Tinplate national standard upgrade, strong foundation defense escort food safety

Tinplate national standard upgrade, strong foundation defense escort food safety

——GB/T 2520-2017 "Cold-rolled tin plate and steel strip" standard publicity and technical seminar held in Zhangzhou, Fujian

Figure 1 April 4th, sponsored by the Metallurgical Industry Information Standards Institute, Fujian Uniform Tinplate Co., Ltd. and Zhongshan Zhongyue Makou Iron Industry Co., Ltd. "GB/T 2520-2017 "Cold Rolled Tinplate and Steel Strip" Standard Declaration The "Technology Seminar" was held in Zhangzhou, Fujian.

Text / 闵耀霞

On April 12, 2018, the "GB/T 2520-2017 "Cold Rolled Tinplate and Steel Strip" standard sponsored by the Metallurgical Industry Information Standards Institute, Fujian Uniform Tinplate Co., Ltd. and Zhongshan Zhongyue Makou Iron Industry Co., Ltd. The "Technology Seminar" was held in Zhangzhou, Fujian. Participants said that the new national standard, which will be implemented more than a month later, is highly focused on the quality and safety of tinplate substrates and coatings. It is a product of upstream technology development and downstream demand. It is to promote the quality of tinplate products and promote tinplate and The long-term healthy and sustainable development of the downstream metal packaging industry and the resolution of international trade barriers are of great significance.

As one of the contact metal materials for food packaging, tin-plated steel sheets (commonly known as tinplate) are not only traditional canning materials, but also the most widely used metal packaging sheets. From the structural point of view, the three lines of defense for the protection of the contents of the metal packaging consist of coatings, coatings and substrates. The quality and safety level determine the safety and quality protection of the contents of the metal packaging. The substrate and coating of tinplate can be said to be the basic line of defense. Therefore, the residue of toxic and harmful substances in the coating and the substrate will directly affect the safety of the contents. At the same time, the substrate is supported as the basic structure of the metal packaging, and the performance and composition quality are proposed. Higher requirements.

Figure 2 The base material and coating of tinplate are used as the basic line of defense. The residue of toxic and harmful substances will directly affect the safety of the contents. At the same time, the substrate is supported by the basic structure of metal packaging, which puts high requirements on performance and composition quality.

Feng Chao, deputy dean of the Metallurgical Industry Information Standards Institute, Lin Guorui, deputy director of the Luzhou City Economic and Trade Commission, He Hongsun, president of the Luzhou Food Industry Association, Lin Jieben, president of the Canned Food Chamber of Commerce, Lin Yihui, secretary general of the China Food Association, and other industry leaders A total of about 80 people from the tinplate production plant and downstream cans (cover) companies attended the conference. In order to promote the new national standard, better understand the downstream demand, and allow the new standard to be implemented smoothly, this meeting specially invited the tinplate industry and downstream experts and scholars to interpret the standards and related food safety policies, and set up an interactive session between the upstream and downstream.

Review: The national standard revised the healthy development of Shaoguan tinplate industry

Relevant information indicates that the national standards related to tinplate have been revised four times since the introduction in 1981. According to one of the co-organizers of this seminar, one of the 100% controlling parent companies of Zhongshan Zhongyue Makou Iron Industry Co., Ltd., the executive director and general manager of Guangnan (Group) Co., Ltd., Mr. He Jinzhou made a speech at the seminar. The new standard, promoting the healthy development of China's food-grade tinplate packaging, the domestic tinplate industry experienced a benign order from the 1990s to the early 2000s. The mainstream tinplate enterprises use standard MR steel and 1# refined tin production and personal health safety. The closely related food-grade tinplate, and the rapid and uneven development from 2004 to the present, seems to have nothing to do with the standard changes. After entering the new millennium, the downstream demand continues to grow. The fourth version introduced in 2008 is followed by the Japanese standard to cancel the control requirements for the MR steel composition of the original tinplate. The domestic tinplate capacity has surged from less than 5 million tons in 2010 to 2015. More than 12 million tons. The severe overcapacity of production capacity and fierce competition for homogenization will easily lead to uncontrolled quality of MR steel. Even some manufacturers use SPCC, Q195 and other steel grades to replace MR and other steel grades and use non-1# refined tin to produce food grade tinplate, which seriously disrupts the market. Let the tinplate industry chain lurk huge food safety risks.

Therefore, in the view of He Jinzhou, the fifth version released on September 7, 2017, will also be implemented on June 1 this year, GB/T 2520-2017 "Cold-rolled tinplate and steel strip", is in response The call for “national deepening standardization reform” promotes quality improvement through “standard upgrade” and guides the inevitable move of regulating the market; it is increasingly attracting attention from brand users and end consumers in food safety issues, such as European standards and food safety. Under the trend of national standards for restricting the toxic and harmful elements of tinplate for food contact, the wise choice of China's tinplate industry chain.

The four major revisions of the new national standard focus on food safety

Mr. Tu Shulin, Director of the Standard Management Office of the Manufacturing Management Department of Baoshan Iron and Steel Co., Ltd., in his report entitled “GB/T 2520-2017 “Standard Analysis of Cold Rolled Tinplate and Steel Strip””, explained the upgrade of this national standard. Background and significance, summed up the four major revision points of the new national standard, the main focus of food safety can be seen.

Increased the chemical composition requirements of the original board to guide the selection of tin-plated original boards, guide and regulate the market. In the new national standard 7.1.1, the original steel type and chemical composition (melting composition) should be in accordance with the following table.

