Hot-rolled pickled enamel steel with good deep drawability and its manufacturing method

Abstract

The chemical components are C, N, S, Al, Mn, Si, P, Ti, the balance being Fe and unavoidable impurities, of which the weight percentages of C, N, S, Al and Ti are C: 0.001-0.006%, N≦0.004%, S≦0.0080%, Als: 0.015-0.040%, 4[C]+3.42[N]+3[S]≦[Ti] A hot-rolled pickled enamel steel with good deep drawability, in which the weight percentages of Si, Mn and P satisfy Mn: 1.0-1.5%, Si: 0.001-0.03%, P≦0.015%, or Si: 0.4-0.6%, Mn: 0.15-0.3%, P≦0.015%, or Si: 0.001-0.03%, Mn: 0.15-0.3%, P: 0.035-0.055%, and a manufacturing method thereof. The enamel steel of the present invention has a yield strength of 210-245 MPa, a tensile strength of 320 MPa or more, an elongation of 46% or more, an r-value of 1.3 or more, an n-value of 0.3 or more and a TH value of 7.0 or more, and has good formability, particularly good deep drawability, and also has high tensile strength and finger skip resistance.

Description

[Technical field]

[0001] The present invention relates to the technical field of manufacturing enamel steel, and more specifically to hot-rolled pickled enamel steel having good deep drawability and a manufacturing method thereof. [Background technology]

[0002] Enamel is a composite material in which inorganic vitreous materials are fixed to a matrix metal by melting, and are firmly bonded to the metal. Enamel products not only have the inherent strength, toughness and processability of metal materials, but also the corrosion resistance, aging resistance, wear resistance, high temperature resistance, non-toxicity and decorativeness of ceramic materials, and thus combine the advantages of metal and ceramic materials. Enamel products using steel plate as the metal substrate play a very important role in the national economy and are widely used in light industry, home appliances, metallurgy, chemical industry, construction and other industries.

[0003] There are many types of enameled steel sheets, which can be divided into hot-rolled pickled sheets, cold-rolled sheets, clad sheets, etc. depending on the manufacturing process. Among these, the use of hot-rolled sheets is increasing due to their economical efficiency. For example, they are used in the manufacture of water heater liners. Their thickness is generally 1.5 to 2.5 mm, and there is an annual demand of more than 500,000 tons.

[0004] At present, water heater liners are generally manufactured by edge rolling or welding methods, which has low production efficiency and poor yield. In order to improve production efficiency and yield, the water heater industry has gradually begun to use the deep drawing process to manufacture water heater liners, and it is necessary to improve the tensile properties of enameled steel products.

[0005] When the process conditions are relatively stable, the deep drawability of hot-rolled enamel steel is mainly related to several performance indexes, such as:

[0006] (1) Plastic strain ratio r-value: A high plastic strain ratio r-value is advantageous for deep drawing. (2) Hardening exponent n value: A large n value for a sheet material means that the material has excellent uniformity in the distribution of plastic deformation, is less likely to experience concentrated deformation, and is relatively resistant to plastic fracture.

[0007] (3) Yield ratio: Generally, the lower the yield ratio, the more advantageous it is for deep drawing of the compressor shell.

[0008] (4) Elongation: A high elongation is favorable for the unidirectional deep drawing deformation of the part, and generally, a high elongation is an important guarantee for satisfying the smooth forming of the part.

[0009] Chinese patent CN201310547968.1 discloses "Hot-rolled sheet enamel steel with yield strength of 245MPa and its manufacturing method", the thickness of the manufactured enamel steel is 1.0-2.5mm, the chemical composition is C: 0.001-0.010%, Si≦0.05%, Mn: 0.10-0.50%, P≦0.020%, S≦0.010%, Ti: 0.04-0.10%, Als: 0.02-0.08%, N≦0.008%, and the manufacturing process is heating temperature 1230-1270℃, initial rolling temperature 1100-1150℃, final rolling temperature 860-930℃, coiling temperature 600-700℃. The product has a yield strength of 245-330 MPa, a tensile strength of 300 MPa or more, and an elongation of 37-42%.

