Saw blade steel with excellent repeated welding performance and manufacturing method thereof

Abstract

The invention relates to the technical field of black metal materials, in particular to saw blade steel with excellent repeated welding performance and a manufacturing method of the saw blade steel. The high-strength and high-toughness steel comprises the following chemical components in percentage by weight: 0.46%-0.55% of C, 0.3%-0.8% of Si, 0.4%-0.6% of Mn, less than or equal to 0.025% of P, less than or equal to 0.010% of S, 0.0010%-0.0020% of B, 0.10%-0.20% of Zr, 0.24%-0.35% of Co, 1.2%-1.5% of Co / (C / 10 + Mn / 5 + 60B) and the balance of Fe and inevitable impurities. According to the method, Zr, B and Co are added, and the processes of converter smelting, VD refining, continuous casting, slab heating, rolling and heat treatment are carried out, so that the steel strength and sufficient hardenability are guaranteed, the brittleness of a welding part and a heat affected zone is reduced, and the repeated welding performance of the saw blade steel is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ferrous materials, in particular to a saw blade steel with excellent repeated welding performance and a manufacturing method thereof. BACKGROUND

[0002] A diamond saw blade is a key tool for processing hard stone such as granite and marble. The structure of the diamond saw blade usually takes a saw blade steel as a base body, and a diamond cutter head is welded at a tooth tip. In actual use, the diamond cutter head will be worn out and fail. At this time, the old cutter head can be stripped and a new cutter head is welded again, so that the saw blade base body can be repeatedly used. Therefore, the repeated welding times of the diamond cutter head that the saw blade base body can withstand directly determines the service life and production cost of the entire saw blade.

[0003] The currently widely used saw blade steel usually has high carbon content and alloy element content, and has good hardenability. However, in the cutter head welding process, the welding position will undergo repeated high-temperature heating and subsequent cooling. Under the action of the heat cycle, the heat-affected zone of the saw blade steel is prone to grain coarsening and forms a hard and brittle martensite structure. This organizational change leads to a decrease in toughness and an increase in brittleness of the region, which is prone to microcracks due to stress concentration in use. These cracks continue to expand under the action of sawing load, eventually leading to base body cracking or failure. The conventional repeated welding times of the currently marketed diamond saw blade base body is only 4-5 times, which severely limits the service life of the saw blade and also brings higher comprehensive use cost to the user.

[0004] There are some patent documents about the improvement of saw blade steel materials in the prior art. For example, the patent document with the publication number CN100366779C discloses "a stone cutting saw blade steel and a manufacturing method thereof". The technology can make the hardness of the saw blade body reach more than 40HRC, and the hardness is uniform, but it does not propose a specific solution to the organization performance regulation of the welding heat-affected zone and the improvement of the repeated welding times. Another patent with the publication number CN104532150B discloses "an economic ultra-wide saw blade steel". The technical focus of the technology is to realize high strength and toughness and economic production of the ultra-wide saw blade, and it does not involve how to improve the organizational stability and crack resistance of the material under the condition of multiple welding heat cycles.

[0005] In summary, although the prior art has improved the strength, hardness or toughness of the saw blade base body to some extent, it has not effectively solved the key technical problem of the brittle heat-affected zone and the easy production of microcracks under the repeated welding condition, resulting in a limited repeated welding times of the base body. SUMMARY

[0006] In order to overcome the deficiencies of the prior art, the present application provides a saw blade steel with excellent repeated welding performance and a manufacturing method thereof, which significantly improves the repeated welding performance of the saw blade steel while maintaining the necessary mechanical properties of the substrate, thereby prolonging the service life of the saw blade and reducing production costs.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A saw blade steel with excellent repeated welding performance is composed of the following chemical components by weight percentage:

[0009] C: 0.46%~0.55%, Si: 0.3%~0.8%, Mn: 0.4%~0.6%, P≤0.025%, S≤0.010%, B: 0.0010%~0.0020%, Zr: 0.10%~0.20%, Co: 0.24%~0.35%, Co / (C / 10+Mn / 5+60B): 1.2~1.5, and the rest is Fe and unavoidable impurities.

