TECHNICAL CONDITIONS OF CONCAST BILLETS

Concast billets designed for rolling and die forging

CONTENTS:
1. Introduction
2. General stipulations
3. Technical conditions of the order
4. Requirements
5. Inspection
6. Test certificate and acceptance certificate
7. Sampling of test pieces
8. List of documents connected with TCCB

1. Introduction

These Technical Conditions of Concast Billets (TCCB) are valid for ordering and delivering of concast billets with round section O 170 mm, rectangular section 140x165 mm and square sections 100, 120, 140 and 160 mm cast on the CC machine at  FERROSTAL LABɄY.
The subject of TCCB are concast steel billets produced in the process of continuous casting designed for rolling. The billets can be also raw material for die forging.

2. General stipulations

The steel is melted in a high-power electric arc furnace of EBT type in the quantity of 65 +/- 2mt/heat, refined in a ladle furnace (without vacuum degassing) and cast on an arc steel continuous casting machine using the technology of submerged casting or the open casting technology. Round concast billets are cast only by using submerged casting. All concast billets are cast with the use of electromagnetic mixing in a continuous casting mould.

It is possible to cast the following steels in accordance with national and foreign standards:

• constructional carbon steels with carbon content in the range: 0,06-0,80%,
• low-alloy steels with microadditions,
• special medium-alloy steels.

The steel is cast in the following sizes and lengths:

• square: 100x100, 120x120 ,140x140 i 160x160mm,
• rectangle: 140x165mm
• circle O 170 mm
• in lengths 5,6-12,4 running metres.

3. Technical conditions of the order

The order must contain the following data:

• weight in mt of the concast billets,
• steel grade,
• number of standard,
• section of the concast billet,
• length (permissible deviations),
• quantity of shorts in the delivery,
• application of concast billets,
• for special quality steels additional requirements, exceeding the scope of TCCP, must be mutually coordinated.

4. Requirements

The surface is typical for the steel continuous casting process. On the surface of concast billets the following defects with depth lower than 1.5% of the crosswise dimension are permitted:

• oscillatory teeming laps,
• scratches,
• pinholes,
• slag inclusions,
• shrinkage depressions,
• dents.

Upon agreement with the orderer it is permitted to deliver billets with surface defects deeper than 1.5% of the crosswise dimension, if the intensity and depth of these defects do not cause worsening of the surface quality of the finished products under further processing.
It is allowed to remove surface defects of greater depth by flame desurfacing (rinsing) or mechanical cleaning (chiselling, grinding), whereas the machined surface should have soft cavities and rounded edges, and the depth at the place of the removed defect should not exceed 6% of the billet crosswise dimension in accordance with standard PN-75/H-93022.

I. For concast billets with square and rectangular sections:

Standards for the evaluation of internal quality according to BN-76/0601-10 should be agreed in the order. For concast billets designed for responsible products it s possible to make Baumann prints according to the standard PN-87/H-04514.
Pursuant to BN-76/0601-10, FERROSTAL LABɄY confirms the internal quality of concast billets according to the below mentioned classes:

• axial porosity:

  I / 2 - min. 90 % of billets

• axial micro-shrinkage:

  II / 2 - min. 90 % of billets

• internal cracks over grain boundaries:

  III / 2

• cracks over diagonals:

  IV / 2

• star-shaped cracks:

  V / 2

• pinholes and subcutaneous blowholes:

  VI / 2

II. For concast billets with round section:

The concast billets should meet the undermentioned requirements according to the classification of Mannesman Demag concerning internal defects in the continuously cast material.

FERROSTAL LABɄY confirms the internal quality of concast billets according to the below mentioned classes:

• Degree of purity:

  2

• Surface zone:

  2

• Middle zone:

  2

• Core zone:

  2

In case the orderer is interested in other standards, it should be each time stated in the order.

Nominal dimensions of the cross section, acceptable dimensional deviations, weight of 1 running metre of billet are presented on the drawings and table.

I. For concast billets with square and rectangular sections

II. For concast billets with round section

Weight of 1running metre of concast billet amounts to 175.0 kg

I. For concast billets with square and rectangular sections
The acceptable skewness of the cross section measured as the difference of section diagonals should not exceed:

• 8mm (for square 100x100,120x120 i 140x140mm),
• 10mm (for rectangle 140x165 i kwadratu 160x160mm),
• 12mm (for square 160x160mm – only for grades with carbon content C > 0,17% open cast).

II. For concast billets with round section:

• Diameter tolerance     +1/-3 mm
• Local ovality              max 2,5%

The ovality is calculated according to the formula:

• Concast billets are delivered in lengths 5,6-12,4m.
• The delivery of concast billets in shorter lengths is permitted upon additional agreement. The minimum length of the concast billet mechanically cut amounts to 4,6m.
• The permissible deviation of the concast billet length should not exceed +/- 100mm.
• In the delivery of concast billets up to 5% of shorts resulting from the technological process of the CC machine is permitted.

• Concast billets are delivered as not straigthened.
• The permissible straightness deviation should not exceed 1% of the measured length.

Twist along the longitudinal axis of max. 1 degree over the length of 1m is permitted.

• On the end faces of concast billets the occurrence of out-of-flatness, grooves, partial melting and pits typical for the cutting process with gas and oxygen torches is accepted.
• At the ends of concast billets the occurrence of fin typical for cutting of concast billets with gas and oxygen torches is permitted.
• In the axial zone the occurrence of fine cracks, micro-shrinkage and porosity is accepted.

The minimum processing reduction ratio of concast billets should be 6,0:1.

Concast billets are marked with the following marks on the end face or lateral surface:

• number of heat,
• grade of steel.

k) Dispatch

Concast billets are dispatched together with a documentation (specification of delivery), which should include the following information:

• heat No,
• length of billets,
• wagon No/truck No,
• number of billets,
• weight of billets,
• order No.

5. Inspection

The inspection of surface, dimensions and internal quality is performed by the Quality Inspection and Department in accordance with these TCCB and order confirmation. The results of testing the samples performed in the works laboratory are used for the quality evaluation.

6. Test certificate and acceptance certificate

For each batch of production FERROSTAL LABɄY issues an acceptance certificate or test certificate according to PN-EN 10204+A1/1997 including:

• name of producer,
• product designation,
• chemical composition,
• quality inspection mark stating the conformity of the product with the requirements,
• name of orderer.

7. Sampling of test pieces

Sampling of test pieces is carried out according to the Instruction:
"Instruction of sampling and testing".

8. List of documents connected with TCCB

PN-88/H-04420 - Metals. Steel semi-products and products. Measurement of shape deviations.
PN-87/H-04514 - Steel, cast steel and cast iron. Tests of macrostructure. Baumann test.
PN-75/H-93022 - Rolled blooms and billets designed for rolling and forging.
BN-76/0601-10 - Tests of the macrostructure of steel concast billets. Macro-etch test.
PN-EN 10204/2006 - Metal products. Types of inspection documents.
Procedure according to PN EN ISO 9001:2001 - PP:7-01.11. Final inspection of blooms.
Criteria of Mannesman Demag AG - Classification of internal defects on round blooms cast on steel continuous casting equipment.