[0010] Chinese patent CN2013105483 10.2 discloses "Hot-rolled sheet enamel steel with yield strength of 330MPa and its manufacturing method", the thickness of the manufactured enamel steel is 1.0-2.5mm, and the chemical components are C:0.02-0.07%, Si≦0.05%, Mn:0.10-0.50%, P≦0.020%, S≦0.010%, Ti:0.04-0.10%, Als:0.02-0.08%, N≦0.008%, the rest is Fe and unavoidable inclusions, and Ti / C=1.0-1.5. The manufacturing process is heating temperature 1200-1250℃, final rolling temperature 860-930℃, coiling temperature 650-700℃. The product has a yield strength of 330-450 MPa, a tensile strength of 400 MPa or more, and an elongation of 38-41%.

[0011] Chinese Patent CN201510280022.2 discloses "Enameled steel with excellent pinch resistance and a manufacturing method for the steel sheet", and the chemical components of the steel are, in weight percentage, C: 0.04~0.10%, Si≦0.10%, Mn: 0.30~1.0%, Ti: 0.03~0.10%, P≦0.015%, S: 0.010~0.045%, N: 0.003~0.009%, Als: 0.005~0.050%, Cr: 0.05~0.25%, Ti / C: 0.5~1.2. The heating temperature of the continuous casting slab is 1180~1250℃, the initial rolling temperature of the finish rolling is 980~1100℃, and the final rolling temperature is 880~950℃. After rolling, a pre-cooling method is adopted, and the slab is rapidly cooled to 630~700℃ at a cooling rate of 30℃ / s or more within 6s, and then coiled. The yield strength of the product is 390~500MPa, the tensile strength is 476~598MPa, and the elongation is 26~38%.

[0012] China Patent 201510398485.9 discloses "Subway Decorative Sheet Enameled Steel and Its Manufacturing Method", in which the thickness of the enameled steel is 1.0-2.0mm, and the weight percentages of its chemical components are C: 0.001-0.003%, Si≦0.10%, Mn: 0.05-0.10%, P≦0.010%, S≦0.005%, Als: 0.01-0.02%, Ti: 0.20-0.25%, N: 0.010-0.020%. The discharge temperature is 1100-1150℃, the final rolling temperature is 800-850℃, and the coiling temperature is 700-750℃. The product has a yield strength of 460 MPa or more, a tensile strength of 550 Pa or more, an elongation of 38-42%, an r-value of 1-1.5, and an n-value of 0.1-0.3.

[0013] China Patent 201810663362.7 discloses "Low-cost high-oxygen enameled steel by CSP process and its manufacturing method", the weight percentage of its chemical components is C≦0.01%, Mn:0.10~1.00%, O≦0.0500%, Si≦0.01%, P≦0.020%, S≦0.030%, Als≦0.01%, and the rest is Fe and unavoidable impurities. This patent increases the oxygen content in the steel to form more oxide inclusions, which act as traps for hydrogen storage and improve the finger-snatch resistance of the steel sheet. Its manufacturing process is discharge temperature 1160~1200℃, final rolling temperature 860~900℃, coiling temperature 600~640℃, yield strength 151~214MPa, tensile strength 256~282MPa, and elongation 35.2~45.4%.

[0014] Chinese Patent CN201910697103.0 discloses "260MPa-class hot-rolled pickled enamel steel and its manufacturing method", and its weight percentages of chemical components are C: 0.030-0.060%, Si≦0.030%, Mn: 0.30-0.60%, P≦0.020%, S≦0.010%, Als≦0.060%, B: 0.0015-0.0040%, and N: 0.0040-0.0100%. The manufacturing method is to control the steel sheet heating temperature before rolling to 1132-1212°C, the final rolling temperature to 881-890°C, the coiling temperature to 687-696°C, the free acid concentration in the pickling solution to 105-119g / L, and the acid temperature to 71.4-74°C. The product has a yield strength of 260 MPa or more, a tensile strength of 360 MPa or more, and an elongation of 33-34%.

