eprintid: 208
rev_number: 4
eprint_status: archive
userid: 6
dir: disk0/00/00/02/08
datestamp: 2009-02-18
lastmod: 2015-05-29 19:49:25
status_changed: 2009-04-15 09:25:54
type: report
metadata_visibility: show
item_issues_count: 0
creators_name: McGuinness, Mark
creators_name: Sweatman, Winston
creators_name: Baowan, Duangkamon
creators_name: Barry, Steve
contributors_name: Mills, Jason
contributors_name: Bagshaw, Phil
title: Annealing steel coils
ispublished: pub
subjects: materials
studygroups: misg25
companyname: New Zealand Steel
full_text_status: public
abstract: Cold rolled steel in the form of coiled sheets requires heat treatment (annealing) in order to release stresses and reform the crystalline structure. During this process the whole coil must be heated to the required temperature and then maintained at this temperature for a period of time.

At New Zealand Steel the process takes place inside a batch annealing furnace. The MISG group considered the problem of where the cold point lies within the steel coils, i.e. what is the last part of the coil to reach the required temperature, and how long does it take to reach this temperature? Challenges include deciding what the boundary conditions are on a coil, and dealing with the nonlinearity and anisotropy caused by height-dependent gaps within coils.
problem_statement: Heat treatment (annealing) of cold rolled annealed (CRA) steel coils is critical to ensure the correct mechanical properties of the final product. At NZ Steel, coils of steel are batch annealed 9 coils at a time in a 3x3 grid in a uniflow annealing furnace (UAS). There are 5 annealing time/temperature profiles (cycles) in use at NZ Steel, each with the aim of producing a different range of mechanical properties.

For a coil to be correctly annealed, both the annealing time and temperature need to be correct. It takes time for the entire coil to reach the atmosphere temperature inside the furnace. The rates of axial and radial heat transfers are what will determine the cold point of the coil and how long it will take to reach annealing temperature. Depending on the cycle type that a batch of coils is to be annealed, there is an equation relating heating time to a set point cold temperature.

Knowledge of the theoretical cold point and how long it will take to reach the set point temperature for the soak period will allow optimisation of the annealing heating formulas and provide an improvement of furnace through put and product quality.
date: 2008
date_type: published
pages: 20
citation:   McGuinness, Mark and Sweatman, Winston and Baowan, Duangkamon and Barry, Steve  (2008) Annealing steel coils.  [Study Group Report]     
document_url: http://miis.maths.ox.ac.uk/miis/208/1/misg2008nzsteel.pdf