1. Chaw Tsim Khoom ntawm Slag Shovels: Muaj thiab Peev Xwm ntawm Womic Steel
Womic Steel yog ib lub chaw tsim khoom thiab xa tawm ntawmcov thoob slag(tseem hu ua slag dredging shovels, slag buckets, lossis foundry shovels) nyob hauv Suav teb. Nrog ntau tshaj 20 xyoo ntawm kev paub hauv kev tsim cov hlau carbon thiab cov khoom siv tubular steel alloyed, peb lub Hoobkas foundry siv cov khoom siv modular siab thiab cov thev naus laus zis computer-aided simulation (CAE) los xyuas kom meej tias txhua yam khoom cam khwb cia ua ib daim.
Kev Tsim Khoom Txhua Hli:Tshaj 2,000 tons ntawm cov hlau castings, suav nrog slag ladles nrog cov khoom ib leeg hnyav txog li 100 tons.
Kev kho kom haum siab heev:Peb tsim thiab tsim txhua lub peev xwm (5 - 100 t), tuab, khoom siv, thiab tiav raws li cov duab kos ntawm tus neeg siv khoom thiab cov xwm txheej ua haujlwm ntawm lawv lub cub tawg.
2. Cov Khoom Siv Sib xyaw & Kev Ua Haujlwm ntawm Sludge Diav
2.1 Cov Khoom Siv Hlau Qib (ZG)
Raws li cov qauv thoob ntiaj teb siv hauv kev lag luam hlau (ASTM, DIN, ISO, JIS), Womic Steel slag spoons feem ntau yog molded nrog cov qib uas twb tau tsim lawm, xws li cov hauv qab no, txhua tus muaj tus cwj pwm tshwj xeeb kom tiv taus qhov kub siab (+1,600 ° C):
| Qib | Lub Zog Tawm (MPa) | Lub zog Tensile (MPa) | Kev ntev (%) | Daim Ntawv Thov Pom Zoo |
| ZG270-500 | ≥270 | ≥500 | ≥18 | Lub thoob siv dav dav (pheej yig) |
| ZG310-570 | ≥310 | ≥570 | ≥15 | Cov voj voog ua haujlwm hnyav |
| GS-20Mn5 | ≥300 | 480-630 | ≥22 | Cov kev xav tau zoo tshaj plaws, huab cua txias |
| ASTM A27 65-35 | ≥241 | ≥448 | ≥24 | Daim ntawv pov thawj Asmeskas, cov haujlwm |
2.2 Cov Khoom Siv Tshuaj (Kev Tshuaj Xyuas, Feem Pua ntawm Cov Khoom, %)
| Khoom | ZG270-500 (Tus Qauv) | GS-20Mn5 (Tus Qauv) | ASTM A27 60-30 |
| Cov pa roj carbon (C) | 0.30 – 0.37% | 0.18 – 0.23% | 0.28 – 0.32% |
| Silicon (Si) | 0.30 – 0.50% | 0.30 – 0.50% | 0.30 – 0.60% |
| Manganese (Mn) | 1.10 – 1.40% | 1.00 – 1.50% | 0.90 – 1.20% |
| Phosphorus (P) | ≤ 0.030% | ≤ 0.020% | ≤ 0.040% |
| Sulfur (S) | ≤ 0.030% | ≤ 0.020% | ≤ 0.040% |
| Chromium (Cr) | – | ≤ 0.30% | – |
| Nickel (Ni) | – | ≤ 0.40% | – |
| Molybdenum (Mo) | – | ≤ 0.10% | – |
Cov diav slate rau cov cub hluav taws xob (EAF) txhawb nqa qhov nruab nrab ntawm 15-20 lub voj voog hauv ib hnub. Cov hlau tsis muaj carbon (<0.23%) thiab ntxiv molybdenum thiab nickel txhim kho nws cov tawv thiab tiv taus kev tawg thermal fatigue.
2.3 Cov khoom siv kho tshuab
Kev txwv tsis pub hloov pauv:270 - 310 MPa (ZG), 300 MPa (GS 20Mn5). Qhov siab dua ntawm elastic txwv (GS 20Mn5) ncua cov yas deformations nyob rau hauv cov xwm txheej overload.
