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Characterization of surface decarburization and oxidation behavior of Cr–Mo cold heading steel

  • Jilin Chen , Guanghong Feng , Yaxu Zheng EMAIL logo , Jian Ma , Peng Lin , Ningtao Wang , Honglei Ma and Jian Zheng
Published/Copyright: October 28, 2022
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High Temperature Materials and Processes
From the journal High Temperature Materials and Processes Volume 41 Issue 1

Abstract

Herein, the surface decarburization and oxidation characteristics of Cr–Mo cold heading steel are investigated via optical microscopy, scanning electron microscopy, and electron backscatter diffraction under different temperatures. Furthermore, the competitive mechanisms of decarburization and oxidation are analyzed. The results indicate that the heating temperature considerably affects the decarburization and oxidation characteristics of the steel sample. With an increase in the temperature, the depth of the total decarburization layer increases. The fully decarburized layer is prominent between 750 and 850°C and culminates at 800°C. The oxide thickness parabolically increases, and Cr2O3 is present, which inhibits oxidation. Between 700 and 950°C, the oxidation weight gain is slow. The main structure of the oxide scale is the dense Fe3O4 layer, inhibiting decarburization. The oxidation rate increases at 950°C, and the proportion of loose FeO layer in the oxide scale exceeds 66%, promoting decarburization. At >1,000°C, the surface decarburization and oxidation rate simultaneously increase.

Keywords: Cr–Mo cold heading steel; decarburization; oxidation; competitive mechanisms

1 Introduction

The factors affecting the surface decarburization of materials include the heating atmosphere, temperature, and time [1–3]. Evidently, the surface decarburization of steel is inevitable during industrial production. The surface decarburization mechanism is investigated and optimized simultaneously to control the depth by reducing the heating temperature and time as well as regulating the oxidizing atmosphere [4,5]. In addition, few reports exist on developing and applying antidecarburization coatings [6,7], which are medium- to high-carbon coatings. The surface oxidation of steel is comparable to that of decarburization. The influencing factors include atmosphere, temperature, and time [8,9], as well as alloying elements such as Al and Nb, on the oxide layer structure [10–12]. Surface oxidation causes oxidative burning loss to steel, affects steel yield, and negatively impacts the surface oxidation control of materials, thereby creating a concern for steel mills. Several scholars [13,14] related the decarburization and oxidation of steel surfaces. Most researchers reported that the iron-oxide scale formed by surface oxidation inhibits decarburization. However, the mechanism of action is unclear, and the interaction between the two is not profound.

In practical applications, surface decarburization considerably affects the fatigue life and delayed fracture performance of steel, particularly at bolt-rolling and R angles, which can easily cause the decarburized layers to accumulate, resulting in a stress concentration that leads to bolt failure and fracture [15–17]. Thus, the surface decarburization of medium- and high-carbon steel needs to be systematically analyzed and controlled.

In this article, the surface decarburization and oxidation behavior of 35CrMo are studied. Further, the relation between surface decarburization and oxidation behavior is analyzed, and the law of decarburization and oxidation of 35CrMo and the competitive mechanisms between these two phenomena are revealed.

2 Materials and methods

The chemical composition of 35CrMo is presented in Table 1. Its smelting process involves the following: 80t converter smelting, ladle furnace refining, Ruhrstahl–Hausen vacuum degassing, and continuous casting under dynamic light reduction to 280 mm2 × 325 mm2. The square billet transforms to a rectangular billet with a size of 160 mm2 × 160 mm2 after nine bloom passes. The process was conducted on the industrial production line of a high-speed wire rod mill.

Table 1

Chemical composition of Cr–Mo microalloyed steel (wt%)

Steel C Si Mn P S Cr Mo
35CrMo 0.35 0.18 0.82 0.001 0.0008 0.98 0.22

The Ø14 mm wire rods were straightened to remove the decarburized and oxide layers from the sample surface. Subsequently, the Ø14 mm sample rods were cut into short 100 mm rods.

