Rebar
2014-07-30
Rebar, commonly known as steel bars, is also referred to as fine-grained hot-rolled rebar; its grade is indicated by adding the first letter of the English word 'Fine' after the English abbreviation for hot-rolled ribbed steel bars. For example: HRBF335, HRBF400, HRBF500. The grades suitable for high seismic requirements are indicated by adding 'E' to the existing grades (e.g., HRB400E, HRBF400E).
1. Overview
Rebar, commonly known as steel bars, is also referred to as fine-grained hot-rolled rebar; its grade is indicated by adding the first letter of the English word 'Fine' after the English abbreviation for hot-rolled ribbed steel bars. For example: HRBF335, HRBF400, HRBF500. The grades suitable for high seismic requirements are indicated by adding 'E' to the existing grades (e.g., HRB400E, HRBF400E).
Rebar, commonly known as steel bars, is also referred to as fine-grained hot-rolled rebar; its grade is indicated by adding the first letter of the English word 'Fine' after the English abbreviation for hot-rolled ribbed steel bars. For example: HRBF335, HRBF400, HRBF500. The grades suitable for high seismic requirements are indicated by adding 'E' to the existing grades (e.g., HRB400E, HRBF400E).
2. Types
(1) Performance classification: According to China's rebar execution standard (GB1499.2-2007), rebar is divided into three grades based on strength levels (yield point/tensile strength); (2) Classification by use: such as ordinary rebar and prestressed rebar for reinforced concrete, and heat-treated rebar for concrete; (3) Classification by appearance: divided into ribbed rebar and smooth round rebar.
Difference between ribbed steel and smooth round steel
The difference between ribbed steel and smooth round steel is that it has longitudinal ribs and transverse ribs on its surface, usually with two longitudinal ribs and evenly distributed transverse ribs along its length. Ribbed steel belongs to small section steel materials and is mainly used as a framework in reinforced concrete building components. It requires certain mechanical strength, bending deformation performance, and welding process performance during use. The raw material for producing ribbed steel is carbon structural steel or low-alloy structural steel that has undergone quiet melting treatment; finished rebars are delivered in hot-rolled formed, normalized or hot-rolled state.
Main production areas: North China, East China, Northeast China, such as Shougang, Tangshan Steel, Xuan Steel, Cheng Steel, Xinxing Casting Pipe, Jianlong, Xilin Steel, Beitai Steel, Fugang Steel, Shagang Steel, Hebei Iron and Steel etc.
Specifications
The specifications of ribbed steel should be specified in import and export trade contracts. Generally includes standard grade (type code), nominal diameter of the rebar, nominal weight (mass), specified length and allowable deviation values of the above indicators etc. China's standard recommends a series of ribbed steels with nominal diameters of 6mm to 50mm including: 6、8、10、12、16、20、25、32、40、50mm. Supply lengths are divided into fixed lengths and multiple lengths. The fixed length selection range for exported ribbed steel from China is 6 to 12m; Japanese produced ribbed steel has a fixed length selection range of 3.5 to 10m; if there are no specific requirements stated in domestic sales contracts for Chinese produced ribbed steel it is usually set at two lengths of 9m or 12m.
(1) Performance classification: According to China's rebar execution standard (GB1499.2-2007), rebar is divided into three grades based on strength levels (yield point/tensile strength); (2) Classification by use: such as ordinary rebar and prestressed rebar for reinforced concrete, and heat-treated rebar for concrete; (3) Classification by appearance: divided into ribbed rebar and smooth round rebar.
Difference between ribbed steel and smooth round steel
The difference between ribbed steel and smooth round steel is that it has longitudinal ribs and transverse ribs on its surface, usually with two longitudinal ribs and evenly distributed transverse ribs along its length. Ribbed steel belongs to small section steel materials and is mainly used as a framework in reinforced concrete building components. It requires certain mechanical strength, bending deformation performance, and welding process performance during use. The raw material for producing ribbed steel is carbon structural steel or low-alloy structural steel that has undergone quiet melting treatment; finished rebars are delivered in hot-rolled formed, normalized or hot-rolled state.
Main production areas: North China, East China, Northeast China, such as Shougang, Tangshan Steel, Xuan Steel, Cheng Steel, Xinxing Casting Pipe, Jianlong, Xilin Steel, Beitai Steel, Fugang Steel, Shagang Steel, Hebei Iron and Steel etc.