Tensile:ZG270 500 slag diav muaj elongation ntawm 18%, thaum ASTM A27 thiab GS 20Mn5 qib ncav cuag 22 24%; Qhov no qhia tau hais tias muaj peev xwm nqus tau lub zog ntau dua ua ntej tawg.
Kev tiv thaiv kev qaug zog ntawm cua sov (CAE simulation):Cov khoom siv GS 20Mn5, kho cua sov nrog kev tswj cua txias, tiv taus ~ 3,200 lub voj voog (ΔT 1,300 ° C) ua ntej tawg, ntau dua 115% dua li cov hlau carbon txheem.
2.4 Qhov kub siab tshaj plaws thiab kev tiv taus thermal shock
Kub siab tshaj plaws tas mus li:~600°C rau ZG270 500 thiab ASTM A27; ~650 °C rau GS 20Mn5.
Kev tiv thaiv thermal poob siab:Cov hlau zoo (GS 20Mn5) tiv taus ntau dua 3,000 lub voj voog tiav (ua kom sov ntawm 300 ° C txog 1,600 ° C thiab cua txias tam sim ntawd), ua rau lub neej ntev dua li cov qib txheem.
3. Daim Ntawv Qhia Loj: Peev Xwm, Qhov Hnyav, thiab Qhov Ntev (Piv txwv rau 30t Slag Shovel)
| Peev xwm (t) | Kwv yees li qhov hnyav (t) | Qhov Nruab Nrab (m³) | Qhov Ncauj Txoj Kab uas hla (hli) | Qhov Siab Tag Nrho (hli) |
| 20 t (Tus Qauv) | 25 – 30 t | 12 – 16 m³ | 1,800 | 1,500 |
| 30 t | 33 – 40 t | 18 – 22 m³ | 2,200 | 1,800 |
| 40 t | 42 – 52 t | 24 – 28 m³ | 2,500 | 2,100 |
| 50 t | 52 – 62 t | 29 – 35 m³ | 2,800 | 2,400 |
| 70 t | 60 – 72 t | 40 – 50 m³ | 3,200 | 2,700 |
| 85 – 100 t | 75 – 105 t | 45 – 65 m³ | 3,600 | 3,000 |
Cov qauv tsim thiab qhov ntev kawg yog ua raws li qhov ntev thiab qhov xav tau teev tseg hauv daim phiaj xwm ntawm tus neeg siv khoom (qhov pom siab, qhov dav tshaj plaws ntawm crane, qhov siab hauv qab lub tshuab nchuav dej, thiab lwm yam).
4. Kev Tsim Khoom: Ib Daim Integral Casting
Cov txheej txheem tsim khoom ntawmdiav slagyog raws li nram no:
Kev Siv Computer-Aided Engineering (CAE) nrog Huazhu® Solidification Simulation SoftwarePeb cov kws tshaj lij txhais cov qauv 3D thiab ua qauv qhia txog qhov khov ntawm cov hlau uas yaj. Lub hom phiaj yog los nrhiav txhua qhov tsis zoo ntawm kev ua casting (qhov ntsws, porosity, inclusions) ua ntej tsim cov qauv ntoo lossis luam ntawv 3D ntawm cov pwm.
Kev Tsim Qauv thiab Cov Pwm Xuab Zeb Luam Tawm 3D (Resin Fusion)Cov qauv ntoo lossis hlau raug tsim raws li tus neeg siv khoom tsim. Rau cov khoom siv siab, peb tuaj yeem siv cov pwm xuab zeb luam tawm 3D.
Kev yaj thiab kev ua kom zooCov hlau seem uas xaiv tau raug them. Lub Tshuab Hluav Taws Xob Arc (EAF) yaj cov nqi; cov hlau uas yaj ces dhau mus rau lub tshuab Ladle Furnace (LF) rau kev ua kom huv - txo S, P, O₂, H₂ - thiab kho cov khoom sib xyaw. Tom qab ua kom huv, kev nqus dej degassing (VD) raug ua kom tshem tawm cov pa roj uas yaj (H₂ < 2 ppm).
Kev Casting Ib Zaug XwbTag nrho lub cev, ua ke nrog ob lub trunnions, raug nchuav rau hauv ib qho kev ua haujlwm casting tas mus li. Tsis muaj kev vuam ntawm txhua yam siv.
