Cwj mem, uas yog cov cuab yeej yooj yim tshaj plaws rau kev sau ntawv thiab pleev xim, tuaj yeem pom yuav luag txhua qhov chaw hauv peb lub neej. Kuv ntseeg hais tias feem coob ntawm cov neeg kev nkag siab kev sau ntawv pib los ntawm kev siv cwj mem! Thiab koj paub ntau npaum li cas txog qhov me me no uas feem ntau saib tsis tau hauv lub neej? Cia peb tham txog "xiav".
Kev loj hlob & keeb kwm
Nyob rau hauv 1564, ib tug dub ntxhia graphite tau pom nyob rau hauv Barodale, England. Lub sijhawm ntawd, tib neeg tsis paub txog cov graphite, yog li lawv hu ua graphite "dub lead", uas yog lub hauv paus ntawm lub npe xaum.
Cov neeg yug tsiaj hauv zos pom tias lawv tuaj yeem siv graphite los kos cov yaj. Kev tshoov siab los ntawm qhov no, tib neeg txiav graphite blocks rau hauv me me strips rau kev sau ntawv thiab pleev xim. Txawm li cas los xij, graphite strips yooj yim kom tau qias neeg thiab tawg.
Nyob rau hauv 1761, German chemist Faber sib tov sulfur, antimony, rosin thiab lwm yam tshuaj mus rau hauv lub purified graphite hmoov thiab nias nws mus rau hauv cov duab ntawm ib tug cwj mem, uas yog qhov ntxov tshaj plaws qauv ntawm ib tug cwj mem. Tab sis qhov tseeb, tus cwj mem tsuas yog txhuas.
Xyoo 1812, Asmeskas William Monroe tau muab lub raj ntoo rau ntawm tus cwj mem coj los ua tus qauv ntxov tshaj plaws ntawm cov cwj mem niaj hnub no. Tom qab ntawd, nws tau nruab ib lub lwv ntawm lub taub hau ntawm tus cwj mem, uas tseem siv niaj hnub no.
cwj mem hardness
Cov cwj mem coj peb siv niaj hnub no yog ua los ntawm graphite thiab av nplaum hauv ib qho kev faib ua feem. Vim tias cov graphite yog mos thiab nplua, nws tsuas yog siv los ua cov xaum xaum, uas yooj yim tawg thiab hnav. Yog li ntawd, ib co av nplaum hmoov yog ntxiv rau hauv graphite hmoov los ua kom lub hardness ntawm tus cwj mem core. Cov av nplaum sib xyaw ntau dua, cov cwj mem nyuaj dua; cov av nplaum tsawg dua yog sib xyaw, qhov softer tus cwj mem yog.
Feem ntau, "H" sawv cev rau ib tug cwj mem tawv, "B" sawv cev rau ib tug cwj mem mos, "HB" sawv cev rau ib tug cwj mem nrog hardness, thiab "F" sawv cev rau ib tug cwj mem nrog hardness ntawm HB thiab H.
Cov cwj mem hardness qib: 9B, 8B, 7B, 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H, 10H los ntawm mos mus rau tawv.
Qhov loj dua tus lej nyob rau hauv pem hauv ntej ntawm H, qhov nyuaj nws cov hlau lead yog, thiab qhov sib zog nws cov xim yog. Qhov loj dua tus naj npawb nyob rau hauv pem hauv ntej ntawm B, lub softer cov hlau lead core, cov xim tsaus dua.
Chav kawm H mem hluav muaj qhov tseem ceeb ntawm qhov nyuaj, uas yog tsim rau cov khoom uas muaj qhov cuam tshuam nyuaj los yog meej, xws li cov kws ntoo sau ntawv, kos duab kos duab, thiab lwm yam;
HB mem hluav core muaj nruab nrab hardness, uas yog haum rau kev sau ntawv los yog piav qhia nyob rau hauv ib txwm muaj xwm txheej;
Chav kawm B cwj mem, nrog cov hmoov txhuas me me, yog tsim rau kev pleev xim, thiab tseem tuaj yeem siv los sau rau hauv daim npav uas tuaj yeem lees paub los ntawm cov tshuab.