Heat treatment was performed under air atmosphere using a VF-1401T box-type resistance furnace. The wire rod samples with a size of Ø14 mm2 × 100 mm2 were maintained at 700–1,100°C at an interval of 50°C for 30 and 60 min and then clamped out, as shown in Figure 1. Afterward, the furnace was air-cooled to room temperature (15–40°C). Using a weighing balance, the sample rods were weighed before and after the heat treatment. Next, the samples obtained after each heat-treatment process were cut into five sections, and the average value (AVG) of the five test data was used for the experimental data. The metallographic samples were produced, ground, and then polished in the vertical rolling direction. Additionally, the ISO 3887:2003 standard: “Steels – Determination of Depth of Decarburized,” was used to detect the decarburized layer via a metallographic microscope. The depth of the decarburized layer includes the thickness of the fully decarburized (FD) layer and the totally decarburized (TD) layer. The thickness of the FD layer refers to the width of all the ferrite regions on the sample surface, and the thickness of the TD layer is the sum of the thickness of the FD and partially decarburized layers. Furthermore, the oxide-scale structures on the samples were examined via scanning electron microscopy (SEM, JSM-5610LV), and the surface layer of the substrates was explored via field emission SEM (FEI QUANTA FEG450). In addition, electron backscatter diffraction (EBSD) was used to detect the iron-oxide scale of the sample and its internal phase structure.

Figure 1 Heat-treatment process curves at varying temperatures.
Figure 1

Heat-treatment process curves at varying temperatures.

3 Results

3.1 Changing law of surface decarburization at different temperatures

The microstructures of the decarburized surfaces of the steel samples at various temperatures were observed metallographically. Figure 2 presents the decarburized structures of the steel samples at different temperatures for 30 min. At 700°C, although no decarburization occurs on the material surface, partially and completely decarburized layers are formed locally at the boundary, appearing as a bright white area as in Figure 2a. With the increasing temperature, the depth of the FD layer gradually increases. At 800°C, the increase in the depth of the FD layer culminates; this layer appears as a bright columnar ferrite block perpendicular to the matrix structure (Figure 2c). The depth of the FD layer decreases when the temperature reaches 850°C. Between 750 and 850°C, the partially decarburized layer gradually intensifies in addition to the FD layer, exhibiting bright white areas of polygonal ferrite and matrix phases. A mixed structure coexists, and the amount of polygonal ferrites gradually decreases along the inner side of the completely decarburized area toward the matrix and tends to form a normal structure of the matrix. Unlike the completely decarburized layer, the depth of the partially decarburized layer continuously increases with the increasing temperature.

Figure 2 Decarburization of original steel samples observed at different temperatures for 30 min: (a) 700°C, (b) 750°C, (c) 800°C, (d) 850°C, (e) 900°C, (f) 950°C, (g) 1,000°C, (h) 1,050°C, and (i) 1,100°C.
Figure 2

Decarburization of original steel samples observed at different temperatures for 30 min: (a) 700°C, (b) 750°C, (c) 800°C, (d) 850°C, (e) 900°C, (f) 950°C, (g) 1,000°C, (h) 1,050°C, and (i) 1,100°C.

The thickness values of the decarburized layers after the heat treatment of the steel sample at different temperatures and durations are shown in Table 2; the standard deviation (σ) values of the thickness values are presented in the table. Figure 3 presents the depth variation of the decarburized layer of 35CrMo at different temperatures. The decarburization behavior of the steel sample is mainly attributed to the outward diffusion of carbon atoms from the surface, which conforms to Fick’s law (diffusion law) [18,19]. Therefore, the factors influencing diffusion also align with the description of decarburization on the material surface.

Table 2

Decarburized layer thickness values

T (°C) Time: 30 min Time: 60 min
FD (μm) TD (μm) FD (μm) TD (μm)
AVG σ AVG σ AVG σ AVG σ
700 23.2 1.15 33.2 1.65 33.4 1.65 65.1 3.25
750 29.8 1.52 69.7 3.5 43.2 2.15 136.2 6.82
800 55.1 2.75 140.5 7.34 67.1 3.35 178.9 8.95
850 38.9 1.95 156.4 7.87 42.5 2.17 199.6 10.47
900 27.3 1.35 162.2 8.13 31.6 1.55 220.5 11.34
950 22.2 1.17 178.8 8.95 32.4 1.63 222.1 11.16
1,000 20.4 1.24 197.2 9.85 30.1 1.54 276.8 13.85
1,050 24 1.28 240 12.27 34 1.76 298 14.98
1,100 21 1.25 300 15.34 31 1.55 349 17.45
Figure 3 Decarburization depth variation of steel at different heating temperatures: (a) total and (b) full decarburization.
Figure 3

Decarburization depth variation of steel at different heating temperatures: (a) total and (b) full decarburization.