Kev Kho Mob Kub: Ua kom zoo li qub thiab/lossis quenching hauv lub cub tawg hom tswb, nrog rau kev sau cia kub tas mus li (kab nkhaus kub-lub sijhawm) uas muab kev taug qab tiav.
Kev Siv Xuab Zeb Tua, Kev Ntxuav, Kev Ua Tiav thiab Kev Siv Tshuab (yog tias xav tau): Cov burrs los ntawm lub tshuab pub mis raug tshem tawm thiab cov nplaim raug sib tsoo kom ua tiav qhov chaw zoo.
100% Kev Ntsuas Tsis Ua Rau Puas Tsuaj (NDT)Kev tshuaj xyuas pom, kev sim ultrasonic tag nrho (UT) ntawm cov hlau raug ua, thiab kev sim cov khoom sib nqus (MT) thiab kev sim kua nkag mus (PT) raug siv rau thaj chaw tseem ceeb (trunnions, junction radii).
Kev Cim thiab Kev Ntim Khoom: Kos tus lej casting, peev xwm, qhov hnyav, hnub tsim khoom. Cov xim sab nraud (grey nyiaj) muab kev tiv thaiv thaum thauj mus los hauv hiav txwv.
5. Kev Tswj Xyuas Zoo thiab Daim Ntawv Pov Thawj
5.1 Kev tshuaj xyuas thiab kev sim zoo
| Theem | Hom Kev Tshuaj Xyuas | Tus Qauv / Txoj Kev | Cov Qauv Txais Yuav |
| Daim Ntawv Txais Nyiaj Pov Tseg | Cov Tshuaj Lom Zem | OBLF GS‑1000 Spectrometer | Kev Txheeb Xyuas Qib Hlau (ZG / ASTM / DIN) |
| Cov Txheej Txheem Yaj | Cov Qauv Ladle | Spectrometer + Thermocouple | Ua raws li Cov Lus Qhia Txog Cov Neeg Siv Khoom Tag Nrho |
| Kev Ua Qauv Simulation | Kev Tshuaj Xyuas Qhov Ntev | Cov Khoom Siv CMM / Laser Tracker | ±5 hli (rau cov trunnions) / ±10 hli (qhov ntev geometric) |
| Kev Kho Mob Kub Hlau Cast | Kev Sau Npe Kub | Lub Sijhawm Kaw Cov Kub thiab Txias Tsis Tu Ncua | Tau Txais Kev Tshawb Pom thiab Daim Ntawv Pov Thawj |
| Kev Ntsuas Ultrasonic NDT (UT) | JB/T5000.14 Tus Qauv Qib 1 thiab Qib 2 (Tsab Thib 2) | Cov Khoom Siv Ntsuas Ultrasonic Tsis Siv Neeg | Qib 1 rau cov trunnions (qhov tob 500 hli). Qib 3 rau lub cev dav dav |
| Kev Ntsuas Cov Khoom Sib Nqus (MT) | ASTM E709 / GB/T 9444 Tus Qauv | Cov Khoom Siv Sib Nqus Sib Nqus | Tsis pub cov cim qhia linear > 2 hli |
| Kev Ntsuas Cov Kua Nkag Mus (PT) | ASTM E165 / GB/T 9443 Tus Qauv | Tshuaj tsuag | Tsis muaj cov cim qhia txog kev tawg |
| Kev Tshuaj Xyuas Qhov Ntev | Nrog Laser Tracker | Cov Khoom Siv Ntsuas Nqa Tau | ±10 hli ntawm qhov ntev sab nraud |
| Qhov nyuaj | Kev Ntsuas Qhov Nyuaj Leeb | 20 Cov Ntsiab Lus - 150 Kev Ntsuas | Kev sib xws ± 10 HB |
Daim Ntawv Pov Thawj Kawg: EN 10204 Hom 3.1(tus qauv),EN 10204 Hom 3.2(yog thov, nrog rau lub koom haum tshuaj xyuas nyob ntawd).
5.2 Daim Ntawv Pov Thawj Womic Steel
ISO 9001: 2015- Kev tswj xyuas zoo uas tau pom zoo.
PED 2014/68/EU (Cim CE)- Ua raws li European Pressure Equipment Directive.
ISO 14001: 2015– Kev cog lus rau kev tswj hwm ib puag ncig (peb xav tiv thaiv ib puag ncig).
ISO 45001:2018- Kev saib xyuas tshwj xeeb rau kev noj qab haus huv thiab kev nyab xeeb hauv chaw ua haujlwm.
