Hyundai Kia MS121-04 Cold Rolled Mild Steel Sheets

Developed by Hyundai-Kia Motors, the oldest motor vehicle manufacturer in Korea, the “ Hyundai Kia MS121-04 Cold-Rolled Mild Steel Sheets” standard defines the requirements for cold-rolled mild steel sheets.

The classification of cold rolled mild steel sheets is given in the table given in the standard:

• SPCC: Overall quality
• SPCD: Tensile quality
• SPCEN: Deep drawing quality (for non-aging indication, N is added to the end of the string)
• SPCUD: Deep drawing quality, non-aging
• SPCSD: Not for new design

The classification of rolled soft sheets with skin transition is given in a separate table given in the standard:

• Skin impermeable: Stretch mark may occur in the shaping process.
• Standard skin transition: Skin transition rolling should be done. If there is no special comment, standard skin transition is done.
• 1/8 hardening: Hardness increase by controlling the rolling speed during skin pass rolling. Also hardness increase by adjusting the chemical composition.
• 1/4 hardening: Hardness increase by controlling the rolling speed during skin pass rolling. Also hardness increase by adjusting the chemical composition.
• 1/2 hardening: Hardness increase by controlling the rolling speed during skin pass rolling. Also hardness increase by adjusting the chemical composition.
• Hardening: Hardness increase by controlling the rolling speed during skin pass rolling. Also hardness increase by adjusting the chemical composition.

The classification of surface treatments is given in a separate table given in the standard:

• Dull process: The surface is finished by rolling, which is roughened mechanically or chemically. If there is no additional comment, the dull process is done.
• Polished process: The surface of the sheet is finished with a smooth roll to obtain a smooth surface.

Examples of indicators for drawings are given in a separate table provided in the standard:

• Inner panel display: SPCC t0.8
• Open panel indicator: SPCC-E t0.8 (open)
• Hardened steel sheet gauge: SPCC-8D t0.8 (hardening and surface treatment)

In terms of general requirements, steel sheets must be free from surface defects that affect the quality of forming, painting and welding. Unless otherwise specified, steel sheets must be coated with oil.

The chemical composition of the steel sheet shall be measured according to this standard and the requirements shall be in accordance with the table titled “Chemical composition of the steel sheet”.

The mechanical tests of steel sheets must be carried out in accordance with this standard and the properties must be in accordance with the tables titled “Mechanical properties” and “Mechanical properties of hardened cold rolled mild steel sheets” given in the standard. In the case of bending tests, the samples must be free from surface cracks.

The hardness of standard leather transition milled and non-leather transition milled soft plates shall comply with the table titled “Hardness of standard leather transition milled and non-leather transition milled soft plates”.

The thickness tolerances of steel sheets must be within plus/minus 5 percent of the sheet thickness.

Dimensional tolerances must comply with the table titled “Width tolerance of steel sheets (coils)” given in the standard.

In terms of shape, the flatness of the steel sheets must be in accordance with the table titled “Flatness” given in the standard. The flatness of SPFC1470 class sheets must be in accordance with the agreement between the buyer and the supplier company.

The camber of the steel sheets must be in accordance with the table titled “camber” given in the standard. If the length of the steel sheet is more than 2000 mm, the measurement should be made after the steel sheet is cut to 2000 mm length.

The average surface roughness of the steel sheet for the exposed panel should be between 0,6 and 1,2 μm.

In terms of heavy metals and harmful substances, each material must comply with the standard “MS201-02 Prohibition and notification of the use of harmful substances - Parts and materials”.

In this standard, test methods are described as follows:

• The sample sampling method for ladle analysis must comply with the standard “KS D 0001 General rules for steel inspection”.
• The sampling method for product analysis must comply with the standard “KS D 0228 Product analysis and tolerance for forged steel”
• The amount of each element should be determined by the following methods:
  • KS D 1659 Atomic absorption spectrochemical analysis of iron and steel
  • KS D 1804 Method for determination of carbon in iron and steel
  • KS D 1805 Method for determination of silicon in iron and steel
  • KS D 1806 Method for determination of manganese in iron and steel
  • KS D 1802 Determination method of phosphorus in iron and steel
  • KS D 1803 Method for determination of sulfur in iron and steel
  • KS D 1808 Method for determination of nickel in iron and steel
  • KS D 1807 Method for determination of chromium in iron and steel
  • KS D 1809 Method for determination of molybdenum in iron and steel
  • KS D 1810 Method for determination of copper in iron and steel
  • KS D 1878 Method for determination of boron in iron and steel
  • KS D 1876 Method for determination of titanium in iron and steel
  • KS D 1811 Method for determination of nitrogen in iron and steel

The general subjects of mechanical tests should be as described in the standard “KS D 0001' General rules for steel inspection”:

• When preparing the sample, the centre of each test piece should be located at a distance of ¼ of the distance in the width direction of the coil. The test piece should be taken perpendicular to the rolling direction.
• In the tensile test, the sample must be as specified in the standard “KS B 0801 Test pieces for tensile testing of metallic materials”. The test method must be in accordance with the standard “KS B 0802 Tensile test method for metallic materials”.
• The specimen from the bending test must be as specified in the standard "KS B 0804 Metallic materials - Bending test'. The test method must be in accordance with the standard "KS B 0804 Metallic materials - Bending test".

In the surface roughness test,

• The sample should be sampled at least 90 mm x 70 mm in the vertical direction (30 degrees) of the rolling direction. The surface should be cleaned with ethanol and the like, and there should be no rust preventive oil, grease, dust, paint, scale.
• The surface roughness is measured using surface roughness equipment at a cutting depth of 2,5mm, a measuring length of 12,5mm, and a testing speed of 0,1 to 1mm/s.
• Five other positions perpendicular to the rolling direction (90 degrees) should be measured and the average calculated excluding the maximum and minimum values. The measured values ​​should be displayed to the second decimal place.

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