[0015] Chinese patent CN202010986947.X discloses "Hot-rolled enamel steel for deep drawing and its manufacturing method", the weight percentages of its components are C<0.01%, Si≦0.05%, Mn:0.10-0.80%, P≦0.030%, S≦0.015%, Ti:0.01-0.08%, Al:0.01-0.07%, N≦0.010%, 4≦Ti / N≦10, Ca:0.0010-0.0040%, Ca / S≦1.25. The manufacturing method is as follows: the heating temperature is 1150-1190°C, the final rolling temperature is 800-900°C, the coiling temperature is 710-760°C, and the cumulative deformation rate of the rough rolling of the hot rolling is controlled to 70% or more, and the cumulative deformation rate of the finish rolling is controlled to 70% or more. The leveling pressure is 700-900 tons, and the leveling elongation of the leveling is 7-12%. The yield strength of the product is 359-402 MPa, the tensile strength is 447-483 MPa, and the elongation is 30-41%.

[0016] Chinese patent CN202010986956.9 discloses "Enameled steel and its manufacturing method and application", and the weight percentages of its components are C: 0.01-0.14%, Si≦0.10%, Mn: 0.20-1.6%, P≦0.040%, S≦0.040%, Ti: 0.01-0.12%, Al: 0.01-0.07%, N≦0.010%, Mn / S≧30. The manufacturing method is as follows: the heating temperature is 1200-1350 ° C, the final rolling temperature is 810-980 ° C, the coiling temperature is 500-700 ° C, the cumulative deformation rate of the rough rolling of the hot rolling is controlled to 70% or more, the cumulative deformation rate of the finish rolling of the hot rolling is controlled to 70% or more, the leveling pressure is 450-650 tons, the leveling elongation is 6% or less, and in the pickling process by shot blasting, the rotation speed of the shot blasting machine is 1650-1850 rpm, the grain size of the shot blasting is 0.18-0.85 mm, the hardness of the shot blasting is 40-52 HRC, and the concentration of the pickling solution is 5-20%. The yield strength of the product is 410 MPa or more, the tensile strength is 490 MPa, and the elongation is 25-43.5%.

[0017] For the reasons described above, the previously disclosed enamel steels have high yield strength, low elongation, and poor deep drawability, and are prone to quality problems such as fuzz and cracks during deep drawing. Therefore, the development of hot-rolled enamel steel with good deep drawability is of great significance for upgrading the water heater liner manufacturing industry and promoting the green transformation of the home appliance industry. Summary of the Invention [Problem to be solved by the invention]

[0018] The object of the present invention is to provide a hot-rolled pickled enamel steel with good deep drawability and a manufacturing method thereof, the hot-rolled pickled enamel steel having a yield strength of 210 to 245 MPa, a tensile strength of 320 MPa or more, an elongation of 46% or more, an n value of 0.3 or more, an r value of 1.3 or more, a TH value of 7.0 or more, good formability, particularly good deep drawability, and also having high strength and pinch resistance, and capable of meeting the production requirements for water heater liners. [Means for solving the problem]

[0019] In order to achieve the above object of the invention, the technical solution of the present invention is as follows: The weight percentages of the chemical components are C: 0.001~0.006%, N≦0.004%, S≦0.0080%, Als: 0.015~0.040%, when strengthened with Mn, Mn: 1.0~1.5%, Si: 0.001~0.03%, P≦0.015%, when strengthened with Si, Si: 0.4~0.6%, Mn: 0.15~0.3%, P≦0.015%, when strengthened with P, Si: 0.001~ 0.03%, Mn: 0.15~0.3%, P: 0.035~0.055%, Ti is also included, and the rest is Fe and other unavoidable impurities. Hot rolled pickled enamel steel with good deep drawability.

[0020] In some embodiments, the Ti content is 0.025-0.065%. In some embodiments, when strengthened with Mn, Mn: 1.0 to 1.5%, Si: 0.005 to 0.025%, and P≦0.015%.

[0021] In some embodiments, when strengthened with P, the Si content is 0.003 to 0.006%, the Mn content is 0.15 to 0.3%, and the P content is 0.035 to 0.055%.

[0022] The microstructure of the hot-rolled pickled enamel steel according to the present invention is polygonal ferrite grains with uniform {111} plane texture, and the grain size is not more than 7 grade.

[0023] The hot-rolled pickled enamel steel described in the present invention has a yield strength of 210 to 245 MPa, a tensile strength of 320 MPa or more, an elongation of 46% or more, an r-value of 1.3 or more, an n-value of 0.3 or more, and a TH value of 7.0 or more.

