Dilution and Slag–Metal Reactions Control the Titanium Concentration in Submerged-Arc Weld Metal

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Several aspects should be improved before the manuscript can be considered for publication.

1. Some figures could be improved by increasing the font size and making the labels and symbols easier to read.
2. The captions of the figures should provide slightly more information to make them understandable without referring too much to the main text.
3. The quality and readability of the microstructure images should be improved, particularly regarding scale bars and annotations.
4. The results presented in the tables are useful, but the formatting and alignment of the numerical values should be checked for consistency.
5. Some tables could benefit from clearer headings and units to facilitate comparison between the different samples and conditions.
6. The discussion of the experimental and calculated values in the tables could be strengthened, especially where noticeable differences are observed.
7. Please ensure that all figures and tables are cited consistently in the text and that the information in the captions agrees with the corresponding data.
8. Could the authors provide a clearer explanation of the differences between the experimental and predicted titanium concentrations?

Author Response

1. Some figures could be improved by increasing the font size and making the labels and symbols easier to read.
   The font size has been increased.
2. The captions of the figures should provide slightly more information to make them understandable without referring too much to the main text.
   Brief discussion has been added to several of the figure captions.
3. The quality and readability of the microstructure images should be improved, particularly regarding scale bars and annotations.
   The image contrast has been adjusted. The lettering of annotations has been enlarged.
4. The results presented in the tables are useful, but the formatting and alignment of the numerical values should be checked for consistency.
   The width of several columns has been increased for improved readability.
5. Some tables could benefit from clearer headings and units to facilitate comparison between the different samples and conditions.
   Several table headings have been expanded. All units have been verified.
6. The discussion of the experimental and calculated values in the tables could be strengthened, especially where noticeable differences are observed.
   The differences between the experimental and predicted values of the apparent equilibrium constant (Table 6) is discussed in section 4.1 (Table 6 is the only table that compares experimental and calculated values.)
7. Please ensure that all figures and tables are cited consistently in the text and that the information in the captions agrees with the corresponding data.
   This has been verified.
8. 1. Could the authors provide a clearer explanation of the differences between the experimental and predicted titanium concentrations?
      Additional explanation has been added in the text, as follows:
      Both the approximate analytical model and the full kinetic model predicted somewhat higher titanium concentrations in the weld metal than found experimentally. As the sensitivity analysis in Figures 9 indicates, a possible reason for the difference is a higher than estimated mass transfer coefficient; roughening of the steel-slag interface (under the influence of rapid flow in the weld metal) would have a similar effect. Both a higher mass transfer coefficient and an increased steel-slag reaction area would cause the titanium concentration to approach the (low) equilibrium value more closely (as shown by Equation 4). Given the dominant role of dilution and steel-flux reactions in setting the weld metal composition, uncertainty in the mass transfer conditions is a more likely explanation for the difference between predicted and actual titanium concentrations.
   As a further test of the current approach, experimental results recently reported by Wang et al. were compared with the predictions of the model developed in the current work. Wang et al. prepared single-bead welds with a dilution ratio of 0.53, using CaO-SiO₂-MnO-TiO₂ fluxes with constant (%SiO₂) = 30% and (%CaO) = 20%, and varying (%MnO) and (%TiO₂). In that work, the wire contained no titanium, and [%Ti] = 0.011% for the base metal. In the absence of other information, the weld pool dimensions and welding speed were taken to be the same as in the current work. Figure 12 shows that the analytical model (developed in the present work) predicted titanium concentrations in the weld metal that are close to the experimental results of Wang et al., for all except the case with the highest titanium oxide concentration in the flux.  Notably, all the compositions remained close to the average composition of the parent metal and wire (calculated with the reported dilution ratio); this emphasizes the limited effect of chemical reaction on the titanium concentration in the weld metal, compared with the effect of dilution.

Reviewer 2 Report

Comments and Suggestions for Authors

Comment on paper titled “Dilution and slag-metal reactions control the titanium concentration in submerged-arc weld metal ”

This work is dedicated to study the effect of reaction between the steel melt pool and the liquid slag (molten flux) on the titanium control during submerged-arc welding. Some comments must be addressed to improve the quality of this work.

• Please add more details and references on kinetic of metal transferred from the wire to the melt pool. Introduction must be more developed to show the state of art related to what happening in the weld in term of chemical reactions
• In the end of the introduction add the novelty of this work.
• Please add in experimental work the picture of the machine used and the set-up of experiment.
• Please add some references as evidence to support the discussion in” discussion and result - Kinetic models” section
• Please rewrite the conclusion in bullet form.

