TR201921223A2 - Composition of micro-alloyed steel with improved mechanical properties - Google Patents

Composition of micro-alloyed steel with improved mechanical properties

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Publication number
TR201921223A2
TR201921223A2 TR2019/21223A TR201921223A TR201921223A2 TR 201921223 A2 TR201921223 A2 TR 201921223A2 TR 2019/21223 A TR2019/21223 A TR 2019/21223A TR 201921223 A TR201921223 A TR 201921223A TR 201921223 A2 TR201921223 A2 TR 201921223A2
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max
micro
weight
steel composition
alloyed steel
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TR2019/21223A
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Çulha Osman
Eyçi̇n Fulya
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Tirsan Kardan Sanayi Ve Ticaret Anonim Sirketi
Ti̇rsan Kardan Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇
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Priority to TR2019/21223A priority Critical patent/TR201921223A2/en
Priority to PCT/TR2020/051354 priority patent/WO2021133345A1/en
Publication of TR201921223A2 publication Critical patent/TR201921223A2/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
    • B21J1/06—Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Laminated Bodies (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

Buluş özellikle, 475-550 MPa akma mukavemeti, 680-720 MPa çekme mukavemetine sahip, ağırlıkça %0,15-0,2 oranında karbon (C), ağırlıkça maks. %0,007 oranında azot (N), ağırlıkça maks. %0,25 oranında silisyum (Si), ağırlıkça maks. %1,1 oranında mangan (Mn), ağırlıkça maks. %0,6 oranında krom (Cr), ağırlıkça maks. %0,1 oranında molibden (Mo), ağırlıkça maks. %0,1 nikel (Ni), ağırlıkça maks. %0,15 oranında vanadyum (V), ağırlıkça %0,05-0,15 oranında alüminyum (Al), ağırlıkça maks. %0,03 oranında fosfor (P), ağırlıkça maks. % 0,03 oranında kükürt (S) ve ağırlıkça maks. %0,25 oranında bakır (Cu) içeren mikro alaşımlı çelik kompozisyonu ile ilgilidir.In particular, the invention has a yield strength of 475-550 MPa, a tensile strength of 680-720 MPa, carbon (C) at the rate of 0.15-0.2% by weight, max. 0.007% nitrogen (N), max. 0.25% silicon (Si), max. 1.1% manganese (Mn), max. 0.6% chromium (Cr), max. 0.1% molybdenum (Mo), max. 0.1% nickel (Ni), max. Vanadium (V) 0.15%, aluminum (Al) 0.05-0.15% by weight, max. 0.03% phosphorus (P), max. 0.03% sulfur (S) and max. It is related to the composition of micro-alloyed steel containing 0.25% copper (Cu).

Description

TARIFNAME Mekanik özellikleri gelistirilmis mikro alasimli çelik kompozisyonu Teknik Alan Bulus, yüksek mukavemet gerektiren, dövme ile üretilen otomotiv parçalarinda kullanilmak üzere, akma mukavemeti, çekme mukavemeti gibi mekanik özellikleri gelistirilen mikro alasimli çelik kompozisyonu ile ilgilidir. agirlikça %0,15-0,2 oraninda karbon (C), agirlikça maks. %0,007 oraninda azot (N), agirlikça maks. %0,25 oraninda silisyum (Si), agirlikça maks. %1,1 oraninda mangan (Mn), agirlikça maks. %0,6 oraninda krom (Cr), agirlikça maks. %0,1 oraninda molibden (M0), agirlikça oraninda alüminyum (AI), agirlikça maks. %0,03 oraninda fosfor (P), agirlikça maks. % 0,03 oraninda kükürt (S) ve agirlikça maks. %0,25 oraninda bakir (Cu) içeren mikro alasimli çelik kompozisyonu ile ilgilidir. Teknigin Bilinen Durumu Mikro alasimli çelikler, dünya çelik üretiminin yaklasik %12"sini olusturarak çelik türleri arasinda önemli bir yere sahiptir. Dünyanin birçok bölgesinde tüm büyük çelik pazarlarinda kullanilmakta olan bu çelikler, otomotiv, gaz ve petrol boru hatlari, insaat, ulasim (transport) endüstrilerinde önemli rol oynamaktadir. Mikro alasimli çeliklerin spesifik gelisim yönlerini, az perlitli ve perlitsiz çelikler olusturmaktadir. Karbon oraninin bariz sekilde düsürülmesi ile sekil verilebilirlik, tokluk, kaynak edilebilirlik gibi özellikler önemli oranda yükseltilmektedir. Bahsedilen bu özellikler genellikle sekil vermek suretiyle yüksek mukavemetli ve hafif parçalarin üretiminde istenilmektedir. Düsük karbon oranina ragmen bu çeliklerde, mikro alasim elementleri olan alüminyum (AI), niobyum (Nb), titanyum (Ti), vanadyumun (V) tane inceltici ve sertlestirici etkileri ile kontrollü haddelemeyle akma siniri ancak 500 N/mm2 ye ulasabilmektedir. Mikro alasimli çeliklerde, alasim elementi olarak kullanilan niobyum (Nb), titanyum (Ti), vanadyum (V) ve alüminyum (AI), malzemenin mekanik özelliklere dogrudan önemli etkileri bulunmakta olup, karbür, nitrür veya karbonitrür olusturmaktadir. Mikro alasim elementlerinin olusturdugu karbür, nitrür ve karbonitrür, sicak sekillendirme islemleri sirasinda çözünme sicakliklarinin üzerine çikilmadigi takdirde östenit fazi içerisinde çözünmeden kalmaktadir. Çözünmeyen bu sert yapilar östenit tane büyümesini engelleyerek hem küçük taneli bir çelik yapisi elde edilmesini hem de malzemenin toklugunun artmasini saglamaktadir. Mevcut teknikte yüksek mukavemet elde etmek amaci ile alasimdaki karbon miktarinin arttirilmasi veya mikro alasim elementlerinin tane inceltme özelliginden faydalanilmaktadir. Yüksek karbonlu çelik alasimi, sicak dövme isleminden sonra isil isleme tabi tutulmakta ve mukavemet arttirmak üzere ikincil bir islem gereksinim duyulmaktadir. Diger yandan bilinen teknikte mikro alasimli çelikler, dövülmüs malzemenin mukavemetini isil islemli yüksek karbonlu alasim kadar arttiramamaktadir. Yüksek karbonlu C45E standardindaki çelik alasiminin akma mukavemeti 500 MPa, çekme mukavemeti 750-850 MPa iken, mikro alasimli çelikte ise akma mukavemeti 435 MPa ve çekme mukavemeti 580-780 MPa arasindadir. Bilinen teknikte dövme ile üretilen otomotiv parçalarinda üretiminde 1141M ve C45E alasim bu çeliklerin otomotiv parçalarinda kullanilabilmesi için mutlak suretle islah islemine gönderilmesi gerekmektedir. Islah islemi üretim maliyetlerini arttirmaktadir. Bunun yani sira bilinen teknikte kullanilan çelikler, birçok otomotiv parçasi için istenilen yüksek mukavemet degerlerine ulasilamamaktadir. Dolayisiyla zamanla bahsedilen bu parçalarda kirilmalar görülmektedir. Bahsedildigi üzere islah islemiyle maliyetli bir uygulama sonucu mukavemet arttirilmasi ve mikro alasimli çelikte akma mukavemetinin düsük olmasi, yeni bir çelik alasimi gelistirilmesi ihtiyacini ortaya koymaktadir. Literatürde konu ile ilgili olarak CA2666677A1 numarali patent basvurusuna rastlanilmistir. Bulus, çelik ve yüksek mukavemetli, bölünerek kirilabilen makine parçalarinin üretim prosesi ile ilgilidir. Bulusa konu çeligin kimyasal kompozisyonu agirlikça %0,40-0,60 karbon (C), (Ni), maks. %02 molibden (Mo), maks. %0,050 niobyum (Nb), maks. %0,3 vanadyum (V), elementlerle dengede demir (Fe) ve safsizliklardan olusmaktadir. maks. %0,5 alüminyum (Al), maks. %0,03 azot (N), vanadyum ve demir içeren bir çelik kompozisyonu ile ilgilidir. Söz konusu basvurularda görüldügü üzere, bilinen teknikte birçok çelik kompozisyonu bulunmaktadir. Hali hazirda yüksek mukavemet gerektiren, dövme ile üretilen otomotiv parçalarinin üretiminde kullanilmak üzere, yüksek mukavemetli, düsük alasimli çelik kompozisyonlara ihtiyaç duyulmaktadir. Sonuç olarak yukarida bahsedilen olumsuzluklardan ve eksikliklerden dolayi, ilgili teknik alanda bir yenilik yapma ihtiyaci ortaya çikmistir. Bulusun Amaci Mevcut bulus, yukarida bahsedilen gereksinimleri karsilayan, tüm dezavantajlari ortadan kaldiran ve ilave bazi avantajlar getiren, mekanik özellikleri gelistirilmis mikro alasimli çelik kompozisyonu ile ilgilidir. Bulusun ana amaci, yüksek mukavemet gerektiren, dövme ile üretilen otomotiv parçalarinda kullanilmak üzere, akma mukavemeti, çekme mukavemeti, sertlik gibi mekanik özellikleri açisindan mevcut ürünlere göre daha yüksek degerlere sahip bir mikro alasimli çelik Bulusun amaci, yüksek mukavemetli düsük alasimli bir çelik kompozisyonu ortaya koymaktir. Bulusun amaci, kontrollü dövme sonrasinda akma mukavemeti 475-550 Mpa, çekme elde etmektir. Bulusun amaci, agirlikça %0,15-0,2 oraninda karbon ve agirlikça maks. %0,15 oraninda vanadyumun birlikte kullanilmasi ile mukavemet arttirma mekanizmasini aktive etmektir. Bulusun amaci, vanadyum ile birlikte alüminyumun tane inceltici etkisinden faydalanmaktir. Bulusun amaci, dövme sicakligi ve dövme sonrasi sogutma ortami için gerekli olan birincil 