[0024] In some embodiments, the hot-rolled pickled enameled steel described in the present invention has a yield strength of 210-245 MPa, a tensile strength of 320-450 MPa, an elongation of 46-52%, an r-value of 1.3-1.8, an n-value of 0.3-0.4, and a TH value of 7.0-8.5.

[0025] In some embodiments, there are no solute C, N interstitials in the ferrite of the hot-rolled pickled enameled steel according to the present invention.

[0026] In some embodiments, the present invention provides a water heater liner, and a steel portion of the water heater liner is the hot-rolled pickled enamel steel having good deep drawability described in any of the embodiments of the present invention. In some embodiments, the water heater liner of the present invention is manufactured by deep drawing the hot-rolled pickled enamel steel having good deep drawability described in any of the embodiments of the present invention.

[0027] In the composition design of the hot-rolled pickled enamel steel described in the present invention, C: Solute C improves the yield strength and tensile strength of steel, but reduces plasticity. Solute C is also detrimental to the formation of {111} texture, lowering the r-value of the product. Materials with a high limiting drawing ratio require low yield strength, high elongation, and high {111} texture strength, so the less solute C the better. However, the lower the C content, the higher the refining cost and the longer the refining time required to reduce the C content. In order to balance the mechanical properties and manufacturing costs, the C content in the steel of the present invention is controlled to 0.001-0.006%.

[0028] N: A strong solid solution strengthening element, it is disadvantageous to the formation of {111} texture, causes aging, and affects the press quality of the steel sheet. However, if the N content is too low, it leads to an increase in manufacturing costs. Considering all factors, the N content in the steel of the present invention is controlled to 0.004% or less. In some embodiments, the N content is 0.002 to 0.004%.

[0029] S: A harmful impurity element in steel. It is prone to segregation in steel, reducing the toughness and weldability of the steel, and forming plastic sulfides that cause delamination in the steel sheet and deteriorate the performance of the steel sheet. Therefore, the lower the S content, the better. Taking all factors into consideration, the S content in the steel of the present invention is controlled to 0.008% or less.

[0030] Als: Al is a strong deoxidizing agent and can reduce oxide inclusions in steel and make the steel pure. However, if the Al content is too high, it tends to refine crystal grains and improve the yield strength and yield ratio. Considering all factors, the Als content in the steel of the present invention is controlled to 0.015 to 0.040%.

[0031] Ti: Ti has a high affinity with C and N in steel, and by forming TiC and TiN, it fixes C and N interstitial atoms, reduces the solute C and N content in steel, and is advantageous in promoting the formation of {111} texture and increasing the r value. In addition, since the bonding strength between Ti and S is greater than that between Ti and C, in order to reliably remove the solute C atoms, it is necessary to ensure that 4[C]+3.42[N]+3[S]≦[Ti]≦0.065% based on the weight percentage of the formed TiC, TiN, and Ti4C2S2. The formed TiC, TiN, and Ti4C2S2 function as hydrogen storage traps and improve the finger-snatch resistance of the steel plate.

[0032] Si, Mn, P: These elements dissolve in ferrite and austenite to increase strength, but at the same time reduce plasticity. Considering these elements comprehensively, when strengthening with Mn, the Mn content is controlled to 1.0-1.5%, Si≦0.03%, for example, 0.005-0.025%, and P≦0.015%, for example, 0.005-0.013%. When strengthening with Si, the Si content is controlled to 0.4-0.6%, the Mn content is controlled to 0.15-0.3%, and P≦0.015%, for example, 0.005-0.015%. When strengthening with P, the P content is controlled to 0.035-0.055%, Si≦0.03%, for example, ≦0.01%, and the Mn content is controlled to 0.15-0.3%.

[0033] The present invention adopts ultra-low C and micro-alloying (addition of Ti) to eliminate solute C and N interstitial atoms in ferrite, and performs lubricated rolling under low temperature and high pressure and high temperature coiling to obtain coarse, uniformly sized ferrite grains with {111} plane texture, improving the deep drawability of the product, and further improves the tensile strength and elongation of the product by solid solution strengthening of Si, Mn, and P. In addition, by controlling the component ratio of Ti, C, N, and S, coarse ferrite grains (TiC, TiN, and Ti4C2S2) are formed, which function as hydrogen storage traps, improving the finger-snatch resistance of the steel sheet, achieving a product yield strength of 210-245MPa, a tensile strength of ≧320MPa, an elongation of ≧46%, an n value of ≧0.3, an r value of ≧1.3, and a TH value of ≧7.0, and the product has good formability, especially good deep drawability, and at the same time has high tensile strength and finger-snatch resistance.