Specifications
The specifications of ribbed steel should be specified in import and export trade contracts. Generally includes standard grade (type code), nominal diameter of the rebar, nominal weight (mass), specified length and allowable deviation values of the above indicators etc. China's standard recommends a series of ribbed steels with nominal diameters of 6mm to 50mm including: 6、8、10、12、16、20、25、32、40、50mm. Supply lengths are divided into fixed lengths and multiple lengths. The fixed length selection range for exported ribbed steel from China is 6 to 12m; Japanese produced ribbed steel has a fixed length selection range of 3.5 to 10m; if there are no specific requirements stated in domestic sales contracts for Chinese produced ribbed steel it is usually set at two lengths of 9m or 12m.
3. Uses
Widely used in civil engineering construction such as buildings, bridges, roads etc.
(1) Surface quality: Relevant standards specify surface quality requirements for ribbed steel which state that ends should be cut straight without cracks or scars or folds present that could be harmful during use.
(2) Allowable values for dimensional deviations: Requirements regarding curvature and geometric shape of rebars are specified in relevant standards. For example: China's standards stipulate that the curvature of straight rebars should not affect normal use with total curvature not exceeding 0.4% of the total length of the rebar.
Widely used in civil engineering construction such as buildings, bridges, roads etc.
(1) Surface quality: Relevant standards specify surface quality requirements for ribbed steel which state that ends should be cut straight without cracks or scars or folds present that could be harmful during use.
(2) Allowable values for dimensional deviations: Requirements regarding curvature and geometric shape of rebars are specified in relevant standards. For example: China's standards stipulate that the curvature of straight rebars should not affect normal use with total curvature not exceeding 0.4% of the total length of the rebar.
4. Technical Standards
GB1499.2-2007 (Steel for Reinforced Concrete Part II: Hot-Rolled Ribbed Rebars)
GB1499.2-2007/XG1－2009 National Standard No.1 Amendment Sheet for "Steel for Reinforced Concrete Part II: Hot-Rolled Ribbed Rebars"; GB700—2006 (Carbon Structural Steel); GB/T2101—2008 (General Provisions on Acceptance Inspection , Packaging , Marking , and Quality Certificate of Section Steel); GB1499.1～GB1499.3 (Reinforcing Bars for Concrete); JIS G3112—87(98) (Bar Steel for Reinforced Concrete); JISG3191—66(94) (Shape , Dimensions , Weight , and Allowable Deviation of Hot-Rolled Bar Steel); BS4449—97 (Hot-Rolled Reinforcing Bars for Concrete Structures).
GB1499.2-2007 (Steel for Reinforced Concrete Part II: Hot-Rolled Ribbed Rebars)
GB1499.2-2007/XG1－2009 National Standard No.1 Amendment Sheet for "Steel for Reinforced Concrete Part II: Hot-Rolled Ribbed Rebars"; GB700—2006 (Carbon Structural Steel); GB/T2101—2008 (General Provisions on Acceptance Inspection , Packaging , Marking , and Quality Certificate of Section Steel); GB1499.1～GB1499.3 (Reinforcing Bars for Concrete); JIS G3112—87(98) (Bar Steel for Reinforced Concrete); JISG3191—66(94) (Shape , Dimensions , Weight , and Allowable Deviation of Hot-Rolled Bar Steel); BS4449—97 (Hot-Rolled Reinforcing Bars for Concrete Structures).
5. Chemical Composition
[Grade] Chemical composition (%), C Si Mn P S Ceq
[HRB400] [0.25] [0.80] [1.60] [0.045] [0.045] [0.54]
[HRB500] [0.25] [0.80] [1.60] [0.045] [0.045] [0.55]
(1) Component Inspection
(1) Inspection methods: Common standard inspection methods used when analyzing chemical compositions include GB/T223，JISG1211?1215，BS1837，BS Handbook No .19 etc.
(2) Component indicators: The main indicators assessing the content of components in ribbed steel include C，Mn，P，S，Si etc., with different grades having varying contents within approximate ranges: C(0 .10～0 .40%)，Mn<1 .80%，P<0 .050%，S<0 .050%，Si(0 .60～1 .00%).