As the temperature increases, the diffusion coefficient of the carbon atoms continuously increases, and the diffusion rate gradually accelerates, resulting in an increase in the thickness of the TD layer on the surface of the wire rod (Figure 3a). The depth of the FD layer on the material surface is noticeably different. The formation mechanism of the FD layer is more prominently affected by phase change. Moreover, the FD layer mainly occurs in the two-phase temperature zone of austenite and ferrite. In the thermal expansion testing experiment, the steel’s Ar1 = 732°C, Ar3 = 826°C; the temperature range of 750–850°C represents the two-phase zone of 35CrMo. When the temperature is in the two-phase zone, as the decarburization progresses, the carbon concentration on the material surface gradually decreases, the concentration balance is distorted, and a new structural concentration balance is established. It must be in the austenite grain boundary and partially transformed ferrite. The ferrite phase precipitates continuously [20], and a sudden change in the completely decarburized layer occurs. Consequently, the increase in the depth of the FD layer culminates at 800°C, and with a further increase in the temperature, the FD structure is affected by the low-concentration gradient. The columnar dense ferrite phase ceases to exist and is replaced by a broken “granular” dense ferrite phase. The extension of the heating time can promote the formation of the FD layer and the total decarburization.

3.2 Variation of surface oxidation at different temperatures

Figure 4 presents the morphology of the iron-oxide scale formed after the oxidation of the steel sample surface. At ≤800°C, the oxidation effect on the sample surface is not apparent. At 850°C, the sample surface presents a light-gray iron-oxide scale visible to the naked eye. Under SEM, the iron-oxide scale appears thin. The sample’s cross-section shows that the continuity of the surface oxide scale is poor and intermittently distributed on the sample surface. As the temperature increases to 900–950°C, the iron-oxide scale on the material surface gradually thickens, producing lumpy adhesion and appearing dark gray. SEM images revealed close adherence between the iron-oxide scale and substrate. At 1,000°C, the scale considerably thickens and covers the sample surface. In addition, bubbles and voids locally appear, and some scale bulges emerge. With a further increment in temperature, the layering of the oxide scale is gradually apparent, and its interior and exterior are presented in gray and gray-black, respectively. As the temperature increases, the oxide-scale thickness gradually increases, the bubbles between the oxide scales burst, and horizontal and vertical cracks appear. The oxide scale exhibits noticeable bumps and shedding (Figures 4e and f).

Figure 4 Oxide-scale morphologies of the steel sample at different temperatures for 30 min: (a) 850°C, (b) 900°C, (c) 950°C, (d) 1,000°C, (e) 1,050°C, and (f) 1,100°C.
Figure 4

Oxide-scale morphologies of the steel sample at different temperatures for 30 min: (a) 850°C, (b) 900°C, (c) 950°C, (d) 1,000°C, (e) 1,050°C, and (f) 1,100°C.

The thicknesses of the oxide scale and the oxidation weights at different temperatures and durations are shown in Table 3 (the standard deviation (σ) of the test value is in the table). Figure 5 displays the change in the oxide-scale thickness of the steel sample after heat treatment. As the temperature increases, the iron-oxide-scale thickness on the material surface increases parabolically, and the holding time considerably enhances the formation of the iron-oxide scale. The extension of the heating time promotes the complete diffusion of oxygen atoms and gradually increases the thickness of the iron-oxide scale.

Table 3

Thickness of oxide scale and detection value of oxidation weight

T (°C) Oxide thickness (°)
Time: 30 min Time: 60 min Oxidation weight (g·cm−2)
AVG σ AVG σ AVG AVG
700 3.1 0.16 3.2 0.16 0.026 0.071
750 3.1 0.16 3.9 0.20 0.041 0.094
800 4.2 0.21 6.3 0.32 0.049 0.106
850 4.9 0.25 7.1 0.36 0.063 0.187
900 6.1 0.31 9.4 0.47 0.091 0.256
950 8.2 0.41 11.6 0.58 0.201 0.316
1,000 11.8 0.59 16.1 0.81 0.304 0.42
1,050 12.7 0.64 18.5 0.93 0.368 0.563
1,100 15.1 0.76 21.2 1.06 0.417 0.687
Figure 5 Oxide-scale thickness of steel.
Figure 5

Oxide-scale thickness of steel.