[0034] The method for producing hot-rolled pickled enamel steel having good deep drawability according to the present invention comprises the steps of: 1) Smelting and casting The above ingredients are smelted, refined, and continuously cast to obtain slag. 2) Rolling The final rolling temperature is 750-800°C, the total reduction ratio at the rolling temperature ≦840°C is 60% or more, and a lubricating emulsion is added in the rolling process at the rolling temperature ≦840°C, and the oil-water ratio of the lubricating emulsion is 1-5%; 3) Cooling Cooling rate ≦6℃ / s 4) Winding The coiling temperature is 720 to 780°C. 5) Slow cooling After the steel sheet is coiled, it is slowly cooled. 6) Pickling After slow cooling, the process includes a step of pickling to remove the oxide film on the surface of the steel sheet.

[0035] Preferably, in step 2), the final rolling temperature is 750 to 780°C. Preferably, in step 4), the coiling temperature is 730 to 760°C.

[0036] Preferably, in step 5), the slow cooling is performed by slow cooling using a stack and a heat insulating cover, and when the slow cooling using the stack is performed, a heat roll is laminated around the stack.

[0037] In some embodiments, in the rolling of step 2), the total rolling reduction at a rolling temperature ≦840° C. is 60-85%.

[0038] In some embodiments, the cooling rate in step 3) is 1-6° C. / s. In the method for producing hot-rolled pickled enamel steel according to the present invention, By controlling the final rolling temperature in the rolling process to 750-800°C, it is possible to promote the formation of {111} texture, increase the r-value of the product, and coarsen the ferrite grains. If the final rolling temperature exceeds 800°C, the ferrite grains become finer, the {111} texture decreases, the product strength improves, and the elongation, n-value, and r-value decrease. If the final rolling temperature is less than 750°C, the coiling temperature of 720°C or higher cannot be ensured, and the deformed ferrite does not recover sufficiently, which actually worsens the formability of the product.

[0039] The rolling process of the present invention adopts low-temperature lubricating rolling, and ferrite rolling of the steel sheet occurs at 840°C or less, and the rolling temperature controls the total reduction rate ≧60% in the ferrite phase region, promoting the formation of {111} texture, obtaining ferrite grains with {111} plane texture, and improving the r-value of the product. The purpose of performing lubricating rolling in the ferrite rolling process at a rolling temperature ≦840°C is to obtain a uniform {111} texture in the thickness direction, avoid the formation of {110} texture on the surface, and improve the r-value of the product. The oil-water ratio of the lubricating emulsion during lubricating rolling is controlled to 1-5%, and when the oil-water ratio is less than 1%, the friction coefficient between the steel sheet and the roll is large, and it is easy to form a shear texture that is unfavorable to forming. When the oil-water ratio exceeds 5%, it becomes easy to slip during rolling, the rolling stability is deteriorated, and the product yield is low. The oil used in the lubricating emulsion of the present invention may be an oil that has been conventionally used for rolling in this field.

[0040] In order to promote sufficient recovery of ferrite, the cooling rate is controlled to 6° C. / s or less. The coiling is performed at a high temperature, and the coiling temperature is controlled to 720-780°C. In combination with the slow cooling of the steel coil, the ferrite stretched in the rolling direction at the end of rolling is fully restored to form coarse and uniform ferrite grains to obtain the desired performance. If the coiling temperature is less than 720°C, the deformed ferrite is not fully restored, which deteriorates the formability of the product. Under the existing process and equipment conditions, the temperature is reduced in the cooling process, and at the set final rolling temperature, the maximum temperature at which the ferrite can be fully restored and coarse and uniform ferrite grains can be realized is 780°C. If the coiling temperature is higher than 780°C, it does not have a significant effect on the performance, but it becomes more difficult to achieve.