(2) Surface Quality
[Reinforcing bars must not have cracks , scars , or folds on their surfaces.] The surface may have protrusions but they must not exceed the height of transverse ribs; other defects on the surface must not exceed allowable deviations based on their respective dimensions.
(3) Dimensional Appearance
(1) Nominal diameter range and recommended diameters
The nominal diameter range for reinforcing bars is from six mm to fifty mm; recommended nominal diameters include six mm , eight mm , ten mm , twelve mm , sixteen mm , twenty mm , twenty-five mm , thirty-two mm , forty mm , fifty mm.
(2) Surface shape and size allowable deviations for ribbed reinforcing bars
The angle β between transverse ribs and the axis of reinforcing bars should not be less than forty-five degrees; when this angle does not exceed seventy degrees,the direction relative to both sides should be opposite;
The nominal spacing l between transverse ribs must not exceed zero point seven times the nominal diameter;
The angle α between side surfaces of transverse ribs and reinforcing bar surfaces must not be less than forty-five degrees;
The total gap between ends of adjacent transverse ribs on both sides(including width of longitudinal ribs )must not exceed twenty percentof nominal circumference.
When the nominal diameter of the rebar does not exceed 12mm, the relative rib area should not be less than 0.055; when the nominal diameter is 14mm and 16mm, the relative rib area should not be less than 0.060; when the nominal diameter exceeds 16mm, the relative rib area should not be less than 0.065. The calculation of relative rib area can refer to Appendix C.
Ribbed rebar usually has longitudinal ribs, but may also lack longitudinal ribs.
3) Length and allowable deviation
a. Length: Rebar is usually delivered in fixed lengths, and specific delivery lengths should be specified in the contract; rebar can be delivered in coils, with each coil being a single piece of rebar. It is allowed for each batch to have up to 5% of coils (two coils are allowed if there are fewer than two) consisting of two pieces of rebar. The weight and diameter of the coil are determined through negotiation between supply and demand parties.
b. Allowable length deviation: The allowable deviation for rebar delivered at fixed lengths must not exceed ±25mm;
When a minimum length is required, its deviation is 50mm;
When a maximum length is required, its deviation is -50mm.
c. Bending degree and ends: The bending degree of straight rebar should not affect normal use, with total bending degree not exceeding 0.4% of the total length of the rebar; the ends of the rebar should be cut straight, and local deformation should not affect use.
[Grade] Chemical composition (%), C Si Mn P S Ceq
[HRB400] [0.25] [0.80] [1.60] [0.045] [0.045] [0.54]
[HRB500] [0.25] [0.80] [1.60] [0.045] [0.045] [0.55]
(1) Component Inspection
(1) Inspection methods: Common standard inspection methods used when analyzing chemical compositions include GB/T223，JISG1211?1215，BS1837，BS Handbook No .19 etc.
(2) Component indicators: The main indicators assessing the content of components in ribbed steel include C，Mn，P，S，Si etc., with different grades having varying contents within approximate ranges: C(0 .10～0 .40%)，Mn<1 .80%，P<0 .050%，S<0 .050%，Si(0 .60～1 .00%).
(2) Surface Quality
[Reinforcing bars must not have cracks , scars , or folds on their surfaces.] The surface may have protrusions but they must not exceed the height of transverse ribs; other defects on the surface must not exceed allowable deviations based on their respective dimensions.
(3) Dimensional Appearance
(1) Nominal diameter range and recommended diameters
The nominal diameter range for reinforcing bars is from six mm to fifty mm; recommended nominal diameters include six mm , eight mm , ten mm , twelve mm , sixteen mm , twenty mm , twenty-five mm , thirty-two mm , forty mm , fifty mm.
(2) Surface shape and size allowable deviations for ribbed reinforcing bars
The angle β between transverse ribs and the axis of reinforcing bars should not be less than forty-five degrees; when this angle does not exceed seventy degrees,the direction relative to both sides should be opposite;
The nominal spacing l between transverse ribs must not exceed zero point seven times the nominal diameter;
The angle α between side surfaces of transverse ribs and reinforcing bar surfaces must not be less than forty-five degrees;
The total gap between ends of adjacent transverse ribs on both sides(including width of longitudinal ribs )must not exceed twenty percentof nominal circumference.
When the nominal diameter of the rebar does not exceed 12mm, the relative rib area should not be less than 0.055; when the nominal diameter is 14mm and 16mm, the relative rib area should not be less than 0.060; when the nominal diameter exceeds 16mm, the relative rib area should not be less than 0.065. The calculation of relative rib area can refer to Appendix C.