Variations in the oxidation weight gain of 35CrMo after heat treatment are shown in Figure 6. At the same holding time, the oxidation weight gain increases with the increasing heating temperature, and the oxidation weight–gain curve approximates a parabola. Based on the appearance and thickness of the iron-oxide scale on the material surface, the effect of the heating temperature on the iron-oxide scale is pronounced. When the temperature rises, the iron-oxide scale changes from discontinuous to dense, and blistering and bulging are visible again. In essence, the oxidation of the material is the chemical reaction between the iron atoms in the matrix and the external oxygen atoms. As the temperature increases, the internal energy of the abovementioned diffused atoms increases, and gradually, atomic diffusion and transition become active, increasing the oxidation rate. The oxidation weight–gain curve between 700 and 900°C reveals that at the holding time of 30 min, the oxidation weight gain is only 0.091 g·cm−2. However, above 950°C (at 1,100°C), the oxidation weight gain doubles, reaching 0.417 g·cm−2, which is related to the thickness of the iron-oxide scale. When the holding time is 60 min, the parabolic curve of the oxidation weight gain is more prominent. From the curve, it is divided into three stages of growth rate, between 700 and 800°C, the growth rate of oxidation is slow. The oxidation rate increases when the temperature is between 800 and 950°C. Additionally, when the temperature reaches above 950°C, the oxidation rate is the fastest, and the bubbles and bulges of the iron-oxide scale formed in this temperature range are apparent. In this case, sufficient oxygen atoms can contact the substrate through the transverse cracks of the iron-oxide scale. Similarly, it provides convenient conditions for the external diffusion of carbon atoms in the matrix.

Figure 6 Oxidation weight of steel.
Figure 6

Oxidation weight of steel.

4 Analysis and discussion

4.1 Surface decarburization mechanism

Figure 7 presents the schematic of the decarburization mechanism at different temperatures. When the material is heated between the initial temperature of austenite precipitation of ferrite (A3) and the final temperature of ferrite precipitation (A1), the material surface is decarburized alongside austenite (γ) and ferrite (α). According to the phase-law expression [3,21–23], at a constant temperature, pressure, and composition, the austenite and ferrite two-phase region equilibrates with a zero degree of freedom. The carbon concentration in the system equilibrates through the continuous austenite-to-ferrite transformation and primarily promotes the decarburization of the ferrite layer [24]. The carbon content on the material surface decreases from C 0 to C α1 (Figure 7b). With a further increase in temperature, between A3 and the G-point temperature (912°C) of the phase diagram, the matrix exists as a single austenite phase with a carbon content of C 0. Under a constant temperature, constant pressure, and constant composition, the degree of freedom of the austenite single-phase system is one, and carbon diffusion can spontaneously proceed, resulting in the formation of a partially decarburized layer on the surface. The surface carbon concentration decreases from C 0 to C γ1. As decarburization proceeds, the decarburized ferrite layer gradually precipitates on the surface, decreasing the material’s surface carbon content from C γ1 to C α2 (Figure 7c) and forming a complete surface. The diffusion coefficient of the carbon atoms, as well as the thickness of the partially decarburized layer, increases with the increasing temperature due to the coexistence of the FD and partially decarburized layers. When the temperature increases above the G-point temperature presented in the phase diagram, the same carbon atoms diffuse into the austenite single-phase region. The depth of the decarburization layer gradually increases with the continuous diffusion of carbon atoms, decreasing the carbon content from C 0 to C γ2 (Figure 7d). Further, the decarburization is mainly based on the partially decarburized layer.

Figure 7 Schematic of decarburization for different temperature ranges: (a) Fe–C phase diagram. Decarburization schematic: (b) A1 < T < A3, (c) A3 < T < G, and (d) G < T.
Figure 7

Schematic of decarburization for different temperature ranges: (a) Fe–C phase diagram. Decarburization schematic: (b) A1 < T < A3, (c) A3 < T < G, and (d) G < T.

