Dissolution of Scrap in Hot Metal under Linz–Donawitz (LD) Steelmaking Conditions
, Johannes Schenk 1,2, Rainer Ammer 3, Gerald Klösch 4 and Krzysztof Pastucha 5Round 1
Reviewer 1 Report
The techniques used to investigate the dissolution of scrap in hot metal under LD steelmaking conditions are well chosen. The experimental investigations have been conducted and evaluated well.
The experiments delivered valid results for the comparison of static and dynamic diffusive melting situations and also for the understanding of the diffusive melting process under the investigated circumstances. Ablation rates and mass transfer coefficients could be determined from the experiments for static and dynamic conditions.
The references are up-to-date and appropriate. There are very current references, even from 2018, but also references to older fundamental publications, giving a good picture of publications on the paper topic.
However, the paper could be improved by adding at least an exemplary picture of one of the cylinders before and after a melting test. That way, the surface condition of the cylinder after a certain dissolution time as well as the reduction of the radius would be easy to comprehend.
Another information currently missing in the paper is a comparison of the turbulent conditions in the initial stages of the LD steelmaking process and the experiments with rotating cylinder. Without proof or discussion it is simply stated the rotation of the cylinder with 100 rpm leads to similar conditions. Therefore the level of turbulence should be discussed and compared in more detail, e.g. based on a similarity analysis of both situations.
Author Response
Point 1: The techniques used to investigate the dissolution of scrap in hot metal under LD steelmaking conditions are well chosen. The experimental investigations have been conducted and evaluated well.
The experiments delivered valid results for the comparison of static and dynamic diffusive melting situations and also for the understanding of the diffusive melting process under the investigated circumstances. Ablation rates and mass transfer coefficients could be determined from the experiments for static and dynamic conditions.
Response: No further action requested
Point 2: The references are up-to-date and appropriate. There are very current references, even from 2018, but also references to older fundamental publications, giving a good picture of publications on the paper topic.
Response: No further action requested
Point 3: However, the paper could be improved by adding at least an exemplary picture of one of the cylinders before and after a melting test. That way, the surface condition of the cylinder after a certain dissolution time as well as the reduction of the radius would be easy to comprehend.
Response: In section 4 an additional picture was integrated. On this picture the evolution of the steel cylinder after certain submerging time could be seen in reference to the initial status (0s). A short explanation and connection of the Figure in the text are given in the upper lines (119 to 121).
Point 4: Another information currently missing in the paper is a comparison of the turbulent conditions in the initial stages of the LD steelmaking process and the experiments with rotating cylinder. Without proof or discussion, it is simply stated the rotation of the cylinder with 100 rpm leads to similar conditions. Therefore, the level of turbulence should be discussed and compared in more detail, e.g. based on a similarity analysis of both situations.
Response: In section 3 the explanation how the definition of receiving a turbulent regime was made. Additionally, to references [17] and [18] where inserted to underline the procedure. Including the whole mathematically explanation was not considered otherwise the manuscript will get to extensive.
The Paragraph included to the manuscript reads as follows:
The determination of the real level of turbulence during the entire blowing process will, inter alia, be possible through CFD-Simulation or related methods. Measurements directly in an LD converter are difficult to realize but it may be reasonable that turbulent conditions are present. According to the geometric and physical parameters of the experiments and the present case of a rotating cylinder in a cylindrical crucible the theory of Taylor-Couette flow is used to define when laminar flow becomes unstable and further turbulent. The mathematical executions are not explained in detail in this work but are well described by A. Esser and S. Grossmann in [17] or A. Racina in [18]. For the present system a rotating sample with 100 rpm was found to be definitely in turbulent mixing regime.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors,
this paper shows some knowledge about liquid steel behavior from thermodynamic aspects.
it can be published after follwoing correction.
title: LD need to be replaced to Linz-Donawitz (LD) or something to indicate meaning.
Figure 1 is unclear.
Talbe 2, [(m/s)*10^-6] -> [(m/s)x10-6]
numbers, -1.98...-5.3 -> -1.98 ~ -5.30
Author Response
Point 1: title: LD need to be replaced to Linz-Donawitz (LD) or something to indicate meaning.
Response: The Title has to be changed using your suggestion to:
Dissolution of Scrap in Hot Metal under Linz-Donawitz (LD) Steelmaking Conditions
Point 2: Figure 1 is unclear.
Response: In this case it was not very clear for us what you meant, we tried to solve your request in case of increasing the picture quality first to 1200 dpi. Secondly I put more information about the content of Figure 1 in the paragraph above Figure 1.
At least the figure should show the specific phase diagram of the used scrap having a Silicon content of 0.073% and a Manganese content of 0.479% like indicated in Table one. For the used equilibrium temperatures given in Table 1 (1230°C, 1300°C and 1385 °C) the liquidus concertation are marked with a violet star and their value is written beside it.
Point 3: Table 2, [(m/s)*10^-6] -> [(m/s)x10-6]
numbers, -1.98...-5.3 -> -1.98 ~ -5.30
Response: These points we changed as you wished. Due to the negative algebraic sign, and the size of the Table it is not possible to bring the numbers of the ablation rate (-1.98...-5.3 -> -1.98 ~ -5.30) into a single line.
Author Response File: Author Response.pdf