1500 saniye, isi transfer katsayisinin 25-60 W/mzK olmasi sayesinde, tane inceltici elementlerin etkisini ortaya koyabilmesini saglamaktir. Bulusun amaci, standart mikro alasimli çelige oranla minimum çekme kuvveti %17'den daha yüksek degerde baslayan bir çelik kompozisyonu ortaya koymaktir. Bulusun bir amaci, C, N gibi ara yer atomlari ile Mn, Si, Ni, V ve Al gibi elementlerin nitrür, karbür ve karbonitrür yapma özelliklerinden faydalanilarak çelik kompozisyonunun mekanik özelliklerini gelistirilmektir. Bulusun bir amaci, karbürlerin alasim kompozisyonu içerisindeki varligindan olusabilecek kaynaklanabilirlige olumsuz etkiyi ortadan kaldiracak bir çelik kompozisyonu ortaya koymaktir. Bulusun bir amaci, TTT ve CCT diyagramlarinin alasim elementine göre degismesi özelliginden faydalanilarak ince taneli ve çok fazli mikro yapi elde etmektir. Yukarida anlatilan amaçlarin yerine getirilmesi için bulus, mikro alasimli çelik kompozisyonu olup, özelligi; agirlikça %0,15-0,2 oraninda karbon (C), agirlikça maks. %0,007 oraninda azot (N), agirlikça maks. %025 oraninda silisyum (Si), agirlikça maks. %1,1 oraninda mangan (Mn), agirlikça maks. %0,6 oraninda krom (Cr), agirlikça maks. %01 oraninda molibden (Mo), agirlikça maks. %0,1 nikel (Ni), agirlikça maks. %0,15 oraninda vanadyum (V), agirlikça %0,05-0,15 oraninda alüminyum (AI), agirlikça maks. %0,03 oraninda fosfor (P), agirlikça maks. % 0,03 oraninda kükürt (S) ve agirlikça maks. %025 oraninda bakir (Cu) içermektedir. Bulusun amaçlarini gerçeklestirmek üzere, 0 mikro alasimlama ile üretilen çelik kompozisyonun sürekli döküm yöntemi ile kütük formunda elde edilmesi, o üretilen kütüklerin sicak haddeleme ile yuvarlak uzun grubunda silindirik yari mamul haline getirilmesi, 0 uzun yari mamüllerin kontrollü sicak dövme ve sogutma asamalarindan geçirilerek çökelti olusmasi, islem adimlarini içeren mikro alasimli çelik kompozisyon üretim yöntemi olup, özelligi; - bahsedilen dövme sicakliginin 950-1150 °C'de, dövme sonrasi birincil sogutmanin saniye süreyle isi katsayisi 25-60 W/mZK olacak atmosfer kosullarinda olmaktadir. Bulusun yapisal ve karakteristik özellikleri ve tüm avantajlari asagida verilen detayli açiklama sayesinde daha net olarak anlasilacaktir ve bu nedenle degerlendirmenin de bu detayli açiklama göz önüne alinarak yapilmasi gerekmektedir. Bulusun Detayli Açiklamasi Bu detayli açiklamada, mekanik özellikleri gelistirilmis mikro alasimli çelik kompozisyonu, sadece konunun daha iyi anlasilmasina yönelik olarak ve hiçbir sinirlayioi etki olusturmayacak sekilde açiklanmaktadir. Bulus, yüksek mukavemet gerektiren, dövme ile üretilen otomotiv parçalarinda kullanilmak üzere, akma mukavemeti, çekme mukavemeti gibi mekanik özellikleri gelistirilen mikro alasimli çelik kompozisyonu olup, özelligi; agirlikça %0,15-0,2 oraninda karbon (C), agirlikça maks. %000? oraninda azot (N), agirlikça maks. %0,25 oraninda silisyum (Si), agirlikça maks. %1,1 oraninda mangan (Mn), agirlikça maks. %0,6 oraninda krom (Cr), agirlikça maks. %0,1 oraninda molibden (Mo), agirlikça maks. %0,1 nikel (Ni), agirlikça maks. %0,15 oraninda vanadyum (V), agirlikça %0,05-0,15 oraninda alüminyum (AI), agirlikça maks. Bulusa konu mikro alasimli celik kompozisyonunun formüi'asvonu; Içerik Agirlikça Kullanilabilir Miktar (%) Karbon (C) 0,15-0,2 Silisyum (Si) 5 0,25 Molibden (M0) 5 0,1 Vanadyum (V) 5 0,15 Alüminyum (AI) 0,05-0,15 Fosfor (P) 5 0,03 Bakir (Cu) 5 0,25 Bulusa konu mikro alasimli çelik kompozisyonunu elde etmek üzere, ilk olarak alasim elementleri belirlenmektedir. Çelik kompozisyonu içerisindeki alasim elementi miktari ve çesitliligi, mekanik özelliklerin gelistirilmesinde önemli parametrelerdir. Farkli mukavemet arttirma mekanizmalarinin birlikte ortaya çikmasini saglamak üzere, C, N gibi ara yer atomlari ile Mn, Si, Ni ve Al gibi elementlerin nitrür, karbür ve karbonitrür yapma özelliklerinden faydalanilmaktadir. Diger yandan TTT ve CCT diyagramlarinin alasim elementine göre degismesi özelliginden faydalanilarak da ince taneli ve çok fazli mikro yapi elde edilmektedir. Ikinci olarak sicak dövme metodolojisi olusturulmaktadir. Sicak dövme islemindeki