4.2 Analysis of surface oxidation mechanism

Figure 8 displays the scale structure of the steel sample at different temperatures. EBSD was used to detect the phase structure of the iron-oxide scale of the steel sample at various temperatures. The result shows that the iron-oxide-scale structure is relatively tight in the range of 800–900°C without apparent gaps. At 800°C, the iron-oxide scale mainly comprises Fe3O4 and FeO, and the proportion of Fe3O4 reaches 38.3% (Figure 8a). At 900°C, the two phases of Fe3O4 and FeO remain unchanged, but the proportion of Fe3O4 increases to 57.3% (Figure 8b). At 1,000°C, the thickness of the iron-oxide scale rapidly increases, and two changes occur. However, the proportion of FeO gradually increases to 66%. In addition, the broken state and morphology of the iron-oxide scale correspond, as observed via SEM.

Figure 8 EBSD analysis of the oxide sheet of the steel sample at: (a) 800°C, (b) 900°C, and (c) 1,000°C.
Figure 8

EBSD analysis of the oxide sheet of the steel sample at: (a) 800°C, (b) 900°C, and (c) 1,000°C.

The EBSD phase analysis revealed that ∼5.8% of Cr2O3 exists in the iron-oxide scale. The Cr atoms in the steel sample are prone to surface oxygen bonding and gradually diffuse from the matrix to the outside to form oxides. Cr2O3 enrichment forms a dense protective film on the surrounding oxide scale, inhibiting further matrix oxidation [25]. When the diffusion activation energy of iron and oxygen atoms is insufficient, the dense protective film formed via Cr2O3 remains unbroken, resulting in the formation of a thinner oxide-scale surface. Cr2O3 remains close to the metal–oxide interface and comprises small columnar crystals distributed along the oxide growth direction. With further Cr diffusion, Cr2O3 combines with FeO to form Fe–Cr spinel (FeCr2O4). Fe–Cr spinel has a dense structure [26], which inhibits the oxidation behavior of steel to a certain extent. Although the compactness of Cr spinel (formed due to Fe) strengthens the oxide scale–substrate bond, it is difficult to remove in the subsequent pickling and phosphating. Furthermore, online scanning of the elemental distribution revealed the segregation of Mn between the oxide scale and the substrate. In stainless steel, Mn and Cr are commonly combined to form Mn–Cr spinel, distributed between the oxide scale and the substrate, and have an inhibitory effect. However, this spinel was not found in the phase structure. It will further be studied and analyzed herein.

4.3 Interaction of surface decarburization and oxidation

During heating and high-temperature cooling of steel, decarburization and oxidation occur simultaneously. Figure 9 presents the schematic of the decarburization process and oxidation behavior of the material surface. During surface decarburization, carbon atoms diffuse from the substrate matrix to the surface layer, and a chemical reaction occurs in the atmosphere around the surface layer so that the carbon content at the substrate edge is reduced. The diffusion is unidirectional, and only the carbon concentration (or carbon potential) in the surrounding atmosphere is low. When the concentration of the matrix carbon increases, the diffusion activation energy can initiate the movement of the diffused atoms. CO or CO2 is obtained as the product of decarburization. As the oxidation conditions vary, the structure of the iron-oxide scale includes FeO, Fe3O4, and Fe2O3 from the inside to the outside (near the substrate to the inside).

Figure 9 Mechanism of surface decarburization and oxide-scale formation.
Figure 9

Mechanism of surface decarburization and oxide-scale formation.