[0041] In some embodiments, the present invention provides a method for manufacturing a water heater liner, the method including the steps of manufacturing the hot-rolled pickled enamel steel with good deep drawability by the method according to any one of the embodiments of the present invention, and deep drawing the hot-rolled pickled enamel steel with good deep drawability to form the water heater liner. The water heater liner of the present invention can be manufactured by a deep drawing method well known in the art.

[0042] The present invention has the following beneficial effects: 1. The composition design of the present invention adopts the chemical composition design of ultra-low carbon and Ti micro-alloy, and further solid solution strengthening of Si, Mn, and P makes the ferrite free of solute C and N interstitial atoms, and the microstructure of the hot-rolled pickled enamel steel becomes polygonal ferrite grains with coarse and uniform size and {111} plane texture, which improves the deep drawability of the product. In addition, by controlling the composition ratio of Ti, C, N, and S, irreversible hydrogen storage traps such as TiC, TiN, and Ti4C2S2 are formed, which reduces the dissolved hydrogen in the matrix and reduces the risk of finger skipping, and improves the finger skipping resistance of the steel sheet, so that the hot-rolled pickled enamel steel product produced has good formability, especially good deep drawability, and also has high tensile strength and good finger skipping resistance.

[0043] 2. In the present invention, based on the composition design, the rolling temperature in the rolling process is controlled in the ferrite phase region with a total reduction of more than 60%, and combined with lubricating rolling, ferrite grains with {111} plane texture are obtained. Then, slow cooling and high-temperature coiling are performed to fully recover the ferrite, and coarse and uniform polygonal ferrite grains are formed. The hot-rolled pickled enamel steel has a yield strength of 210-245 MPa, a tensile strength of 320 MPa or more, an elongation of 46% or more, an n value of 0.3 or more, and an r value of 1.3 or more. The product not only has good deep drawability, but also has high tensile strength, a TH value of 7.0 or more, and good finger skip resistance.

[0044] 3. In the rolling process of low-temperature ferrite, the present invention adopts lubricating rolling, and controls the oil-water ratio of the lubricating emulsion to 1-5%, thereby avoiding the formation of shear texture that is unfavorable to forming. The ferrite phase accumulates a certain rolling reduction rate, and generates a {111} plane texture that is favorable for press forming. Combined with the subsequent slow cooling and high-temperature coiling, coarse and uniform ferrite grains are formed, and the desired mechanical properties are obtained.

[0045] 4. The hot-rolled pickled enamel steel obtained by the present invention has good deep drawability and can be used to manufacture water heater liners by deep drawing, instead of edge rolling and welded forming methods, which have low production efficiency and yield. This is of great significance in upgrading the water heater liner manufacturing industry and promoting the green transformation of the home appliance industry. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] The present invention will now be described in detail with reference to examples. Specific components of the examples of the present invention are shown in Table 1, process parameters of the examples are shown in Table 2, and performance of the hot-rolled pickled enamel steel of each example is shown in Table 3.

[0047] After cutting the samples to a standard size, the yield strength, tensile strength, n value, and r value are measured using a tensile tester in accordance with the EN10002 standard.The TH value, which is the pinch resistance sensitivity of the enamel, is measured using a hydrogen permeation test method in accordance with the EN10209 standard.

[0048] The microstructure of the hot-rolled pickled enamel steel obtained by the present invention is a polygonal ferrite grain with a coarse and uniform size and a {111} plane texture. Its yield strength is 210-245 MPa, tensile strength is 320 MPa or more, elongation is 46% or more, n value is 0.3 or more, r value is 1.3 or more, and TH value is 7.0 or more. It has good formability, especially good deep drawability, and also has high tensile strength and good finger skip resistance. It can be used to manufacture water heater liners by deep drawing instead of edge rolling or welded forming methods which have low production efficiency and yield, and is of great significance in upgrading the water heater liner manufacturing industry and promoting the green transformation of the home appliance industry.