[0010] The effects of selecting the types and contents of the above alloying elements are as follows:

[0011] 1. C is an important element for ensuring the strength, hardness and wear resistance of the saw blade steel. High C content can reduce the corrosion resistance of the steel and significantly increase the quenching cracking tendency of the steel. Therefore, the C content in the steel is precisely controlled to be 0.46%~0.55%.

[0012] 2. Si is a good deoxidizer that can improve the strength and wear resistance of the steel, but an increase in Si content will reduce the plasticity and toughness of the steel. Therefore, the Si content in the steel is precisely controlled to be 0.3%~0.8%.

[0013] 3. Mn can improve the hardenability of the steel, while refining the pearlite interlamellar spacing and improving the strength of the pearlite. However, excessive Mn content will reduce the ductility of the steel. Therefore, the Mn content in the steel is precisely controlled to be 0.4%~0.6%.

[0014] 4. P is a harmful element in steel that can cause cold brittleness in the steel, but strict control of P content will increase production costs. Therefore, the P content in the steel is precisely controlled to be ≤0.025%.

[0015] 5. S is a harmful element in steel that causes hot brittleness in the steel, reducing the ductility and toughness of the steel. Therefore, the S content in the steel is precisely controlled to be ≤0.010%.

[0016] 6、Zr is called the "vitamin" of metallurgical industry, has strong deoxidation, denitrogenation, desulfurization effect, can significantly refine the austenite grain of steel. But excessive addition of Zr will reduce the strength of steel, damage the weldability of steel. Therefore, the Zr content in the steel is accurately controlled to be 0.10%-0.20%.

[0017] 7、Co can reduce the stability of supercooled austenite, increase the pearlite transformation speed of supercooled austenite, thereby promoting the generation of pearlite, but too high Co content will make the plastic deformation performance of the steel worse, and bring difficulties to forging and rolling production. Therefore, the Co content in the steel is accurately controlled to be 0.24%-0.35%.

[0018] 8、Trace B can significantly improve the hardenability of the steel, but too much B will easily cause grain coarsening. Therefore, the B content in the steel is accurately controlled to be 0.0010%-0.0020%.

[0019] 9、The Co / (C / 10+Mn / 5+60B) is controlled to be 1.2-1.5, on the one hand, it ensures that the steel has sufficient hardenability when quenched, on the other hand, it inhibits the generation of hard and brittle martensite structure at the welding position and heat affected zone, and promotes the generation of better plastic and ductile pearlite structure, thereby reducing the brittleness of the welding position and heat affected zone, and improving the plasticity and ductility.

[0020] The saw blade steel has a thickness of 6-12mm, a hardness HRC of 43-48, a yield strength of ≥1225MPa, a tensile strength of ≥1513MPa, and an elongation of ≥8%.

[0021] The saw blade steel has a room temperature impact energy AKV of ≥31J, a hardness HRC change of welding heat affected zone of each welding of ≤0.8, and a repeated welding number of ≥7.

[0022] The manufacturing method of the saw blade steel with excellent repeated welding performance specifically comprises the following steps:

[0023] 1) Converter smelting and VD refining:

[0024] The converter is used for blocking slag tapping, and the thickness of the slag layer is controlled to be 50-60mm; the VD refining pressure maintaining time is controlled to be 15-25min, [H] is controlled to be ≤2ppm, [O] is controlled to be <20ppm, and [N] is controlled to be <50ppm; the static time before the ladle is put into the machine is controlled to be 20-30min.

[0025] 2) Continuous casting:

[0026] The electromagnetic stirring is used in the secondary cooling zone, and the current intensity is controlled to be 400-600A; the pressing operation is located in the interval of the center solid phase rate of 0.5-0.7 of the casting blank, the pressing amount is 8-9mm, and the pressing rate is kept at 1.2-1.5mm / min.

[0027] 3) slab heating:

[0028] The temperature of the second heating section of the slab is controlled to be 1160-1230 DEG C, the temperature of the soaking section is controlled to be 1180-1220 DEG C, and the total furnace time is 0.8-1.2 min / mm.

[0029] 4) rolling:

[0030] The opening rolling temperature is not less than 1100 DEG C, the reduction of the first three passes is greater than or equal to 30%, the reduction of the last two passes is 8-10%, and the final rolling temperature is 880-900 DEG C.