Table 1 Requirements for the chemical composition of the original tinplate in the new national standard

Increase the lead content of the tin plate used for direct contact with food, medicines and beverages (with or without organic coating on the surface) to ensure food safety. In the new national standard 7.3.5, the requirements for the production of direct contact with food, medicine and beverage containers (with or without organic coating on the surface) of the steel plate and steel strip, the tin content of the tin plating layer shall not exceed 0.0100% ( Based on the mass fraction of the coating).

In addition, in the new national standard 7.8, the raw material tin required for tin plating of steel plates and steel strips should meet the requirements of GB/T 728-2010 in the number of Sn99.90, and the mass fraction of Pb content should not exceed 0.0100%.

A reliable method for testing the Pb content of the coating was established and served as a normative appendix to the new national standard. The “Measurement of Pb content in tinplate plating” is listed as a normative appendix in Appendix F of the new national standard, which clarifies the measurement principle, equipment, main reagents and instruments, detailed testing procedures and calculation of results.

According to the new national standard Appendix F, the principle of measuring the lead content in the tinplate plating is: using the sample as the anode, dissolving the tin plating layer of the sample through a certain current density in the hydrochloric acid electrolyte, and dissolving the tin plating layer by recording the sample. During the process, the potential is changed with time, the time taken for the tin plating layer to dissolve and the amount of electricity consumed are calculated. The amount of tin plating is calculated according to Faraday's law, and then determined by atomic absorption spectrometry or inductively coupled plasma optical emission spectrometry. The lead content can be used to measure the lead content in the tin plating layer.

Consensus: Upstream and downstream to jointly revise and refine grading standards

Figure 3 The national standards related to tinplate have been revised four times since they were introduced in 1981. The fifth edition released on September 7, 2017, GB/T 2520-2017 "Cold-rolled tinplate and steel strip" will be implemented on June 1 this year.

In view of the compatibility and adaptability of the national standard, the new national standard including the size and shape tolerance of the tinplate has not been classified and subdivided in combination with the professional application field. At this seminar, several downstream user representatives proposed the food tank in the future national standard revision. The tinplate standards used in special fields such as beverage cans and color printing are called for refinement and grading to further meet the needs of downstream sub-sectors.

Mr. Li Ziyang, Manager of Quality Control Department of Fujian Biaoxin Yikai Group Co., Ltd. suggested that there should be more detailed standards for downstream applications such as cans. For the tinplate length and width tolerance of 0~3mm, this is far from the requirement that the overprinting error should not exceed 0.1mm in the tinplate printing standard for high-speed printing presses. For example, the thickness deviation of the tin plate is ±7%, and the thickness deviation of the thin side is 8.0%. The current standard allows the range to be too large, which has a certain influence on the welder on the can line, and may appear concave at the necking; and lead to production. The size of the easy-opening engraving line has fluctuations, which has a certain influence on the pressure resistance, breaking force and full opening force of the easy-opening cover. In addition, the pinhole and the trachoma as a tinplate can cause a leaking tank. Is there any more advanced equipment in the tinplate production plant that can detect the rejection?

Ms. Xi Zhilan, Minister of Quality Control Department of Shengxing Group, shares this feeling. She particularly emphasized that as the speed of downstream canning production lines continues to increase, and the thinning of canning materials has become an irresistible trend, the existing necking machines and sealing machines have placed higher demands on the stability and uniformity of the size of tinplate materials. The provisions of the new national standard 6.2.2 on thin edges will allow downstream beverage can manufacturers to cut the multilateral edges for uniform and stable materials, resulting in a large waste of tinplate materials. In addition, the new national standard 6.3.3 clause on the degree of unevenness (also known as wave height) is not more than 3mm, and the requirements of the downstream canning industry within 1.5mm.

For the voice of downstream customers, Mr. Zhang Weixu, Secretary General of the National Steel Standards Committee of Steel Plate and Steel Strips, said that in the future revision of the tinplate standard, downstream users will be invited to participate in the use of a set of material standards for upstream and downstream, so that they can Do more on one platform.

In addition, the author learned from the seminar that when the chrome plate national standard is revised, it will consider refining the standard of special steel. It will meet the user's expectations, improve the tolerance and shape requirements, and make the measurement methods of side waves, medium waves, warping and other indicators more suitable for users. At the same time, it will increase the roughness requirements, surface passivation requirements, and DI material performance requirements.

 Tinplate processing and packaging development trends

Figure 4: Lightweight canning, processing and product food safety have promoted the development of new technology for tinplate.

According to the report “Safety and Processing Technology of Tinplate for Food Industry” by Mr. Huang Yuyuan, Deputy Manager of Quality Control and Customer Service Center of Fujian Uniform Tinplate Co., Ltd., the development trend of tinplate production and processing technology includes chromium-free passivation process, environmentally friendly plating process, low Lead plating process, tin recycling technology, etc.

Chen Hongxing, Principal Investigator of Baosteel Central Research Institute, summarized the development trend of tinplate processing and packaging in his report entitled "Tornel Technology Development and New Process New Products", namely: light weight of can lid, processing and product food safety promoted the new technology of tinplate Development; the development of tinplate technology presents the main features of thinning high performance, energy saving and environmental protection in the industrial chain; secondary cold rolling, chromium-free passivation and coated iron will join hands in the technological transformation of the tinplate packaging industry.