Ribbed rebar usually has longitudinal ribs, but may also lack longitudinal ribs.
3) Length and allowable deviation
a. Length: Rebar is usually delivered in fixed lengths, and specific delivery lengths should be specified in the contract; rebar can be delivered in coils, with each coil being a single piece of rebar. It is allowed for each batch to have up to 5% of coils (two coils are allowed if there are fewer than two) consisting of two pieces of rebar. The weight and diameter of the coil are determined through negotiation between supply and demand parties.
b. Allowable length deviation: The allowable deviation for rebar delivered at fixed lengths must not exceed ±25mm;
When a minimum length is required, its deviation is 50mm;
When a maximum length is required, its deviation is -50mm.
c. Bending degree and ends: The bending degree of straight rebar should not affect normal use, with total bending degree not exceeding 0.4% of the total length of the rebar; the ends of the rebar should be cut straight, and local deformation should not affect use.
6. Performance Inspection
1) Performance indicators: The inspection items for assessing mechanical properties of threaded steel include tensile tests (tensile strength, yield strength, elongation), bending tests (initial bending and reverse bending). Specific indicators are listed in Table 6-7-7.
2) Inspection methods: i) Tensile test methods: Common standard inspection methods include GB/T228.1-2010, JISZ2201, JISZ2241, ASTMA370, ГОСТ1497, BS18 etc.; ii) Bending test methods: Common standard inspection methods include GB/T232-88, YB/T5126-2003, JISZ2248, ASTME290, ГОСТ14019 etc.
3) Bending performance
According to the specified bending radius in the table below, after bending at a radius of curvature by 180 degrees, no cracks shall appear on the surface at the bent part of the rebar.
1) Performance indicators: The inspection items for assessing mechanical properties of threaded steel include tensile tests (tensile strength, yield strength, elongation), bending tests (initial bending and reverse bending). Specific indicators are listed in Table 6-7-7.
2) Inspection methods: i) Tensile test methods: Common standard inspection methods include GB/T228.1-2010, JISZ2201, JISZ2241, ASTMA370, ГОСТ1497, BS18 etc.; ii) Bending test methods: Common standard inspection methods include GB/T232-88, YB/T5126-2003, JISZ2248, ASTME290, ГОСТ14019 etc.
3) Bending performance
According to the specified bending radius in the table below, after bending at a radius of curvature by 180 degrees, no cracks shall appear on the surface at the bent part of the rebar.
4) Reverse bending performance
According to buyer requirements, reverse bending performance tests can be conducted on rebars. The radius for reverse bending tests increases by one diameter compared to that for regular bending tests. First bend forward by 90 degrees and then bend backward by 20 degrees. After reverse bending tests, no cracks shall appear on the surface at the bent part of the rebar.
According to buyer requirements, reverse bending performance tests can be conducted on rebars. The radius for reverse bending tests increases by one diameter compared to that for regular bending tests. First bend forward by 90 degrees and then bend backward by 20 degrees. After reverse bending tests, no cracks shall appear on the surface at the bent part of the rebar.
7. Identification of Genuine and Fake Threaded Steel
"Currently in the steel market, inferior hot-rolled ribbed steel bars (commonly known as threaded steel) have several non-conformance factors: i) Actual dimensions are about one specification smaller than nominal dimensions; dealers purchase based on actual weight while delivering theoretical weight to profit from metal quantity; ii) Low strength; iii) High rate of non-conformance in chemical composition due mainly to unqualified raw materials from small rolling mills using low-quality steel billets to roll threaded steel."