[0031] 5) heat treatment:

[0032] The heat treatment adopts a quenching and tempering process, the quenching temperature is 850-880 DEG C, the holding time is 8-12 min, the tempering temperature is 450-470 DEG C, and the holding time is 4-6 h.

[0033] Further, in 1), the target superheat of the tundish is controlled to be 20-25 DEG C.

[0034] Further, in 2), the whole process is protected casting.

[0035] Further, in 2), the continuous casting process adopts constant speed casting, and the casting speed is stabilized at 0.9-1.1 m / min.

[0036] Further, in 2), the cast blank is stacked and slowly cooled for more than 48 h.

[0037] Further, in 5), the heat treatment adopts an oil quenching and tempering process, the oil quenching temperature is 850-880 DEG C, the holding time is 8-12 min, the tempering temperature is 450-470 DEG C, and the holding time is 4-6 h.

[0038] Further, in 5), the saw blade steel obtained after heat treatment is a tempered troostite structure.

[0039] Compared with the prior art, the beneficial effects of the present application are:

[0040] 1. Excellent repeated welding performance and microstructure stability: through the synergistic effect of C-Mn-B-Co multi-element alloy system, and by precisely controlling the Co / (C / 10+Mn / 5+60B) ratio in the range of 1.2~1.5, the formation of hard and brittle martensite structure in the welding heat affected zone is significantly inhibited, and the generation of pearlite structure with better plasticity and toughness is promoted. This design effectively reduces the brittleness tendency of the welding area, significantly improves the crack resistance of the welded joint. With the addition of an appropriate amount of Zr element, the original austenite grains are effectively refined and the grain coarsening under the influence of welding cycle heat is inhibited, thereby ensuring the long-term stability of the welding heat affected zone structure, so that the saw blade substrate can withstand ≥7 times of repeated welding, which is much higher than the current market product level of 4~5 times.

[0041] 2. Through the design of smelting process, the casting blank defects are reduced, and good casting blank quality is obtained; through the design of rolling process, the microstructure uniformity is improved and the grains are refined, which lays the foundation for obtaining good strength and plasticity; through the design of heat treatment process, the tempered troostite structure with reasonable matching of strength and toughness is obtained, which provides reliable guarantee for the high performance and consistency of the product.

[0042] 3. Excellent comprehensive mechanical property matching: the saw blade steel obtained by the present application has a stable hardness of 43~48HRC, a yield strength of ≥1225MPa, a tensile strength of ≥1513MPa, an elongation of ≥8%, and an impact energy AKV of ≥31J at room temperature. The various performance indicators are well matched, which realizes high strength and hardness while maintaining sufficient toughness and plasticity, significantly improving the load capacity, wear resistance and impact failure resistance of the saw blade in actual use.

[0043] 4. The performance degradation of the welding heat affected zone is extremely low: the hardness fluctuation of the welding heat affected zone is strictly controlled at ≤0.8HRC / welding, which is significantly better than conventional saw blade steel materials. This indicates that the material can maintain excellent microstructure stability and mechanical property consistency after multiple high-temperature welding thermal cycles, greatly prolonging the service life of the saw blade substrate.

[0044] 5. Significant economic benefits and broad application prospects: under the premise of not significantly increasing the production cost, the repeated welding times and service life of the saw blade steel are significantly improved, the user's overall use cost and resource consumption are reduced, and it is suitable for high-end stone processing fields with extremely high reliability and service life requirements, which has important popularization and application value. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is the metallographic structure diagram of Example 1 of the present application. DETAILED DESCRIPTION

[0046] The application discloses a saw blade steel with excellent repeated welding performance and a manufacturing method thereof. Those skilled in the art can refer to the content herein and appropriately improve process parameters to realize. It is particularly pointed out that all similar replacements and changes are obvious to those skilled in the art and are regarded as being included in the application. The method and application of the application have been described through preferred embodiments, and relevant personnel can obviously make changes or appropriate changes and combinations to the method and application described herein without departing from the content, spirit and scope of the application, to realize and apply the technical solution of the application.