sicaklik ve deformasyon oranlari özgün alasima göre yeniden düzenlenmektedir. Son olarak da sogutma islemi uygulamaktir. TTT ve CCT diyagramlarina göre hedef mikro yapi (ferrit, perlit, beynit) için sogutma rejimi belirlenmektedir. Demir-karbon faz diyagraminda martenzit ve beynit dönüsüm alasimin sertlesme mekanizmasinda önemli bir yere sahiptir. Ancak endüstriyel çelik üretiminde proses kosullarindan dolayi soguma hizlari denge kosullarina göre oldukça yüksektir. Soguma hizinin artmasi ile birlikte faz dönüsümlerinin belirlenmesinde kullanilan demir-karbon faz diyagrami kullanilmamaktadir. Bunun en önemli nedeni söz konusu diyagramin çok yavas soguma kosullarinda olusturulmasidir. Bu nedenle yüksek soguma hizlarinda TTT adi verilen ve faz dönüsümünün sicakliga ve zamana bagli olarak degisimini gösteren diyagramlari kullanilmaktadir. Hizli sogutulan çeliklerde östenitin ne zaman dönüsüme baslayacagi, dönüsümün ne kadar süre sonunda tamamlanacagi ve sonuçta hangi ürünlerin olusacagi hususlari izotermal dönüsüm diyagramlari yardimiyla belirlenmektedir. Dolayisiyla, TTT diyagramlari sicakligin ve zamanin fonksiyonu olarak alasim içerisinde asiri soguma kosullarinda bagli olarak olusacak faz dönüsümlerinin belirlenmesinde tercih edilmektedir. Dönüsme reaksiyonunda zaman ve sicaklik etkilerini ayri ayri görebilmek amaciyla dönüsme egrisini degistirmek gerekmektedir. Bu durumu gösteren egrilere de sürekli soguma dönüsüm egrileri (CCT) adi verilmektedir. Sürekli sogumayi kapsayan bütün isil islemler için CCT diyagramlari kullanilabilmektedir. CCT diyagramlarinin ana amaci hangi yapi elemanlarinin elde edilecegi ve buna karsilik hangi sertliklerin elde edilebileceginin soguma egrisinden faydalanarak önceden bilinmesidir. Bu diyagramlar, hem sicakligin sabit tutuldugu izotermal isil islemler hem de sürekli sogumadaki dönüsüm sonrasinda elde edilecek son mikroyapilarin içerdigi faz veya fazlarin belirlenmesine imkan saglamaktadir. Bulus konusu çelik kompozisyonu içerisinde vanadyum ile birlikte kullanilan alüminyumun tane inceltici etkisi göstermektedir. Agirlikça %0,15-20 oraninda karbon ve agirlikça maks. aktive edilmektedir. Bulusa konu çelik kompozisyonunun çekme kuvveti standart mikro alasimli çelige oranla minimum %17'den daha yüksek degerde baslamaktadir. Bulusa konu çelik kompozisyonunu olusturan elementler ve agirlikça kullanilabilir miktarlari sayesinde, karbürlerin alasim kompozisyonu içerisindeki varligindan olusabilecek kaynaklanabilirlige olumsuz etki ortadan kaldirilmaktadir. Bulus konusu mikro alasimli çelik kompozisyonunu Üretim yöntemi; . Mikro alasimlama ile üretilen çelik kompozisyonu sirasiyla, elektrik ark ocagi, pota ocagi, vakum ocagi ve tundish daldirma kapali seramik tüp kullanilarak sürekli döküm yöntemi ile kütük formunda elde edilir, - Üretilen kütükler sicak haddeleme ile yuvarlak uzun grubunda silindirik yari mamul haline getirilir, . Uzun yari mamüller kontrollü sicak dövme ve sogutma asamalarindan geçirilir, o Olusan çökelti sertlesme mekanizmasi ile istenilen mekanik degerlerde çelik alasim Bulusa konu üretim yönteminde kullanilan sicak dövme sicakligi 950-1150 °C, dövme gerçeklestirilmektedir. çökeltileri olusmaktadir. Bulus konusu üretim yöntemi ile elde edilen mikro alasimli çelik kompozisyonu tercihen yüksek tork ( altinda kirilmayan özellikte otomotiv parçalarinda ve kardan milinde kullanilabilir özellikte bir çeliktir. Bulusa konu mikro alasimli çelik kompozisyonun mekanik özellikleri; Akma mukavemeti 475-550 MPa, Çekme mukavemeti 680-720 MPa, Sertligi 210-230 HV, Esdeger karbon degeri 0,43-0,45 Ceq seklindedir. TR TR DESCRIPTION Micro-alloyed steel composition with improved mechanical properties Technical Field The invention relates to micro-alloyed steel composition with improved mechanical properties such as yield strength and tensile strength, to be used in automotive parts produced by forging that require high strength. 