"When purchasing threaded steel bars, first check their appearance dimensions using calipers to measure whether actual dimensions are about one specification smaller or more than indicated dimensions (generally marked with specifications on threaded steel). For example?12 threaded steel has a standard inner diameter of approximately11.5±0.4mm while inferior threaded steels often have an inner diameter around10mm). Additionally some inferior threaded steels deceive visually by being flattened during rolling so that their end faces appear oval rather than round as they should be; secondly check surface quality as inferior threaded steels made from low-quality billets often have poor surface quality with defects like scars giving an overall rough feel; some small rolling mills also produce them with insufficient heating temperature or rolling speed resulting in reddish surface color; thirdly genuine steel products are mostly packaged in large bundles upon leaving manufacturers with corresponding metal tags indicating manufacturer name ,steel grade ,batch number ,specifications ,and inspection codes etc., whereas inferior rebars often come from poorly equipped production conditions without large lifting equipment resulting mostly in small bundles (about ten pieces bundled together ) or loose packaging without metal tags or quality certificates . To fundamentally avoid purchasing inferior rebars , it’s best to buy directly from reputable manufacturers’ authorized dealers especially local brand rebars (like Sansteel’s "Minguang" brand threaded steel ) which ensure stable quality making dispute resolution easier . Experienced individuals can also identify other chemical compositions through spark testing."
"It is recommended that users purchase genuine steel materials only from legitimate steel trading units or points when buying threaded steels , request quality certificates for these materials ,and conduct acceptance checks . For any doubts regarding quality , consult professional testing institutions for quality inquiries and inspections."
"Currently in the steel market, inferior hot-rolled ribbed steel bars (commonly known as threaded steel) have several non-conformance factors: i) Actual dimensions are about one specification smaller than nominal dimensions; dealers purchase based on actual weight while delivering theoretical weight to profit from metal quantity; ii) Low strength; iii) High rate of non-conformance in chemical composition due mainly to unqualified raw materials from small rolling mills using low-quality steel billets to roll threaded steel."
"When purchasing threaded steel bars, first check their appearance dimensions using calipers to measure whether actual dimensions are about one specification smaller or more than indicated dimensions (generally marked with specifications on threaded steel). For example?12 threaded steel has a standard inner diameter of approximately11.5±0.4mm while inferior threaded steels often have an inner diameter around10mm). Additionally some inferior threaded steels deceive visually by being flattened during rolling so that their end faces appear oval rather than round as they should be; secondly check surface quality as inferior threaded steels made from low-quality billets often have poor surface quality with defects like scars giving an overall rough feel; some small rolling mills also produce them with insufficient heating temperature or rolling speed resulting in reddish surface color; thirdly genuine steel products are mostly packaged in large bundles upon leaving manufacturers with corresponding metal tags indicating manufacturer name ,steel grade ,batch number ,specifications ,and inspection codes etc., whereas inferior rebars often come from poorly equipped production conditions without large lifting equipment resulting mostly in small bundles (about ten pieces bundled together ) or loose packaging without metal tags or quality certificates . To fundamentally avoid purchasing inferior rebars , it’s best to buy directly from reputable manufacturers’ authorized dealers especially local brand rebars (like Sansteel’s "Minguang" brand threaded steel ) which ensure stable quality making dispute resolution easier . Experienced individuals can also identify other chemical compositions through spark testing."
"It is recommended that users purchase genuine steel materials only from legitimate steel trading units or points when buying threaded steels , request quality certificates for these materials ,and conduct acceptance checks . For any doubts regarding quality , consult professional testing institutions for quality inquiries and inspections."
"8. Production Process"
"Threaded steel bars are ribbed bars with surfaces featuring ribs also known as ribbed bars typically having two longitudinal ribs along their length uniformly distributed across transverse ribs which come in three shapes : spiral shape , herringbone shape , crescent shape . They are represented by their nominal diameters measured in millimeters . The nominal diameters for ribbed bars correspond to those for smooth round bars having equal cross-sectional areas . Nominal diameters range from8to50millimeters with recommended diameters being8、12、16、20、25、32、40millimeters . Ribbed bars primarily bear tensile stress within concrete structures due largely due their ribs providing significant bonding capacity with concrete allowing them better resistance against external forces . Ribbed bars find extensive applications across various construction structures particularly large heavy lightweight thin-walled high-rise buildings."
"Threaded steels are produced using small rolling mills which mainly fall into three categories : continuous type semi-continuous type horizontal type . Currently most newly built or operational small rolling mills worldwide utilize fully continuous types . Popular modern rod mills include general high-speed rod mills along with four-split high-yield rod mills."