[0049] [Table 1]

[0050] [Table 2]

[0051] [Table 3]

Claims

1. The chemical components are C, N, S, Al, Mn, Si, P, Ti, with the balance being Fe and unavoidable impurities, of which the weight percentages of C, N, S, Al and Ti are as follows: C: 0.001-0.006%, N≦0.004%, S≦0.0080%, Als: 0.015-0.040%, 4[C]+3.42[N]+3[S]≦[Ti] ≦0.065%, and the weight percentages of Si, Mn and P satisfy Mn: 1.0 to 1.5%, Si: 0.001 to 0.03%, P≦0.015%, or Si: 0.4 to 0.6%, Mn: 0.15 to 0.3%, P≦0.015%, or Si: 0.001 to 0.03%, Mn: 0.15 to 0.3%, P: 0.035 to 0.055%.

2. 2. The hot-rolled pickled enamel steel having good deep drawability according to claim 1, characterized in that the Ti content is 0.025 to 0.065%.

3. 2. The hot-rolled pickled enamel steel having good deep drawability according to claim 1, characterized in that the weight percentages of Si, Mn and P satisfy Mn: 1.0-1.5%, Si: 0.005-0.025%, and P≦0.015%.

4. 2. The hot-rolled pickled enamel steel having good deep drawability according to claim 1, characterized in that the weight percentages of Si, Mn and P satisfy the following: Si: 0.003 to 0.006%, Mn: 0.15 to 0.3%, P: 0.035 to 0.055%.

5. The hot-rolled pickled enamel steel having good deep drawability according to claim 1, characterized in that the microstructure of the hot-rolled pickled enamel steel is polygonal ferrite grains having uniform {111} plane texture, and the grain size does not exceed class 7.

6. The hot-rolled pickled enamel steel having good deep drawability according to claim 1, characterized in that the hot-rolled pickled enamel steel has a yield strength of 210 to 245 MPa, a tensile strength of 320 MPa or more, an elongation of 46% or more, an r-value of 1.3 or more, an n-value of 0.3 or more, and a TH value of 7.0 or more.

7. The hot-rolled pickled enamel steel having good deep drawability according to claim 6, characterized in that the hot-rolled pickled enamel steel has a yield strength of 210 to 245 MPa, a tensile strength of 320 to 450 MPa, an elongation of 46 to 52%, an r-value of 1.3 to 1.8, an n-value of 0.3 to 0.4, and a TH value of 7.0 to 8.

5.

8. 1) Smelting and casting Obtaining slag by smelting, refining, and continuous casting the composition according to any one of claims 1 to 4; 2) Rolling The final rolling temperature is 750-800°C, the total reduction ratio at the rolling temperature ≦840°C is 60% or more, and a lubricating emulsion is added in the rolling process at the rolling temperature ≦840°C, and the oil-water ratio of the lubricating emulsion is 1-5%; 3) Cooling Cooling rate ≦6℃ / s 4) Winding The coiling temperature is 720 to 780°C. 5) Slow cooling After the steel sheet is coiled, it is slowly cooled. 6) Pickling After slow cooling, the steel sheet is pickled to remove the oxide film on the surface. The method for producing hot-rolled pickled enamel steel having good deep drawability according to any one of claims 1 to 7, comprising the steps of:

9. The method for producing hot-rolled pickled enamel steel having good deep drawability according to claim 8, characterized in that in step 2), the final rolling temperature is 750 to 780°C.

10. The method for producing hot-rolled pickled enamel steel having good deep drawability according to claim 8, characterized in that in step 4), the coiling temperature is 730 to 760°C.

11. 9. The method for producing hot-rolled pickled enamel steel with excellent deep drawability according to claim 8, characterized in that in step 5), the slow cooling is performed by slow cooling using a stack and a heat insulating cover, and when the slow cooling using the stack is performed, a heated roll is stacked around the stack.

12. The method for producing hot-rolled pickled enamel steel with good deep drawability according to claim 8, characterized in that in the rolling in step 2), the total reduction rate at a rolling temperature ≦840° C. is 60 to 85%.

13. The method for producing hot-rolled pickled enamel steel with good deep drawability according to claim 8, characterized in that the cooling rate in step 3) is 1 to 6 ° C. / s.

14. A water heater liner manufactured by deep drawing the hot-rolled pickled enamel steel having good deep drawability according to any one of claims 1 to 7.

15. 9. A method for manufacturing a water heater liner, comprising: a step of manufacturing the hot-rolled pickled enamel steel having good deep drawability by the method according to claim 8; and a step of deep-drawing the hot-rolled pickled enamel steel having good deep drawability to form the water heater liner.