LT – B3 hot rolled round steel technical agreement
1、Rang
The provisions of this standard: The size, shape, weight and allowable deviation, technical requirements, test method, inspection rules, packing, mark, and quality certificate of grinding steel ball billet.
This standard applies the diameter and thickness ∮65-110mm hot rolled round steel.
2、 Quoted standard
GB/T222 Style sampling method for steel chemical composition analysis of the chemical components and finished products allow deviation
GB/T226 Steel macrostructure and defect of the acid corrosion test method
GB/T702 Hot rolled round steel and square steel size, shape, quality, and allowable deviation
GB/T1979 Macrostructure defect is just the rating figure
GB/T2101 Sections of the acceptance certificate, packing, marking, and quality general provisions
GB/T4336 Carbon steel and low alloy steel photoelectric emission spectrum analysis method
ASTM E45 The determination method of non-metallic inclusion content in steel
GB/T13299 The steel microstructure evaluation methods
GB/T17505 General technical conditions of delivery of steel and steel products
GB/T3077 structural alloy steel
3、Size, Shape, Weight
-3.1The size, shape, weight, and allowable deviation of hot rolled round steel should match the stipulation of GB/T702 in the second group.
-3.2 Steel scale 6 meters,
4、Technical requirements
4.1Grades and chemical component
4.1.1 The grades and chemical composition of steel should match the stipulation of table 1
Table 1 Steel chemical component(The percentage of weight %)
Grade C Si Mn P S Cr Ni Cu
LT-B2 Max 0.66 1.9 0.80 0.030 0.030 0.90 ≤0.25 0.15
Min 0.58 1.6 0.65 0.70
4.1.2 The chemical component allowable deviation of round steel(billet) is executed according to GB/T222 table 2
4.2 Smelting process electric furnace/converter+Outdoor vacuum refining to gas
4.3Delivery condition
Delivery at hot rolled condition, cold hole process, the compression ratio of steel billet≥14
4.4 macro
4.4.1 The cross-section of steel pickling macrostructure specimens can’t have visually visible contraction cavity, bubble, flaw, entrainment, skull patch, fisheye, intercrystalline crack
4.4.2 The qualified level of pickling macrostructure should match the stipulation of table 2
Table 2
center porosity（Grade） General porosity（Grade） Ingot shape segregation（Grade）
≤1.5 ≤1.5 ≤1.5
4.5 nonmetallic inclusion
Round steel should inspect according to ASTM E45, Its qualified grade should match the stipulation of table 3 parameter requirement.
Table 3
A B C D
Thin department Thich department Thin department Thich department Thin department Thich department Thin department Thich department
≤2.5 ≤2.5 ≤2.5 ≤2.5 ≤2.5 ≤2.5 ≤2.5 ≤2.5
4.6 metallographic structure
Hot rolled state organizations are not allowed to bainite or martensite exists.
4.7 Products of billet required compression ratio shall not be less than 14
4.8 Hot upsetting qualified
4.9 Surface quality: According to GB/T3077-1999 Article 6.6.1 to execute, Sampling pickling ensure
5、experimental method
Each batch of steel test method should be executed according to table 4
Table 4
S.N. Inspection item Sample number Sampling location Experimental method
1 Chemical component 1 GB/T222 GB/T223、GB/T4336
2 Macro 2 Different billet or steel GB/T226、GB/T1979
3 nonmetallic inclusion 2 Different billets or steel ASTM E45
4 metallographic structure 1 Any steel rod GB/T13299
5 Size One by one Any steel rod calipers 、micrometer
6 Surface quality One by one Whole steel rod visual
7 Hot upsetting 2 Different steel rod GB/T233
6、Inspection stipulation
6.1 check and accept
6.1.1 Steel factory inspection and acceptance conducted by the supplier quality and technical supervision department
6.1.2 The supplier must ensure that delivery of steel in accordance with this agreement or contract
6.2 Organization Rule
Steel should be according to the number of inspection and acceptance， Each batch should be composed of the same grade, the same furnace number, the same processing method, the same size, the same delivery condition, the same heat treatment system(melt)
6.3 Sample quantity and sampling location.
The sample quantity and sampling location of each batch of steel should accord with the stipulation of table 4.
6.4 The reinspection decision rules
6.4.1 The reinspection decision rules of steel is executed according to GB/T17505
7、Packing, Mark, and quality certificate.
The packing, mark, and quality certificate of steel should accord with the stipulation of GB/T2101
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