The raw materials used for continuous small rolling mills are generally continuous casting small square billets, with a side length typically ranging from 130 to 160 mm and a length of about 6 to 12 meters. The single weight of the billets is between 1.5 to 3 tons. The rolling lines are mostly arranged in a flat-vertical alternating layout to achieve twist-free rolling throughout the line. Depending on different billet specifications and finished product sizes, there are small rolling mills with 18, 20, 22, and 24 stands, with the 18-stand being mainstream. Currently, bar rolling mostly adopts new processes such as step-type heating furnaces, high-pressure water descaling, low-temperature rolling, and headless rolling. The roughing and intermediate rolling are developing towards accommodating large billets and improving rolling precision, while the finishing mill mainly focuses on increasing precision and speed (up to 18 m/s). The product specifications generally range from ф10-40 mm, with some also being ф6-32 mm or ф12-50 mm. The types of steel produced include low, medium, and high carbon steel as well as low alloy steel; the maximum rolling speed is 18 m/s. Its production process flow is as follows:
Step-type heating furnace → Roughing mill → Intermediate mill → Finishing mill → Water cooling device → Cooling bed → Cold shears → Automatic counting device → Bundling machine → Unloading platform provided by Shanghai Jiuzheng Environmental Building Materials Co., Ltd. Rebar theoretical weight calculation formula: Outer diameter × Outer diameter × 0.00617 = kg/m Specification theoretical weight Manufacturer: 6.50 - Jiuzheng Steel; 8.00 - Jiuzheng Steel; 10.0 - Jiuzheng Steel; 12.0 - Jiuzheng Steel; 14.0 - Jiuzheng Steel; 16.0 - Jiuzheng Steel; 18.0 - Jiuzheng Steel; 20.0 - Jiuzheng Steel; 22.0 - Jiuzheng Steel; ...
Production distribution
Reinforced steel and wire rods have always occupied a significant share of China's steel production market. Before the year 2000, the proportion of small profiles (mainly reinforced steel) was around 25%; after 2001, with the transfer of global manufacturing to China, the proportion of plate pipe strip production and sales gradually increased while the share of construction steel decreased year by year. From 2001 to 2007, China's reinforced steel output increased from approximately 43.89 million tons (small profile output) to about 101.37 million tons but its share in total steel output dropped from 28% to around18%. Affected by the economic crisis in2008 , reinforced steel output was approximately95 .12 million tons , slightly down from2007 . According to the latest data from the National Bureau of Statistics , from January to September in2009 , cumulative reinforced steel output was9003 .37 million tons , an increase of27 .50% . It is estimated that in2009 , reinforced steel capacity was about13324 .79 million tons , with actual output around12128 .22 million tons.
The East China region is China's largest production area for reinforced steel; from2001to2005 , this region's reinforced steel output accounted for35%-39%of national production . In2006and2007 , this further increased to over40%. Next is North China region where from2001to2005 , its reinforced steel output accounted for23%-29%of national production but dropped to22 .1%in2007 . Following that is Central South region where its share ranged between13%-18%from2001to2007 . Southwest , Northeast , and Northwest regions had lower shares at9 .3%,4 .5%,and5 .9%respectively in2007.
The production of rebar is very decentralized.In2007,the top ten producers by rebar output were Shagang,Tangshan Iron & Steel,Laiwu Iron & Steel,Jinan Iron & Steel,Wuhan Iron & Steel,Baosteel,Masteel,Pinggang,Jianlong,and Xinxing Ductile Iron Pipes.The top three producers Shagang,Tangshan Iron & Steel,and Laiwu Iron & Steel accounted for over5%of total rebar output while other companies had shares below4%. This indicates that rebar production is quite decentralized and primarily dominated by local enterprises and private companies which aligns with characteristics such as low added value for rebar and wire rod products,a relatively short transportation radius,and mainly catering to regional markets.
"Threaded steel bars are ribbed bars with surfaces featuring ribs also known as ribbed bars typically having two longitudinal ribs along their length uniformly distributed across transverse ribs which come in three shapes : spiral shape , herringbone shape , crescent shape . They are represented by their nominal diameters measured in millimeters . The nominal diameters for ribbed bars correspond to those for smooth round bars having equal cross-sectional areas . Nominal diameters range from8to50millimeters with recommended diameters being8、12、16、20、25、32、40millimeters . Ribbed bars primarily bear tensile stress within concrete structures due largely due their ribs providing significant bonding capacity with concrete allowing them better resistance against external forces . Ribbed bars find extensive applications across various construction structures particularly large heavy lightweight thin-walled high-rise buildings."
