-Cong nghe u:

.U thap(u non):

+La phuog phap u tien hanh o nhiet do tu 200-600

+Giam hay khu bo ung suat ben trong o vat duc hay san pham wa gia cong co khi

+nhiet do u tu 200-300 khu bo 1 phan ung suat ben trong

+nhiet do tu 450-600 khu bo hoan toan ung suat ben trong

Cong dung:

+Dung cho cac vat duc lon nhu than may cat got,lo xokhi uon xo lo khi uon nguoi..

+phuong phap nay k lam thay doi do cung of thep,con gang thi 1 it do wa trinh graphit hoa

.U ket tinh lai:

+tien hah o nhiet do ket tinh lai(thepcarbon la 600-700)

Cong dung:

+giam do cung va lam thay doi kich thuoc hat

+dung cho cac thep qua bien dang nguoi,bi bien cung de khoi phuc lai co tinh nhu trc khi bien dang

+ngay nay hau nhu k su dung vi de lam hat lon do ket tinh lai lan thu 2.De dat dc muc dich nay t thuong dung cac phuong phap u co chien bien pha

.U hoan toan:

+la u nong thep den trang thai hoan toan la austenit o nhiet do cao hon Ac3

T u= ?c3+(30-50)

Cong dung:

+lam nho hat thep:do cung cap cao hon ?c3 nen hat austenit van con nho do do khi lam nguoi se nhan dc to chuc pherit-peclit co hat nho

+lam jam do cug va tang do deo de dap nguoi va cat got

+dung cho cac thep trc cug tich voi luong cacbon tu 0,3-0,65%

+sau khi u hoan toan ta co to chuc pheric-peclit,trong do peclit o dang tam

.U k hoan toan:

+la phuong phap u nong thep den nhiet do cao hon Ac1 va nho hon Acm tuc la trang thai k hoan toan la austenit

T u= Ac1+(30-50)

+to chuc tao thanh sau khi u k hoan toan la peclit hat chu k fai la peclit tam

CD:+dung cho thep co ham luong carbon>0,7% ma chu iu la thep sau cug tich

.U cau hoa:

+dang dac biet of u k hoan toan

+nhiet do dao dong quanh Ác,nung nong 750-760 ju nhiet do 5' sau do lam nguoi xuong 650-660 ju nhiet 5'...

lap di lap lai nhiu lan tao ra wa trinh cau hoa xemetit nen nhan dc toan la peclit hat

So luong chu trinh phu thuoc vao kich thuoc chi tiet va muc do cau hoa

.U dang nhiet:

+doi voi thep hop kim co do cung kha cao,k cat got dc.Luc nay ta dung pp u dang nhiet

+sau khi ju nhiet lam nguoi thap xuong thap hon Ac1 khoang 50 va tien hah lam nguoi dang nhiet tai do 1 thoi jan nhat dinh

+pp nay nhan dc to chuc peclit dong nhat

CD:dung cho thep hop kim de rut ngan thoi jan u

.U khuech tan:

+la pp u nong den nhiet do rat cao tu 1100-1500 voi thoi jan ju nhiet rat dai tu 10-15h de tang kha nang khuech tan lam dong deu

thanh phan hoa hoc trong cac vung of hat

CD:dung cho vat duc thep hop kim cao sau thien tich.Sau khi u khuech tan hat rat to nen fai tien hah u hay can nog de lam nho hat thep

-Thuong Hoa Thep:

+la pp nhiet luyen,nung nong thep den trang thai hoan toan la austenit ju nhiet va lam nguoi ngoai kk tinh.

+thong thuong sau khi ju nhiet xog lay chi tiet ra va lam nguoi treen nen xuong

+to chuc nhan dc khi thuong hoa tuong tu nhu khi u nhung do cung cao hon 1 it va hat nho min hon do toc do nguoi lon hon.

T thuong hoa= Ac3 hay Acm +(30-50)

CD:

+do to chuc gan voi trang thai can bang nen thuong hoa co cog dung nhu tu u,tuy nhien co 1 so diem khac:

Dat dc do cung thich hop de ja cong cho thep carbon thap<0,25%C.Voi thep nay neu u se rat deo kho gay,kho cat got

Lam nho xementit chuan bi cho nhiet luyen ket thuc.Khi thuong hoa se tao ra to chuc peclit phan tan hay xoocbit,trong do

kich thuoc of xementit nho min nen khi nung nong nhan dc austenit nho min.Duoc ap dung khi toi

Pha luoi xementit hai of thep sau cung tich.Trong thep sau cung tich xementit hai thuong o dang rat cung va gion.

Vi vay khi gia cong cat got kho nhan dc be mat nhan bong cao.

Khi thuong hoa lam nguoi nhanh hon nen u xementit k kip tiet ra dang luoi nua.