Author Response

1. Please add more details and references on kinetic of metal transferred from the wire to the melt pool. Introduction must be more developed to show the state of art related to what happening in the weld in term of chemical reactions.
   The following additional discussion on the available literature has been added to the Introduction:
   As reviewed in detail by Sengupta et al., the available experimental data support the mechanism formulated by Mitra and Eagar, that the main role of the arc reactions is to cause oxygen transfer to the weld metal, whereas dilution and steel-slag reaction control the concentrations of the other elements in the weld metal. Work on quantifying the reactions in the arc region has been reviewed in detail; as shown by that thorough review, recent work on reactions in the arc has focused on improved prediction of oxygen transfer. It was also emphasized that slag-metal reactions do not reach equilibrium; this is the reason for the focus of the current work on quantifying the role of the kinetics of the slag-metal reactions.
   Some recent work indicated a possible minor role of reactions in the arc cavity in titanium transfer: Wang et al. analyzed both quenched metal droplets and weld metal, for submerged-arc weldments produced with fluxed with titanium oxide concentrations ranging from zero to 25%. Even at a high TiO₂ concentration in the flux of 10%, there was zero pick-up of titanium by the weld metal, and the droplets contained just 23 ppm of titanium. The fluxes used in the current work contained 1.3-1.6 % TiO₂, which would give an even smaller role of titanium transfer to metal in the arc region. In fact – as shown later in this paper – the experimental results of Wang et al. follow the predictions of the kinetic expressions developed in this work (and summarized in Figure 1).
2. In the end of the introduction add the novelty of this work.
   The following statement has been added:
   Part of the novelty of the current work is that it derives an analytical model that clearly shows the competing effects of dilution and steel-slag reaction on the steady-state concentration of titanium in the weld metal. In addition, microanalysis of the weld metal shows how the inclusion compositions respond to differences in the titanium concentration.
3. Please add in experimental work the picture of the machine used and the set-up of experiment.
   The experimental set-up has been well documented in previous papers, including diagrams, so the references to previous work is sufficient, in our opinion.
4. Please add some references as evidence to support the discussion in” discussion and result - Kinetic models” section.
   Additional comparison to the recent results of Wang et al. (2026) has been added.
5. Please rewrite the conclusion in bullet form.
   No change has been made, since it is not a requirement of the JMMP template.

Reviewer 3 Report

Comments and Suggestions for Authors

This paper investigates the deposition behavior of titanium during SAW. Through welding experiments, laboratory slag-metal equilibrium experiments, inclusion characterization, and kinetic model analysis, this study clarifies that the titanium content in the deposited metal of SAW is co-regulated by both the slag-metal reaction kinetics and base metal dilution. Under SAW conditions, titanium is highly susceptible to oxidation and subsequent migration into the slag phase, with the slag-metal distribution coefficient of titanium reaching approximately 1000. While the reported findings offer certain engineering value, the manuscript still requires necessary revisions prior to acceptance. The specific recommendations are outlined as follows:

• The implementation details require further supplementation. During multi-layer welding, interlayer temperature influences molten pool behavior and the remelting process. Whether interpass cooling is applied, and the appropriate control range of interlayer temperature, remain to be clarified.
• Partial data presented in Table 1 are derived from experimental results. It is recommended that this portion of the content be relocated to Section 3 entitled "Results and Discussion".
• The titanium content measured in the weld of Sample B6 is 0.022%, which is substantially higher than the 45 ppm threshold. Nevertheless, no statistically significant variations in microstructure or hardness were detected relative to Sample A2. I propose that further clarification and elaboration on this observation be provided.
• Table 6 summarizes the experimental results: the C_Si-Ti value of the 0.3% Si group is significantly lower than that of the 0.2% Si group. The authors of the original paper attribute this difference solely to errors in the titanium content testing and analysis. I recommend that the source of this deviation be discussed in greater depth.
• Both the analytical model and the full-order dynamic model predicted that the Ti content in the first-layer weld is approximately 0.020%, while the experimentally measured value is only 0.014%. Although the existing literature attributes this deviation to minor variations in the remelting ratio, no quantitative analysis of parameter sensitivity has been performed to date. I propose that future work should provide the specific value of the remelting ratio that requires adjustment to align with the experimental measurements.

