Chromium: Chromium yog cov khoom siv feem ntau thiab pheej yig tshaj hauv cov cuab yeej hlau hlau. Hauv Tebchaws Meskas, cov ntsiab lus ntawm Cr hauv H-hom kub ua haujlwm tuag steel yog li ntawm 2 feem pua rau 12 feem pua. Hauv 37 qib steel ntawm cov cuab yeej hlau hlau (GB / T1299) hauv Suav teb, tshwj tsis yog 8CrSi thiab 9Mn2V, txhua tus muaj Cr. Chromium muaj txiaj ntsig zoo rau kev hnav tsis kam, siab kub lub zog, kub hardness, toughness thiab hardenability ntawm hlau. Nyob rau tib lub sijhawm, nws qhov kev sib cais rau hauv cov matrix yuav ua rau muaj kev txhim kho corrosion ntawm hlau. Cov ntsiab lus ntawm Cr thiab Si hauv H13 steel yuav ua rau oxide zaj duab xis compact los txhim kho oxidation tsis kam ntawm hlau. Tsis tas li ntawd, cov txiaj ntsig ntawm Cr ntawm cov khoom siv tempering ntawm 0.3C-1Mn steel raug tshuaj xyuas. Ntxiv<6% Cr is beneficial to improve the tempering resistance of steel, but it does not constitute secondary hardening; When the steel containing Cr>6 feem pua yog quenched thiab tempered ntawm 550 degree, qhov thib ob hardening nyhuv yuav tshwm sim. Cov neeg feem ntau xaiv qhov sib ntxiv ntawm 5 feem pua chromium rau kub-ua haujlwm steel tuag steel.
One part of chromium in tool steel is dissolved into the steel for solid solution strengthening, and the other part is combined with carbon, which exists in the form of (FeCr) 3C, (FeCr) 7C3 and M23C6 according to the content of chromium, thus affecting the performance of steel. In addition, the interaction effect of alloying elements should also be considered. For example, when the steel contains chromium, molybdenum and vanadium, when Cr>3 feem pua[14], Cr tuaj yeem tiv thaiv kev tsim ntawm V4C3 thiab ncua sijhawm los nag lossis daus ntawm Mo2C. V4C3 thiab Mo2C yog cov txheej txheem ntxiv dag zog uas txhim kho qhov kub thiab txias zog thiab kev ua haujlwm zoo ntawm cov hlau.[14]. Qhov kev sib cuam tshuam no txhim kho cov khoom thermal deformation ntawm cov hlau.
Chromium dissolves rau hauv cov hlau austenite kom nce hardenability ntawm hlau. Cr, Mn, Mo, Si thiab Ni yog tib yam alloying ntsiab uas ua rau kom cov hardenability ntawm hlau. Cov neeg siv los siv cov khoom hardenability kom characterize nws. Feem ntau, cov ntaub ntawv muaj nyob hauv tsev tsuas yog siv cov ntaub ntawv ntawm Grossmann thiab lwm tus. Tom qab ntawd, Moser thiab Legat [16,22] ua hauj lwm ntxiv tau npaj siab tias qhov yooj yim hardenability txoj kab uas hla Dic txiav txim los ntawm cov ntsiab lus ntawm C thiab austenite grain loj thiab cov hardenability yam txiav txim los ntawm cov ntsiab lus ntawm alloying ntsiab (pom 3) yuav siv tau rau xam qhov zoo tshaj plaws txoj kab uas hla Di ntawm alloy steel, uas kuj yuav approximated los ntawm cov nram qab no mis:
Di=Dic × 2.21Mn × 1.40Si × 2.13Cr × 3.275Mo × 1.47Ni (1)
(1) Hauv cov qauv, txhua lub ntsiab lus alloy tau qhia hauv qhov feem pua. Los ntawm cov qauv no, tib neeg muaj kev nkag siab meej ib nrab ntawm kev cuam tshuam ntawm Cr, Mn, Mo, Si thiab Ni ntawm hardenability ntawm hlau.
Cov nyhuv ntawm Cr ntawm eutectoid taw tes ntawm hlau yog roughly zoo ib yam li Mn. Thaum cov ntsiab lus ntawm Cr yog kwv yees li 5 feem pua, cov ntsiab lus ntawm C ntawm eutectoid point txo mus txog li 0.5 feem pua . Tsis tas li ntawd, qhov sib ntxiv ntawm Si, W, Mo, V thiab Ti tuaj yeem txo cov ntsiab lus ntawm C ntawm eutectoid point. Vim li no, peb tuaj yeem paub tias kub-ua haujlwm tuag steel thiab high-speed steel yog hypereutectoid steel. Kev txo qis ntawm eutectoid C cov ntsiab lus yuav ua rau kom cov ntsiab lus ntawm alloy carbides nyob rau hauv lub austenite thiab zaum kawg qauv.