The competitive mechanisms of the decarburization and oxidation behavior of the steel surface with varying temperatures are as follows. The surface oxidation of steel parabolically increases as the temperature changes. In contrast, the increase in the oxide-scale thickness is relatively slow below 900°C. In the parabolic concave region, this temperature range represents the rapid formation zone of the completely decarburized layer. Above 900°C, the oxide-scale thickness is in the parabolic up zone while the surface decarburization rate decreases. Moreover, the rate of decarburization increases at 1,000°C. The first-order derivation of the surface decarburization and oxide-scale thickness is converted into the surface decarburization and oxidation rate. Figure 10b presents a comparison chart for surface decarburization and oxidation changes. Surface decarburization and oxidation occur at 950°C at the critical point and below 950°C. Furthermore, the competition between both processes is fierce. Above 950°C, the surface decarburization and oxidation rates harmonize and increase together, and the figure can be divided into three regions. First, decarburization dominates below 850°C mainly because the complete decarburization behavior of the two-phase region provides the driving force. At ∼900°C, surface decarburization and oxidation achieve a short-term equilibrium, the inhibitory effect of the oxidation products on the diffusion of carbon atoms in the matrix sets in, and the surface decarburization rate decreases. At ∼950°C, the inhibitory effect of surface oxidation on surface decarburization culminates, and the decarburization rate decreases. Above 950°C, the iron-oxide scale foams and cracks under high-temperature stress. The carbon atoms eliminate the bondage in the iron-oxide scale, and several oxygen atoms enter through the gap and react with the carbon atoms. Simultaneously, the decarburization produces CO or CO2 and further intensifies the crushing process of the oxide scale.

Figure 10 Comparison of surface decarburization and oxidation changes: (a) depth and (b) rate.
Figure 10

Comparison of surface decarburization and oxidation changes: (a) depth and (b) rate.

The influence of the phase structure of the oxide scale on the decarburization behavior is discussed next. In addition to the competition between oxidation and decarburization rates, the influence of the phase structure of the iron-oxide scale on the diffusion of carbon atoms plays an important role in the process of surface decarburization and oxidation. The FeO layer in the inner layer of the oxide scale is flocculent and willow-like, and its structure is loose. The gap between the iron-oxide scales promotes the diffusion of carbon atoms, causing the decarburization chemical reaction to proceed rapidly. That is, the FeO layer promotes the surface decarburization behavior. The phase structure of the outer layer of the iron-oxide scale comprises Fe3O4, which is a densely connected, block-like particle with a dense structure and has a denser bond with the substrate. However, it is not easy to remove. Between 850 and 950°C, the Fe3O4 layer is the main structure of the iron-oxide scale, and its proportion is ∼57%. Its dense structure inhibits the outward diffusion of carbon atoms, which slows down the decarburization rate. Thus, the Fe3O4 layer inhibits surface decarburization.

The impact of the thickness of the iron-oxide scale on the decarburization layer is subsequently discussed. In principle, the thicker the iron-oxide scale, the greater the barrier between the matrix and the outside atmosphere; the diffusion of carbon atoms is reduced, and the decarburization is inhibited. However, it is necessary to analyze the phase structure of the iron-oxide scale comprehensively. As mentioned above, FeO has a loose texture, which easily causes cracks to form in the iron-oxide scale. Fe3O4 has a dense texture and can be closely combined with the matrix. Therefore, the thicker FeO phase promotes the decarburization behavior compared with the thinner Fe3O4 phase.

5 Conclusions

  1. The depth of the total decarburization layer of Cr–Mo cold heading steel increases as the temperature increases. Between 750 and 850°C, the FD layer is more prominent, and the peak temperature of the completely decarburized layer is 800°C. Above 1,000°C, the total decarburization rate is the fastest. After the material surface changes, the completely decarburized layer intensifies, and the TD depth is considerably reduced. The reduction rate exceeds 50% of the original steel sample at the same temperature.

  2. The thickness of the surface oxide scale of the Cr–Mo cold heading steel parabolically increases as the temperature increases. Between 700 and 950°C, the oxidation weight gain is 0.091 g·cm−2, and the main structure is the Fe3O4 layer. It is dense, and the oxidation rate begins to accelerate at 950°C. At 1,100°C, the oxidation weight gain reaches 0.417 g·cm−2, the proportion of the FeO layer reaches 66%, the oxide scale is loose, and Cr2O3 enrichment occurs in the oxide scale.

  3. The competitive mechanism of surface decarburization and oxidation behavior of Cr–Mo cold heading steel is as follows. Below 950°C, the competition between the surface decarburization and oxidation rate is fierce. Below 850°C, the decarburization rate exceeds the oxidation rate, and the surface decarburization rate exceeds the oxidation rate. At 900°C, surface decarburization and oxidation achieve a short-term equilibrium, and the Fe3O4 layer inhibits decarburization. The decarburization rate drops to a trough at 950°C. Above 950°C, the FeO layer promotes surface decarburization, and the surface decarburization and oxidation rates simultaneously increase.

