Anchor Bolt Steel Grades GB standard TECHNICAL REQUIREMENTS 1 Environmental requirements

ANCHOR BOLTS TECHNICAL REQUIREMENTS

1 Environmental requirements

The anchor bolts for wind turbine foundation have an operating temperature range of -40℃～50℃, and relative humidity ≤ 95%. Outdoor climatic conditions for wind turbine foundation anchor bolrs, include areas with high air humidity, salt, wind and sand.

2 Appearance and surface discontinuities

Visual inspection and rule measurement shall be conducted to inspect surface discontinuities of anchor bolts, in accordance with GB/T 5779.1-2000 regulations, satisfying Table 1

                Table 1 Surface Discontinuities of Anchor Bolts

3 Dimensional and Geometrical Tolerance

Dimensional and geometrical tolerance inspection according to drawings and standards below, by visual and rulers measuring, in accordance with Table 2 requirements.

3.1 Bolts   

Permittable length tolerance shall be 0mm-20mm; straightness per meter shall be not more than 2mm/m; total straightness percentage shall be not more than 0.1%

3.2 Thread

Dimension and tolerance of thread shall be in accordance with GB/T 196-2003, GB/T 197-2003, roughness of lateral surface not more than Ra6.3, unspecified areas less than Ra12.5

3.3 Dimensions of Thread Ends

    Threaded ends of anchor bolts shall comply to GB/T 1228-2006 and GB/T2-2001.

               Table 2  Dimensions of Thread of Anchor Bolts

4 Materials

Otherwise other materials specified, steel grade of anchor bolt shall be in accordance with Table 3.

Table 3 Anchor Bolt Steel Grades

According to clients’ requirements, we must perform axial and radical ultrasonic tests on raw materials. If raw materials have been UT tested before stocking in, then take 3 pieces each heat for retest; if not, UT test must be 100% performed. Acceptance standard shall comply to grade A in GB/T4162-2008.

5 Manufacturing

Anchor bolts are manufactured by heat-treatment procedures, with both ends threaded after heat-treatment.

6 Surface Preparation

Before coating, bolts’ surface cleanness shall be up to Sa2.5, by remove oxide scale, rust and oil stains. Surface treatment and formula shall be left at the discretion of the manufacturer. This surface preparation is not fitable for bolts with grease corrosion protection method.

7 Non-destructive Test

Before surface preparation, magnetic particle testing shall be performed according to JB/T 4730.4-2005, specified in Annex , and level I is the qualified grade.

8 Mechenical Properties

8.1 Tensile properties of anchor bolts

Perform tensile test according to GB/T228.1-2010, results shall be in accordance with Table 4 regulations.

Preparation of specimen for anchor bolts should preserve pitch length in order to obtain norminal diamter length. For anchor bolt product which is larger than M39，take specimens from center located at quater of norminal diamter, and machined its diameter 3/8 of norminal diameter, location shown in the following Figure:   

Table 1

Table 4  Tensile Properties of Anchor Bolts

 8.2 Impact Energy at Low Temperature

Test pieces shall be prepared from finished anchor bolt products in accordance with GB/T 229-2007 chapy V-notch regulations, with dimensions of 10×10×55mm, 2mm depth.

The position of notch shall be opposite of the side which is closer to the surface. Average absorbed energy at -40℃ shall be in accordance with Table 5.

Table 5 Impact behavior of anchor bolts

8.3 Hardness Properties

Hardness inspection shall be performed according to GB/T230.1 -2009, prepare polished cylindrical test pieces with height 10-20mm, in accordiance with Table 6.

Table 6  Hardness of anchor bolts

8.4 Stress Relaxation Property

According to GB/T10120-2013 regulations, perform test on relaxion testing machine. The specimen is subjected to an increasing force until the specified initial strain is attained(within 3-5 minutes), then take readings after holding 1 minutes.

Specimen shall be cut from anchor bolt product, and machined into a ribbed round-section with two ends of 16mm diameter and waist of 10mm diameter, see Figure 2.

                                                          Figure 2 ribbed round-section

With specimen subjected to 70% of nominal yield strength as initial stress, measure relaxation rate after 10hrs and 120hrs, and calculate the relaxation rate of 1000hrs.

Single 10hrs stress relaxation test will be permitted to conduct only when 1000hrs stress relaxation test can be succesful, and relaxation rate shall be not more than 1.5%.

Table 7 Stress Relaxation property of anchor bolts

If user requires full cross section specimen, we may attend to places where there are faclities with large forcing capacity.

8.5 Fatigue Property

Fatigue testing shall be conducted according to GB/T 3075-2008 or GB/T 13682-1992.

Specimen shall be cut from finished anchor bolt products, then machined into M16 ends and center d=12mm, r=2d, shown as Figure 3.

Figure 3 Fatigue Specimen

Our factory will send specimen to authorized party to perform fatigue testing. Under condition of 15HZ frequency and range of stress 40-100 MPa ,results shall be free of facture during 12000000 times fatige tests.

If specified in contracts, fatigue times shall performed as users’ requirements.

If user requires full corss section as specimen, we may attend to departments which have faclity of large forcing capacity, according to annex B.

Due to different fan-powers requirements, frequency and stress tests shall be conducted according to contracts.

8.6 Depth of Decarburization

(1)Decarburization of anchor bolts shall be performed by metallographic method according to GB/T3098.1 regulations.

(2)Decarburization of threaded parts shall be performed by metallographic method according to GB/T224-2008.

(3)Specimen shall be taken from finished anchor bolt products, cutting direction is longitudinal cross-section.

Test results shall comply to Table 8.

Table 8 Decarburization Measurement of Anchor Bolts

 H1 refers to max pitch hight.