A tape for a measuring tape and a method for manufacturing the same

Abstract

This invention relates to the field of metallurgical technology, specifically to a high-quality tape for measuring instruments and its preparation method. Through composition optimization—increasing the carbon content to 0.51-0.56%, manganese content to 0.70-0.90%, and chromium content to 0.20-0.40%—and synergistic optimization of the preparation process, this invention yields a high-purity tape for measuring instruments with a uniform and fine microstructure and minimal surface decarburization. After subsequent cold rolling, slitting, and heat treatment to produce an ultra-thin tape of 0.06-0.08 mm, this tape possesses both high hardness and excellent straightness and rigidity, solving the problems of insufficient hardness and poor shape in existing materials at thin dimensions. Currently, there are no products with comparable performance on the market. This invention's product is highly competitive and can be widely used in the manufacture of high-end measuring instruments.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a high-quality tape for measuring tapes and its preparation method. Background Technology

[0002] The tape of a standard measuring tape is typically made of 50 steel, with a thickness of 0.09–0.12 mm. After quenching and tempering, its hardness is 48–52 HRC. In use, the tape is pulled out of the casing; after use, a spiral spring inside the casing rotates the tape reel to wind it up.

[0003] The current market demands lighter and longer-lasting measuring tapes, driving the development of thinner tapes. However, when using existing materials to manufacture tapes thinner than 0.08mm, issues arise such as hardness below 51HRC and substandard straightness, failing to meet the standard requirements for measuring tapes. Therefore, developing a thin, high-hardness material for measuring tapes and its manufacturing method is of great significance. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a superior tape for measuring tapes and its preparation method, thereby solving the problem of insufficient hardness and straightness of existing materials at thin dimensions.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: Firstly, a type of tape measure tape, by mass percentage, comprises the following elemental components: C: 0.51~0.56%, Si: 0.25~0.35%, Mn: 0.70~0.90%, Cr: 0.20~0.40%, P≤0.020%, S≤0.020%, Al≤0.010%, Fe.

[0006] Optionally, by mass percentage, it includes the following elemental composition: C: 0.52~0.54%, Si: 0.28~0.33%, Mn: 0.80~0.90%, Cr: 0.25~0.35%, P≤0.018%, S≤0.010%, Al≤0.005%, with the balance being Fe and unavoidable impurities.

[0007] Optionally, the preferred strip is a hot-rolled steel strip with a decarburized layer depth ≤0.06mm and a grain size ≥8.

[0008] This invention optimizes the composition, increasing the carbon content to 0.51-0.56%, manganese content to 0.70-0.90%, and chromium content to 0.20-0.40%. Carbon is the primary strengthening element in steel, crucial for ensuring high strength and hardness in the tempered microstructure after quenching and tempering heat treatment. Manganese and chromium primarily function as solid solution strengthening elements and can improve the steel's resistance to relaxation by inhibiting the nucleation and growth of cementite during tempering, thereby altering its morphology and distribution. This significantly improves the fatigue life of the coil springs used in the production of measuring tapes.

[0009] In a second aspect, the present invention provides a method for preparing a measuring tape as described in the first aspect, comprising the following steps: Converter primary refining: Molten iron and scrap steel are primary refined in a converter to obtain primary steel with carbon ≤0.05% and oxygen ≤500ppm; Ferrosilicon, ferromanganese and ferrochrome alloys are added during tapping for alloying, and aluminum is not allowed for deoxidation in order to reduce the formation of brittle alumina inclusions and improve the cleanliness of the steel. LF refining: The molten steel from the converter primary refining process is transferred to the LF furnace for refining, and the chemical composition of the molten steel is adjusted to the target range to obtain refined molten steel; Continuous casting: Refined molten steel is continuously cast at a constant casting speed of 1.0 m / min to obtain a continuously cast billet; Billet heating: The continuously cast square billet is heated, with a soaking temperature of 1000~1180℃ and a heating time of 2h~4h; Rolling: Perform multi-pass rolling, control the deformation of the strip in the non-recrystallization zone during the finishing rolling stage to ≥30%, and the final rolling temperature to be below 880℃; Coiling: The rolled steel strip is cooled and coiled at a temperature not exceeding 630°C to obtain the high-quality strip for the measuring tape.

[0010] Optionally, the mass ratio of the molten iron is 70% to 90%, the proportion of scrap steel is 10% to 30%, and the initial smelting time is 30 to 45 minutes; the carbon content of the initial smelted steel is ≤0.04%, and the oxygen content is 300 to 500 ppm.

[0011] Optionally, the refining process includes: adding slag-forming materials to form white slag, followed by white slag refining for 30-60 minutes. Slag-forming materials such as lime or fluorite are added to form high-basicity, low-oxidizing white slag. Refining is carried out under stable white slag conditions, utilizing the strong reducing properties of the white slag to deeply deoxidize and desulfurize the molten steel, thereby obtaining highly clean refined steel.

[0012] Optionally, the heating of the continuously cast billet can be carried out using a pusher furnace or a walking beam furnace; and a steam-water spray cooling method can be used during continuous casting.