  4. For controlling the surface decarburization and oxidation of Cr–Mo cold heading steel, priority should be given to flame peeling or billet grinding, and the heating and cooling processes should be controlled to shorten the temperature in the two-phase zone. In addition, the temperature range can be 900–950°C, the phase structure of the surface oxide scale should be controlled, surface decarburization should be inhibited, and the thickness of the decarburization layer should be reduced.

Acknowledgments

The work is financial supported by Hebei Provincial Foundation under grant Nos. E2021208006, E2021208017, and E2019208308. National Nature Science Foundation of China under grant Nos. 51974102 and 52174311. Key R & D projects in Hebei Province, Nos. QN2019029 and 19211009D.

  1. Funding information: The work is financial supported by National Nature Science Foundation of China under grant Nos. 51974102 and 51974103, Hebei Provincial Foundation under grant Nos. E2021208006, E2021208017 and E2019208308, Key R&D projects in Hebei Province Nos. QN2019029, 20311003D and 19211009D.

  2. Author contributions: Jilin Chen and Yaxu Zheng conceived the work. Jilin Chen, Guanghong Feng, Jian Ma, Peng Lin, Ningtao Wang, Honglei Ma, and Jian Zheng performed the experiment and analyzed the date. Jilin Chen wrote the manuscript with help from all the other authors. Guanghong Feng supervised the whole project.

  3. Conflict of interest: The authors declare that Authors state no conflict of interest.

  4. Informed consent: The authors claim that this paper consists of original, unpublished work which is not under consideration for publication elsewhere. All authors have read the manuscript and approved to submit to your journal.

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Received: 2022-03-31
Revised: 2022-07-01
Accepted: 2022-08-22
Published Online: 2022-10-28

© 2022 Jilin Chen et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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https://doi.org/10.1515/htmp-2022-0237
Keywords for this article
Cr–Mo cold heading steel; decarburization; oxidation; competitive mechanisms
Creative Commons
BY 4.0

