DCCT Diagrams of X70 Pipeline Grade Influenced by Preheating Conditions

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61989100%3A27360%2F17%3A10238595" target="_blank" >RIV/61989100:27360/17:10238595 - isvavai.cz</a>

Result on the web

—

DOI - Digital Object Identifier

—

Result language

angličtina

Original language name

DCCT Diagrams of X70 Pipeline Grade Influenced by Preheating Conditions

Original language description

Heavy seamless tubes are produced by the Big Mannesmann Rolling Mill in Třinecké železárny plant. Their final microstructures and properties are not only given by steel chemistry, they are also largely influenced by cooling conditions after finish-rolling. Continuous cooling transformation (CCT) analysis of various steel grades has been increasingly an object of the researchers&apos; attention. Nevertheless, the phase transformations are also affected by the initial microstructure (e.g. austenite grain size) and previous deformation (ratio of residual hardening and softening). For that reason the DCCT diagrams (including the influence of defined deformation e = 0.35) of the HSLA steel X70 were designed for two states of the initial microstructures. In rough outline, the tested steel has the following chemical composition: 0.16 C-1.0 Mn-0.2 Cr-0.05 V-0.03 Nb (in wt. %). Phase transformations in the course of cooling were studied by dilatometer tests (performed in the Gleeble 3800 hot deformation simulator, to wide cooling rates range, from 0.15°C/s to 80 °C/s), metallographic analysis and hardness as well as micro-hardness measurement. Coarse gamma grains (G = 3) were produced by high-temperature preheating (1280 °C) of the dilatometer samples made from the continuously cast bloom with diameter of 400 mm. Fine initial microstructure (G = 11) was obtained by severe laboratory hot rolling of the cast material and normalizing. Lower temperature of austenitization (900 °C) has been set in the dilatometer to make such samples from the normalized material. Great differences were observed, some coarse-grain samples containing acicular ferrite, whereas mixture of martensite and austenite appeared in the fine-grain samples cooled with rates of at least 12 °C/s. Lower heating temperature substantially accelerated the gamma/alpha transformation at high cooling rates.

Czech name

—

Czech description

—

Type

D - Article in proceedings

CEP classification

—

OECD FORD branch

20501 - Materials engineering

Project

<a href="/en/project/LO1203" target="_blank" >LO1203: Regional Materials Science and Technology Centre - Feasibility Program</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>S - Specificky vyzkum na vysokych skolach

Publication year

2017

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Article name in the collection

METAL 2017: conference proceedings : 26th International Conference on Metallurgy and Materials : (reviewed version) : May 24th-26th 2017, Hotel Voroněž I, Brno, Czech Republic, EU

ISBN

978-80-87294-79-6

ISSN

—

e-ISSN

neuvedeno

Number of pages

8

Pages from-to

375-382

Publisher name

Tanger

Place of publication

Ostrava

Event location

Brno

Event date

May 24, 2017

Type of event by nationality

WRD - Celosvětová akce

UT code for WoS article

—