0.15-0.2% carbon (C) by weight, max. 0.007% nitrogen (N), by weight max. 0.25% silicon (Si), by weight max. 1.1% manganese (Mn), max. 0.6% chromium (Cr), by weight max. 0.1% molybdenum (M0), aluminum (Al) by weight, max. 0.03% phosphorus (P), max. 0.03% sulfur (S) and max. It is related to the micro-alloyed steel composition containing 0.25% copper (Cu). State of the Art Micro-alloyed steels have an important place among steel types, constituting approximately 12% of world steel production. These steels are used in all major steel markets in many regions of the world, automotive, gas and oil pipelines, construction, transportation. It plays an important role in industries. The specific development directions of micro-alloyed steels are steels with and without pearlite. By significantly reducing the carbon content, properties such as formability, toughness and weldability are significantly increased. These properties are generally obtained by shaping high-strength and lightweight parts. Despite the low carbon content, the yield limit of these steels can only reach 500 N/mm2 with controlled rolling due to the grain thinning and hardening effects of the micro alloying elements aluminum (Al), niobium (Nb), titanium (Ti) and vanadium (V). In micro-alloyed steels, niobium (Nb), titanium (Ti), vanadium (V) and aluminum (Al), used as alloying elements, have significant direct effects on the mechanical properties of the material and form carbide, nitride or carbonitride. Carbide, nitride and carbonitride formed by microalloy elements remain undissolved in the austenite phase unless their dissolution temperatures are exceeded during hot forming processes. These hard, insoluble structures prevent austenite grain growth, allowing a small-grained steel structure to be obtained and increasing the toughness of the material. In the current technique, in order to obtain high strength, increasing the amount of carbon in the alloy or the grain refining feature of microalloy elements is used. High carbon steel alloy is subjected to heat treatment after hot forging and a secondary process is required to increase strength. On the other hand, in the known art, micro-alloyed steels cannot increase the strength of the forged material as much as heat-treated high carbon alloys. While the yield strength of the high carbon C45E standard steel alloy is 500 MPa and the tensile strength is 750-850 MPa, the yield strength of micro-alloyed steel is 435 MPa and the tensile strength is between 580-780 MPa. In the production of automotive parts produced by forging in the known technique, 1141M and C45E alloy steels must be sent to the reclamation process in order to be used in automotive parts. The breeding process increases production costs. In addition, the steels used in the known technique cannot reach the desired high strength values for many automotive parts. Therefore, over time, fractures are observed in these parts. As mentioned, increasing the strength as a result of a costly application through the reclamation process and the low yield strength of micro-alloyed steel reveals the need to develop a new steel alloy. A patent application numbered CA2666677A1 was found in the literature regarding the subject. The invention is related to the production process of steel and high-strength, breakable machine parts. The chemical composition of the steel subject to the invention is 0.40-0.60% carbon (C), (Ni) by weight, max. 02% molybdenum (Mo), max. 0.050% niobium (Nb), max. It consists of 0.3% vanadium (V), iron (Fe) in balance with elements and impurities. max. 0.5% aluminum (Al), max. It relates to a steel composition containing 0.03% nitrogen (N), vanadium and iron. As can be seen in the applications in question, there are many steel compositions in the known art. Currently, there is a need for high-strength, low-alloy steel compositions to be used in the production of forged automotive parts that require high strength. As a result, due to the negativities and deficiencies mentioned above, the need for innovation in the relevant technical field has emerged. Purpose of the Invention The present invention relates to a micro-alloyed steel composition with improved mechanical properties that meets the above-mentioned requirements, eliminates all disadvantages and brings some additional advantages. The main purpose