Daim ntawv pov thawj tshuaj xyuas sab nraud (SGS, BV, TÜV, ABS, DNV, LR) thaum thov.
6. Cov Ntawv Thov Sludge Spoon
Ua tsaug rau nws cov qauv ruaj khov thiab kev hloov pauv tau yooj yim, Womic Steel slag ladles tau siv dav hauv ntau qhov chaw lag luam. Cov xwm txheej tseem ceeb ntawm daim ntawv thov yog raws li nram no:
Cov Hoobkas Hlau thiab Hlau Ua Ke:Siv tau rau lub cub tawg thiab cov txheej txheem ua hlau BOF/LD. Cov ladles no siv los hloov cov slag los ntawm cov converters mus rau cov slag yards thiab cov chaw deslagging.
Cov Chaw Tsim Hlau Hluav Taws Xob Arc (EAF):Cov tais EAF slag tshwj xeeb hloov kho rau kev sau thiab tso tawm sai, tsim nyog rau cov chaw tsim khoom nrog qhov kub ua haujlwm siab dua 1600 ° C.
Cov Chaw Ua Hlau thiab Hlau:Siv rau kev sau thiab tso tawm slag los ntawm cupola furnaces, medium-frequency induction furnaces thiab blast furnaces.
Cov Chaw Ua Hlau Uas Tsis Yog Hlau (Tooj Liab, Zinc, Lead):Cov slag ladles uas tsis yog ferrous muaj cov ntaub thaiv kev nplaum kom tiv thaiv cov tshuaj lo rau ntawm cov ntaub ntawv.
Cov Chaw Tsim Tshuaj thiab Cov Chaw Rov Siv Slag.
7. Cov txiaj ntsig ntawm Womic Steel dua li lwm cov chaw tsim khoom
Tshaj 20 xyoo kev tsim cov khoom siv hlau foundryrau cov hlau thiab cov lag luam mining.
Kev siv tshuab simulation CAE siab heev:Peb lav qhov zoo ua ntej pwm tsim.
Qhov zoo ntawm cov hlau tau lees paub:Los ntawm EAF + Ladle Furnace (LF) + Vacuum Degassing (VD) cov txheej txheem yaj. Pib los ntawm cov hlau seem zoo uas tau xaiv.
Kev kuaj tsis ua puas tsuaj tag nrho (NDT):UT (100%), MT (kev tshuaj xyuas cov khoom sib nqus), PT (kev tshuaj xyuas cov xim nkag mus) nrog cov duab qhia.
Kev hloov kho kom haum thiab lub sijhawm xa khoom sai:35–50 hnub txij li kev pom zoo kos duab.
Muaj peev xwm tsim khoom loj:Ib daim txog li 300 tons.
Cov ntim khoom xa tawm loj:Xa khoom mus rau qhov chaw nres nkoj ntawm ntau hom kev thauj mus los (thawv, khib tiaj tus, khoom thauj project) raws li CIF, FOB, thiab lwm yam.
Cov ntaub ntawv tiav:Peb muab cov phau ntawv qhia txij nkawm, cov duab kos raws li tau tsim thiab daim qauv digital (daim ntawv pov thawj raws li EN 10204 3.1/3.2).
8. Kev Ntim Khoom thiab Kev Thauj Mus Los Hauv Kev Thauj Mus Los Thoob Ntiaj Teb
8.1 Lub thawv ntim sludge
Kev Tiv Thaiv Nto:Cov roj tiv thaiv xeb siv rau ntawm cov chaw ua haujlwm (sab hauv, trunnions); cov khoom me me qhwv nrog cov yas nyias nyias.
Cov Hlau Flanges & Lub Rooj Sib Tw:Tiv thaiv cov npoo thiab cov trunnions tiv thaiv kev puas tsuaj.
Cov Khoom Txhawb Hlau / Cov Thaiv Ntoo:Lub ladle muab tso rau ntawm cov hlau thav duab uas txuas rau ntawm cov hauv paus ntoo kom tiv thaiv kev txav mus los thaum lub sijhawm thauj khoom thiab kev thauj mus los.
Txheej Sab Nraud:Tag nrho cov khoom yog npog tag nrho nrog cov yas tarpaulin tsis muaj dej, ua ke nrog cov hnab silica gel desiccant sab hauv.