Articles in the same Issue

  1. Research Articles
  2. Numerical and experimental research on solidification of T2 copper alloy during the twin-roll casting
  3. Discrete probability model-based method for recognition of multicomponent combustible gas explosion hazard sources
  4. Dephosphorization kinetics of high-P-containing reduced iron produced from oolitic hematite ore
  5. In-phase thermomechanical fatigue studies on P92 steel with different hold time
  6. Effect of the weld parameter strategy on mechanical properties of double-sided laser-welded 2195 Al–Li alloy joints with filler wire
  7. The precipitation behavior of second phase in high titanium microalloyed steels and its effect on microstructure and properties of steel
  8. Development of a huge hybrid 3D-printer based on fused deposition modeling (FDM) incorporated with computer numerical control (CNC) machining for industrial applications
  9. Effect of different welding procedures on microstructure and mechanical property of TA15 titanium alloy joint
  10. Single-source-precursor synthesis and characterization of SiAlC(O) ceramics from a hyperbranched polyaluminocarbosilane
  11. Carbothermal reduction of red mud for iron extraction and sodium removal
  12. Reduction swelling mechanism of hematite fluxed briquettes
  13. Effect of in situ observation of cooling rates on acicular ferrite nucleation
  14. Corrosion behavior of WC–Co coating by plasma transferred arc on EH40 steel in low-temperature
  15. Study on the thermodynamic stability and evolution of inclusions in Al–Ti deoxidized steel
  16. Application on oxidation behavior of metallic copper in fire investigation
  17. Microstructural study of concrete performance after exposure to elevated temperatures via considering C–S–H nanostructure changes
  18. Prediction model of interfacial heat transfer coefficient changing with time and ingot diameter
  19. Design, fabrication, and testing of CVI-SiC/SiC turbine blisk under different load spectrums at elevated temperature
  20. Promoting of metallurgical bonding by ultrasonic insert process in steel–aluminum bimetallic castings
  21. Pre-reduction of carbon-containing pellets of high chromium vanadium–titanium magnetite at different temperatures
  22. Optimization of alkali metals discharge performance of blast furnace slag and its extreme value model
  23. Smelting high purity 55SiCr automobile suspension spring steel with different refractories
  24. Investigation into the thermal stability of a novel hot-work die steel 5CrNiMoVNb
  25. Residual stress relaxation considering microstructure evolution in heat treatment of metallic thin-walled part
  26. Experiments of Ti6Al4V manufactured by low-speed wire cut electrical discharge machining and electrical parameters optimization
  27. Effect of chloride ion concentration on stress corrosion cracking and electrochemical corrosion of high manganese steel
  28. Prediction of oxygen-blowing volume in BOF steelmaking process based on BP neural network and incremental learning
  29. Effect of annealing temperature on the structure and properties of FeCoCrNiMo high-entropy alloy
  30. Study on physical properties of Al2O3-based slags used for the self-propagating high-temperature synthesis (SHS) – metallurgy method
  31. Low-temperature corrosion behavior of laser cladding metal-based alloy coatings on EH40 high-strength steel for icebreaker
  32. Study on thermodynamics and dynamics of top slag modification in O5 automobile sheets
  33. Structure optimization of continuous casting tundish with channel-type induction heating using mathematical modeling
  34. Microstructure and mechanical properties of NbC–Ni cermets prepared by microwave sintering
  35. Spider-based FOPID controller design for temperature control in aluminium extrusion process
  36. Prediction model of BOF end-point P and O contents based on PCA–GA–BP neural network
  37. Study on hydrogen-induced stress corrosion of 7N01-T4 aluminum alloy for railway vehicles
  38. Study on the effect of micro-shrinkage porosity on the ultra-low temperature toughness of ferritic ductile iron
  39. Characterization of surface decarburization and oxidation behavior of Cr–Mo cold heading steel
  40. Effect of post-weld heat treatment on the microstructure and mechanical properties of laser-welded joints of SLM-316 L/rolled-316 L
  41. An investigation on as-cast microstructure and homogenization of nickel base superalloy René 65
  42. Effect of multiple laser re-melting on microstructure and properties of Fe-based coating
  43. Experimental study on the preparation of ferrophosphorus alloy using dephosphorization furnace slag by carbothermic reduction
  44. Research on aging behavior and safe storage life prediction of modified double base propellant
  45. Evaluation of the calorific value of exothermic sleeve material by the adiabatic calorimeter
  46. Thermodynamic calculation of phase equilibria in the Al–Fe–Zn–O system
  47. Effect of rare earth Y on microstructure and texture of oriented silicon steel during hot rolling and cold rolling processes
  48. Effect of ambient temperature on the jet characteristics of a swirl oxygen lance with mixed injection of CO2 + O2
  49. Research on the optimisation of the temperature field distribution of a multi microwave source agent system based on group consistency
  50. The dynamic softening identification and constitutive equation establishment of Ti–6.5Al–2Sn–4Zr–4Mo–1W–0.2Si alloy with initial lamellar microstructure
  51. Experimental investigation on microstructural characterization and mechanical properties of plasma arc welded Inconel 617 plates
  52. Numerical simulation and experimental research on cracking mechanism of twin-roll strip casting
  53. A novel method to control stress distribution and machining-induced deformation for thin-walled metallic parts
  54. Review Article
  55. A study on deep reinforcement learning-based crane scheduling model for uncertainty tasks
  56. Topical Issue on Science and Technology of Solar Energy
  57. Synthesis of alkaline-earth Zintl phosphides MZn2P2 (M = Ca, Sr, Ba) from Sn solutions
  58. Dynamics at crystal/melt interface during solidification of multicrystalline silicon
  59. Boron removal from silicon melt by gas blowing technique
  60. Removal of SiC and Si3N4 inclusions in solar cell Si scraps through slag refining
  61. Electrochemical production of silicon
  62. Electrical properties of zinc nitride and zinc tin nitride semiconductor thin films toward photovoltaic applications
  63. Special Issue on The 4th International Conference on Graphene and Novel Nanomaterials (GNN 2022)
  64. Effect of microstructure on tribocorrosion of FH36 low-temperature steels
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