Author Response

1. The implementation details require further supplementation. During multi-layer welding, interlayer temperature influences molten pool behavior and the remelting process. Whether interpass cooling is applied, and the appropriate control range of interlayer temperature, remain to be clarified.
   The following comment has been added (to the discussion) to address this point:
   Because of the strong effect of dilution, the development of the titanium concentration in the weld metal during multipass welds would be strongly affected by welding conditions. For example,  higher interpass temperatures would increase the melt-pool size, with more dilution and less of an effect of titanium introduced in the wire on the weld metal titanium concentration. The importance of welding conditions is shown by the wide range of dilution ratios reported in the literature: At the lower end, Mitra stated that the dilution ratio can be as low as 0.45, and the lowest dilution ratio in the work of Saini and Singh was 0.41; these are much lower than the estimated dilution ratio of 0.8 in the current work.
2. Partial data presented in Table 1 are derived from experimental results. It is recommended that this portion of the content be relocated to Section 3 entitled "Results and Discussion".
   Combining these values in Table 1 facilitates comparison of the compositions of the input materials and the welds, so we would prefer to keep these together.
3. The titanium content measured in the weld of Sample B6 is 0.022%, which is substantially higher than the 45 ppm threshold. Nevertheless, no statistically significant variations in microstructure or hardness were detected relative to Sample A2. I propose that further clarification and elaboration on this observation be provided.
   This is already discussed in the text, in the context of the relatively high manganese concentration of the weld metal, that leads to the formation of acicular ferrite whether or not the weld metal contains titanium.
4. Table 6 summarizes the experimental results: the CSi-Ti value of the 0.3% Si group is significantly lower than that of the 0.2% Si group. The authors of the original paper attribute this difference solely to errors in the titanium content testing and analysis. I recommend that the source of this deviation be discussed in greater depth.
   We did consider other possible reasons, such as a lower oxidation state (than +IV) of titanium in the slag, and this is mentioned in the manuscript. However – as also mentioned in the manuscript – conditions are so oxidizing with respect to titanium that the equilibrium titanium concentration in the weld metal is near zero, whichever apparent equilibrium constant holds.
5. Both the analytical model and the full-order dynamic model predicted that the Ti content in the first-layer weld is approximately 0.020%, while the experimentally measured value is only 0.014%. Although the existing literature attributes this deviation to minor variations in the remelting ratio, no quantitative analysis of parameter sensitivity has been performed to date. I propose that future work should provide the specific value of the remelting ratio that requires adjustment to align with the experimental measurements.
   Additional discussion has been added to address this difference:
   Both the approximate analytical model and the full kinetic model predicted somewhat higher titanium concentrations in the weld metal than found experimentally. As the sensitivity analysis in Figures 9 indicates, a possible reason for the difference is a higher than estimated mass transfer coefficient; roughening of the steel-slag interface (under the influence of rapid flow in the weld metal) would have a similar effect.  Both a higher mass transfer coefficient and an increased steel-slag reaction area would cause the titanium concentration to approach the (low) equilibrium value more closely (as shown by Equation 4). Given the dominant role of dilution and steel-flux reactions in setting the weld metal composition, uncertainty in the mass transfer conditions is a more likely explanation for the difference between predicted and actual titanium concentrations. As a further test of the current approach, experimental results recently reported by Wang et al. were compared with the predictions of the model developed in the current work. Wang et al. prepared single-bead welds with a dilution ratio of 0.53, using CaO-SiO2-MnO-TiO2 fluxes with constant (%SiO2) = 30% and (%CaO) = 20%, and varying (%MnO) and (%TiO2). In that work, the wire contained no titanium, and [%Ti] = 0.011% for the base metal. In the absence of other information, the weld pool dimensions and welding speed were taken to be the same as in the current work. Figure 12 shows that the analytical model (developed in the present work) predicted titanium concentrations in the weld metal that are close to the experimental results of Wang et al., for all except the case with the highest titanium oxide concentration in the flux.  Notably, all the compositions remained close to the average composition of the parent metal and wire (calculated with the reported dilution ratio); this emphasizes the limited effect of chemical reaction on the titanium concentration in the weld metal, compared with the effect of dilution.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

dear authors, the manuscript has been improved. all comments have been taken in account. More clarifications have been added.  The manuscript can be accepted in this form.