Cim:Cov cim meej thiab ruaj khov suav nrog lub peev xwm, qhov hnyav tag nrho, qhov chaw ntawm lub ntiajteb txawj nqus, cov ntsiab lus nqa thiab tus lej xaj ntawm cov neeg siv khoom.
8.2 Cov Kev Xaiv Xa Khoom
20GP / 40GP / 40HQ Cov Thawv Dej Hiav Txwv:Haum rau cov khoom ib zaug txog li 25-28 tons. Cov khoom uas hnyav dua 30 tons (qauv txog li 35 tons) raug ntim rau hauv cov thawv ntoo thiab xa mus rau lwm lub thawv.
Thawv Tiaj Tiaj & Cov Thawv Qhib Sab Saum Toj:Zoo tagnrho rau cov khoom thauj txog li 45 tons (30-50 ton ladles), ruaj khov nrog cov saw hlau thiab cov xauv.
Ua kom tawg ntau thiab RORO xa khoom:Siv rau cov khoom thauj uas hnyav tshaj 20 tons. Cov khoom hnyav loj heev raug xa los ntawm cov nkoj thauj khoom dav dav thiab ruaj ntseg nrog cov nqaj nqa.
8.3 Cov ntaub ntawv xa khoom suav nrog
Daim ntawv them nqi lag luam
Daim Ntawv Teev Khoom
Daim Ntawv Pov Thawj Keeb Kwm (Daim Ntawv E lossis CO, nyob ntawm lub tebchaws uas koj xav mus)
Kev Paub Txog Kev Thauj Khoom Maritime
Daim ntawv pov thawj xeem (EN 10204 3.1 / 3.2)
XAUS daim ntawv qhia (UT, MT, PT)
Cov duab ntawm kev cim, qhov ntev thiab kev ntim khoom kawg
Daim ntawv pov hwm kev thauj khoom hiav txwv (yog thov)
9. Cov Lus Nug Feem Ntau (FAQ)
Q1: Qhov txawv ntawm lub ladle slag thiab lub ladle pouring yog dab tsi?
A: Lub ladle slag yog tsim los rau kev xa thiab nchuav cov slag molten (silicate, lime, MgO, thiab lwm yam). Lub ladle pouring yog siv los thauj cov hlau ua kua ncaj qha thiab feem ntau yog lined nrog cov ntaub ntawv refractory. Peb tshwj xeeb hauv slag ladles thiab slag pots.
Q2: Womic Steel slag ladles tuaj yeem ua tiav pes tsawg lub voj voog kev pabcuam?
A: Cov hlau carbon slag ladles txheem ncav cuag tsawg kawg yog 5,000 lub voj voog. Cov ladles ua los ntawm GS-20Mn5 khoom siv nrog quenching thiab tempering cua sov kho tuaj yeem tshaj 8,000 lub voj voog thaum siv hauv cov chaw tsim khoom nrog cov sijhawm saib xyuas txhua hnub nruj.
Q3: Lub sijhawm ua tus qauv rau cov ladles slag hnyav yog dab tsi?
A: 35-45 hnub tom qab kev lees paub zaum kawg ntawm cov neeg siv khoom kos duab. Ntxiv 10 txog 15 hnub yog qhov yuav tsum tau rau cov khoom siv tshwj xeeb lossis daim ntawv pov thawj. Kev txiav txim sai yog txais tau thaum thov.
Q4: Peb puas tuaj yeem ua qhov kev tshuaj xyuas ntawm qhov chaw thaum lub sijhawm tsim khoom?
A: Yog, peb txais tos cov koom haum thoob ntiaj teb sab nraud xws li SGS, BV, TÜV, ABS, LR, DNV thiab lwm yam kev tshuaj xyuas ntawm qhov chaw raws li kev pom zoo ua lag luam ua ntej.
Q5: Koj puas muab kev lees paub rau cov qauv tsis muaj vuam?
A: Yog. Tag nrho peb cov slag ladles yog tsim los ntawmib daim integral castingtsis muaj qhov sib txuas vuam. Nws zam cov ntsiab lus tawg, uas yog 70% ntawm kev ua tsis tiav ua ntej ntawm cov ladles vuam ib txwm muaj.
Q6: Koj txais cov nqe lus them nqi twg?
