GB/T 3078-1994 High-quality structural steel cold-drawn steel decarburization layer

GB／T 3078-1994 Quality Structural Steel Cold-Rolled Steel De-Carbonization Layer

1 Introduction

This standard GB/T 3078-1994 Quality Structural Steel Cold-Rolled Steel De-Carbonization Layer specifies the technical requirements and test methods of the quality of structural steel cold-rolled steel de-carbonization layer.

2 Normative References

The following articles or documents are required by this standard and are hereby referred to:

GB/T223.12 Methods for Chemical Analysis of Iron_Steel and Alloy- The Deter-minant Content of Carbon and Sulfur

GB/T223.13 Methods for Chemical Analysis of Iron_Steel and Alloy- The Deter-minant Content of Carbon and Sulfur

GB/T223.35 Metallic Materials 3.2 Method of Indication of Transition Temperature

GB/T223.38 Methods for Magnetic Particles Testing of Ferromagnetic Products

(GB/T223.46 Metallic Materials 3.2 Method of Impact Test

GB/T223.49 Metallurgical Testing of Steel Products- Tension Tests

GB/T223.55 Methods for Magnetic Particles Testing of Ferromagnetic Products

GB/T223.60 Metallic Materials-methods for Ultrasonic Testing for joints

GB/T223.61 Methods for Hardness Testing of Metal Materials_ Brinell

GB/T223.62 Methods for Hardness Testing of Metal Materials_ Rockwell

GB/T223.63 Methods for Hardness Testing of Metal Materials_ Vickers

GB/T223.64 Steel Products- Inspection of Internal Defects by Magnetic Particle Testing

GB/T223.68 Metallic Materials- Ultrasonic Testing-Detectable Sensitivity)

GB/T223.69 Methods for Macro and Macro Testing of Steel Castings

GB/T223.70 Methods for Hardness

3 Ordering

When ordering, the following information should be given:

3.1 Product name;

3.2 Grade, steel code and corresponding symbol number (steelyield strength);

3.3 Designation;

3.4 Dimensions, shape, weight and tolerances;

3.5 Mechanical properties and chemical composition;

3.6 Technical requirements;

3.7 Inspection requirement when ordering;

3.8 Other requirements.

4 Technical Requirements

4.1 Size, appearance and general requirement

4.1.1 The size, shape, appearance and structural dimension requirements of the product shall meet the requirements of the product drawings.

4.1.2 The surface of the product should be clean, flat and free of defects such as pits, cold-rolled lines, roll marks, burrs, scabbs, scratching, etc.

4.2 Chemical composition

The chemical composition of the product conforms to the requirements of Table 1.

Table 1 Chemical Composition ( % )

Element

C

Si

Mn

P

S

Ni

Cr

Requirements

≤ 0.08

0.15~0.30

0.30~0.60

≤ 0.035

≤ 0.035

≤ 0.30

≤ 0.30

4.3 Mechanical properties

The mechanical properties of the product conform to the requirements of Table 2.

Table 2 Mechanical Properties

Grade

Tensile Strength(MPa)

Yield Point(MPa)

Elongation after Breach (%)

Q235-Q550A

380~520

215~390

≥ 25

4.4 De-carbonization layer

There should be no white insulating layer and mild corrosion under the visible de-carbonization layer.

5 Test Methods

5.1 Size inspection

Inspect the product size and shape according to GB/T223.49 and GB/T223.60.

5.2 Chemical composition test

Determine the chemical composition of the product according to GB/T223.12 and GB/T223.13.

5.3 Mechanical properties test

Test the mechanical properties of the product according to GB/T223.46, GB/T223.49 and GB/T223.50.

5.4 Appearance test

Inspect the product appearance according to GB/T223.55 and GB/T223.60.

5.5 Hardness test

Test the hardness of the product according to GB/T223.61, GB/T223.62 and GB/T223.63.

5.6 Macro and micro testing

Test the internal defects of the product according to GB/T223.64 and GB/T223.68.

5.7 Transit temperature test

Test the transition temperature of the product according to GB/T223.35.

6 Packaging, Storage, Transportation and Acceptance

6.1 Packaging, storage and transportation

The product shall be packaged, stored and transported in a dry, ventilated and clean environment, and shall not be mixed with moisture, dirt and other substances.

6.2 Acceptance

The product acceptance shall be carried out in accordance with the relevant regulations of the state. All inspection and test shall meet the requirements of this standard.

GB/T 3078-1994 specifies cold rolled steel with decarburised layer requirement, chemical composition, mechanical property, process method, inspection and acceptance, packaging, and quality certificate.

This standard applies to cold-rolled steel strip with a decarburization layer, which is used as raw material to produce, stamping or cold-forming parts. According to the process requirements in different the industry, the steel can be referred to as deep-drawing cold rolled sheet, can also be referred to as general cold-rolled sheet.

Chemical composition:

The chemical composition of the steel should conform to the requirements of Table 1, expressed in mass fraction. It is allowable to replace any element for any other element without affecting the class of steel. The sum of mass fraction of each element should not exceed 1% for silicon, 1% for manganese, 0.60% for aluminum, 0.50% for titanium, 0.50% for vanadium, and 0.10% for boron.

Mechanical property:

The tensile strength of the steel should not be less than 380MPa, and the yield strength should not be less than 240MPa. The elongation should be not less than 10%.

Process method:

The steel should be made into decarburization layer with alkali removing method. When cold rolled, the diameter of backup roll should be at least twice as large as normal cold rolled steel. The steel should be stress relived after cold-rolled.

Inspection and acceptance:

The surface quality, dimension and mechanical property of the steel should be in compliance with the requirements of GB/T 3078-1994. The product should be inspected one by one according to the related national standards.

Packaging:

The steel should be rolled into coils and packed in the factory. Additionally, each coil should be tied up with four hoops and wrapped with two waterproof plastic bags.

Quality certificate:

The manufacturer should provide the quality certificate of the product in compliance with GB/T 3079-1994. The certificate should include the marking, nominal weight and actual weight, chemical composition, name of manufacturer, date of manufacture, mechanical property, and product level, in order to guarantee the quality of the product.