of the invention is to produce a micro-alloyed steel with higher values than existing products in terms of mechanical properties such as yield strength, tensile strength and hardness, to be used in automotive parts produced by forging that require high strength. The purpose of the invention is to introduce a high-strength low-alloy steel composition. . The aim of the invention is to obtain a yield strength and tensile strength of 475-550 Mpa after controlled forging. The purpose of the invention is to produce carbon at a rate of 0.15-0.2% by weight and max. It is to activate the strength increasing mechanism by using 0.15% vanadium together. The purpose of the invention is to benefit from the grain thinning effect of aluminum together with vanadium. The purpose of the invention is to ensure that the grain thinning elements can demonstrate their effect, thanks to the primary 1500 seconds required for the forging temperature and the post-forging cooling environment, and the heat transfer coefficient is 25-60 W/mzK. The aim of the invention is to introduce a steel composition whose minimum tensile strength starts at a value greater than 17% compared to standard micro-alloyed steel. One purpose of the invention is to improve the mechanical properties of the steel composition by taking advantage of the nitride, carbide and carbonitride forming properties of interstitial atoms such as C, N and elements such as Mn, Si, Ni, V and Al. An aim of the invention is to provide a steel composition that will eliminate the negative impact on weldability that may occur due to the presence of carbides in the alloy composition. One aim of the invention is to obtain a fine-grained and multiphase microstructure by taking advantage of the feature that TTT and CCT diagrams change depending on the alloy element. In order to fulfill the above-mentioned purposes, the invention is a micro-alloyed steel composition and its feature is; 0.15-0.2% carbon (C) by weight, max. 0.007% nitrogen (N), by weight max. 025% silicon (Si), by weight max. 1.1% manganese (Mn), max. 0.6% chromium (Cr), by weight max. 01% molybdenum (Mo), max. 0.1% nickel (Ni), max. by weight. 0.15% vanadium (V), 0.05-0.15% by weight aluminum (AI), max. 0.03% phosphorus (P), max. 0.03% sulfur (S) and max. It contains 025% copper (Cu). In order to realize the objectives of the invention, the steel composition produced by 0 micro alloying is obtained in billet form by the continuous casting method, the produced billets are turned into cylindrical semi-products in the round long group by hot rolling, the 0 long semi-products are passed through controlled hot forging and cooling stages to form a precipitate, It is a micro-alloyed steel composition production method that includes process steps, and its feature is; - The mentioned forging temperature is 950-1150 °C, and the primary cooling after forging takes place under atmospheric conditions where the heat coefficient for a second is 25-60 W/mZK. The structural and characteristic features and all the advantages of the invention will be more clearly understood thanks to the detailed explanation given below, and therefore the evaluation should be made taking this detailed explanation into consideration. Detailed Description of the Invention In this detailed explanation, the micro-alloyed steel composition with improved mechanical properties is explained only for a better understanding of the subject and in a way that does not create any limiting effects. The invention is a micro-alloyed steel composition with improved mechanical properties such as yield strength and tensile strength, to be used in forged automotive parts that require high strength, and its feature is; 0.15-0.2% carbon (C) by weight, max. 000%? rate of nitrogen (N), by weight max. 0.25% silicon (Si), by weight max. 1.1% manganese (Mn), max. 0.6% chromium (Cr), by weight max. 0.1% molybdenum (Mo), max. 0.1% nickel (Ni), max. by weight. 