"Threaded steels are produced using small rolling mills which mainly fall into three categories : continuous type semi-continuous type horizontal type . Currently most newly built or operational small rolling mills worldwide utilize fully continuous types . Popular modern rod mills include general high-speed rod mills along with four-split high-yield rod mills."
The raw materials used for continuous small rolling mills are generally continuous casting small square billets, with a side length typically ranging from 130 to 160 mm and a length of about 6 to 12 meters. The single weight of the billets is between 1.5 to 3 tons. The rolling lines are mostly arranged in a flat-vertical alternating layout to achieve twist-free rolling throughout the line. Depending on different billet specifications and finished product sizes, there are small rolling mills with 18, 20, 22, and 24 stands, with the 18-stand being mainstream. Currently, bar rolling mostly adopts new processes such as step-type heating furnaces, high-pressure water descaling, low-temperature rolling, and headless rolling. The roughing and intermediate rolling are developing towards accommodating large billets and improving rolling precision, while the finishing mill mainly focuses on increasing precision and speed (up to 18 m/s). The product specifications generally range from ф10-40 mm, with some also being ф6-32 mm or ф12-50 mm. The types of steel produced include low, medium, and high carbon steel as well as low alloy steel; the maximum rolling speed is 18 m/s. Its production process flow is as follows:
Step-type heating furnace → Roughing mill → Intermediate mill → Finishing mill → Water cooling device → Cooling bed → Cold shears → Automatic counting device → Bundling machine → Unloading platform provided by Shanghai Jiuzheng Environmental Building Materials Co., Ltd. Rebar theoretical weight calculation formula: Outer diameter × Outer diameter × 0.00617 = kg/m Specification theoretical weight Manufacturer: 6.50 - Jiuzheng Steel; 8.00 - Jiuzheng Steel; 10.0 - Jiuzheng Steel; 12.0 - Jiuzheng Steel; 14.0 - Jiuzheng Steel; 16.0 - Jiuzheng Steel; 18.0 - Jiuzheng Steel; 20.0 - Jiuzheng Steel; 22.0 - Jiuzheng Steel; ...
Production distribution
Reinforced steel and wire rods have always occupied a significant share of China's steel production market. Before the year 2000, the proportion of small profiles (mainly reinforced steel) was around 25%; after 2001, with the transfer of global manufacturing to China, the proportion of plate pipe strip production and sales gradually increased while the share of construction steel decreased year by year. From 2001 to 2007, China's reinforced steel output increased from approximately 43.89 million tons (small profile output) to about 101.37 million tons but its share in total steel output dropped from 28% to around18%. Affected by the economic crisis in2008 , reinforced steel output was approximately95 .12 million tons , slightly down from2007 . According to the latest data from the National Bureau of Statistics , from January to September in2009 , cumulative reinforced steel output was9003 .37 million tons , an increase of27 .50% . It is estimated that in2009 , reinforced steel capacity was about13324 .79 million tons , with actual output around12128 .22 million tons.
The East China region is China's largest production area for reinforced steel; from2001to2005 , this region's reinforced steel output accounted for35%-39%of national production . In2006and2007 , this further increased to over40%. Next is North China region where from2001to2005 , its reinforced steel output accounted for23%-29%of national production but dropped to22 .1%in2007 . Following that is Central South region where its share ranged between13%-18%from2001to2007 . Southwest , Northeast , and Northwest regions had lower shares at9 .3%,4 .5%,and5 .9%respectively in2007.
The production of rebar is very decentralized.In2007,the top ten producers by rebar output were Shagang,Tangshan Iron & Steel,Laiwu Iron & Steel,Jinan Iron & Steel,Wuhan Iron & Steel,Baosteel,Masteel,Pinggang,Jianlong,and Xinxing Ductile Iron Pipes.The top three producers Shagang,Tangshan Iron & Steel,and Laiwu Iron & Steel accounted for over5%of total rebar output while other companies had shares below4%. This indicates that rebar production is quite decentralized and primarily dominated by local enterprises and private companies which aligns with characteristics such as low added value for rebar and wire rod products,a relatively short transportation radius,and mainly catering to regional markets.
Shenyang Tengfei Iron Corporation
Shenyang Tengfei Steel Pipe Co., Ltd.
Address: No.6 A 3, No.13 Road, Economic and Technological Development Zone, Shenyang City, Liaoning Province
E-mail:tfwelcome@163.com
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