A: Peb txais T/T xa nyiaj thiab pom/siv L/C. Cov nqe lus yooj ywm thiab cov phiaj xwm tso nyiaj muaj rau cov xaj ntau zaus.
Q7: Cov ntaub ntawv twg yuav muab ua ke nrog cov khoom xa tuaj?
A: Koj yuav tau txais Daim Ntawv Pov Thawj Xeem Khoom Siv (MTC) ua raws liEN 10204 3.1, thiab3.2muaj nyob rau ntawm tus nqi ntxiv ua ntej.
Cov ntaub ntawv tag nrho suav nrog daim ntawv qhia txog kev sib xyaw ua ke ntawm cov tshuaj lom neeg, daim ntawv qhia txog cov khoom siv kho tshuab, daim ntawv qhia txog kev kho cua sov, cov duab kos uas tau tsim, cov ntawv qhia NDT tag nrho suav nrog cov ntaub ntawv kuaj tuab ultrasonic, nrog rau cov lus qhia ua haujlwm thiab kev saib xyuas kom muaj kev nyab xeeb.
10. Keeb Kwm Kev Xa Khoom Tawm thiab Cov Kev Kawm Txog Cov Ntaub Ntawv
Womic Steel tau muab ntau tshaj 500 pawg ntawm cov slag ladles rau cov chaw ua hlau, cov chaw tsim khoom thiab cov chaw ua hlau thoob plaws ntau tshaj 23 lub tebchaws. Hauv qab no yog cov ntaub ntawv qhia txog qhov project (cov ntaub ntawv zais cia ntawm tus neeg siv khoom tau raug tshem tawm):
Qhov Project 1 – Lub Hoobkas Hlau Sib Koom Ua Ke hauv Sab Qab Teb Es Xias (Indonesia):
Peb muab cov ladles slag uas muaj peev xwm loj li 85 tuj uas yog ib daim uas sib xyaw ua ke. Tsim los ua raws li cov qauv khoom siv OEM qub los hloov cov ladles uas vuam ib txwm muaj. Tom qab 4,200 lub voj voog kev pabcuam, cov ladles tau ua haujlwm tau ntau dua28 lub hlisnrog xoom kab nrib pleb lossis qhov tsis zoo.
Qhov Project 2 - Lub Hoobkas Hlau Hluav Taws Xob hauv Cheeb Tsam Balkan (Eastern Europe):
Tus neeg siv khoom xav tau cov chromium-nickel-molybdenum alloy slag ladles uas haum rau kev ua haujlwm ntawm -35 ° C qhov kub qis heev. Peb tau siv GS-20Mn5 hlau uas ua tau raws li cov qauv xeem Charpy impact, muab EN 10204 3.2 daim ntawv pov thawj thiab cov ntawv qhia kev tshuaj xyuas NDT tag nrho. Tus neeg siv khoom no tau tso peb qhov kev txiav txim ntau rov ua dua txog tam sim no.
Qhov Project 3 – US Steel Mill uas muaj peev xwm thauj khoom tsawg ntawm Crane:
Tus neeg siv khoom xav tau cov slag ladles uas sib dua kom phim cov kev txwv ntawm cov crane uas twb muaj lawm. Los ntawm kev siv cov thev naus laus zis CAE casting simulation, peb tau txiav qhov hnyav ntawm lub ladle tag nrho los ntawm18%, thaum tswj thiab txhim kho kev ua tau zoo ntawm kev nyab xeeb ntawm cov qauv.
Tiv tauj tus Chaw Tsim Khoom
Yog tias koj xav tau nyiaj txiag yam tsis tas yuav cog lus lossis xav tau cov lus qhia txog kev siv tshuab rau koj qhov project tshiab, tsis txhob yig tiv tauj peb.
Womic Steel - Koj Tus Neeg Muab Khoom Siv Sludge Diav Uas Ntseeg Tau Hauv Suav Teb
Lub Vas Sab: www.womicsteel.com
Email: sales@womicsteel.com
Xov tooj / WhatsApp / WeChat:
Victor: +86 15575100681
Nkaus: +86 18390957568
Womic Steel tsim thiab tsim cov slag ladles uas tau kho kom haum rau cov neeg siv khoom xav tau. Peb cov pab pawg engineering thiab muag khoom muab kev sab laj tshaj lij txhua lub sijhawm.