[0047] A saw blade steel with excellent repeated welding performance is composed of the following chemical components in percentage by weight:

[0048] C: 0.46%~0.55%, Si: 0.3%~0.8%, Mn: 0.4%~0.6%, P≤0.025%, S≤0.010%, B: 0.0010%~0.0020%, Zr: 0.10%~0.20%, Co: 0.24%~0.35%, Co / (C / 10+Mn / 5+60B): 1.2~1.5, and the rest is Fe and inevitable impurities.

[0049] The manufacturing method of the above-mentioned saw blade steel with excellent repeated welding performance mainly includes a converter smelting, VD refining, continuous casting, slab heating, rolling and heat treatment process flow, and specifically includes the following steps:

[0050] 1) Converter smelting + VD refining:

[0051] Converter slag blocking is adopted to control the slag layer thickness to be 50~60mm, so as to improve the alloy element yield and reduce the inclusion content; the VD refining pressure maintaining time is controlled to be 15~25min to reduce the gas content, and the requirements are [H]≤2ppm, [O]<20ppm and [N]<50ppm; the static time before the tundish is controlled to be 20~30min to make the molten steel composition uniform; and the target superheat degree of the tundish is controlled to be 20~25℃ to ensure the casting blank quality and production efficiency.

[0052] 2) Continuous casting:

[0053] The whole process is protected pouring, and electromagnetic stirring is adopted in the secondary cooling zone to refine the grains, and the current intensity is 400~600A; in order to eliminate the defects such as segregation, porosity and shrinkage hole of the casting blank, light press-down is adopted at the solidification end, the press-down interval is at the position of the center solid phase rate of 0.5~0.7, the press-down amount is 8~9mm, the press-down rate is 1.2~1.5mm / min, and the constant speed casting of 0.9~1.1m / min is adopted in the continuous casting process; and the casting blank is stacked and slowly cooled for more than 48h.

[0054] 3) Slab heating:

[0055] The slab second heating section temperature is 1160-1230 DEG C, the soaking section temperature is 1180-1220 DEG C, and the total furnace time is 0.8-1.2 min / mm, so as to ensure that the alloy elements are dissolved fully and uniformly.

[0056] 4) Rolling:

[0057] The open rolling temperature is not less than 1100 DEG C, and the first three pass reduction rate is greater than or equal to 30%, so that the rolling force penetrates to the core of the blank, the uniformity of the structure is improved, the last two pass reduction rate is 8-10%, so as to improve the rolling shape, and the final rolling temperature is 880-900 DEG C, so as to refine the grain and improve the plasticity of the steel.

[0058] 5) Heat treatment:

[0059] The heat treatment adopts oil quenching + tempering process, the oil quenching temperature is 850-880 DEG C, the holding time is 8-12 min, the tempering temperature is 450-470 DEG C, and the holding time is 4-6 h, and the structure of the steel is tempered troostite structure.

[0060] The steel smelting chemical components of the embodiment and the comparative example of the application are shown in table 1, the steel process parameters of the embodiment and the comparative example of the application are shown in table 2, table 3, table 4, table 5, the steel heat treatment process parameters of the embodiment and the comparative example of the application are shown in table 6, and the mechanical properties and repeated welding properties of the embodiment and the comparative example of the application are shown in table 7.

[0061] Table 1 Steel smelting chemical components (wt%) of the embodiment and the comparative example of the application

[0062]

[0063] Table 2 Steel process parameters one of the embodiment and the comparative example of the application

[0064]

[0065] Table 3 Steel process parameters two of the embodiment and the comparative example of the application

[0066]

[0067] Table 4 Steel process parameters three of the embodiment and the comparative example of the application

[0068]

[0069] Table 5 Steel process parameters four of the embodiment and the comparative example of the application

[0070]

[0071] Table 6 Steel heat treatment process parameters of the embodiment and the comparative example of the application

[0072]

[0073] Table 7 Mechanical properties and repeated welding properties of inventive examples and comparative examples

[0074]

[0075] As can be seen from the data in Table 7, the saw blade steel prepared in the inventive examples is significantly superior to the comparative examples in terms of mechanical properties and repeated welding properties. Specifically, the yield strength (Rp 0.2 ) of the inventive examples is higher than 1225 MPa, the tensile strength (Rm) is more than 1513 MPa, the elongation (A) is maintained at more than 8%, the room temperature impact energy (AKV) is not less than 31 J, and the hardness is stable in the range of 43-48 HRC. More importantly, in terms of hardness change in the welding heat affected zone, the inventive examples only show a slight fluctuation of 0.5-0.8 HRC per welding, which is far lower than the 56-58 HRC per welding of the comparative examples, reflecting excellent resistance to temper softening and microstructure stability. Finally, the saw blade steel of the present application achieves a repeated welding life of ≥7 times, which greatly exceeds the level of 2-4 times of the comparative examples, fully proving the effectiveness and advancement of the composition design and process control.