[0013] Optionally, the rolled steel strip has a thickness of 1.5~4mm and a width of 285~380mm.

[0014] Optionally, the final rolling temperature during the rolling process is 860~870℃; the coiling temperature during the coiling process is 600~630℃. By adjusting the speed of the last flat roll mill and the flow rate of the process cooling pipes, the deformation in the non-recrystallization zone of the strip during the finishing rolling stage is ensured to be ≥30%; at the same time, the final rolling temperature is ensured to be below 880℃ to obtain an ideal hot-rolled microstructure. A suitable coiling temperature is key to controlling the final mechanical properties of the steel strip and avoiding abnormal structures, ensuring uniform and stable strip performance, and obtaining the superior strip for the measuring tape.

[0015] Thirdly, the present invention provides a measuring tape, which is made by cold rolling, slitting and quenching and tempering heat treatment of the measuring tape described in the first aspect using high-quality strip, wherein the measuring tape has a thickness of 0.06~0.08mm and a hardness of 53~57HRC.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: This invention, through synergistic optimization of chemical composition and preparation process, yields a high-purity tape for measuring instruments with uniform and fine microstructure and minimal surface decarburization. After subsequent cold rolling, slitting, and heat treatment, this tape is produced into an ultra-thin tape of 0.06-0.08 mm, exhibiting both high hardness and excellent straightness and rigidity. This solves the problems of insufficient hardness and poor shape in existing materials at thin dimensions. Currently, there are no products with comparable performance on the market. This invention's product is highly competitive and can be widely used in the manufacture of high-end measuring instruments. Detailed Implementation

[0017] The present invention will now be described in further detail: Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0018] All reagents and materials used in this example can be purchased routinely. The quantitative experiments involved in the examples were all repeated at least three times, and the results were averaged.

[0019] The final steel compositions of Examples 1 to 3 are shown in Table 1 below: Table 1. Smelting endpoint composition of each embodiment (unit: mass percentage wt%) Example 1 0.52 0.28 0.80 0.005 0.002 0.25 0.001 Example 2 0.53 0.30 0.85 0.007 0.003 0.30 0.002 Example 3 0.54 0.33 0.90 0.010 0.003 0.35 0.005 Example 1

[0020] A type of tape for measuring tape, prepared by the following method: (1) Converter primary refining: 70% molten iron and 30% scrap steel are primary refined in a converter for 30 minutes to obtain primary steel with 0.03% carbon and 300ppm oxygen. When tapping the steel, ferrosilicon, ferromanganese and ferrochrome alloys are added. It is strictly forbidden to add aluminum for deoxidation.

[0021] (2) LF refining: The primary molten steel is transferred to the LF furnace, and lime and other slag-forming materials are added to form white slag. After that, the steel is refined for 30 minutes under the white slag conditions to adjust the chemical composition of the molten steel to the target range in Table 1 and obtain refined molten steel.

[0022] (3) Continuous casting: Molten steel is hoisted to the continuous casting platform and cooled by steam-water spray with a constant casting speed of 1.0m / min to obtain a 250mm×300mm square billet without corner cracks and subcutaneous cracks.

[0023] (4) Billet heating: After the billet is inspected by the naked eye and found to be free of defects, it is sent to a walking beam furnace for heating. The temperature of the soaking zone is 1000℃ and the heating time is 2h to reduce the formation of decarburized layer.

[0024] (5) Rolling: Adjust the speed of the last flat roll mill and the flow rate of the cooling pipe in the process to ensure that the deformation of the non-recrystallized zone in the finishing rolling stage reaches 30% and the final rolling temperature is 860℃.

[0025] (6) Coiling: After the rolled piece enters the transport chain, it is air-cooled to the coiling temperature and then coiled. The coiling temperature is controlled at 600℃ to obtain hot-rolled premium strip.

[0026] Example 2

[0027] A type of tape for measuring tape, prepared by the following method: (1) Converter primary refining: 80% molten iron and 20% scrap steel are primary refined in a converter for 40 minutes to obtain primary refined molten steel with carbon 0.04% and oxygen 400ppm. Alloying is carried out when tapping the steel, and aluminum deoxidation is strictly prohibited.

[0028] (2) LF refining: The molten steel is transferred to the LF furnace, and after slag formation to form white slag, white slag refining is carried out. The refining time is 40 minutes. The chemical composition of the molten steel is adjusted to the target range in Table 1 to obtain refined molten steel.

[0029] (3) Continuous casting: The process is the same as in Example 1, and a 250mm×300mm square billet is obtained.

[0030] (4) Billet heating: A walking beam furnace is used, with a soaking zone temperature of 1000℃ and a heating time of 3 hours.

[0031] (5) Rolling: Ensure that the deformation in the non-recrystallization zone is 30% and the final rolling temperature is 870℃.

[0032] (6) Coiling: After the rolled piece enters the transport chain, it is air-cooled to the coiling temperature and then coiled. The coiling temperature is 610℃ to obtain hot-rolled premium strip.