0.15% vanadium (V), 0.05-0.15% by weight aluminum (AI), max. Formulation of the microalloyed steel composition subject to the invention; Content Usable Amount by Weight (%) Carbon (C) 0.15-0.2 Silicon (Si) 5 0.25 Molybdenum (M0) 5 0.1 Vanadium (V) 5 0.15 Aluminum (AI) 0.05- 0.15 Phosphorus (P) 5 0.03 Copper (Cu) 5 0.25 In order to obtain the micro-alloyed steel composition subject to the invention, the alloying elements are first determined. The amount and diversity of alloying elements in the steel composition are important parameters in improving mechanical properties. In order to ensure the emergence of different strength increasing mechanisms together, the nitride, carbide and carbonitride forming properties of interstitial atoms such as C and N and elements such as Mn, Si, Ni and Al are used. On the other hand, by taking advantage of the fact that TTT and CCT diagrams change depending on the alloy element, a fine-grained and multiphase microstructure is obtained. Secondly, the hot forging methodology is created. Temperature and deformation rates in the hot forging process are rearranged according to the original alloy. Finally, apply the cooling process. The cooling regime for the target microstructure (ferrite, pearlite, bainite) is determined according to the TTT and CCT diagrams. In the iron-carbon phase diagram, martensite and bainite transformation has an important place in the hardening mechanism of the alloy. However, due to the process conditions in industrial steel production, cooling rates are quite high compared to equilibrium conditions. The iron-carbon phase diagram used to determine phase transformations as the cooling rate increases is not used. The most important reason for this is that the diagram in question was created under very slow cooling conditions. For this reason, diagrams called TTT, which show the change of phase transformation depending on temperature and time, are used at high cooling rates. In rapidly cooled steels, when the austenite will begin to transform, how long the transformation will take to complete, and what products will be formed as a result are determined with the help of isothermal transformation diagrams. Therefore, TTT diagrams are preferred in determining the phase transformations that will occur in the alloy under undercooling conditions as a function of temperature and time. It is necessary to change the transformation curve in order to see the effects of time and temperature separately in the transformation reaction. Curves showing this situation are called continuous cooling transformation curves (CCT). CCT diagrams can be used for all heat processes involving continuous cooling. The main purpose of CCT diagrams is to know in advance which structural elements will be obtained and which hardness will be obtained by using the cooling curve. These diagrams enable the determination of the phase or phases contained in the final microstructures to be obtained after both isothermal heat treatments in which the temperature is kept constant and the transformation in continuous cooling. Aluminum used together with vanadium in the steel composition of the invention shows a grain refining effect. 0.15-20% carbon by weight and max. is activated. The tensile strength of the steel composition subject to the invention starts at a minimum of 17% higher than the standard micro-alloyed steel. Thanks to the elements that make up the steel composition subject to the invention and their usable amounts by weight, the negative impact on weldability that may occur due to the presence of carbides in the alloy composition is eliminated. Production method of the micro-alloyed steel composition of the invention; . The steel composition produced by micro alloying is obtained in billet form by continuous casting method using electric arc furnace, ladle furnace, vacuum furnace and tundish dip-closed ceramic tube, respectively. - The produced billets are turned into cylindrical semi-products in the round and long group by hot rolling. Long semi-finished products are passed through controlled hot forging and cooling stages, o With the resulting precipitate hardening mechanism, the steel alloy is forged at the desired mechanical values. The hot forging temperature used in the production method of the invention is 950-1150 °C. precipitates are formed. The micro-alloyed steel composition obtained by the production method of the invention is preferably a steel that does not break under high torque and can be used in automotive parts and cardan shafts. Mechanical properties of the micro-alloyed steel composition subject to the invention; Yield strength 475-550 MPa, Tensile strength 680-720 MPa , Hardness is 210-230 HV, Equivalent carbon value is 0.43-0.45 Ceq. TR TR