[0076] The above description is only the preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art, according to the technical solution and the inventive concept of the present application, within the technical range disclosed by the present application, makes equivalent replacement or change, should be covered within the protection scope of the present application.

Claims

1. A saw blade steel with excellent repeatable welding performance, characterized in that, It is composed of the following chemical components in weight percentage: C: 0.46%~0.55%, Si: 0.3%~0.8%, Mn: 0.4%~0.6%, P≤0.025%, S≤0.010%, B: 0.0010%~0.0020%, Zr: 0.10%~0.20%, Co: 0.24%~0.35%, Co / (C / 10+Mn / 5+60B): 1.2~1.5, the remainder being Fe and unavoidable impurities; The thickness of the saw blade steel is 6~12mm, the hardness is HRC 43~48, the yield strength is ≥1225MPa, the tensile strength is ≥1513MPa, and the elongation is ≥8%; The room temperature impact energy of the saw blade steel is AKV≥31J, the hardness HRC change of the heat-affected zone per weld is ≤0.8, and the number of repeated welds is ≥7.

2. A method for manufacturing saw blade steel with excellent repeatable welding performance as described in claim 1, characterized in that, The manufacturing method specifically includes the following steps: 1) Converter smelting and VD refining: The slag-blocking tapping method in the converter is adopted to control the slag layer thickness to 50~60mm; The holding time for VD refining is controlled at 15~25min, and [H] ≤2ppm, [O] <20ppm, [N] <50ppm; The sedation time of the ladle before loading it into the machine should be controlled at 20-30 minutes. 2) Continuous casting: The second cooling zone uses electromagnetic stirring, with the current intensity controlled at 400~600A; The pressing operation is performed in the range of 0.5~0.7 solid fraction at the center of the billet, with a pressing amount of 8~9 mm and a pressing rate of 1.2~1.5 mm / min; 3) Slab heating: The temperature of the second heating section of the slab is controlled at 1160~1230℃, the temperature of the soaking section is 1180~1220℃, and the total time in the furnace is 0.8~1.2min / mm; 4) Rolling: The initial rolling temperature is not less than 1100℃, the reduction rate of the first three passes is ≥30%, the reduction rate of the last two passes is 8%~10%, and the final rolling temperature is 880~900℃. 5) Heat treatment: The heat treatment adopts quenching and tempering processes. The quenching temperature is 850~880℃ and the holding time is 8~12min. The tempering temperature is 450~470℃ and the holding time is 4~6h.

3. The method for manufacturing saw blade steel with excellent repeatable welding performance according to claim 2, characterized in that, 1) In the intermediate batch, the target superheat is controlled at 20~25℃.

4. The method for manufacturing saw blade steel with excellent repeatable welding performance according to claim 2, characterized in that, 2) During the entire pouring process, protection is provided.

5. The method for manufacturing saw blade steel with excellent repeatable welding performance according to claim 2, characterized in that, 2) In the continuous casting process, constant casting speed is adopted, and the casting speed is stabilized at 0.9~1.1m / min.

6. The method for manufacturing saw blade steel with excellent repeatable welding performance according to claim 2, characterized in that, 2) During the process, the billets are stacked and slowly cooled for more than 48 hours after being removed from the production line.

7. The method for manufacturing saw blade steel with excellent repeatable welding performance according to claim 2, characterized in that, 5) The heat treatment adopts oil quenching and tempering process. The oil quenching temperature is 850~880℃ and the holding time is 8~12min. The tempering temperature is 450~470℃ and the holding time is 4~6h.

8. The method for manufacturing saw blade steel with excellent repeatable welding performance according to claim 2, characterized in that, In 5), the microstructure of the saw blade steel obtained after heat treatment is tempered troostite.

Images