[0033] Example 3

[0034] A type of tape for measuring tape, prepared by the following method: (1) Converter primary refining: 90% molten iron and 10% scrap steel are primary refined in a converter for 45 minutes to obtain primary steel with 0.03% carbon and 500ppm oxygen. Alloying is carried out during tapping, and the addition of aluminum for deoxidation is strictly prohibited.

[0035] (2) LF refining: The molten steel is transferred to the LF furnace, and after slag formation to form white slag, white slag refining is carried out. The refining time is 45 minutes. The chemical composition of the molten steel is adjusted to the target range in Table 1 to obtain refined molten steel.

[0036] (3) Continuous casting: The process is the same as in Example 1, and a 250mm×300mm square billet is obtained.

[0037] (4) Billet heating: A walking beam furnace is used, with a soaking zone temperature of 1000℃ and a heating time of 2 hours.

[0038] (5) Rolling: Ensure that the deformation in the non-recrystallization zone is 30% and the final rolling temperature is 860℃.

[0039] (6) Coiling: After the rolled piece enters the transport chain, it is air-cooled to the coiling temperature and then coiled. The coiling temperature is 630℃ to obtain hot-rolled premium strip.

[0040] Using the methods in Examples 1 to 3, high-quality tapes for measuring instruments with a surface decarburized layer depth ≤0.06mm and a grain size ≥8 can be obtained. These high-quality tapes are then hot-rolled to thicknesses of 2.0mm, 2.5mm, and 3.0mm, and subsequently subjected to conventional cold rolling, slitting, and quenching and tempering heat treatments to produce tapes of 0.06mm, 0.07mm, and 0.08mm. Testing shows that the tapes obtained using the high-quality tapes from Examples 1-3 can consistently achieve a hardness of 53~57HRC after quenching and tempering, while their straightness and rigidity meet the requirements of the QB / T 2443-2011 "Steel Tape Measure" standard.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made based on the technical essence of the present invention should be included within the scope of protection of the present invention.

Claims

1. A type of tape for measuring tapes, characterized in that, By mass percentage, it includes the following elemental components: C: 0.51~0.56%, Si: 0.25~0.35%, Mn: 0.70~0.90%, Cr: 0.20~0.40%, P≤0.020%, S≤0.020%, Al≤0.010%, Fe.

2. The tape measure as described in claim 1, characterized in that, By mass percentage, it comprises the following elemental components: C: 0.52~0.54%, Si: 0.28~0.33%, Mn: 0.80~0.90%, Cr: 0.25~0.35%, P≤0.018%, S≤0.010%, Al≤0.005%, with the balance being Fe and unavoidable impurities.

3. The tape measure as described in claim 1, characterized in that, The superior strip is a hot-rolled steel strip with a decarburized layer depth ≤0.06mm and a grain size ≥8.

4. A method for preparing a high-quality tape for measuring tape as described in any one of claims 1-3, characterized in that, Includes the following steps: Converter primary refining: Molten iron and scrap steel are primary refined in a converter to obtain primary molten steel with carbon ≤0.05% and oxygen ≤500ppm; ferrosilicon, ferromanganese and ferrochrome alloys are added for alloying during tapping, and aluminum is not allowed for deoxidation. LF refining: The molten steel from the converter primary refining process is transferred to the LF furnace for refining, and the chemical composition of the molten steel is adjusted to the target range to obtain refined molten steel; Continuous casting: Refined molten steel is continuously cast at a constant casting speed of 1.0 m / min to obtain a continuously cast billet; Billet heating: The continuously cast square billet is heated, with a soaking temperature of 1000~1180℃ and a heating time of 2h~4h; Rolling: Perform multi-pass rolling, control the deformation of the strip in the non-recrystallization zone to be ≥30% in the finishing rolling stage, and the final rolling temperature to be below 880℃; Coiling: The rolled steel strip is cooled and coiled at a temperature not exceeding 630°C to obtain the high-quality strip for the measuring tape.

5. The preparation method according to claim 4, characterized in that, In step (1), the mass ratio of molten iron is 70%~90%, the proportion of scrap steel is 10%~30%, and the initial smelting time is 30~45min; the carbon content of the initial smelting steel is ≤0.04%, and the oxygen content is 300~500ppm.

6. The preparation method according to claim 4, characterized in that, The refining process includes: adding slag-forming material to form slag, and then refining the white slag after it is formed. The refining time is 30-60 minutes.

7. The preparation method according to claim 4, characterized in that, Heating of the continuously cast billet is carried out using a pusher furnace or a walking beam furnace; steam-water spray cooling is used during continuous casting.

8. The preparation method according to claim 4, characterized in that, The rolled steel strip has a thickness of 1.5~4mm and a width of 285~380mm.

9. The preparation method according to claim 4, characterized in that, The final rolling temperature during the rolling process is 860~870℃; the coiling temperature during the coiling process is 600~630℃.

10. A measuring tape, characterized in that, The measuring tape according to any one of claims 1-3 is obtained by cold rolling, slitting and quenching and tempering heat treatment of a superior strip, wherein the strip thickness is 0.06~0.08mm and the hardness is 53~57HRC.