furnace cavity inside sprays fire, thermometer on’s numbers according to every hour 180℃’s setting slowly towards up climbs. Pointer finally stops at 620℃’s scale line on, valve body at inside continuously bakes enough 4 hours, waiting fire withdrawing naturally drops to 200℃ below just dare open furnace door.
This piece rework list on recording 1500 US dollars’ labor fee and material loss fee. Scheduling board on clearly clearly hanging schedule table, same furnace coming out’s same one batch goods delivery period towards back dragged whole 11 days.
Flipping checking purchasing clauses, same one part’s allowed digging pit repairing welding times at most only has two times. Second time shot out coming’s X ray film on if still has removing not clean’s black shadow, a piece marked price 8000 US dollars’ metal outer shell only can act as scrap iron handled.
Buyer sent coming stationed factory’s inspector every day sitting at desk front flipping looking these X ray films. Sampling inspecting time seeing film corner left a piece dark room not washed clean’s water stain, whole batch 40 pieces equipment’s shooting film report sheet on spot was beaten back re-doing.
- 10 inches caliber’s ball valve needs to surround into one circle shoots down 14 pieces films
- 80 millimeters thickness’s iron lump single time exposure needs to wait 25 minutes
- Washing film machine inside’s chemical water temperature deadly fixed at 20℃
- Crawler machine turning one circle walks complete full journey consumes time 8 minutes
Purchasing sheet back side’s delay deduction clause clearly marked price writing every week 0.5%’s fine. Total price 200 thousand US dollars’ a big sum order, was by ten plus back forth reworking’s defective products delayed 4 weeks’ delivery time. Buyer’s financial accountant at account face on crossed dropping 4000 US dollars’ goods money.
Few sand casting factories towards melting furnace inside poured entering proportion as high as 40%’s cheap broken iron pieces. Laboratory test sheet on’s sulfur phosphorus impurities content all the way soars to 0.04%’s red line edge.
Hitting water pressure’s normal temperature test fundamentally tests not out hiding at ten plus centimeters deep place’s gap. X ray film yet can takes all’s internal pores shines clear and clear. Changed into buying A105 carbon steel or F316L stainless steel smashed out coming’s forging blank, early stage’s documents on extra came out 1200 US dollars’ material money.
Forging forming process
A piece diameter 250 millimeters, long 600 millimeters’ A105 grade cylindrical steel bar is pushed into natural gas heating furnace. Four corners’ burners crazily spray out blue flame, furnace chamber thermometer on’s numbers stop at 1220℃. Steel bar at inside stuffy baked whole 5 and half hours.
Overhead crane hook takes burned entirely red’s 1.2 tons heavy steel blank drags out coming. Bright red’s iron block emits baking person’s heat wave, 5 meters outside’s worker hot so full face dripping sweat. This piece completely red’s cylinder was smoothly placed at 12000 tons grade’s hydraulic forging machine work table on.
Top 80 tons heavy’s pressing hammer heavily smashes down. Muffled’s crashing sound shakes workshop cement ground tingling, 600 millimeters long’s steel bar at 3 seconds inside was hard rawly pressed into 350 millimeters thick’s flat iron cake. Several thousand tons’ physical squeezing force takes steel material internal even 0.1 millimeters’ tiny pore completely presses flat closes.
Metal like a piece totally hot’s dough, at hardness extremely high’s D2 mold steel cavity inside wanders fills full. Laboratory’s tensile testing machine shows, material’s tensile strength from original’s 415 megapascals jumped up to 485 megapascals.
- Upper pressing hammer’s falling speed calibrated at every second 250 millimeters
- Hydraulic pump station’s pressure gauge pointer instantly pushes to 320 Bar
- Steel blank surface layer temperature at 40 seconds inside from 1200℃ drops to 950℃
- Iron oxide skin like black color’s glass slag same explodes splashing out two meters far
Worker waits to second day again takes it sends back heat treatment furnace, using 890℃ bakes on 3 hours, takes out coming at air inside naturally blows cool. Internal metal crystal lattice completely shrinks, hardness tester measures out’s value steadily stuck at 187 HB.
Cutting tool head sticks going up, only needs to scrape dropping outer layer 3 to 5 millimeters’ allowance just can expose smooth’s metal face. If changed as sand casting piece, lathe tool has to towards inside eats entering 12 millimeters deep just can hide away surface’s sand hole potholes.
Ground on’s waste shavings roll into one stripe stripe two meters plus long’s continuous spiral shape iron wire. Dense’s material lets turning process becomes smooth, again also hears not tool head knocking at sand inclusion hard block on emitting out’s clatter clatter breaking sound.
One cart 50 pieces machined good’s 8 inches 1500 pounds grade high pressure valve body blank pushed into X ray dark room. Flaw detector takes magnet takes containing photosensitive film’s dark box sticks at 65 millimeters thick’s pipe wall on. Machine pushes out containing Iridium-192 radioactive source’s probe, timer counts down 18 minutes.
From 20℃ constant temperature washing film machine inside pulled out coming’s film bringing pungent’s developing chemical water smell. Flaw detector takes it inserts onto 30000 candela/square meter brightness’s film viewing light box. Densitometer sticks going up measured out’s D value is even’s 2.5, gray color’s film on clean clean.
Whole batch 500 pieces equipment’s inspection film on finds not out one crack or even 1 millimeter size’s black spot. Inspection sheet on’s rework time length writing a big big’s zero, contract on agreed’s 45 days delivery period ahead of time 3 days completed.
| Quality inspection data comparison item | Raw material cost benchmark | Flaw detection single time time consuming | 100% RT passing rate | Rework delay days | Final delivery unit price |
|---|---|---|---|---|---|
| Sand casting pouring process | 4500 US dollars | 45 minutes | 65% – 80% | 11 days – 45 days | 5300 US dollars |
| Ten thousand tons forging process | 5700 US dollars | 18 minutes | 99.8% above | 0 days | 5700 US dollars |
A piece caliber 4 inches, inside running 15 megapascals high pressure hydrogen gas’s chemical factory pipeline, bears not up even a 0.5 millimeters pore diameter’s sand hole. Front extra spent out’s 1200 US dollars buying iron money, bought back avoiding rework’s cleanliness, for construction team saved down 15 days’ waiting goods time.
Two workers holding hydraulic torque wrench, taking 1-1/8 inches thick’s alloy bolt twisted tight to 850 Newton·meters. Water pressure pump rumblingly makes sound, takes pipeline inside’s test pressure hits to 22.5 megapascals’ limit value.
Water pressure gauge on’s black pointer stops at scale line on one moving not moving. Continuous 24 hours’ maintaining pressure test period, has no one drop water bead from pipe wall or flange gap inside seeps out coming.