Claims (7)

1.ISTEMLER 1.1.CLAIMS 1. 2.Mikro alasimli çelik kompozisyonu olup, özelligi; agirlikça %0,15-0,2 oraninda karbon (C), agirlikça maks. %000? oraninda azot (N), agirlikça maks. %0,25 oraninda silisyum (Si), agirlikça maks. %1,1 oraninda mangan (lVln), agirlikça maks. %06 oraninda krom (Cr), agirlikça maks. %01 oraninda molibden (M0), agirlikça maks. %0,1 nikel (Ni), agirlikça maks. %0,15 oraninda vanadyum (V), agirlikça %0,05-0,15 oraninda alüminyum (Al), agirlikça maks. %003 oraninda fosfor (P), agirlikça maks. °/o 0,03 oraninda kükürt (S) ve agirlikça maks. %025 oraninda bakir (Cu) içermesidir. o mikro alasimlama ile üretilen çelik kompozisyonun sürekli döküm yöntemi ile kütük formunda elde edilmesi, - üretilen kütüklerin sicak haddeleme ile yuvarlak uzun grubunda silindirik yari mamul haline getirilmesi, 0 uzun yari mamüllerin kontrollü sicak dövme ve sogutma asamalarindan geçirilerek çökelti olusmasi, islem adimlarini içeren, istem 1'de bahsedilen mikro alasimli çelik kompozisyonunun o bahsedilen dövme sicakliginin 950-1150 °C'de, dövme sonrasi birincil sogutmanin saniye süreyle isi katsayisi 25-60 W/mzK olacak sekilde atmosfer kosullarinda olmasidir.2. It is a micro-alloyed steel composition and its feature is; 0.15-0.2% carbon (C) by weight, max. 000%? rate of nitrogen (N), by weight max. 0.25% silicon (Si), by weight max. 1.1% manganese (lVln), max. 06% chromium (Cr), by weight max. 01% molybdenum (M0), max. 0.1% nickel (Ni), max. by weight. 0.15% vanadium (V), 0.05-0.15% by weight aluminum (Al), max. 003% phosphorus (P), by weight max. °/o 0.03 sulfur (S) by weight and max. It contains 025% copper (Cu). o Obtaining the steel composition produced by micro alloying in billet form by continuous casting method, - turning the produced billets into cylindrical semi-products in the round long group by hot rolling, 0 forming a precipitate by passing the long semi-products through controlled hot forging and cooling stages, The forging temperature of the micro-alloyed steel composition mentioned in 1 is 950-1150 °C, and the primary cooling after forging is at atmospheric conditions such that the heat coefficient is 25-60 W/mzK for a second. 3. Istem 2'ye uygun mikro alasimli çelik kompozisyon üretim yöntemi olup, özelligi; olusan3. It is a micro-alloyed steel composition production method in accordance with claim 2, and its feature is; formed 4. Istem 2'de bahsedilen üretim yöntemi ile elde edilen mikro alasimli çelik kompozisyonu olup, özelligi; 475-550 MPa akma mukavemetine sahip olmasidir.4. It is a micro-alloyed steel composition obtained by the production method mentioned in Claim 2, and its feature is; It has a yield strength of 475-550 MPa. 5. Istem 2'de bahsedilen üretim yöntemi ile elde edilen mikro alasimli çelik kompozisyonu olup, özelligi; 680-720 MPa çekme mukavemetine sahip olmasidir.5. It is a micro-alloyed steel composition obtained by the production method mentioned in Claim 2, and its feature is; It has a tensile strength of 680-720 MPa. 6. Istem 2'de bahsedilen üretim yöntemi ile elde edilen mikro alasimli çelik kompozisyonu olup, özelligi; 210-230 HV sertlige sahip olmasidir.6. It is a micro-alloyed steel composition obtained by the production method mentioned in Claim 2, and its feature is; It has a hardness of 210-230 HV. 7. Istem 2'de bahsedilen üretim yöntemi ile elde edilen mikro alasimli çelik kompozisyonu olup, özelligi; 0,43-0,45 Ceq esdeger karbon degerine sahip olmasidir. TR TR7. It is a micro-alloyed steel composition obtained by the production method mentioned in Claim 2, and its feature is; It has an equivalent carbon value of 0.43-0.45 Ceq. TR TR
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